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IntroductionSimply put, an oscillator is a device that can convert DC power into AC power without external signal excitation. The so-called "oscillation" implies alternating current. This article will mainly explain the circuits of different sine wave oscillators, including their working principles, how to realize their functions, circuit composition and comparison of advantages and disadvantages of different forms of circuits. This article uses a large number of circuit diagrams and formulas to explain in detail, which can help you understand in a better way.Basics of oscillators and their different typesCatalogIntroductionCatalogI The Principle of Feedback Oscillator1.1 How Does the Feedback Oscillator Work?1.2 Equilibrium Conditions1.3 Starting Conditions of the Oscillator1.4 Stable Conditions of the Oscillator1.5 General Composition of Sine Wave OscillatorII LC Oscillator Circuit2.1 The Composition Principle of the Oscillator2.2 Capacitive Feedback Oscillator2.3 Inductive feedback oscillatorIII RC Oscillator Circuit3.1 Brief Introduction of RC Oscillator and its Circuit3.2 RC Phase Shift Oscillator3.3 Wien Bridge OscillatorIV Quartz Crystal Oscillator Circuit4.1 What is a Quartz Crystal Oscillator?4.2 Quartz Crystal4.3 Quartz Crystal Oscillator CircuitV Non-sine Wave Generating Circuit5.1 What is a Non-sine Wave Generating Circuit?5.2 Rectangular Wave Generator5.3 Triangle Wave and Sawtooth Wave Signal GeneratorVI QuizⅦ FAQI The Principle of Feedback Oscillator1.1 How Does the Feedback Oscillator Work?The feedback oscillator is when the power is turned on, the various electrical disturbance signals in the loop are selected by the frequency selection network, and the signal of a certain frequency is fed back to the input terminal, and then the cycle of amplification → feedback → amplification → feedback , The amplitude of the signal increases continuously, and the oscillation is established from small to large. As the signal amplitude increases, the amplifier will enter a non-linear state, and the gain will decrease. When the feedback voltage is exactly equal to the input voltage, the oscillation amplitude will no longer increase and enter a balanced state. As can be seen from the figure below, the feedback oscillator is a closed loop composed of an amplifier and a feedback network. The amplifier is usually a tuned amplifier with an oscillation circuit as a load. The feedback network is generally a linear network composed of passive components.Figure1. Block Diagram of Feedback OscillatorIn order to generate self-oscillation, there must be positive feedback, that is, the signal fed back to the input terminal and the signal at the input terminal of the amplifier have the same phase. For the above figure, suppose the voltage amplification factor of the amplifier is K(s), the voltage feedback coefficient of the feedback network is F(s), and the closed-loop voltage amplification factor is Ku(s), thenby We can writeIf a certain frequency ω1=ω, then T(jω1) is equal to 1. From the above formula, we can see that Ku(jω) will tend to infinity. This shows that there is no external signal, and self-excited to produce signal output, namely self-oscillation. Therefore, the condition of self-oscillation is that the loop gain is 1.Definition:1.2 Equilibrium ConditionsThe equilibrium condition of the oscillator isthis can also be expressed asIf a certain frequency ω1=ω, then T(jω1) is equal to 1. From the above formula, we can see that Ku(jω) will tend to infinity. This shows that there is no external signal, and self-excited to produce signal output, namely self-oscillation. Therefore, the condition of self-oscillation is that the loop gain is 1. The above two formulas are the amplitude and the phase equilibrium conditions respectively. Equilibrium conditions are also called "two conditions for maintaining self-oscillation". The amplitude balance condition determines the amplitude of the oscillator output signal, and the phase equilibrium condition determines the frequency of the oscillator output signal. But it must be pointed out that the loop can only meet the phase equilibrium condition at a certain frequency (f), which is the resonant frequency (f0) of the loop.1.3 Starting Conditions of the OscillatorWhen the oscillator is in actual application, there should be no external signal Us(s) shown in Figure 1. The initial source of oscillation is electrical signals such as electrical shock and various thermal noises that inevitably exist when the oscillator is switched on.It can be seen from the establishment process of the oscillation that in order to make the oscillator start-up, the feedback voltage Uf and the input voltage Ui should be in phase at the beginning of the oscillation (that is, positive feedback); Uf>Ui should be required in amplitude, that is:Vibration conditions: φA+φF=2nπ(n=0,1,2,•••)AF>1 Simply put, as we know, the condition of unity gain must be met to make the oscillation continue. But to start the oscillation, the voltage gain of the positive feedback loop must be greater than 1, so that the amplitude of the output voltage can reach the required potential. Then the gain must be reduced to 1, so that the output voltage can be maintained at the required potential and the oscillation phenomenon can continue. Transition from |T(jω)|>1 to |T(jω)|=1 when the oscillator is workingThe amplifier must work in the linear amplification region of the transistor when amplifying small signals.When the oscillation is started, the amplifier works in the linear region. At this time, the output of the amplifier increases linearly with the increase of the input signal; as the amplitude of the input signal increases, the amplifier gradually enters the saturation or cut-off region from the amplification region, and enters a nonlinear state. The closed-loop gain of will decrease with the increase of the input signal, as shown in the figure below:Figure2. Graphical Representation of Amplitude ConditionsWhen the loop gain drops to |T(jω)|=1, the growth process of the amplitude will stop, and the oscillator will reach a balanced state and perform constant amplitude oscillation. It can be seen that the transition of the oscillator from amplified oscillation to steady amplitude oscillation is realized by the non-linear characteristics of the amplifier. When the oscillating circuit is powered on, the current of the transistor increases abruptly from zero, and the sudden change current contains a wide spectrum component. The start-up process of the circuit is very short! As long as the circuit satisfies the starting conditions, after the oscillator is powered on, there will be an output signal with stable amplitude at the output.Figure3. Circuit Start-up Process1.4 Stable Conditions of the OscillatorIf the loop gain characteristic has two equilibrium points A and B, among them, point A is stable and point B is unstable.Figure4. Stable Conditions of the OscillatorIt can be seen from the above discussion that in order to stabilize the equilibrium point, |T(ω0)| must have a negative slope change near UiA.Stable conditions are divided into amplitude stable conditions and phase stable conditionsTo make the amplitude stable, the oscillator must have the ability to prevent amplitude changes at its equilibrium point. Then the amplitude stability condition should beSince the feedback network is a linear network, which means the size of the feedback coefficient does not change with the input signal, so the amplitude stability condition can be written asThe phase stability depends on the increase of ω, and the decrease of , meaning that the phase characteristic of the parallel oscillator circuit ensures the phase stability.Therefore, the phase stability condition is. The higher the Q value of the loop,  the larger of the value of , and the better phase stability.1.5 General Composition of Sine Wave Oscillator(1) Amplifying circuit-realize energy control.(2) Positive feedback network-meets the conditions for starting vibration.(3) Frequency selection network-only one frequency satisfies the oscillation condition to obtain a sine wave output of a single frequency. Commonly used frequency selection networks include RC frequency selection and LC frequency selection(4) Amplitude stabilization link-makes the circuit easy to start and oscillate stably, with little waveform distortion. Examples of oscillation circuits:High frequency resonant amplifier and sine wave oscillatorFigure5. High Frequency Small Signal Resonant AmplifierFigure6. Mutual Inductance Coupled OscillatorII LC Oscillator CircuitLC oscillators can be divided into three types: mutual inductance coupled oscillators, inductive feedback oscillators and capacitive feedback oscillators according to their different feedback networks.This section focuses on different types of feedback LC oscillators and three-point oscillators.2.1 The Composition Principle of the OscillatorFigure7. General Form of Three-terminal OscillatorThe basic circuit is the so-called three-terminal (also called three-point) oscillator, which means the circuit formed by connecting the three terminals of the LC loop and the three electrodes of the transistor respectively, as shown in the figure. The three-terminal LC oscillator is a feedback type LC oscillator. In order to obtain positive feedback, the feedback circuit must make the instantaneous polarity of the transistor's AC voltage meet a certain phase relationship: when Vbe is negative, Vce should be positive, namely, Vbe and Vce are in reverse phase, and Veb and Vce are in phase. Only when the reactance Xce and Xeb have the same properties can they be guaranteed to be in phase. When the resistance of the loop element is very small, its influence can be ignored, and the influence of the input impedance and output impedance of the transistor can also be ignored. To maintain oscillation, the circuit must meet the requirements. Otherwise, the loop resonance condition cannot be met.The criteria for the three-terminal oscillator circuit to meet the phase equilibrium condition is as follows:(1) The reactance properties of Xce and Xeb are the same, but the reactance properties of Xcb are opposite. That is, ce and be are the same resisting piece, and cb resisting piece.(2) The oscillation frequency should satisfy 1Xo+Xcl-XolBased on this criterion, it can be quickly judged whether the oscillating circuit composition is reasonable or not.Three-terminal LC oscillatorThe three-terminal LC oscillation circuit is often used, and its operating frequency is about a few MHz to a few hundred MHz. The frequency stability is also higher than that of the transformer coupled oscillation circuit, which is about 10-3~10-4. After some frequency stabilization measures, it can be higher. There are many types of three-terminal LC oscillators, mainly: Inductance three-terminal type, also known as Hartley oscillator; capacitor three-terminal type, also known as Colpitts oscillator; series type improved capacitor three-terminal type, also known as Clapp parallel type improved capacitor three-terminal type , Also known as Sellier oscillator. The three-terminal oscillator has two basic circuits, as shown in the figure below.Figure8. Capacitive Feedback Oscillator and Inductive Feedback Oscillator2.2 Capacitive Feedback OscillatorCapacitive feedback three-terminal oscillator is an electronic component, also called Colpitts oscillator, which is a kind of self-excited oscillator. It is composed of a series capacitor, an inductance circuit and a positive feedback amplifier. It is named because the three end points of the two series capacitors of the oscillating circuit are connected to the three pins of the oscillating tube respectively.Figure9. Capacitive Feedback OscillatorAs shown in the figure, use C2 to feed back part of the voltage of the resonant tank to the base. The three end points of the LC resonant tank are respectively connected to the three electrodes of the transistor, so it is called a capacitive feedback three-terminal oscillator, or Colpitts oscillator. The vector analysis method can be used to prove that the circuit meets the phase balance condition. As long as the ratio of C1 and C2 is appropriately selected and the amplifier has enough amplification, the circuit can oscillate.Figure10. Capacitive Feedback OscillatorAdvantages of Colpitts circuit:(1) Good oscillation waveform;(2) The frequency stability of the circuit is high. If the capacitance of the circuit is increased appropriately, the influence of unstable factors on the oscillation frequency can be reduced;(3) The operating frequency of the three-terminal circuit of the capacitor can be made higher. The output and input capacitors of the oscillator tube can be directly used as the oscillation capacitor of the loop, and the operating frequency can reach a very high frequency range of tens of MHz to hundreds of МHz. Disadvantages of Colpitts circuit:When adjusting C1 and C2 to change the oscillation frequency, the feedback coefficient will also change, which will affect the starting conditions and working status. But as long as a variable capacitor is connected to both ends of L and C1 and C2 are fixed capacitors, the feedback coefficient will not be affected when the frequency is adjusted.2.3 Inductive feedback oscillator(1) Circuit compositionIn order to overcome the shortcomings that the transformer primary coil and the secondary coil in the transformer feedback oscillation circuit are not tightly coupled, the N1 and N2 of the transformer feedback oscillation circuit can be combined into one coil. As shown in the figure below, in order to strengthen the resonance effect, the capacitor C is connected across the entire coil. This is the inductive feedback oscillator circuit, or Harley oscillator.Figure11. Inductive Feedback Oscillator Circuit(2) Working principle✿The circuit includes four parts: amplifier circuit, frequency selection network, feedback network and non-linear element (transistor), and the amplifier circuit can work normally.✿Use the instantaneous polarity method to judge whether the circuit meets the phase condition of sine wave oscillation: disconnect the feedback, add the input voltage with frequency f0, give its polarity, and judge that the polarity of the feedback voltage obtained from N2 is the same as the input voltage , So the circuit satisfies the phase condition of sine wave oscillation.✿As long as the circuit parameters are selected properly, the circuit can meet the amplitude condition and produce sine wave oscillation. The following figure shows the AC path of the inductive feedback oscillation circuit. The three ends of the primary coil are connected to the three poles of the transistor, so the inductive feedback oscillation circuit is called an inductive three-point circuit.Figure12. AC Path of Inductive Feedback Oscillator Circuit(3) Advantages and disadvantagesThe coupling between N2 and N1 in the inductance feedback oscillation circuit is tight, the amplitude is large, and it is easy to oscillate; when C uses a variable capacitor, a wide adjustment range of oscillation frequency can be obtained, and the highest oscillation frequency can reach tens of MHz. Since the feedback voltage is taken from inductance, it has greater reactance to high-frequency signals, and the feedback signal contains more high-order harmonic components, and the output voltage waveform is not good. The following introduces two improved capacitor three-terminal oscillation circuits:Clap oscillator:The following figure (a) is the principle circuit of the Krapper oscillator, and (b) is its AC equivalent circuit. Its characteristic is that a capacitor C3 is added to the inductance branch of the aforementioned capacitive three-point oscillating resonant tank. Its value is relatively small, requiring C3<< C1, C3<< C2.Figure13. Clapp OscillatorRegardless of the influence of the capacitance between the poles, the total capacitance CΣ of the resonant circuit is the series connection of C1, C2 and C3, namely. Thus, the oscillation frequency is .The condition for the above formula to be true is that C1 and C2 must be selected relatively large. It can be seen that the influence of C1 and C2 on the oscillation frequency is significantly reduced, so the influence of the capacitance between the transistors connected in parallel with C1 and C2 is also very large. It is smaller, and the stability of the oscillation frequency is improved. Sellier oscillator:Figure14. Sellier Oscillator so the oscillation frequency:L is the inductance of the inductance coil of the resonant amplifier circuit; C is the total capacitance of the resonant circuit. In the LC resonance circuit, the inductance L(H)/capacitance C(F)=105~106, which can achieve better results.III RC Oscillator Circuit3.1 Brief Introduction of RC Oscillator and its Circuit● What is an RC oscillator?(1) The sine wave oscillator has no input signal and is a positive feedback amplifier with a frequency selection network. If resistors and capacitors are used to form a frequency selection network, it is called an RC oscillator, which is generally used to generate 1Hz-1MHz low-frequency signals. The frequency selection effect of the RC frequency selection network is not as good as that of the LC resonant circuit, so the waveform and stability of the RC oscillator are worse than that of the LC oscillator.(2) RC oscillator can be divided into sine wave oscillator and non-sine wave oscillator according to whether the output wave type is sine wave.(3) There are many kinds of RC oscillation circuits: bridge type, phase shift type, double T type, the most commonly used is bridge type oscillation circuit, namely RC series-parallel frequency selection network. ● Features of RC oscillator(1) RC phase-shift oscillator features: simple, poor frequency selection, unstable amplitude, inconvenient frequency adjustment, generally used in occasions with fixed frequency and low stability requirements. Frequency range: several hertz-tens of kilohertz(2) RC series-parallel network oscillator features: it can easily and continuously change the oscillation frequency, it is convenient to add negative feedback to stabilize the amplitude, and it is easy to get a good oscillation waveform.(3) Double T frequency selective network oscillator characteristics: good frequency selection characteristics, difficult frequency modulation, suitable for generating single frequency oscillation. ● RC oscillator circuitThe oscillating circuit composed of RC frequency selection network is called RC oscillating circuit, which is suitable for low-frequency oscillation, and is generally used to generate low-frequency signals of 1Hz~1MHz. The circuit is composed of four parts: amplifier circuit, frequency selection network, positive feedback network, and amplitude stabilization link. The main advantage is simple structure, economic and convenient. According to the different forms of the RC frequency selection network, the RC oscillator circuit can be divided into an RC lead (or lag) phase shift oscillator circuit and a Wien circuit oscillator circuit. For RC oscillator circuits, increasing the resistance R can reduce the oscillation frequency, and increasing the resistance does not need to increase the cost. The frequency of the sine wave generated by the commonly used LC oscillator circuit is relatively high. If a sine wave with a lower frequency is to be generated, the oscillation circuit must have a larger inductance and capacitance. This will not only cause the components to be bulky, heavy and inconvenient to install, but also difficult to manufacture. high cost.  Therefore, the sinusoidal oscillation circuit below 200kHz generally adopts an RC oscillation circuit with a lower oscillation frequency.3.2 RC Phase Shift OscillatorThe phase shift oscillator is an oscillator composed of an advanced phase shift or a lag phase shift circuit as a frequency selection network and an inverting amplifier. It has the advantages of simple circuit, economy and convenience, but the effect of frequency selection is poor, the amplitude is not stable enough, and the frequency adjustment is inconvenient. Therefore, it is generally used for occasions with fixed frequency and low stability requirements. Its oscillation frequency is:Figure15. RC Phase Shift Oscillator Schematic Diagram3.3 Wien Bridge OscillatorThe RC series-parallel frequency selection network and amplifier can be combined to form an RC oscillator circuit, and the amplifier part can be an integrated operational amplifier. As shown in the figure, the RC series-parallel frequency selection network is connected between the output of the operational amplifier and the non-inverting input to form positive feedback. Rt and R1 are connected between the output of the operational amplifier and the inverting input to form negative feedback. . The positive feedback circuit and the negative feedback circuit constitute a Wien bridge circuit, and the input and output ends of the operational amplifier are respectively connected across the diagonal of the bridge. Therefore, this kind of oscillation circuit is called a Wien bridge oscillation circuit.Figure16. Wien Bridge OscillatorThe oscillating signal is input from the non-inverting terminal, so a non-inverting amplifier is formed. The output voltage is in phase with the input voltage, and the closed-loop voltage amplification factor is equal to: When the RC series-parallel frequency selection network is ω=ω0=1/RC, Fu=1/3, εf=0, so as long as |Au|=1+(Rt/R1)>3, that is, Rt>2R1, oscillation The circuit can meet the self-excited oscillation amplitude and phase start-up conditions to produce self-excited oscillation, the oscillation frequency f0=1/2πRC. Using double adjustable potentiometer or double adjustable capacitor can easily adjust the oscillation frequency. In the commonly used RC oscillator circuit, the high stability capacitor is generally used to switch the frequency band (coarse frequency adjustment), and then the double variable potentiometer is used to fine-tune the frequency.IV Quartz Crystal Oscillator Circuit4.1 What is a Quartz Crystal Oscillator?Quartz crystal oscillator refers to a device made on the principle that the crystal resonates due to the piezoelectric effect when the frequency of the electrical signal is equal to the natural frequency of the quartz crystal. It is a key component of crystal oscillators and narrow-band filters.Although the appearance, size and frequency of the quartz crystal oscillator are different, the structure principle is basically the same. In order to improve the stable and reliable operation of the quartz crystal, the shell components of the quartz crystal oscillator will be sealed and evacuated. Or fill with nitrogen.4.2 Quartz Crystal(1) StructureFigure17. Structure of the Quartz Crystal(2) Basic characteristicsApplying an electric field between the plates→mechanical deformation of the crystalMechanical force is applied between the plates → the crystal generates an electric fieldPiezoelectric effect: alternating voltage → mechanical vibration → alternating voltageWhen the alternating voltage frequency = natural frequency, the amplitude is the largest → piezoelectric resonanceThe natural frequency of mechanical vibration is related to the size of the wafer, and the stability is high.4.3 Quartz Crystal Oscillator CircuitThe high quality factor of quartz crystal is used to form an LC oscillator circuit.(1) Parallel Type quartz crystal oscillatorFigure18. Parallel Type Quartz Crystal Oscillator Quartz crystal works between fs and fp, which is quite a large inductance, and forms a capacitive three-point oscillator with C1 and C2. Because the Q value of the quartz crystal is very high, which can reach more than several thousand, the circuit can obtain high oscillation frequency stability.Figure19. Frequency Characteristics of Parallel Quartz Crystal Oscillator (2) Series type quartz crystal oscillatorFigure20. Series Type Quartz Crystal Oscillator Circuit The quartz crystal works at fs, which is resistive and has the smallest impedance, the strongest positive feedback, and zero phase shift, which meets the phase balance condition of oscillation.For frequencies other than fs, the impedance of the quartz crystal increases, and the phase shift is not zero, then the oscillation condition is not met, and the circuit does not oscillate.Figure21. Frequency Characteristics of Series Quartz Crystal OscillatorV Non-sine Wave Generating Circuit5.1 What is a Non-sine Wave Generating Circuit?It is composed of an integrating circuit and a hysteresis comparator circuit. The role of the integrator circuit is to produce a transient process. The hysteresis comparator acts as a switch, that is, the steady state is destroyed by the continuous closing of the switch, and a transient process is generated.Commonly used non-sine wave generating circuits include rectangular wave generating circuits, triangular wave generating circuits and sawtooth wave generating circuits, etc. They are often used as signal sources in pulse and digital systems.5.2 Rectangular Wave GeneratorIt is composed of hysteresis comparison circuit and RC timing circuit. The output has no steady state and there are two transient states; if the output is high level, it is defined as the first transient state, and the output is low level as the second transient state.Basic components:(1) Switching circuit: The output has only two situations of high level and low level, called two states; therefore, a voltage comparator is used.(2) Feedback network: self-control, when the output is in a certain state, it breeds the condition of turning into another state. Feedback should be introduced.(3) Delay link: Make the two states maintain a certain period of time and determine the oscillation frequency. Use RC circuit to achieve.Circuit composition:Figure22. Rectangular Wave Generating Circuit5.3 Triangle Wave and Sawtooth Wave Signal GeneratorThe circuit structure of the triangle wave generator: hysteresis comparator + inverting integratorworking principle:Figure23. Circuit of Triangle Wave Generator Sawtooth wave generator: change the forward and reverse charging time constant of the integrator, thereby changing the duty cycle.Figure24. Circuit Diagram of Sawtooth Generator uo1=+UZ, D is cut off, charging time constant: R4C.uo1=-UZ, D is on, charging time constant: (R6∥R4)C≈R6C.Figure25. The Waveform of the Sawtooth GeneratorVI QuizLC resonant circuits are used in:a) RF and ultrasonic oscillators.b) AF and ultrasonic oscillators.c) LF sweep oscillators.d) Variable frequency crystal oscillators. Answer: aⅦ FAQ1. What are the uses of an oscillator?Oscillators have very high precision and accuracy usually <100 ppm variation at a max. So with this kind of accuracy, the oscillator can be used as a clock of the microcontroller (the clock is the most essential part of the microcontroller, without an accurate clock, the functionality will be erratic because we cannot expect the output at the same time we have designed it for). All the quartz-based watches use an Oscillator (32kHz quartz crystal) to keep the time. SO if your timekeeping devices are running with an oscillator, you can imagine the accuracy.Oscillators can additionally be used to generate waveforms required in test benches. In almost all the applications where timing and synchronization are very essential, an oscillator finds its place. For example, in communication systems (whichever electronic communication you consider let it be a telephone, lan, anything) an oscillator is the heart.An oscillator can be used in power systems to generate accurate power waveforms. 2. What is the function of a local oscillator?A local oscillator is used in transmitters and receivers to add or subtract an amount to a basic carrier and modulation. Very handy, as it’s easiest to build up a carrier and modulate it at a low frequency, like 445Kc or 10.7MHz, and then add to it a “LO” to get it up to the FM band or the Gigahertz Wifi or radar bands. The same thing on receive, you first use a 'LO' to subtract down to an intermediate frequency where it’s so much easier to amplify and filter. 3. How do you make a crystal oscillator?The simplest is to use a logic inverter. Put a crystal between the input and output. Some schematics show some caps from the crystal legs to the ground and some show a series resistor. 4. Which type of circuit is used in the oscillator?Types of Oscillators: Harmonic Oscillators & Crystal Oscillators. Harmonic or linear oscillators produce a sinusoidal output where a signal increases and decreases at a predictable level over time. Two basic types are RC, or resistor/capacitor circuits, as well as LC, or inductor-capacitor circuits. 5. What is an Oscillator and the types of oscillators?An oscillator is a type of circuit that controls the repetitive discharge of a signal, and there are two main types of the oscillator; a relaxation, or a harmonic oscillator. This signal is often used in devices that require a measured, continual motion that can be used for some other purpose. 6. What is the basic principle of an oscillator?There are many types of electronic oscillators, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback. 7. What is the working of the oscillator?Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices ranging from simplest clock generators to digital instruments (like calculators) and complex computers and peripherals etc. 8. How does an oscillator work without input?An oscillator circuit uses a vacuum tube or a transistor to generate an AC output. ... For continuously generating output without the requirement of any input from the preceding stage, a feedback circuit is used. From the above block diagram, the oscillator circuit produces oscillations that are further amplified by the amplifier. 9. What causes oscillation?If a constant force such as gravity is added to the system, the point of equilibrium is shifted. ... In the spring-mass system, oscillations occur because, at the static equilibrium displacement, the mass has kinetic energy which is converted into potential energy stored in the spring at the extremes of its path. 10. What is the difference between oscillator and inverter?The oscillator is a generalized term for an active circuit that produces a periodic waveform. The inverter is a specialized term for a system that contains an oscillator and produces large amounts of power(such as AC) from a source (like a DC battery). The oscillator has no input and produces an oscillating wave as output. 

IntroductionA band pass filter is an electronic device or circuit that allows signals between two specific frequencies to pass. That is, allowing signals in a specific frequency band to pass while shielding other frequency bands. In other words, a band-pass filter attenuates frequency components in other ranges to an extremely low level, as opposed to the concept of a band-stop filter. For example, the RLC tank is an analog band-pass filter, it is a resistor - inductor - capacitor circuit (RLC circuit). These filtering circuit can also be made by connecting low-pass filters and high-pass filters.How to Design Band Pass Filter CircuitCatalogIntroductionⅠ Band Pass Filter Circuit CharacteristicsⅡ Band Pass Filter Parameters2.1 Center Frequency2.2 Cut-off Frequency2.3 Bandwidth2.4 Quality FactorⅢ Types of Band Pass Filter3.1 Active Band Pass Filter3.2 Passive Band Pass FilterⅣ Band Pass Filter Equation4.1 Cutoff Frequency of Band Pass Filters4.2 General Form of Second-order BPF Transfer Function4.3 Second-order Band Pass Filters4.4 High-Q second-order Band Pass Filters4.5 Dual-operational Amplifier BPF (High-Q)4.6 Second-order Band Pass Filters (Voltage-controlled Type)Ⅴ Band Pass Filter ApplicationsⅠ Band Pass Filter Circuit CharacteristicsAn ideal band pass filter should have a completely flat pass band, no amplification or attenuation. And all frequencies outside the pass band will be completely attenuated. In addition, the conversion outside the pass band is completed in an extremely small frequency range. But in fact, there is no ideal band-pass filter. Because the filter cannot completely attenuate all frequencies outside the desired frequency range, especially there is an attenuated but not isolated frequency range outside the desired pass band. This is usually called the filter roll-off phenomenon, and it is expressed in dB per decade of attenuation amplitude. Generally, the filter design should ensure that the roll-off range is as narrow as possible, so that the performance of the filter is closer to the design requirement. However, as the roll-off range gets smaller and smaller, the pass band becomes no longer flat and causes ripples.The high-pass filter has a low cut-off frequency, and the low-pass filter has a high cut-off frequency. When the high cut-off frequency is lower than the low cut-off frequency, combining the two circuits, and it is possible to design a band pass filter. The gain of the band pass filter is adjusted by the feedback resistor and the current limiting resistor.Figure 1. Band Pass Filter Circuit PartsA band pass filter with a high quality factor refers to a filter with a narrow pass band. In other words, a high-Q factor means that fewer unwanted frequency signals will pass. A low-Q factor means that the pass band is very wide, to allow a wider range of frequencies to pass through.  Ⅱ Band Pass Filter Parameters2.1 Center FrequencyIt usually defined as the midpoint between the two 3dB points of a band pass filter (or a band stop filter), generally expressed by the arithmetic average of the two 3dB points. It is a frequency when the impedance of the entire circuit is a real number.2.2 Cut-off FrequencyIt refers to the frequency point on the right of the low-pass filter and the frequency point on the left of the high pass filter in the pass band. That is, the boundary frequency. It is usually defined as a standard by 1dB or 3dB relative loss point. The band pass filter has two cutoff frequencies, the low cutoff frequency fp1 and the high cutoff frequency fp2. 2.3 BandwidthThe difference between two cut-off frequencies. The bandwidth is defined as B=fp2－fp1.2.4 Quality FactorThe reciprocal of the damping coefficient is called the quality factor, which is an important indicator of the frequency selection characteristics of band pass and band stop filters. In short, it is the ratio of the center frequency to the bandwidth. What’s more, it can be used to describe the shape of the transfer function graph. Ⅲ Types of Band Pass Filter3.1 Active Band Pass FilterFigure 2. Active Band Pass Filter CircuitThe active band pass filter is a cascade of high-pass and low-pass filters and amplifier components. The circuit diagram of the active band pass filter consists of three parts. The first part is the high-pass filter. Then, use the op amp for amplification. The last part of the circuit is the low-pass filter.3.2 Passive Band Pass FilterFigure 3. Passive Band Pass Filter CircuitPassive band pass filters are a combination of passive high-pass and low-pass filters. Passive filters use only passive components, such as resistors, capacitors, and inductors. Therefore, passive band pass filters are also used as passive components and do not use op amps for amplification. Ⅳ Band Pass Filter Equation4.1 Cutoff Frequency of Band Pass FiltersThe characteristic of the band pass filter is that the output signal amplitude in the pass band is independent from the frequency. When f<fp1 or f>fp2, the output signals attenuate quickly. The amplitude-frequency characteristics are shown in the figure:Figure 4. BPF Bandwidth(The broken line is the ideal BPF frequency characteristic, and the solid line is the actual BPF frequency characteristic)The resonance frequency is between fp1 and fp2, where the gain of the filter is the largest, and the bandwidth of the filter is the difference between fp2 and fp1.It can be seen from the frequency characteristics of BPF that it can be composed of LPF and HPF in series, as long as the fpL of LPF (ie, fp2 of BPF) is greater than fpH of HPF (ie, fp1 of BPF).4.2 General Form of Second-order BPF Transfer FunctionFrequency CharacteristicsWhere Aup is the pass-band magnification, center frequency , Q factor Normalized frequency characteristicsNormalized amplitude - frequency characteristicsFigure 5. Amplitude - frequency CharacteristicsFigure 6. Frequency CharacteristicsIt can be seen that the frequency characteristic of the band pass filter is completely determined by the center frequency ωo and the quality factor Q.When f>fo, as the frequency f increases, the amplitude increases. According to the definition of cutoff frequency, the denominator of amplitude-frequency characteristic , that is (since f>fo, take a positive value)1) Upper cutoff frequency（take a positive value）When f<fo, as the frequency f decreases, the output signal amplitude will decrease. According to the definition of cutoff frequency, the denominator of amplitude-frequency characteristic , that is (since f<fo, take a negative value)2) Lower cutoff frequency（take a negative), get the bandwidth When the center frequency fo and bandwidth B (or Q) are known, the upper and lower cutoff frequencies fp1 and fp2 can be calculated. On the contrary, when the upper and lower cutoff frequencies fp1 and fp2 are known, the center frequency fo and bandwidth B (or Q) can be calculated. (where ),  4.3 Second-order Band Pass FiltersA simple second-order band pass filter circuit is shown in the figure below, where R1 and C1 constitute a low-pass filter circuit, and C2 and R3 constitute a high-pass filter circuit.Figure 7. Second-order Band Pass Filter Circuit(1) Transfer FunctionIn order to reduce the amount of parameters matching, generally take C1=C2=CTake , , that is The transfer function can be obtained by using the node current method.(2) Frequency Characteristicswhere band-pass amplification (The negative sign means that the input and output are inverted. Because the filter circuit is an inverting filter.)Center frequency (C1=C2=C), Q factor When Aup, Q, and ωo are known, the resistance of each resistor is (R3 can be calculated with ωo/Q), (Aup<2Q2)When the pass band amplification factor Aup is small, Q should not be too large (that is, the simple second-order BPF has poor selectivity), otherwise R2 will become very small (R2 is generally greater than 1K), which will attenuate the input signal seriously. In order to make the system stable, Aup is generally between 1 and 10, and Q can be between 1 and 20.(3) Design StepsExample: It is known that Aup=5, center frequency fo=450Hz, bandwidth B=200Hz (). Try to calculate the parameters of the band-pass filter and verify.First, according to the center frequency fo, check the parameter table and determine C1, C2, and operational amplifier parameters according to the nominal value.fo=450Hz, take C1=C2=0.01uF(103 capacitor). Since the center frequency is not high, the requirement can be met by using LM358 operational amplifier.Second, calculate the resistance of each resistor. Among them, the range of R1 and R3 should be between 10K ~510K, and R2 should be between 1K ~100K, otherwise the capacitor C needs to be reselected.Substituting the relevant parameters into the above formula, the result is R1=15.9K, R2=15.5K, R3=159K.Third, use simulation software to verify on the computer, and try to take the nominal value of each relevant resistance. The simulation schematic diagram and simulation results are shown in the figure below. The result values obtained from the AC small signal analysis and transmission characteristic analysis basically meet the requirements.Figure 8. Filtering Circuit with LM358Figure 9. Simulation Schematic DiagramFigure 10. Voltage - Time Simulation (ui)Figure 11. Voltage - Time Simulation (ui, uo)The circuit requires a small number of components, and it can work with dual power supplies or with a single power supply (the non-inverting termination is connected to a 1/2Vcc bias potential). In fact, it is widely used in single power supply systems. Because the quality factor Q cannot be too high. Almost all band pass filter circuits with a larger bandwidth B (with a smaller Q value) adopt this circuit form. 4.4 High-Q second-order Band Pass FiltersThe high-Q second-order band pass filter circuit is shown in the following figure. This circuit can work with dual power supplies or single power supplies, which is convenient to use in a single power supply system. Since the Q value can be made larger, it is particularly suitable as a band pass filter.Figure 12. Bandpass Filter Circuit(1) Transfer FunctionIn order to reduce the amount of parameters matching, generally take C1=C2=CWhere , , that is , , getting The transfer function can be obtained by using the node current method.(2) Frequency Characteristics, where band-pass amplification Center frequency , Q factor In order to make the system stable, Aup and Q must be greater than 0, that is, 2RfR4-RFR3>0, which must be guaranteed . Adjusting can control Aup and Q. is more closer to 2, the greater the Aup and Q values. Adjust the capacitor C to select the center frequency ωo. When the values of Aup, Q and ωo are known, and the ratio between and is determined, the resistance of each resistor is , , (3) Design stepsExample: It is known that Aup=5, center frequency fo=1kHz, bandwidth B=50Hz (). Try to calculate the parameters of the band-pass filter and verify.First, according to the center frequency fo, check the parameter table and determine C1, C2, and operational amplifier parameters according to the nominal value. (Aup: 1 ~10)fo=1kHz, take C1=C2=0.01uF. Since the center frequency is not high, the requirement can be met by using LM358 operational amplifier.Second, according to the value of Aup and Q, initially determine the value of and .Since Aup and Q are large, is 1.8, is 0.5, and is 3.6.Third, calculate the resistance of each resistor. The range of R1 and R3 should be between 10K and 510K, and R2 should be between 1K and 100K. Otherwise, the ratio of and needs to be reselected.Substituting the relevant parameters into the above formula, the result is:R1=229K, R3=63.7K, R2=4.18K, R4=127.4K: RF takes 36K, Rf takes 10K.Fourth, use simulation software to verify on the computer, and try to take the nominal value of each relevant resistance. The simulation schematic diagram and simulation results are shown in the figure below. The result values obtained from the AC small signal analysis and transmission characteristic analysis basically meet the requirements.Figure 13. High-Q BPF CircuitFigure 14. Voltage - Frequency SimulationFigure 15. Voltage - Time Simulation4.5 Dual-operational Amplifier BPF (High-Q)The BPF circuit with high-Q value formed by dual operational amplifiers is shown in the figure. With fewer components, a very high-Q value can be obtained when the pass band amplification factor Aup is fixed equal to 2, so it is also a commonly used BPF circuit.Figure 16. Dual-amp BPF(1) Transfer functionAccording to the rule of futility, where, , that is , where , so (2) Frequency CharacteristicsCompared with the standard form of the second-order BPF transfer function, the following parameters can be obtained:pass-band magnification , , center frequency When R4=R5,R2=R3=R,C1=C2=C, Aup=2, , （）It can be seen that when Aup=2 (that is, when R4=R5), the value of Q can be very large.(3) Design stepsAccording to the center frequency fo, check the parameter table to determine C. When C is determined, the resistance R is calculated from the center frequency. Meanwhile, etermine R1 based on the Q value. 4.6 Second-order Band Pass Filters (Voltage-controlled Type)The second-order voltage-controlled BPF is shown in the figure. Among them, R1 and C1 constitute a low-pass filter, R2 and C2 constitute a high-pass filter. (The voltage positive feedback is introduced through the voltage R3 to form a voltage-controlled band-pass filter.)Figure 17. Second-order Bandpass Filter (voltage controlled)Rf/RF cannot be 3 to avoid self-excitation.(1) Transfer FunctionWhere ，that is , , so The transfer function can be obtained by using the node current method.In order to reduce the amount of parameters matching, generally take R1=R3=R,R2=2R,C1=C2=CWhere In order to make the system stable, the coefficient of the first term in the denominator must be larger than 0, that is, 3−Auf>0, in other words, Auf<3.(2) Amplitude - frequency Characteristicswhere band-pass amplification , center frequency , Q factor It can be seen that the closer Auf is to 3, the larger the Q value. The narrower the pass band B, and the better the selectivity.(3) Design StepsAccording to the center frequency, look up the table and initially determine C1=C2=Ccalculate resistance , that is , Calculate bandwidth based on upper and lower cutoff frequencies , Calculate the quality factor Calculate by Q and determine the resistances Rf and RF.As a special case, the center frequency fo=1KHz is known, so C1=C2=C=0.01uF，R2=2R=31.8K, getting Auf=2.95, that is . If Rf=10K, calculate RF=19.5K.For high pass and band pass filters, the output of the op amp is not required to be 0 at static state. And the single power supply operating mode can be selected. In the low-pass or band-stop filter circuit, it is a DC-to-AC DC amplifier circuit, which generally requires the circuit to work in a dual power supply state. Ⅴ Band Pass Filter ApplicationsThe filtering circuit has a wide range of uses.According to different frequency amplitude characteristics, filter circuits can be divided into low pass filter circuit (LPF), high-pass filter circuit (HPF), band pass filter circuit (BPF), band stop filter circuit (BEF) and all-pass filter circuit (APF) . The BPF is mainly used to highlight signals in useful frequency bands and weaken signals or interference and noise in other frequency bands to improve the signal-to-noise ratio. Therefore, band pass filters are often used in wireless receivers and transmitters to receive useful signals while preventing unwanted frequencies from passing through.In addition to the fields of electronics and signal processing, an specific application of band pass filters is in the field of atmospheric sciences. A very common example is to use it to filter the weather data in the last 3 to 10 days, only the cyclone as a disturbance remains in the domain. Frequently Asked Questions about Band Pass Filter1. What is a bandpass filter used for?A band pass filter is an electronic circuit or device which allows only signals between specific frequencies to pass through and attenuates/rejects frequencies outside the range. Band pass filters are largely used in wireless receivers and transmitters, but are also widely used in many areas of electronics. 2. What is the bandwidth of a bandpass filter?The bandwidth of a bandpass filter is usually defined as the 3 dB bandwidth. Similarly, the 1 dB bandwidth is the point at which the signal amplitude decreases by 1 dB from its maximum value (above and below the center frequency). 3. How does bandpass filter work?A bandpass filter works to screen out frequencies that are too low or too high, giving easy passage only to frequencies within a certain range. Band-pass filters can be made by stacking a low-pass filter on the end of a high-pass filter, or vice versa. Attenuate means to reduce or diminish in amplitude. 4. How is bandpass filter calculated?So all frequencies between the low cutoff frequecny and the high cutoff frequency are the passband of the bandpass filter. The gain of the circuit is determined by the formula, gain (AV)= -R2/R1. Thus, for example, to have a gain of 10, R2 must be 10 times the value of R1. 5. What is the use of band pass filter?Bandpass filters are widely used in wireless transmitters and receivers. The main function of such a filter in a transmitter is to limit the bandwidth of the output signal to the band allocated for the transmission. This prevents the transmitter from interfering with other stations.

I Introduction What is a blown fuse? A fuse is an electrical safety device that operates to provide over-current protection of an electrical circuit. Its essential component is a galvanized wire with antimony tin alloy that blows (melts) when too much current flows through it, thereby interrupting the current. This process of self-protection is called a blown fuse. This passage introduces blown fuse in the household circuit and car, mainly including its working principle, causes of a blown fuse, and how to repair it.  CatalogI IntroductionII Blown Fuse in Household Circuit2.1 Blown fuse in Household Circuit2.2 Slow Blow Fuse VS. Fast Blow FuseIII Help3.1 Six Reasons Why Fuses Blow3.2 Causes of Circuit fault From the Perspective of Blown fuse3.3 How to Change Household Fuse?IV Blown Fuse In Car4.1 What Is A Blown Fuse In Car?4.2 Why does a Car Fuse Blow?4.3 What are the Symptoms of a Blown Car Fuse?4.4 How to Replace a Fuse in a CarV One Question Related to Resistor Classification5.1 Question5.2 AnswerVI FAQII Blown Fuse in Household Circuit2.1 Blown Fuse in Household CircuitWith the increase of fire and electricity consumption in modern households, the frequency of household fires is getting higher and higher, which has become a focus of public attention. And a considerable part of the fire is caused by the blown fuse. In the state of high voltage and large current, the fluctuation and surge of the grid voltage will cause the current in the power supply to increase instantaneously and cause the fuse to blow.Figure 1. Fuse Figure 2. Blown Fuse2.2 Slow Blow Fuse VS. Fast Blow FuseLiterally, the difference between a slow blow fuse and a fast blow fuse is reaction speed. One reaction is faster and one reaction is slower. From a technical perspective, slow blow fuses are more resistant to surges than fast-blow fuses. In other words, slow-blow fuses have a higher ability to withstand instantaneous pulse currents than fast-blow wires. They can resist the surge of the surge current brought by the switch and do not act, thus ensuring the normal operation of the device. Therefore, a slow blow fuse is also called a surge resistance fuse. To explain from a deeper level, a slow blow fuse has a relatively large melting heat value I2t, and the energy required when the fuse blows are relatively large. So for fuses of the same rated current, slow blow fuses are much more pulse-resistant than fast-blow fuses. Because the I2t of the slow blow fuse is larger than that of the fast blow fuse of the same specification when the total current of the circuit is too large and the fuse blows, the slow blow will be slower than the fast blow fuse. But it doesn’t mean slow blow fuse is worse than fast blow fuse. Because if there is a fault in the circuit, the over-current will not disappear automatically, and the energy of the continuous over-current will greatly exceed the I2t of the fuse. No matter what kind of fuse, it still will be blown. Therefore, the time difference between fast-blow fuses and slow blow fuses is not so important for the device requirements they protect. Only in the case of sensitive devices in the protected circuit that require special protection, the performance of the slow blow fuse will be affected. Therefore，two kinds of blow fuse will be used in different circuits. For example, a purely resistive circuit, or a circuit that needs to protect some more sensitive and expensive components, the fast-blow fuse is necessary. On the contrary, it is best to use slow blow fuses in the power input/output parts of some circuits. In addition to protecting IC circuits, slow blow fuses can be used in most cases where fast-blow fuses are used to improve pulse resistance; on the contrary, if fast-blow fuses are used in places where slow blow fuses are used, it will often cause the power to be turned off immediately. The fuse cannot work normally.III Help3.1 Six Reasons Why Fuses Blow(1) Overloaded CircuitToo many appliances are operating at the same time,  resulting in household electricity overload, so that the fuse is blown. This situation is especially likely to occur when using air conditioners, electric heaters or adding other larger power appliances. Solution: Cut back on all that power that’s tapping a single circuit. Find outlets on other circuits to plug into or unplug what you aren’t using. (2) Connection ProblemsIn some families, although the fuse selection is reasonable and the load is not too large, it still occurs blown fuse as soon as it uses larger power appliances such as air conditioners, electric heaters, and rice cookers. The reason may be that when the fuse is installed or replaced, the fuse and the screw are in poor contact, causing fire and heating, and the screws fixing the fuse are oxidized and burned out. (3) Short CircuitIf the fuse is replaced but still blows as soon as you closed the switch, there may be a short circuit. May be short circuit or load short-circuit. Electric kettles, rice cookers and other commonly used high-power electrical appliances and inferior electrical appliances are prone to short-circuit failure. Solution: Make sure the faulty device is unplugged and there is no damage to the outlet. First, test the circuit. Then check for any damage on or around the electrical panel. If you see any damage, call an electrician before doing anything else with it. If there is none, flip the breaker switch back to its operating position. If it trips again, though, call an electrician. (4) Ground FaultA particular type of short circuit, a "ground-fault," occurs if a hot wire comes in contact with a ground wire or a metal wall box or touches wood framing members. Ground faults can be especially dangerous when they occur in areas with high levels of moisture, such as kitchens or bathrooms, or outdoor locations. (5) PulseWhen the circuit is started or the power supply is unstable, an instantaneous large current causes the fuse to be disconnected. Also, the screw is not tightened when the fuse is installed, or the fuse is damaged, all will cause the fuse blown. (6) The Wrong Type of Fuse Was InstalledFuses come in many shapes, sizes, and configurations. Many look similar but actually have very different functions. A suitable fuse must be selected and used. The fusing current of the fuse is usually 1.5-2.0 times the rated current. For example, when the total power of all appliances in the household is more than 1100W, choose a 5 amp fuse, and use a number 20 fuse with a diameter of 0.98MM. When the current exceeds 7.5 amps to 10 amps, the fuse will automatically blow to achieve the purpose of protection. 3.2 Causes of Circuit fault From the Perspective of Blown FuseThe blown fuse is one of the common faults of the circuit. If not handled properly, it will cause a new fault. Therefore, we should learn to judge the cause of circuit failure from the fuse blown condition. (1)Situation: The fuse blows fast, often with a "snap" sound. Most fuses are turned into small round beads. The gap between the fuses is large, and sometimes the entire fuse is almost completely melted.Analysis: This situation indicates that the blown fuse is caused by a short circuit in the line. Therefore, the circuit can work normally only after finding the short-circuit place, eliminating the short-circuit fault, and then connecting the fuse. (2)Situation: The fuse is disconnected from the middle, the gap between the disconnection is small, and a very thin residual part is left at both ends.Analysis: This is caused by the fuse being too thin, or the passing current is too large. It should be installed with a slightly thicker fuse. (3)Situation: The connection between fuse and screw joints is blown out, and the disconnection gap is small.Analysis: This is because the fastening screw that fixes the fuse is not tightened, the fuse is not in good contact with the screw, the resistance is too large when the current passes, and the generated heat is also increased. Heat doesn't dissipate as fast as it produces, so the fuse blows. In this case, connect the fuse directly and tighten the fastening screws. (4)Situation: The fuse blowing position is uncertain and the gap is small.Analysis: This situation is generally caused by the longitudinal tension of the fuse or a gap in the radial position, and the local diameter of the fuse becomes thinner. Just replace it with a new one. 3.3 How to Change Household Fuse?• Guide(1) The fuse of Knife Switch① Find the main knife switch of the circuit and check the power supply to make sure that the fuse in the knife switch has blown.② Put on rubber shoes and rubber gloves. Bring the prepared pliers and spare fuse in advance.③ After power off, disassemble the upper and lower body shells of the knife switch and use the pliers to remove the old fuse that has melted. Be careful not to touch the electrical circuit.④ Replace with a new fuse and then check if there is a short circuit. If not, you can install the case and close it. (2) Household fuse① Open the fuse box with a screwdriver and then check to see if the fuse is blown.② Install a fuse of similar length to the previous fuse. After installation, check whether it is done. How to Replace Fuse Wire of a Blown Fuse• AttentionWhen replacing the fuse, please pay attention: remove the cover of the insulation box, and do not directly connect the fuse in the insulation box. When installing the fuse, the two ends of the fuse should be wound clockwise around the screw. It should not be over-tightened or loosened, so as not to damage the fuse or cause poor contact, otherwise, it will be easy to blow.IV Blown Fuse In Car4.1 What Is A Blown Fuse In Car?Just like many other appliances, the purpose of fuses in cars is to protect the electrical system within. The basic components of a fuse are one fuse element and two terminals. And the fuse itself works as a bridge between the vehicle and the particular system. If the system is overheated, the fuse element will heat up and melt, and, eventually, the circuit will stop working.4.2 Why does a Car Fuse Blow?The circuit of a general vehicle has gone through a very detailed experiment before leaving the factory, even at the beginning of the design. It should be fine, but why does the vehicle fuse still break? Normally, there are two main reasons for the breakdown of a car fuse, one is that the load of the electrical appliance is too large, and the other is the short circuit in the car circuit. The electrical appliance is overloaded. This is also the reason why most fuses blow.  After buying a car, some people randomly modify electrical equipment, changing headlights, car audio equipment, using inferior cigarette lighters, adapters, and high-power electrical appliances. The operating power of some electrical equipment may be higher than the factory-set value. Once used, it may cause the fuse of the lamp to blow and short circuit in the automobile circuit. After the car has been used for a long time, some of the wire rubber has deteriorated, which has exposed the metal wire and caused a short circuit. Some car owners will directly flush the engine compartment with water pipes, which may cause water in the fuse box and short circuit.4.3 What are the Symptoms of a Blown Car Fuse?After the car fuse is blown, the most intuitive performance is that the car's related functions are disabled and the car cannot drive normally. The battery has power but the vehicle cannot start. In this case, it is likely that the fuse responsible for starting the motor has burned out. When you find that the vehicle can not start, remember not to start continuously, which will cause the battery to discharge continuously and lead to complete power failure. While the vehicle is running, the tachometer display is normal, but the speedometer display is zero, and the ABS warning light is on, indicating that the fuse corresponding to the ABS is burned out.4.4 How to Replace a Fuse in a Car(1) Turn off the start switch and all electrical equipment(2) Disconnect the negative battery cable(3) Figure out the blown fuse.(4) Using needle-nose pliers or some small tweezers, remove the broken fuse.(5) Replace the blown fuse with another new fuse of the same amperage.If the replacement fuse is damaged, you should immediately go to the relevant car service station for inspection. How To Safely Change A Blown FuseV One Question Related to Blown Fuse5.1 QuestionHow does blown fuse work?A. By having pieces of metal wire that melt when current gets too highB. By having an electromagnet that will break a circuit if the current gets too highC. By having pieces of metal wire that melt when current gets too lowD. By having an electromagnet that will break a circuit if the current gets too low5.2 AnswerA  VI FAQ1. How do I know if a fuse has blown?Remove the fuse from its holder. In some cases, you may need a small screwdriver to unscrew the fuse holder cap. Look at the fuse wire. If there is a visible gap in the wire or a dark or metallic smear inside the glass then the fuse is blown and needs to be replaced. 2. What happens when a fuse blows?When a fuse blows, a metal filament inside the fuse has burned through, meaning that you'll need to replace the fuse with a new one. 3. How long do fuses last?Fuses never need to be replaced unless they are tripped/activated by a failing component or any other even with the circuits of the car. They are encapsulated in plastic and are in a vacuum inside the piece. As long as the current limit isn't reached, that wire will not burn out. 4. Can a blown fuse stop a car from starting?A blown fuse in the starter circuit could be the cause of a no-start problem. Broken or corroded wiring-Damaged or dirty wires to the battery or to the starter solenoid (or wires that are loose) can prevent sufficient power from reaching the starter. 5. Can a blown fuse cause a fire?Absolutely, an outlet that has blown a fuse can start a fire. If the problem was whatever was plugged into it, and that item is no longer there, there should be no problem, but if the problem was within the outlet itself it should be repaired immediately. The time to a fire could be from 2 minutes to 2 years. 6. Do fuses go bad with age?Yes indeed, fuses do expire from old age. Yes, fuses can get tired, but it's equally possible you have an intermittent problem with the switch or perhaps the starting capacitor (assuming it's not 3ph). First, replace the fuse and see if you get lucky, then diagnose further if needed. 7. What causes a fuse to burn?First, and most commonly, when too many lights or plug-in appliances draw power from the circuit, it can overload the capacity of the fuse and cause the metal ribbon inside the fuse to melt through. ... A mis-wired lamp, for example, can cause a short circuit and blown fuse if it is plugged into an outlet. 8. How do you fix a blown fuse in a plug?Lift it with your screwdriver to dislodge it. Replace the fuse with a fuse of the same amperage (check the appliance's instructions if unsure) Reassemble the plug, plug it into the wall and switch the device back on. If a blown fuse was the problem, your appliance should now be working again as normal. 9. How does a fuse in a plug work?A plug fuse is a safety device that is connected to an electrical circuit to prevent excessive current flow during fault conditions. Upon overload, the wire fuse element heats up and melts, or blows with a resounding bang, interrupting and cutting off the current flow. 10. Can a fuse look good and still be bad?Due to the way fuses are engineered, the likelihood that a fuse would become faulty without blowing is pretty slim, but there are rare instances in which a fuse might appear completely fine, even though no current runs through it. 

CatalogIntroductionⅠWhat is a MAP Sensor ?1.1 The Definition of a MAP Sensor1.2 Abbreviations for MAP sensorsⅡ How does a MAP Sensor Works？Ⅲ  The Application of a MAP Sensor on Vehicles3.1 The Problem Caused of a Faulty MAP Sensor3.2 The Factors of Causing This Fault3.3 How to RepairⅣ 7 Symptoms of a Faulty MAP SensorⅤ Common MAP Sensor Fault CodesⅥ The Difference Between MAP and MAF sensorsⅦ Frequently Asked Questions about MAP SensorsIntroductionFirstly, We need to have a general definition of a sensor. A sensor, in the broadest sense, is a device, module, machine, or subsystem whose purpose is to detect events or changes in its environment and transmit the information to other electronics, most commonly a computer processor. A sensor is always used in conjunction with other electronics.Figure1：The function of  a MAP sensorⅠWhat is a MAP Sensor ?1.1 The Definition of a MAP SensorThe manifold absolute pressure sensor (MAP sensor) is one of the sensors used in the electronic control system of an internal combustion engine.MAP sensors are frequently used in engines that inject fuel. The manifold pressure sensor transmits real-time manifold pressure data to the engine's electronic control unit (ECU). The function of data is to calculate the air density and determine the engine's air mass flow rate, determining the fuel metering required for optimal combustion and influencing the ignition timing advance or retardation. In order to detect intake airflow, fuel-injected engines may use a mass airflow sensor (MAF sensor). Aspirated engines typically use one or the other, whereas forced induction engines typically use both at the same time. The MAF sensor on the intake pipe is connected to the throttle body, and the MAP sensor on the intake port is connected to the pre-turbine.The second variable from IAT (intake air temperature sensor) can be applied to convert MAP sensor data to air quality data. It is referred to as the speed-density method. The engine speed (RPM) is also used to determine the position on the lookup table, which determines the amount of fuel to be added, and thus the speed density (engine speed/air density). The MAP sensor can also be used in OBD II (on-board diagnostics) applications to test the function of the EGR (exhaust gas recirculation) valve, which is a common application in OBD II-equipped general automobile engines.1.2 Abbreviations for MAP sensorsAbbreviations often used are:MAPThere are some other common names of MAP sensors：Manifold Absolute Pressure SensorEngine Load SensorPressure SensorBoost Sensor Ⅱ How does a MAP Sensor Works？ Its operation is based on supplying 5 volts of DC power to the sensor from the PCM (Power System Control Module). Inside the MAP sensor is a resistor that moves in response to the intake manifold pressure. The resistor alters the voltage between 1V and 4.5V (depending on engine load), and the voltage signal returns to the PCM to indicate manifold pressure (vacuum). This signal is required by the PCM to determine fuel delivery and is occasionally used to determine whether the EGR valve is functioning properly. The Manifold Pressure Sensor is useful for diagnostics because it measures throttle performance, turbo performance, and leaks in the inlet manifold. Due to its position, it should always read negative pressure unless the turbocharger is boosting pressure. This is depicted in the diagram below. Ⅲ The Application of a MAP Sensor on vehiclesA computer and a series of sensors in modern vehicles control the engine's fuel consumption and other operations. While you may never have to work on any of these sensors, one, in particular, is critical to the smooth operation of an engine — the MAP (manifold absolute pressure) sensor. What exactly is a MAP sensor and what does it do? When your engine runs strangely, it could be due to a MAP sensor failure, so let's take a look at what the MAP sensor does.Figure2: the application on vehicles  3.1 The Problem Caused of a Faulty MAP SensorA faulty MAP sensor can cause a variety of performance issues in your vehicle. If the sensor is faulty, reading too high, the fuel management system may use more fuel than necessary, reducing fuel economy. If the MAP sensor reads too low, the onboard computer will reduce the amount of fuel it believes is required and starve the engine, causing it to run erratically and produce less power. In either case, if the sensor is not properly reading, your vehicle will fail emissions testing. When you connect a diagnostic code reader, you may discover trouble codes P0068, P0069, P1106, or P1107. 3.2 The Factors of Causing This FaultA MAP sensor failure can be caused by several factors. The sensor's operation is dependent on both electronic and mechanical components. A vacuum chamber within the sensor allows the sensor to detect changes in manifold pressure. A leak in the vacuum chamber can develop over time, rendering the sensor unable to read correctly. Years of extreme temperature fluctuations and vibration can also wreak havoc on the internal circuitry due to the sensor's location in the harsh engine compartment environment. Another source of failure is dirt or other contamination that prevents the sensor from physically accessing the intake manifold air flow. 3.3 How to RepairThe difficulty of replacing a bad MAP sensor varies depending on the vehicle. It is typically bolted or screwed to the outside of the intake manifold or throttle body. Unplug the sensor wire, then unscrew the screws and carefully remove the faulty sensor. Simply reinstall the screws and plug the wire back in to get your new one up and running. Depending on the vehicle and whether or not a trouble code was set, resetting the check engine light may necessitate the use of a diagnostic tool.Many people are perplexed when they learn that they have a faulty sensor and wonder, "What is a MAP sensor?" While its function is straightforward, it has been critical to obtaining good fuel economy and performance from your vehicle's engine for many years. If you suspect a MAP sensor failure, your neighborhood NAPA Auto Care center can handle the problem and get you back on the road. Ⅳ 7 Symptoms of a Faulty MAP Sensor 1. Poor Fuel Economy.If the ECM detects low or no vacuum, it assumes the engine is under load and dumps more fuel, and advances the spark timing. This results in excessive fuel consumption, poor fuel economy, and, in extreme cases, detonation. 2. Lack of Power.When the ECM perceives a high vacuum, it assumes that the engine load is low and reduces fuel injection, and retards spark timing. On the one hand, fuel consumption will be cut down, which appears to be a good thing. However, if not enough fuel is consumed, the engine may lack acceleration and passing power. 3.Failed Emissions InspectionWhen the ECM perceives a high vacuum, it assumes that the engine load is low and reduces fuel injection, and retards spark timing. On the one hand, fuel consumption will be cut down, which appears to be a good thing. However, if not enough fuel is consumed, the engine may lack acceleration and passing power. 4. Rough Idle.Inadequate fuel injection deprives the engine of fuel, resulting in rough idling and possibly random cylinder misfiring. 5. Hard Starting.Similarly, an excessively rich or lean mixture makes it difficult to start the engine. You most likely have a MAP sensor problem if you can only start the engine when your foot is on the accelerator. 6. Hesitation or Stalling.Stepping on the gas may not be fun when starting from a stop or attempting a passing maneuver, especially if the ECM is displaying a lean mixture based on faulty MAP sensor readings. 7. Check Engine Light.MAP sensor diagnostic trouble codes (DTC) can range from a simple circuit or sensor faults to correlation or range faults, depending on the age of your vehicle. A dead MAP sensor will not read anything, whereas a failing MAP sensor may send data to the ECM that is illogical, such as low engine vacuum when the throttle position sensor (TPS) and crankshaft position sensor (CKP) both show the engine at idle.Figure3: check dash board light Ⅴ Common MAP Sensor Fault CodesThe following codes are associated with the MAP sensor and should be looked for if your check engine light has illuminated:  P0068: MAP/MAF - Throttle Position CorrelationP0069: Manifold Absolute Pressure - Barometric Pressure CorrelationP0105: MAP Circuit MalfunctionP0106: MAP/Barometric Pressure Circuit Range/Performance ProblemP0107: Manifold Absolute Pressure Figure4: one of the faulty code  Ⅵ The Difference Between MAP and MAF sensorsThe intake manifold pressure sensor is the full name of the map manifold absolute pressure sensor, and the computer uses the speed increase pressure change to adjust the speed. The following conclusions are for reference only.MAF is an air flow sensor with the full name Mass air flow meter. Figure5: the MAF sensor  The first thing I mentioned was the MAP formula, which is MAP+Manifold vacuum = Barometric Sensor. The function of the Barometric Sensor.It indicates the height of the car's altitude, allowing the length of the fuel injection to be determined when the car is cold.In general, there are two variables: the manifold vacuum and the barometric. The manifold vacuum changes with speed, while the barometric is almost constant, unless you're in the sky. 1, Manifold vacuum Full throttle (WOT) = 0 hgidle 18-22 hg2, MAp should be equal to baro in the case of KOEO (manifold vacuum is 0 hg)3, KOEO 3v-4vKOER will drop to about 1v as the vacuum increases4, 5v reference nap throttleFigure6: 5v reference nap throttle  5, KOEO 150 hz KOER will be lower than this in the future6, Reference value sunnyvale 150hz/ 30HG denver 123 hz7, if egr is stuck slightly open, map will also report an error8, The duty cycle and counts of iac will also decrease,9, stft -9% at idle accelerating jumps to lean change map. There is no absolute value, and the calibration of each car manufacturer is not the same MAF-air flow sensor, simple and rude, directly tells the computer how much flow.1, idle 0.5-1v2, egr&tps follow3, If there is another baro (calculate or extra), the method is the same as map, 30 hg4, maf is dirty, will undereportting, cause too much air to enter, fuel trim is too thin5, down side: If there is turbulence in one of the intake and exhaust, the problem cannot be determined6, maf gs/s = liter (known Toyota, Ford.)7, baro relearn( 80% tps with low rpm)Figure7: baro relearn Ⅶ Frequently Asked Questions about MAP Sensors1. Can I drive my car with a bad MAP sensor?It is not advisable to drive your vehicle with the MAP (manifold absolute pressure) sensor disconnected. ... With the MAP sensor disconnected, the fuel delivery will be excessive and could cause harm to the engine and exhaust system (catalytic converters). 2. Will a MAP sensor cause a misfire?Your engine misfires and shakes: If a MAP sensor reports a false high pressure reading, the engine's computer will signal for more fuel. This results in a rich mixture, which can foul the spark plugs and cause a cylinder not to fire. A misfiring engine will shake and transmit that motion into the cabin of the vehicle. 3. Can you clean a MAP sensor?Use an electric parts cleaner on a soft rag or paper towel to clean the outside of the MAP sensor. ... Shake out the excess and let the MAP sensor dry. Check the MAP sensor vacuum hose or intake manifold port for additional contamination. Clean these with electric parts cleaner and a brush if necessary. 4. How much is a MAP sensor?The MAP sensor usually sits in an easy to reach area, on or near the intake manifold. The sensor itself will cost you anywhere from $30 to $200, depending on your vehicle and if you use OEM or aftermarket parts. 5. Can I use alcohol to clean MAP sensor?Clean the outer surface of the MAP sensor using electric parts cleaner. ... Spray the alcohol liberally over the MAF sensor. Be sure to cover the MAF sensor's wires, intake and all its crevasses to thoroughly clean the part. Do not touch or scrub the MAF sensor's wires because they are very delicate and could break. 

Ⅰ IntroductionA shunt is an electrical device that creates a low-resistance route for a current to flow through. This allows the current to flow to a different part of the circuit. Ammeter shunts and current shunt resistors are two terms for shunts. A shunt resistor is used to measure alternating or direct electric current. The voltage drop across the resistor is used to determine this. Shunt resistors were once used to describe a resistor connected in parallel to an ammeter as a shunt to increase the current measurement range, but in recent years, all resistors used to detect circuit current have been referred to as shunt resistors (current sense shunt resistor). This vedio shows a shunt resistor CatalogⅠ IntroductionⅡ What Does a Shunt Resistor Do?Ⅲ How Does a Shunt Resistor Work?Ⅳ How to Measure Current by a Shunt Resistor?Ⅴ Position of the Shunt Resistor in the Circuit When Measuring CurrentⅥ How to Select a Shunt Resistor?6.1 How to Calculate Shunt Resistance?6.2 Shunt Resistor ParametersⅦ How to Wire a Shunt Resistor?Ⅷ Frequently Asked Questions about Shunt Resistor Ⅱ What Does a Shunt Resistor Do?The electrical shunt is a device that creates a low-resistance route that allows electricity to travel through or be redirected past a defined point in a circuit. Some meters have built-in precision current shunts that allow measurements in terms of DC and Watts to be taken. Electrical shunts can also be used to measure the flow of DC. The formula for Ohm's law is as follows: V = I × R This equation applies to the voltage (V) created across the resistance (R in ohms) as a function of the resistance and the current (I in amps) flowing through it. A current shunt with a resistance of 0.002 ohms and a current of 30 amps, for example, will generate 0.002 x 30 = 0.06 volts or 60 millivolts (milliVolts). By including a current shunt into a measurement circuit, you can determine the voltage drop across the shunt. The calculation of current measurement using Ohm's law will be possible thanks to the assessment of current shunt resistance. The current shunt resistance can also be calibrated using Ohm's law. Shunt resistors are commonly used in the following applications:Current circulating through a battery is measured, and power output is monitored.Before the signal reaches the circuit elements, high-frequency noise is redistributed (this requires a shunt with a capacitator).Installation in a DC connects the container with a negative conductor connecting the batteries to the inverter.Control equipment, such as battery chargers and power sources, provides overload protection. Ⅲ How Does a Shunt Resistor Work?The technological limits of a shunt resistor differ from those of a conventional resistor. Shunt resistors allow for high precision while maintaining a low ohmic value. To reach such great precision, a Kelvin connection is recommended. This connection eliminates difficulties like lead sensitivity and resistance. The value of a shunt resistor can be influenced by several reversible and irreversible causes. Long-term stability and irreversible change in resistance are ensured by the accompanying mechanical, electrical, and thermal stresses. The Temperature Coefficient of Resistance (TCR) is measured in ppm/ and represents the drift caused by the transistor cooling or heating due to changes in ambient temperature. The Power Coefficient of Resistance (PCR) or ppm/W is used to express the amount of power that the resistor must dissipate. Electrical shunts are commonly used to safeguard the speed controller from a load that consumes too much current or to limit the motor's speed. By disconnecting the shunt from the sense line, the controller's speed can be increased. After that, the sense line must be linked to the ground. Because there will be no voltage drop, the speed controller will generate the maximum amount of power feasible. However, if the load on the controller transistors is too great, this could be dangerous. A high-precision current shunt can also be utilized for equipment bench testing. This current shunt can be used in conjunction with a voltmeter to determine the amount of current flowing through the circuit. The use of a sensitive voltmeter ensures a high level of safety in the measurement of greater currents than can be achieved with a regular multimeter. Ⅳ How to Measure Current by a Shunt Resistor?An ammeter is a device that measures electric current. The voltage drop across a precision resistor with a known resistance is measured by most modern ammeters. Ohm's law is used to calculate current flow:  To measure current, most ammeters feature a built-in resistor. When the current is too high for the ammeter, however, a different configuration is required. The solution is to connect the ammeter to a precise shunt resistor in parallel. Ammeter shunt is a name that is sometimes used to describe this sort of resistor. This is usually a low resistance manganin resistor with great accuracy. Only a small (known) amount of the current travels through the ammeter after it is divided between the shunt resistor and the ammeter. The remaining current travels through the shunt resistor, bypassing the ammeter. Large currents can still be measured this way. The actual amperage can be measured by accurately scaling the ammeter. The greatest amperage that can be measured using this arrangement is theoretically limitless. However, the measurement device's voltage rating must not be exceeded. As a result, the maximum current multiplied by the ammeter resistance value cannot exceed the voltage rating. To minimize circuit interference, the ammeter resistance should be as low as feasible. A smaller ammeter, on the other hand, creates a smaller voltage drop, which results in a lesser resolution. Example of calculationA series resistor in an ammeter, for example, is a shunt resistor with a resistance of 1 mΩ. A voltage drop of 30 mV is observed across the resistor after it is inserted in a circuit. The current is equal to the voltage divided by the resistance in this case, or:I=V/R=0.030/0.001=30A. With the resistance value unknown and the voltage and current known, the same calculation might be performed. This is how shunt resistance is measured. Ⅴ Position of the Shunt Resistor in the Circuit When Measuring CurrentA.To eliminate the common-mode voltage, the shunt is frequently put on the grounded side. However, there are certain drawbacks.B.The common-mode voltage may be too high for the ammeter in this arrangement. Position of the Shunt Resistor in the Circuit The placement of the shunt resistor in the circuit must be carefully considered. When the circuit and the measurement instrument share a common ground, the shunt is frequently put as close to the ground as practicable. The rationale for this is to safeguard the ammeter from excessive common-mode voltage, which could harm the instrument or cause incorrect results. One downside of this configuration is that leakage currents through the shunt may go undetected. To protect the instrument, the shunt must be isolated from the ground or incorporate a voltage divider or an isolation amplifier if it is put in the ungrounded leg. Other options include employing a Hall Effect sensor instead of directly attaching the measurement instrument to the high voltage circuit. Current shunts, on the other hand, are frequently cheaper. Ⅵ How to Select a Shunt Resistor?Shunt resistors are a type of resistor that creates a low resistance route. Because of their low resistance, they are commonly employed to detect high currents. Many applications necessitate current measuring. Overcurrent protection, 4-20mA systems, battery chargers, high-brightness LED control, H-bridge motor control, and metrology, for example, all require current monitoring. Shunt sensors are simpler to develop and less expensive than magnetic current sensors. They do not, however, afford any seclusion. A Rogowski coil, also known as a Hall effect sensor, is a noninvasive measurement in which the detecting circuitry is not electrically coupled to the monitored system and subsequently isolated. 6.1 How to Calculate Shunt Resistance?Shunt resistors have different technological limits than normal resistors. They have a low ohmic value and are high-precision resistors (they can be expressed in microOhm when several hundreds of Amper currents must be measured). Because accuracy is crucial, current sensing is best accomplished via a Kelvin connection (or four-terminal connection), which eliminates the undesired effects of lead resistance and temperature sensitivity. Four-terminal connection equation A shunt resistor's value can be changed by a variety of causes, which are divided into reversible and irreversible effects. A change in resistance that is irreversible owing to mechanical, electrical, or thermal stresses is referred to as long-term stability. There are two fundamental components to reversible effects:Temperature Coefficient of Resistance (TCR): TCR is measured in parts per million and describes how the resistor drifts as the ambient temperature changes.The Power Coefficient of Resistance (PCR) is a unit of measurement for the amount of power a resistor must dissipate. It is given in ppm/W. 6.2 Shunt Resistor ParametersThe thermal EMF is an important metric for shunt resistors that isn't as critical for ordinary resistors. A voltage changeable with temperature appears at the junction of two different conducting materials (explaining why it's termed thermal EMF or thermocouple effect and expressed in µV/). An intermetallic junction's rate of change of voltage with temperature is a function of the metallic combination. Depending on whether side of the combination is regarded as the input, the voltage produced is either positive or negative. All resistors are assumed to be soldered to copper at some point, and copper becomes the reference metal. Some Thermal EMF values are shown in the table below. Table 1: Thermal EMF of the Metal vs. CopperMetal / AlloyThermal EMF vs copper in μV/°CEvanohm2Cupron-45Manganin-3Zeranin-1.3Nickel-22Gold0.2Silver-0.2Aluminum-4 Table 2. TCR, ppm/  of various Resistor Element MaterialsTemperature range-55°C to +25°C0°C to +25°C+25°C to +60°C+25°C to +125°CManganin5010-5-80Zeranin20±2.5±510Evanohm52.5-2.5-5Foil (Vishay proprietary)-1-0.30.31Thin Film-10-5510Thick Film-100-2550100 Manganin is the preferred material for shunts with exposed blades based on thermal EMF, TCR, and cost. Zeranin, a cousin of Manganin with a lower temperature coefficient, is used to make shunts with exposed parallel wires. Evanohm, which has a near-zero temperature coefficient and a high sensitivity to strain, is commonly used to make shunts contained in heat sinks. Ⅶ How to Wire a Shunt Resistor?First, read and follow any manufacturer's instructions. It will be required to make sure that the ammeter and the shunt can handle the same mV levels. The shunt must then be connected to the negative connection that runs from the battery bank to the electrical circuits. Following the negative lead from the battery to the circuits or fuse box will reveal this. Adjust the negative connections on the battery to the corresponding side of the battery and shunt if you want to measure the current consumed by the connected device and supplied by the alternator. The other side of the shunt should be linked to the battery's negative terminal with a sufficiently thick cable. The shunt resistor must be installed in a location where there is no possibility of shorting cables. The negative cables can be shortened to make the installation process easier. It is also necessary to drill a suitable hole for the ammeter to mount on the panel. The hole must be large enough to connect the meter firmly. The plus and minus pins on the connection between the leads and the DC  or voltage should be properly fitted. You must also confirm that the meter is correctly set (the current can be measured in AC, DC, ohms etc). The wiring procedure should start with a simple check to confirm that the shunt is connected to the load in series. You'll also need to hook up a battery pack and make sure it's linked to the right side of the shunt. The wiring from the shunt should then be fed to the load. The ammeter and the ground should not be connected in any way. The ammeter, on the other hand, should be wired in parallel with the shunt, with the shunt connected to the load in series. The powering of the circuit should be the first step in measuring the current or voltage. After that, you can take the meter reading. When measuring the level of resistance, however, you should not turn on the electricity. Ⅷ Frequently Asked Questions about Shunt Resistor1.What is the meaning of shunt resistor？A resistor having a very low value of resistance such type of resistor is called shunt resistance. The shunt is used in the galvanometer for measuring the large current. It is connected in parallel to the circuit of the galvanometer. 2.Why is it called a shunt resistor?In electronics, a shunt is a device that creates a low-resistance path for electric current, to allow it to pass around another point in the circuit. The origin of the term is in the verb 'to shunt' meaning to turn away or follow a different path. 3.Why a shunt resistor is connected in parallel?A shunt resistor is connected in parallel to the galvanometer so as to keep the resistance low. Such low resistance galvanometer is used in series with the circuit to measure the strength of current through the circuit. 

IntroductionUSB is very common, because it is indispensable for data transmission and charging. In modern life, we can see one or more USB ports on desktop computers, laptops, TVs, game devices, cars, media players, phones, and other electric devices, etc. USB devices are very important for our life. Look at your computer or smart phones, we probably know what it used for, however, fewer people know the full name of USB and what the real meanings of USB protocols and USB types.USB Ports, Cables, Types, & ConnectorsCatalogIntroductionⅠ Figure USB Ports and Standards OutⅡ USB Port Colors MeaningⅢ USB-C vs Type CⅣ USB 2.0 vs USB 3.0Ⅴ According to Labels Behind USB PortsHere are some easy steps to identify USB ports with different standards.Ⅰ Figure USB Ports and Standards OutUSB (universal serial bus) aims for input and output interfaces standard. It is widely used in information transformation products such as personal computers and mobile devices. The USB interface has hot-swappable, plug-and-play functions, and can be connected to a variety of external devices, such as a mouse and keyboard, etc. Our mobile phone charging uses the USB connector. These USB devices give us great convenience. USB chargers, USB connectors, USB hub, USB ports and USB cables, are all USB the same? What is USB 2.0 and USB 3.0? Low speed, full speed, and high speed mean what? What are Type-A, Type-B, and Type-C? Here you will get a full answer.Versions of USBThe USB 1.0/2.0/3.0 we often say refers to the technical specifications. The biggest difference among them is speed, that is, they indicate the speed of USB transfer files. The maximum transmission bandwidth of USB 3.0 is up to 5.0Gbps (640MB/s). Now many high-speed U disks or hard drives of portable electric devices use USB 3.0 or USB 3.1. USB also includes the old USB 1.1 standard and  USB 2.0 standard. The traditional maximum transfer rate of USB 1.1 is 12Mbps. Generally, manufacturers call its products that comply with the USB 1.1 standard as "full-speed USB." When the high-speed USB 2.0 was first introduced, the highest transmission rate was only 240Mbps. Later, the USB Promoter Group increased the rate to 480Mbps in October 1999, which is 40 times faster than the traditional USB 1.1. USB 2.0 is backward compatible with USB 1.1. Of course, USB 1.1 devices are "upward compatible" with USB 2.0, but they cannot reach the transmission speed of USB 2.0 and automatically stay at low speed. The maximum length of the USB 2.0 cable is 5 meters, but if five USB adapters are used, the maximum length can be up to 30 meters.Although you'll still be able to connect old-school devices with USB Type-A or USB Type-B connectors, but now you have more choices, that is USB4. USB4 is a USB system specified in the USB4 specification which was released in version 1.0 on 29 August 2019 by USB Implementers Forum. It leverages the Thunderbolt 3 protocol to deliver speeds up to twice as fast as the USB version it replaces. The USB4 architecture defines a method to dynamically share a single high-speed link with multiple end device types to best serve the transfer of data by type and application. USB-A, USB-B, and USB-C Port Types-Which is faster?Type-A/B/C determines the appearance of the USB ports. For example, the mouse, keyboard, USB flash drive and other interfaces we use are generally Type-A, which is also the most widely used interface. Type-B is more common in printers, monitors and other devices. In the past, Micro USB and Mini USB commonly used in mobile phones were portable versions of USB 2.0. The appearance of Type-C is very recognizable, slimmer. Its biggest feature is flippability, that is, USB-C connector has no up or down orientation, so you never have to flip it over to plug it in.1) Type-A: Standard USB PortType-A is the most common types of USB ports on computers. It has a notable feature: direction requirements. The connector (male port) must be inserted into the interface (female port) from a certain direction, in addition, because the appearance of the two sides of the USB male port is very close, this insertion process often makes mistakes.2) Type-B: Commonly used in printer equipmentType-B is the most common and popular data interface type on printers and displays, and some displays will also use it.3) Type Micro-B: USB standard for mobile devicesCurrently, most Android phones use the Micro USB interface (USB Micro-B), which is still widely used in various mobile portable devices.4) Type-C: It will become mainstreamAlthough Type-C has just appeared, it is foreseeable that as the USB Type-C technology matures, various notebooks, tablets and even smart phones in the future will begin to use the USB Type-C interface. Ⅱ USB Port Colors MeaningColorUSB ConnectorUSB Speed StandardNoteWhiteUSB-A or USB-B  Micro USB-AUSB 1.0 or USB 1.1*BlackUSB-A or USB-B Micro USB-BUSB 2.0 Hi-Speed*BlueUSB-A or USB-BUSB 3.0 Super Speed*RedSleep-and-Charge USB-AUSB 3.1 Gen 2 USB 3.2Usually denotes an "always on" portYellowSleep-and-Charge USB-AUSB 2.0 or USB 3.0Higher power or "always on" portⅢ USB-C vsType CThe Type-C is the same as the USB C, because the USB C is also called USB Type-C. However, there are slight differences between them. Let’s look at the following facts.Features of USB-C Connector:1. Ultra-thinThe old USB port size is 14mm * 6.5mm, while the USB-C is only 8.4mm * 2.6mm.2. No OrientationLike the Lightning, there will be no problem regardless of whether it is plugged in or reversed. It claims to be able to up to 10,000 times of repeated plugging and unplugging.3. Fast Transfer RateThe maximum transfer rate of the USB-C port is 10Gb per second, which is much faster than USB 3.0.4. Two-way TransmissionUnlike the old USB port, the power can only be transmitted in one direction. The USB-C port is bidirectional, so it can have two transmission power ways. Therefore, users can not only use laptops to charge mobile devices, but also use other devices or mobile power sources to charge laptops.5. Strong Power Supply CapabilityThe standard specification cable equipped with Type-C connector can pass 3A current, and it also has a super USB power supply capacity, which can up to 100W of power.6. Backward CompatibilityUSB-C can be compatible with the old USB protocol, but users need an additional adapter.USB-C refers to the Type C port that uses the USB 3.1 standard, but it should be noted that USB-C is not equal to Type C. Because there are many Type C devices that can only reach USB 2.0 or USB 3.0 transfer rate.With the improvement of technology, Type-C also supports the USB3.1 standard. Because the voltage and current increase, the coding consumption is reduced, from 20% of USB 3.0 to 3%. In other words, users can quickly transfer data and video through Type-C, or charge faster. Also users can charge other devices with their mobile phones. As for the display, when using Type-C for data transmission, there is no need to use another power cord to power the display, which solves the problem of messy desktop cables. Even the relatively high-end HDMI and DP ports cannot do it.The USB-C connector can be expanded into three: power supply/ USB transmission/ VGA or HDMI, which is the next-generation mainstream USB interface. The type-c cable is also of great help to the arrival of the 5G. Because the port of it becomes smaller, the flattening of electronic products is promoted. And in the transmission of audio and video, the tc data line has faster speed. At present, well-known technology manufacturers such as Sony and Apple have widely used type-c cables on their electrical devices because they can support multiple formats and reduce the limitations of USB. In short, the arrival of the 5G actually wants everyone to experience faster bandwidth, so the corresponding supporting facilities should also keep up. The type-c cable is undoubtedly one of them. Ⅳ USB 2.0 vs USB 3.0Although USB has developed to the USB3.1 protocol, we often see two types of USB 2.0 and USB 3.0 on devices. How do we distinguish these two interface types in daily use? Some people will say that USB 3.0 port is blue and USB2.0 port is black, which is easy to distinguish. In fact, it is not. Even though most USB3.0 ports use blue, there are many special cases. Here are some examples. The color of the USB ports on some models does not have any special treatment, and it looks no different from USB 2.0 type, and it is all black. However, it is often marked with "SS" in front of the logo. "SS" is the abbreviation of "SuperSpeed USB", which means connector or port that uses the USB 3.0 standard. The black USB type is also suitable for USB 3.0. The USB ports in Apple's new MacBook notebooks are all USB 3.0 standard, but in order to keep in harmony with the color of the computer cover, a white connector design is adopted. The USB ports on the Razer gaming notebooks are also USB 3.0, but in order to match the bright green keyboard backlight on the body and the Razer logo, the color of the USB port adopts "green". It improves the recognition of the machine and the brand, because no third-party manufacturer has adopted a green USB interface design. In addition, distinguish the metal pins of the USB ports. Generally, USB 2.0 uses a row of 4 pins, while USB 3.0 has a two-row pin design, with 5 pins in the front row and 4 pins in the back row. In addition, there is also a hybrid port of eSATA and USB 2.0, which can plug in both USB devices and eSATA interface devices. However, they are common in business models of previous years. Ⅴ According to Labels Behind USB Ports"+" sign - It represents the USB interface with high current output capability. The ordinary USB interface provides a maximum current of 500mA, but it may not be able to drive when encountering "high energy consumption" devices such as mobile hard disks and USB optical drives. Therefore, when it appeared, the output current on this interface can reach 1000mA (1A), which greatly enhances the drive capability."SS" - It is actually a symbol of USB 3.0. If the USB port has “SS” (or “SuperSpeed”) on its label, it’s a USB 3.0 port. If it’s“SS 10”, it’s a USB 3.1 port."Lightning Logo" -It generally appears on notebooks, and the USB port with it has a power-off charging function. That is, it can use its own battery or an external power supply to charge the mobile device when it is turned off. The lightning mark with an arrow indicates the Thunderbolt 3: two-way charging and two-way data transmission. Thunderbolt 3 supports for up to 40Gbps of throughput, alongside reduced power consumption and the ability to move as much as 100 watts of power over the interface. And it also means that a single cable is all you need to push power and transfer a large amount of information (up to and including video data for two 60Hz 4K displays) to and from even a complex device like a computer, something many laptop manufacturers have been quick to take advantage of.USB is an important interface on the computer. Almost 90% of the external devices are connected by it for mobile hard drives, such as U disks, printers, etc. Understanding the above information can analyze and solve the most common problems of unrecognized external devices of USB. At the same time, it is also very useful for us to choose USB products. Ⅵ Frequently Asked Questions about USB Types and USB Versions1. What are the different types of USB ports?Types of USB Ports and ConnectorsUSB-AUSB-BUSB-B MiniUSB-B MicroUSB-CLightning 2. How can I tell the difference between USB 2.0 and 3.0 ports?You can generally tell the difference between USB 1.0, 2.0, and 3.0 by color alone. While the size and shape may be identical, the key is to look at the color of the plastic inside the device. The USB 1.0 features a white plastic color, while USB 2.0 is black, and the USB 3.0 is blue. 3. What is the difference between USB Type A and C?The USB-A has a much larger physical connector than the Type C, Type C is around the same size as a micro-USB connector. ... The beauty of Type C is that it can be inserted any way up as the connector pins are the same on either side. 4. Are USB 2.0 and 3.0 ports the same?The A connectors still work properly so any 2.0 device with a 2.0 cable can be used with 3.0 ports or hubs. To sum up: USB 3.0 devices require 3.0 cables. ... USB 2.0 cables can be used with 3.0 ports but the transfer rate will fall back to 2.0. 5. Why is my USB 3.0 port not working?Update to the Latest BIOS, or Check USB 3.0 is Enabled in BIOS. In many cases, your motherboard will be responsible for software issues related to your USB 3.0 ports or any other ports on the motherboard. For this reason, updating to the latest BIOS may fix things.