Summary of common electronic components identification and detection methods (above)

Electronic components, English name Electronic components, refers to electronic components and electrical components of small machines, instruments, which itself is often composed of a number of parts, can be used in similar products. At present, the more common electronic components include resistors, capacitors, diodes, transistors, inductors and other devices. This article briefly introduces the identification and detection methods of common electronic components.

1. Resistors are mostly used for current limiting, voltage division, shunt and impedance matching in circuits. They are also used as pull-up (pull-up) resistors in digital circuits. They are one of the components that are used more in circuits. The representative symbol of the resistor is R, and the unit is ohm (symbol Ω). In order to express the distinction, the common resistance is generally designated as R, the adjustable resistance is represented by VR, the thermistor is represented by TR, and so on. The method of measuring resistance: The more convenient way to judge whether the resistance is normal is to use a multimeter, and use the two test pens of the multimeter to directly measure the two ends of the resistance. The process of measuring resistance with a multimeter can be broken down into four steps: selecting range → zeroing → testing → reading. The general resistance can be measured on-line, and the difference between the on-line resistance and the nominal resistance is not big. However, some circuit designs connect the two ends of the resistance to other circuits to form a parallel connection, so the resistance value will be reduced, and some will even be reduced by more than half. Then one end of the resistance will be welded with an electric soldering iron for measurement. In most cases, the resistance measured online is lower than the nominal resistance because it belongs to parallel connection. If you measure the resistance higher than the nominal resistance, there are several possibilities: first, the resistance is open circuit, second, the color code is wrong, and third, the multimeter is wrong (wrong use or low battery). Other methods of measuring resistance are: bridge method to measure resistance and voltammetry to measure resistance. When the measurement accuracy of the resistance value is very high, the DC bridge method can be used for measurement. Voltammetry is an indirect measurement method. First, the voltage across the measured resistor and the current flowing through it are directly measured, and then the resistance value of the measured resistor is calculated according to Ohm's law R = U/I. Voltammetry is simple in principle and convenient in measurement, especially suitable for measuring the volt-ampere characteristics of nonlinear resistance. Voltammetry has two kinds of measuring circuits: ammeter internal connection and ammeter external connection. When the internal resistance of the ammeter is less than the measured resistance, use the ammeter internal connection method.

2. Capacitor The representative symbol of capacitor is C, and the unit is Farah (symbol F). Its main parameters are: nominal capacity, allowable error level, working voltage (withstand voltage). Electrolytic capacitor: small size, large capacity, but it has polarity, polarity can not be wrong, and the capacity value is unstable, large leakage, easy to aging, even if not used for a long time also easy to deteriorate capacity decline. The method of measuring capacitance: when measuring electrolytic capacitance with the resistance file of multimeter, the pointer of the meter should return to the starting point or approach the starting point after swinging to a certain value; The greater the swing amplitude of the pointer, the greater the capacitance capacity, and the closer the pointer returns to the starting point, the smaller the capacitance leakage and the greater the insulation resistance. If the pointer does not swing or does not return after swinging, it means that the capacitor is broken or short circuit is damaged.