万能表检测电路（Universal watch circuit）.doc

万能表检测电路（Universal watch circuit） The multimeter is also called multimeter, three meter, multimeter, measuring instrument is a kind of multi-functional, multi range, general multimeter can measure DC current, DC voltage, AC voltage, resistance and audio level, some parameters can also be measured AC current, capacitance, and inductance semi conductor (such as beta). 10 thousand table structure (type 500) The multimeter is composed of three main parts, the meter, the measuring circuit and the change-over switch. (1) meter: it is a high sensitivity magnetoelectric DC ammeter. The main performance index of the meter basically depends on the performance of the meter. The sensitivity of the meter refers to the DC current value of the meter when the meter pointer is full scale deflection. The smaller the value, the higher the sensitivity of the meter. When measuring voltage, the greater the internal resistance, the better the performance. There are four scale lines on the meter. Their functions are as follows: the first (from top to bottom) is marked with R or Omega, indicating the value of resistance. When the switch is in the ohm block, it reads the graduation line. Second marked with ~ and VA, indicating the AC and DC voltage and DC current value, when AC and DC voltage or DC current blocking switch range in other locations except 10V outside the exchange, which read this line. The third is labeled 10V, indicating the AC voltage value of 10V. When the switch is in the alternating current, DC voltage, and the measuring range is at AC 10V, the line is read. The fourth item, labeled dB, indicates the audio level. (2) measuring circuit A measuring circuit is a circuit used to convert a variety of measurements into small DC currents suitable for meter measurements, consisting of resistors, semiconductor devices, and batteries It can be a variety of measurement (such as current, voltage, resistance, etc.) in different range, through a series of processing (such as rectifier,