电子仪表（Electronic instrument）.doc

电子仪表（Electronic instrument） The use of digital multimeter: 1. Measuring voltage One of the basic functions of digital meters is to measure voltage. A typical DC voltage source is a battery, such as a battery used in automobiles. AC voltage is usually generated by generators, and the most common source of AC voltage is the socket on the wall of the home. Some devices will AC into DC, such as television, audio, video, computer and other electronic equipment, the rectifier is plugged into the wall, to put AC into DC power supply; DC voltage is required for these electronic devices. Test voltage is usually the first step to solve a circuit problem. If there is no voltage or voltage is too low, too high, before further inspection, we must first solve the power problem. The waveforms of AC voltage may be sinusoidal (sinusoidal) or nonsinusoidal (sawtooth wave, Fang Bo, etc.). Many digital multimeter such as OI857 and OI859CF can display the RMS (RMS) of AC voltage. The effective value is the value of the AC voltage equivalent to the DC voltage. But most digital multimeter (such as BM805) has only the averageresponding function, which gives a valid value when it enters a pure sine wave. This digital multimeter does not accurately measure the effective value of nonsinusoidal waves. A digital multimeter with true RMS function (True-rms) allows accurate measurement of true RMS values of nonsinusoidal waves (see the design principle and measurement calculations of a multimeter). Crest factor (crestfactor) is the ratio of the peak value of the signal to the effective value. The digital multimeter measures the AC voltage capability limited by the frequency of the signal being measured. Most of the digital multimeter can accurately measure the AC voltage of 50Hz~500Hz, but some digital universal AC measurement bandwidth table to several hundred kilohertz (for example OI859CF digital multimeter to 100KHz). 2 、 digital multimeter to measure the part of voltage: Select the required