数字电压表(DVM)测量电压时、由于DVM的H端(+)、L端(-)接到被测电路的方法不同,往往能测得正、负二个不等的电压值。哪一个测量值正确呢?而对干电地进行测量,则测得正负相等的电压。这是为什么呢? 道理很简单,由于共模电流流过DVM的输入端、使测量误差增大。所以,DVM的H,L输入端决不能随意接入被测电路中。 Digital voltmeter (DVM) voltage measurement, due to DVM’s H-side (+), L-side (-) connected to the circuit under test different methods can often be measured positive and negative voltage values ​​ranging from two. Which one is correct? The measurement of dry ground, then measured positive and negative voltage. Why is this? The reason is very simple, due to the common mode current flowing through the DVM input, the measurement error increases. Therefore, DV, H, L input must not be free access to the circuit under test.