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在工作中,常会遇到测量低电阻的问题.如输出变压器次级的电阻、波段开关的接触电阻、继电器接触点的接触电阻等,由于这些电阻只有十分之几或百分之几欧,故一般不能用万用表直接测量. 测量低电阻的常用方法是利用万用表的高电流量程,再用一个电源和一个可变电阻,接成如图1的电路.假设电源电压为12伏,可变电阻为20欧,电流表的量程为1安,并调节可变电阻,使电流表满度偏转;
In the work, often encounter the problem of measuring low resistance, such as the output transformer secondary resistance, the band switch contact resistance, the contact resistance of the contact point of the relay, etc., because these resistance is only a few tenths or a few percent of Europe, so Generally can not be measured directly with a multimeter to measure the low resistance of the common method is to use the high current range of the multimeter, then a power supply and a variable resistor, connected as shown in Figure 1. Assuming a supply voltage of 12 V, variable resistance 20 ohms, ammeter range of 1 amp, and adjust the variable resistance, ammeter full scale deflection;