If using a separate current source and voltmeter to make low resistance measurements, each instrument must be checked for non-ohmic contacts.
如果使用分离的电流源和电压表来进行低电阻测量，则必须检查每台仪器的非欧姆接触情况。
Because of the low test current level used, a very sensitive voltmeter is required to measure the voltage drop, which is usually in the microvolt range.
由于所使用的测试电流很低，所以就需要非常灵敏的电压表来测量这种通常在微伏范围的电压降。
Ideally, when a voltmeter is connected to a relatively low impedance circuit in which no voltages are present, it should read zero.
在理想的情况下，当把电压表连接到一个没有电压的、阻抗比较低的电路时，电压表的读数应当为零。
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