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。

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Since the voltage drop across the ammeter is negligible, essentially all the test voltage appears across R.

由于安培计上的电压降可以忽略，所以所有的测试电压都出现在电阻R上。

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The Source-Measure Unit can also test other diode parameters, including forward voltage drop and breakdown voltage.

源-测量单元还可以测量其它的二极管参数，包括正向电压降和击穿电压。

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