voltmeter

The technician connected the voltmeter to the battery to check its voltage.

用法提示：此处为名词单数形式 voltmeter，表示用来测量电压的仪表。

You can use a voltmeter to measure the potential difference between the two ends of the wire.

用法提示：voltmeter 是名词，在本句中作 use 的宾语，指电压表。

The electrician read the voltmeter and said the circuit was working normally.

用法提示：单数名词 voltmeter 作 read 的宾语，指电压表。