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A voltmeter is the instrument you use to measure voltage — how much electrical push there is between two points. You touch its two probes (usually one red, one black) to the two points you want to compare, and it shows you a number in . Older ones have a needle that swings across a dial; modern ones show digits on a screen. In real life almost nobody owns a pure voltmeter any more: you buy a multimeter (三用電表), which measures voltage, current and resistance all in one, and you just switch it to the voltage setting. So "voltmeter" now sounds slightly like a school-physics word or a specialist's word. , car mechanics and anyone testing a battery use one constantly — "put a voltmeter on it" means check whether the power is actually there. The key thing about how it is used: you always measure voltage BETWEEN two points, never at one point alone, so a voltmeter always has two probes.
電壓表、伏特計（現在多半是三用電表的電壓檔）
組成volt + -meter. Volt is the unit. The ending -meter comes through French from Ancient Greek métron, meaning a measure, and it makes the name of a measuring instrument.
同家族的字
- thermometersame -meter ending: an instrument that measures heat
- speedometersame -meter ending: measures speed
- ammeterthe matching instrument for current, in amps
- metricfrom the same Greek métron, a measure
原始詞典資料1 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
voltmeternoun/ˈvoʊltˌmitɚ/
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An instrument for measuring electric potential in volts.
- Because most diesel failures can be traced to electrical faults, minor in themselves but often difficult to pin-point, any unscheduled halt during a trial run is often the signal for the frenzied unfolding of wiring diagrams and the appearance of an impressive array of voltmeters and circuit testers.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。