Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

Which type of meter is powered by its own battery?

1. Voltmeter

2. Ammeter

3. Ohmmeter

4. Wattmeter

The correct answer is: Ohmmeter

An ohmmeter is a type of electrical testing device specifically designed to measure resistance, and it is powered by its own internal battery. This self-contained power source is essential because when measuring resistance, the ohmmeter needs to generate a small current through the component being tested. The battery facilitates this process, allowing the device to function independently without needing an external power supply. In contrast, a voltmeter typically measures voltage and is often connected in parallel with the circuit it is testing, which may or may not require an external power source depending on the design. An ammeter measures the current flowing through a circuit and usually needs to be part of a live circuit, as it often requires a shunt resistor to measure current accurately. A wattmeter measures power and may need both voltage and current inputs, which often come from the circuit being tested rather than a built-in battery. Thus, the unique nature of an ohmmeter's operation makes it the correct answer, as it relies completely on a battery for its measurements.