Which instrument for measuring currents in milliamperes?

• A. Voltmeter
• B. Ammeter
• C. Ohmmeter
• D. Milliammeter

Answer: (D)

Measuring small currents requires an instrument that is sensitive enough to read in the milliampere range. A milliammeter is basically an ammeter calibrated specifically for milliamps, so it has the right sensitivity and scale to read accurately when the circuit current is a few tenths to a few milliamps. It also has a low burden (the voltage drop it introduces in the circuit) so it doesn’t significantly alter the current you’re trying to measure.

Voltmeter measures voltage, not current, so it won’t give you a direct reading of how much current flows. Ohmmeter is for resistance, not current. A standard ammeter can measure current, but many ammeters are designed for larger currents in amperes; without a milliamp range, their readings won’t be precise or may saturate when the current is only in the milliamp level. Using a milliammeter ensures the measurement is within the meter’s accurate and readable range.