Which instrument would you use to measure current flowing in a circuit directly?

Which instrument would you use to measure current flowing in a circuit directly?

• A. Voltmeter
• B. Oscilloscope
• C. Megger
• D. Ammeter

Answer: (D)

Measuring current directly means placing the instrument in the path of the circuit so every bit of current flows through it. An ammeter is designed for this purpose: it’s inserted in series with the circuit, has very low resistance to avoid dropping much voltage, and displays the current flowing through the path. A voltmeter measures voltage across a component and is connected in parallel; its high input resistance would not properly pick up current and would disturb the circuit if placed in series. An oscilloscope can visualize waveforms and can measure current with a special probe, but in a basic direct current reading task, the ammeter is the standard tool. A megger is used to test insulation resistance by applying a high DC voltage, not for current measurement.

Measuring current directly means placing the instrument in the path of the circuit so every bit of current flows through it. An ammeter is designed for this purpose: it’s inserted in series with the circuit, has very low resistance to avoid dropping much voltage, and displays the current flowing through the path.

A voltmeter measures voltage across a component and is connected in parallel; its high input resistance would not properly pick up current and would disturb the circuit if placed in series. An oscilloscope can visualize waveforms and can measure current with a special probe, but in a basic direct current reading task, the ammeter is the standard tool. A megger is used to test insulation resistance by applying a high DC voltage, not for current measurement.