What instrument is used to measure 4-20 mA signals?

What instrument is used to measure 4-20 mA signals?

• A. DC clamp meter
• B. AC clamp meter
• C. Oscilloscope
• D. Multimeter

Answer: (A)

4-20 mA signals are a DC current loop used in process instrumentation. To measure that current without breaking the loop, you use a DC clamp meter. It clamps around a single conductor carrying the loop current and reads the actual current in milliamps, giving a direct, noninvasive measurement of the 4-20 mA signal. An AC clamp meter wouldn’t read this steady DC current. An oscilloscope could show the signal’s waveform only if you add a burden resistor to convert current to voltage and then probe that voltage, which is more setup and not as direct. A standard multimeter in current mode requires inserting the meter in series, which can disturb a live loop and is less practical for quick monitoring.

4-20 mA signals are a DC current loop used in process instrumentation. To measure that current without breaking the loop, you use a DC clamp meter. It clamps around a single conductor carrying the loop current and reads the actual current in milliamps, giving a direct, noninvasive measurement of the 4-20 mA signal. An AC clamp meter wouldn’t read this steady DC current. An oscilloscope could show the signal’s waveform only if you add a burden resistor to convert current to voltage and then probe that voltage, which is more setup and not as direct. A standard multimeter in current mode requires inserting the meter in series, which can disturb a live loop and is less practical for quick monitoring.