What device allows current to be measured without breaking a circuit by clamping around a conductor?

What device allows current to be measured without breaking a circuit by clamping around a conductor?

• A. A voltmeter
• B. An ammeter with series connection
• C. A clamp-on ammeter
• D. A megohmmeter

Answer: (C)

Measuring current without breaking the circuit relies on sensing the magnetic field created by the current flowing through a conductor. A clamp-on ammeter achieves this by opening a jaw that clamps around a single conductor. Inside, a sensor—often a transformer for AC or a Hall-effect sensor for DC—detects the magnetic field and converts it into an electrical signal that corresponds to the current, which the meter displays. For AC, the reading is typically the RMS current; some clamp meters that measure DC use Hall-effect technology to capture the steady current. This approach is what makes it possible to measure current non-intrusively. Other devices either measure voltage (a voltmeter) or require being placed in series to read current, which means breaking the circuit, or test insulation resistance with a high voltage (a megohmmeter). The clamp-on design specifically enables current measurement around a conductor without interrupting the circuit.

Measuring current without breaking the circuit relies on sensing the magnetic field created by the current flowing through a conductor. A clamp-on ammeter achieves this by opening a jaw that clamps around a single conductor. Inside, a sensor—often a transformer for AC or a Hall-effect sensor for DC—detects the magnetic field and converts it into an electrical signal that corresponds to the current, which the meter displays. For AC, the reading is typically the RMS current; some clamp meters that measure DC use Hall-effect technology to capture the steady current.

This approach is what makes it possible to measure current non-intrusively. Other devices either measure voltage (a voltmeter) or require being placed in series to read current, which means breaking the circuit, or test insulation resistance with a high voltage (a megohmmeter). The clamp-on design specifically enables current measurement around a conductor without interrupting the circuit.