Clamp meter

Data records

• A calibration laboratory checks a clamp meter against a calibrator's current output passed through a multi-turn coil, so that the current sensed by the jaw is a multiple of the sourced value; annual calibration is typical for the class. Source: Fluke learn index page, web page edition. Verified 2026-10-27. Record instr.clamp-meter.calibration
• In a current-transformer clamp the iron jaws form a magnetic core with the measured conductor as a single-turn primary and a coil wound on the jaws as the secondary; the secondary current is a fixed fraction of the conductor current set by the turns ratio, and the method responds to alternating current only. Source: Fluke learn article, web page edition. Verified 2026-10-27. Record instr.clamp-meter.current-transformer-jaw
• A flexible current probe is a Rogowski coil: a helix of wire with no iron core whose output voltage follows the rate of change of the conductor's magnetic field and is integrated in the meter to a signal proportional to the current. The absence of a core lets the probe bend into cramped spaces, gives a broad frequency response with no saturation, and limits the probe to alternating current. Source: Fluke learn article, web page edition. Verified 2026-10-27. Record instr.clamp-meter.flexible-coil-probe
• A Hall-effect clamp places a semiconductor sensor in a small air gap in the jaw; the flux crossing the gap produces a sensor voltage that is amplified and scaled to a current reading, so the clamp measures both direct and alternating current and is zeroed before a measurement to remove offsets from the Earth's field and nearby magnets. Source: Fluke learn article, web page edition. Verified 2026-10-27. Record instr.clamp-meter.hall-effect-jaw
• An inrush function arms the meter so that the starting current of a motor triggers a short sampling window, and the meter reports the surge current drawn at energization, which a steady reading would miss; the value is compared with the running current and recorded in the maintenance log. Source: Fluke learn article, web page edition. Verified 2026-10-27. Record instr.clamp-meter.inrush-capture
• Only one conductor is placed in the jaw: the supply and return conductors of a circuit carry current in opposite directions whose magnetic fields cancel, so a clamp closed around both conductors reads the difference rather than the load current. Source: Fluke learn index page, web page edition. Verified 2026-10-27. Record instr.clamp-meter.one-conductor
• A clamp meter measures current from the magnetic field around a conductor: the hinged jaw closes around one conductor and the meter converts the sensed field to a current reading without the circuit being disconnected or de-energized. Source: Hioki learning page, web page edition. Verified 2026-10-27. Record instr.clamp-meter.principle
• The current drawn by variable-speed drives, electronic ballasts and computers flows in short pulses rather than as a sine wave, and the wave shape has a strong effect on a clamp reading, so a true-RMS clamp meter is used where such loads are measured. Source: Fluke learn article, web page edition. Verified 2026-10-27. Record instr.clamp-meter.true-rms
• A clamp meter is primarily a current instrument whose jaw measures current while its probes measure voltage, the inverse of a digital multimeter, which is primarily a voltage instrument and measures larger currents only through a clamp accessory. Source: Fluke learn index page, web page edition. Verified 2026-10-27. Record instr.clamp-meter.voltage-functions