How to Choose a Clamp Meter: AC or AC/DC Hall Sensor?
A clamp meter measures current without breaking the circuit. This guide shows when a plain AC clamp is enough and when you need an AC/DC clamp with a Hall sensor, and how measurement range, true RMS accuracy and CAT category shape the right choice.
View clamp metersAC clamp or AC/DC clamp with Hall sensor?
The first decision is the sensing principle. A plain AC clamp meter works like a current transformer: the alternating current in the conductor induces a voltage in the clamp coil. That only works with alternating current. An AC/DC clamp adds a Hall sensor in the jaw gap, so it can also read direct current.
For routine checks on 230 V / 400 V mains an AC clamp is usually enough. As soon as photovoltaics, batteries, charging infrastructure, automotive electrics or the DC side of variable-speed drives are involved, you need an AC/DC clamp with a Hall sensor, because DC components appear there.
- AC only (mains, motors, distribution boards): an AC clamp on the transformer principle is enough.
- AC and DC (PV, batteries, automotive, drives): an AC/DC clamp with Hall sensor.
- Small or earth-leakage currents: a dedicated leakage clamp with mA resolution.
Which range and true RMS accuracy matter?
The range must fit the expected current with headroom. Common clamps cover 0 to 400 A or 0 to 1000 A, heavy-duty models up to 2000 A. For accuracy the decisive feature is true RMS (TRMS) measurement.
TRMS clamps read distorted, non-sinusoidal currents correctly, the kind found downstream of power supplies, LED drivers and variable-speed drives. Simple averaging meters can read up to 40 % low there. Accuracy is stated as a percentage of reading plus digits, for example (2 % + 5 digits).
Which CAT category and features do you need?
The overvoltage category (CAT) to IEC 61010‑2‑032 must match the location. It describes how high the transient voltage spikes at the measuring point may be. Measuring at the service entrance or main distribution board demands a higher category than at a final circuit.
Always choose the CAT category and rated voltage for the worst-case point. A CAT III 600 V clamp is adequate for final loads, while work at the incoming supply calls for CAT IV 600 V or CAT III 1000 V. Useful extras include inrush current capture, Min/Max, Hold and a continuity buzzer.
Frequently asked questions
When do I need an AC/DC clamp with a Hall sensor?
Whenever DC components are present: photovoltaics, batteries, charging infrastructure, automotive systems or the DC circuits of variable-speed drives. A plain AC clamp cannot measure there.
Why does true RMS matter on a clamp meter?
TRMS reads the real effective value even with distorted, non-sinusoidal currents. Downstream of drives, LED drivers and switch-mode supplies, simple averaging meters give clearly wrong, usually low readings.
Which CAT category should my clamp meter have?
Choose it for the worst-case location. CAT III suits distribution boards and fixed installations, while CAT IV is required for measurements at the service entrance. The rated voltage must match too.
How big should the jaw opening be?
It must take the thickest conductor you measure. Small openings suit single cores, while busbars and thick cables need 30 mm or more.
Looking for the right clamp meter?
We stock AC and AC/DC clamp meters with Hall sensor, true RMS and a verified CAT rating for every task - from the socket to the service entrance.
Standards-compliant
Every clamp carries a clear CAT rating to IEC 61010-2-032.
True RMS accurate
Correct readings even on distorted signals.
AC and DC
Hall-sensor models for direct and alternating current.
Expert advice
We help with range, jaw size and category.