Usually made up of a digital measuring device connected to a pair of jaws that can be various different sizes, clamp meters allow accurate measurements of electrical current without needing to physically connect with a circuit.
The jaws – or clamp – fit snugly around most electrical conductors, allowing you to gain readings without taking circuitry apart and performing more complex testing procedures. They’re generally an exceptionally versatile tool that can measure both AC and DC current, but make sure you grab the right model for your needs as lower budget clamp meters generally have a lower measuring range than their more expensive counterparts.
Many clamp meters are also directly integrated into both analogue and digital multimeters, allowing you to complete more tests than just the standard electrical current reading. There’s also a range of clamp meters that use True RMS technology, eliminating damaging waveforms that can make test readings inaccurate.
One of the most truly useful clamp meters available in Tester’s range is none other than the Fluke I3000. Based off the Rogowski principle this tester has a new flexible testing head, this top-of-the-range product is the perfect solution for testing electrical currents in awkward places where normal clamp meters just won’t reach. The device measures up to 3000A, has a CAT III 600V rating and is also extremely portable due its flexibility and compact size.
If you’ve chosen a clamp meter, why not also browse our expanding range of clamp meter accessories? We stock everything from power supply modules to flexible probes, so make sure you check out the full range of accessories and improve your testing capabilities even further!
How Do Clamp Meters Work?
A clamp meter is a test instrument used most frequently to measure large currents in industrial applications. Clamp meters are available that can measure currents up to 400 A.
To measure the current in a conductor, you clamp the meter around the conductor so that the conductor passes through the space between the jaws of the meter. This is shown in the image at right.
The jaws of a transformer-type clamp meter contain coils that are the equivalent of a transformer’s secondary winding. As the current changes, the magnetic field around the conductor changes, and this induces a current in the clamp meter’s coils that is proportional to the current in the wire. Measuring this current will also give you a measure of the current in the conductor.
The drawback of using a transformer-type clamp meter is that you can only measure AC currents or pulse currents with it. Clamping the meter around a conductor carrying a DC current will result in a reading of 0 A. The reason for this is that a transformer only produces an output current when the magnetic flux cutting through the transformer windings changes.
To measure DC currents, some clamp meters use Hall Effect sensors. Hall Effect sensors are transducers whose output varies in response to the strength of the magnetic field. Since the field need not change to produce an output, clamp meters that use a Hall Effect sensor can measure DC as well as AC currents.
In addition to measuring AC and DC currents, modern clamp meters also have the measurement functions that you’d expect to find in a multimeter, including resistance and continuity, voltage, frequency, and in some cases, capacitance. These features make life a lot easier for the industrial technician. Instead of carrying a whole slew of instruments out to the plant floor, into the field, the technician need only carry his or her clamp meter.