7 important facts you must know before calibrating a clamp meter
A current clamp measures current via the non-contact method, making it safer and less troublesome to acquire a measurement. It usually has additional measurement functions such as voltage and continuity. A clamp meter typically requires an annual calibration to ensure that it continues to make measurements within the manufacturer’s specifications.
Here are 7 important things to consider when calibrating a clamp meter:
1. Clamp meters come in all shapes and sizes. Ergonomics and jaw widths can make calibration sometimes difficult. Choose your calibration equipment accordingly.
2. Most clamp meters today are multifunctional. In addition to current, most clamp meters typically measure voltage, resistance, continuity and other functions commonly found in a digital multimeter.
You must know what functions the clamp meter has to calibrate it properly. The Fluke website has a selection guide to help you see the different functions of each Fluke clamp meter.
3. Not all calibrators can do the job. At higher inputs, many calibrators limit how long you can output high-current continuously. In addition, you must use a calibrator with enough compliance voltage to drive a coil with enough accuracy. Fluke uses “L-COMP” (inductive compensation) to increase compliance voltage to drive inductive loads.
Coil inductance can cause problems, so avoid current sources not designed for use with current coils. Transients when turning the current on and off may cause source tripping.
4. Current coil winding (turns) and range matter. You must use a coil with enough turns to test the entire current range of the clamp meter. The coil windings determine the amount of current. For example, a 50-turn coil with a calibrator sourcing 20 amps presents up to 1,000 amps of current to the clamp meter.
5. Don’t forget the accessories. Some clamp meters can be equipped with a flexible current probe such as the Fluke iFlex that must be calibrated with the clamp meter.
6. High current generates heat. Your current coil should be designed to dissipate heat as much as possible. Coils typically have maximum operating time at higher current levels.
7. Positioning can be important. When aligning a clamp meter on a current coil, be aware of clamp stray field and position sensitivity. Avoid interfering fields from other equipment and current carrying leads. Take note of any clamp alignment marks. Align the clamp axis parallel to the coil axis and align the clamp jaw plane perpendicular to the coil conductors.
Fluke Calibration has developed a free web seminar, “Introduction to the Basics of Digital Clamp Meter Calibration.” A recorded on-demand version of this seminar is available here. You’ll be asked to register to view the seminar.
Rich McFadden is in the marketing group of Fluke Calibration. His responsibilities include product management for many electrical metrology instruments. Rich holds a Bachelor of Science degree in Aviation Technology from Everglades University in Florida and a Masters degree in Business... Full Bio
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