Clamp Meters rely on the principle of magnetic induction to make non-contact AC current measurements. Electric current flowing through a wire produces a magnetic field. Since alternating current frequently reverses polarity, it causes dynamic fluctuations in the magnetic field which are proportional to the current flow. A current transformer inside the clamp meter senses the magnetic fluctuations and converts the value to an AC current reading. This type of measurement is convenient for measuring very high AC currents. Direct current, however, flows through conductors in a fixed polarity. Consequently, the magnetic field around the conductor does not change and conventional clamp meters will register no reading. DC clamp meters work on the principle of the Hall Effect. Hall effect sensors sense the magnetic field caused by current flow which causes a small voltage across the Hall effect sensor. That voltage, which is proportional to current is then amplified and measured. Clamp meters often include other sensors such as voltmeters, ohmmeters, etc. which increase the versatility of the instrument. These other sensors use test leads which plug into the clamp meter. As only current measurements can be made with the clamp, other measurements do not benefit from the non-contact nature of the clamp.
Clamp Meter Features
Clamp meters are often available with a number of features that make it easier to take accurate readings and handle the resulting data. Of course, higher end clamp meters are more likely to include these advanced functions. True RMS: Since alternating current reverses directions several times per second, it is represented as a sine wave. Because the amplitude of the sine wave changes continuously over the wave period, current measurements may vary quite a bit at different points in time. True-RMS (root mean square) converts AC signals into DC signals of equivalent value for more stable and accurate AC readings.
Considerations When Purchasing a Clamp Meter.
Do you require DC and AC measurment ? Chose a clamp meter with DC ranges.
Do you require resistance measurments ? Chose a clamp meter with ohms ranges.
Consider the cable size you will encounter. Chose a clamp meter with the correct size jaws to enable it to fit around the cable.
Consider the maximum current and voltage you will want to read and again chose a meter with the correct ranges.
We offer clamp meters from Fluke, Martindale, Kewtech, Megger & Chauvin Arnoux. Secialist clamp meters are also available, for Earth Leakage Measurement & Eart Resistance Measurement.