There are times when the value of the current you want to measure exceeds the range of a digital multi-meter or field conditions do not allow you to open the circuit to measure the current. Current clamps come in handy when testing at high currents (usually greater than 2A) where a high degree of accuracy is not required. A current clamp snares a wire to measure the current and converts it to a value that a digital meter can handle.

Current Transformer Type. Generally 1 mA is used to represent 1 amp. a current value of 100 amps becomes 100 mA, which can be measured well with a digital multi-meter. Connect the wires to the "mA" and "Com" jacks and turn the function selector knob to AC milliamps.

Hall Effect Probes. Use 1 millivolt to represent an AC or DC value of 1 amp. For example, 100 amps AC current would be converted to 100 millivolts AC. Connect the test leads to the "V" and "Com" jacks. Turn the function selector knob to "V" or "mV". At this point the multi-meter represents 1 ampere of current with 1 millivolt of voltage.

Transducer type current probes, like the Fluke 80i-400. digital multi-meters use a 1mA display to represent an actual 1A signal.

Fluke Model I-1010 Hall effect probe that tests very high AC or DC currents. It converts current to a voltage signal.

A 1mV voltage display represents 1A of actual current.