Sometimes, the current value you want to measure exceeds the range of the digital multimeter or the field conditions do not allow you to open the circuit to measure the current. Current clamps are very handy when testing at high currents (usually greater than 2A) without the need for high precision. A current clamp measures the current around the wire and converts it to a value that a digital meter can handle.
There are two basic current probes: the current transformer type, which is used for AC measurements only. Hall-effect probes for measuring AC or DC current.
Current converter type. 1 mA is generally used to represent 1 amp. A current value of 100 amps becomes 100 mA, which can be safely measured with a DMM. Connect the wires to the "mA" and "Com" jacks, and turn the function selector knob to the AC mA position.
Hall effect probe. Use 1 millivolt to represent an AC or DC value of 1 amp. For example, 100 amps of AC current is converted to 100 millivolts of AC voltage. Connect test leads to the "V" and "Com" jacks. Rotate the function selection knob to "V" or "mV". At this time, the multimeter uses 1 millivolt to represent 1 amp of current.
When disconnecting or desoldering a circuit for a current measurement, the power to the circuit to be tested must be disconnected. Small currents can also be dangerous.
Do not test voltages with test leads inserted in the current holes. It may cause damage to the watch or endanger personal safety.
Inverter-type current probes, like the Fluke 80i-400. The DMM uses a 1mA display to represent the actual 1A signal.
Fluke I-1010 Hall-Effect Probe can measure very high AC or DC currents. It converts current into voltage signal.
A voltage display of 1mV represents an actual current of 1A.
