Demystifying the Clamp Multimeter: A Simple User Guide

The multimeter clamp is a portable electrical measuring tool that combines the functions of a current transformer and an ordinary multimeter. It is mainly used for non-contact measurement of AC current, and can also measure various electrical parameters such as voltage and resistance. Its uniqueness lies in its jaw design, which allows users to easily and quickly measure the current value in the circuit without disconnecting the circuit, greatly improving work efficiency and safety.


A precision instrument for electrical measuring tools, the basic structure of the clamp multimeter mainly includes current transformers, rectifier instruments or electromagnetic instruments, and clamp cores. Its function is to measure current quickly without stopping the circuit. Just change the negative pole of the clamp multimeter from the pointer end to the clamp tube, and clamp the measured wire to directly obtain the current value. Secondly, the clamp multimeter can measure high voltage, thanks to its separate design, which isolates the battery from the digital circuit, can withstand higher voltages and output accurate results. In addition, the clamp multimeter can also detect whether the circuit wiring is correct, and can detect the polarity of AC and DC, as well as the coil direction and connection method of AC and DC wires. There are numerous methods for measuring voltage and resistance using it as well.

High test resolution, test accuracy, and additional test features are required of this crucial test tool in everyday maintenance work. Its measurement principle is mainly based on the principle of current transformer (CT). By measuring the current in the measured circuit, the current size is indicated. This design makes the clamp multimeter convenient and accurate when measuring current.

The steps for use are as follows:

Check the power: First, make sure that the battery of the clamp multimeter is sufficient. Insufficient power may affect the measurement accuracy.

Mode selection: Select the required measurement mode through the function switch, such as "AC current", "DC current", "voltage", "resistance", etc.

Range setting: Select the appropriate range according to the estimated value to be measured, and try to make the reading fall in the middle area of the instrument scale to obtain higher accuracy. If you are not sure about the size of the value to be measured, you can first select the maximum range and then gradually reduce it.

Open the jaws: Open the jaws of the clamp current sensor to the maximum extent to ensure that the wire to be measured can pass through completely.

Surround the wire to be measured: Without cutting off the circuit, place the wire to be measured completely inside the jaws and close the jaws to ensure that the wire is evenly surrounded to obtain accurate readings.

Reading data: Observe the value on the display. Note that the unit is usually ampere (A) or other current units.

Voltage measurement: Connect the red and black test probes of the multimeter to the two ends of the circuit to be tested, following the principle of "red positive and black negative".

Resistance measurement: Turn off the power supply, connect the probes to the two ends of the resistor in the specified way, and ensure that no current flows through the circuit.

Different models of clamp multimeters may have additional functional measurement options, such as capacitance, frequency, etc. Refer to the manual to set them correctly before measuring.

Avoid touching live parts during measurement to prevent electric shock.

Do not enter the current clamp range when measuring high-voltage and high-current equipment to prevent excessive current from damaging the instrument.

For AC and DC current measurements, make sure to select the correct measurement mode to avoid misjudgment.


In actual work, clamp multimeters can be used for current detection of electrical equipment such as air conditioners, refrigerators, motors, or for distribution boxes, cable line maintenance and other occasions. When encountering abnormal readings, first check whether the wiring is correct, whether the range selection is appropriate, and whether there are factors such as electromagnetic interference.

After each use, be sure to reset and turn off the clamp multimeter, store it in a dry and ventilated place, check and replace the battery regularly, and avoid dropping or strong vibration. In addition, keep the inside of the jaws clean to prevent foreign matter from affecting the measurement accuracy.

In summary, as an essential tool for electricians' daily work, it is very important to master the correct use of the clamp multimeter. By reasonably selecting the range, correctly placing the wire to be tested, and complying with safe operating procedures, users can not only accurately complete the measurement tasks of various electrical parameters, but also ensure the safety and reliability of the working process.