The clamp ammeter and current clamp test principle
In daily work, for most engineers, a multimeter is selected for testing electrical signals such as voltage, small current, and resistance. When it is necessary to test large currents, they generally tend to use clamp ammeters. Clamp meters are as important a tool as multimeters in the minds of engineers.
Clamp Meter Principle
Clamp meters are divided into single AC clamp meters and AC and DC clamp meters, and the principles of the two are different.
Single AC clamp meter: The clamp head adopts an electromagnetic current transformer. Through a coil with a certain turn ratio, the alternating current can generate electromagnetic induction in the clamp head coil to obtain a current proportional to the alternating current, and then convert the electrical signal converted into a digital signal.
AC and DC clamp meter: the clamp head adopts Hall active current clamp. Active components can not only sense the electromagnetic field of alternating current, but also convert the magnetic field signal into an electrical signal, output a voltage signal proportional to the measured current, rely on the Hall element to measure and amplify, and then test the DC signal.
Test large current: current clamp + multimeter
As we all know, the multimeter can only measure a small current (generally within 10A, 20A can last for several seconds), and the line to be tested needs to be disconnected, and then the multimeter is connected in series to the circuit. There is no clamp meter to measure current conveniently and efficiently. Many industrial sites use the combination of current clamp + multimeter to test large currents, which maximizes the value of the multimeter.
Operation is different when single AC clamp meter, AC/DC clamp meter and multimeter are used in combination
Precautions for combined use of single AC clamp meter + multimeter: because the output signal of single AC clamp meter is generally a signal conversion between mA→A, it is necessary to set the multimeter to the mA range.
Precautions for the combined use of AC-DC clamp meter + multimeter: the output signal of the AC-DC clamp meter is generally a signal conversion between mV→A, so it is necessary to set the gear position of the multimeter to the mV gear.
