In daily work, for most engineers, multimeters are selected to measure electrical signals such as voltage, small current, and resistance, and when large currents need to be tested, clamp ammeters are generally preferred. Clamp meters are as important as multimeters in the minds of engineers.
Clamp ammeter principle
The clamp meter is divided into a single AC clamp meter and an AC and DC clamp meter, 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 turns 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 to the electric signal. converted to 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, and measure and amplify the DC signal by relying on the Hall element.
Test high current: current clamp + multimeter
As we all know, the multimeter can only measure a small current (usually within 10A, 20A can last for several seconds), and it is necessary to disconnect the line under test, and then connect the multimeter in series to the loop. There is no clamp meter to measure the current. It is convenient and efficient. Many industrial sites use the combination of current clamp + multimeter to test high current, which maximizes the value of the multimeter.
When a single AC clamp meter, an AC and DC clamp meter and a multimeter are used in combination, the operation is different
Precautions for the combined use of a single AC clamp meter and a multimeter: Since the output signal of a single AC clamp meter is generally a signal conversion between mA→A, it is necessary to set the multimeter gear to the mA gear.
Precautions for the combined use of AC and DC clamp meter + multimeter: The output signal of the AC and DC clamp meter is generally a signal conversion between mV→A, so it is necessary to set the multimeter gear position to the mV gear
