The clamp meter is a combination of a current transformer and an ammeter in one instrument, it is an important branch of the digital multimeter, its working principle and the current measurement by the current transformer are the same. The clamp meter is a combination of a current transformer and an ammeter. The core of the current transformer can be opened when the key is pinched; the wire through which the current is measured can be passed through the open space in the core without having to be cut, and the core is closed when the key is released. The wire of the measured circuit will pass through the core of the primary coil of the current transformer, which, through the current, will be induced into the current of the secondary coil. So the secondary coil connected to the ammeter will have instructions, to measure the current of the tested line. The clamp meter is originally used to measure AC current, but today the multimeter also has this function, it can measure AC and DC voltage, current, capacitance, diode, transistor, resistance, temperature, frequency, etc. Functions range accuracy DC voltage: 600V 1.0% AC voltage: 450V 1.2% AC current: 20-400A 2.0% Resistance: 200K 1.0% Special features 3 1/2 LCD display, maximum reading 1999 Low battery indicator Overload protection Data hold for easier reading Buzzer on/off and diode test function Product features Battery: 2 x No.7 (AAA) batteries (not included) Jaw diameter: 21.3mm Body color: yellow Body size: 150 x 60 x 28mm Note: The data are all measured manually, please allow 1-3cm error due to differences in light and display, there may be some color differences, please refer to the actual item received.