How Does a DC Clamp Meter Work?

The Clamp

The DC clamp has a pair of jaws that are used to clamp on to a conductor of electricity. Clamping the jaws on to the conductor allows the electric current of a conductor to be measured. A button or jaw trigger is pressed to open the inductive clamp jaw.

The Indicator

The DC voltage or current is displayed on the DC clamp's indicator as a horizontal bar over a dotted horizontal line (or three smaller bars beneath the solid bar). On the handle is a rotary switch selector, which the operator turns to select the type of current or voltage to be tested. A zero button is pressed to cancel out readings, or refresh the LCD display screen (or digital indicator on older DC clamp meters).

Taking Accurate Readings for DC Voltage

The operator or technician sets the rotary switch on the handle of the clamp meter to the voltage symbol (indicated as a capital "V" on most clamp meter models). The test leads are plugged in to the jacks on the clamp meter, with the read lead in the V/O jack and the black lead in the COM jack. The ends of the test leads are touched to the circuit being tested. The reading for the voltage in the circuit shows up on the LCD screen or digital indicator of the clamp meter. The hold button is pressed by the operator to keep the reading on the screen (this is like a pause button). To remove the reading, the operator presses the hold button again.

Taking Accurate Readings for AC

The operator will disconnect all test leads from the terminal. In order to take the most accurate voltage or current meter readings on a DC clamp meter, the operator will place the conductive material within the guides or indicated markings on the inductive clamp jaws. The rotary switch is turned to the appropriate setting for units of measurement. The display screen is read to ensure the reading displays zero. If the reading does not display zero, then the operator or technician will press the zero button on the handle of the DC meter clamp. The conductor is placed in the inductive clamp jaw. A value for the current is indicated on the LCD display screen or digital indicator. The operator presses the hold key on the handle of the clamp meter to keep the value on the screen/ indicator. The reading is removed from the display screen or indicator by pressing the hold button one more time.