How to measure resistance with a clamp meter
Some clamp type ammeters have resistance testing function. If the clamp type ammeter in your hand has this function, you can follow the following steps to measure.
Wire resistance measurement:
① Turn the switch to the appropriate resistance range.
② Keep the switch in the released state.
③ Connect the red lead to the "Ω" end and the black lead to the "COM" end.
④ The red and black probes are connected to both ends of the tested wire. When measuring the resistance of the wire in use, the power should be disconnected first, and the capacitance connected to the wire should be fully discharged before measuring.
Wire on/off test
① Turn the switch to the 200 Ω (or buzzer) position.
② The red and black pens are connected to the "Ω" end and the "COM" end respectively.
③ If the resistance between the red and black probes is less than (50 ± 25) Ω, the built-in buzzer will emit a beep sound.
Five main uses of clamp ammeters
Purpose 1: Measure three-phase three-wire circuit current and three-phase four-wire zero line current
A clamp meter typically measures the current of a single wire. When measuring the three-phase three-wire load current, if two wires are clamped simultaneously, the indicated current value should be the current of the third wire.
The measurement method for three-phase four wire neutral line current is the same as measuring three-phase three wire circuit current, with the three-phase lines clamped simultaneously. The current value displayed at this time is the current value of the neutral wire.
Purpose 2: Clamp meter for measuring small currents
The clamp meter measures small current, and even if the gear is adjusted to the minimum gear, the reading is still not very accurate. Therefore, it is possible to wrap the wire around the clamping arm and read the current value. Then divide the current reading by the number of turns to obtain the actual small current value.
Purpose 3: Determine the name of the current in the circuit to determine whether the equipment is operating properly. It needs to be determined based on the current measured on site. Therefore, it is important to determine what current it is.
Purpose 4: Measure the no-load current of nameless motors and determine the rated power
Estimation formula: Divide the no-load current by zero eight to find the power close to the level.
The steps are as follows: Measure the no-load current value I of the motor, according to the empirical formula: p=I/0.8
Purpose 5: Measure the no-load current of a 380V welding machine without a nameplate, and determine the apparent power S
Estimation formula: The capacity of the 38th welding machine is equal to the no-load current I multiplied by 5.
