How to Measure AC Current with a Clamp Meter
Application, selection and pre-use inspection of clamp ammeter
1. Purpose: It can measure the AC current on the low-voltage line without interrupting the load operation.
2. Selection: Its accuracy and maximum range should meet the needs of the test.
3. Check before use:
(1) Appearance inspection: all parts should be intact; the operation of the pliers should be flexible; the iron core of the jaws should be rust-free and tightly closed; the core insulation sheath should be intact; the pointer should be able to swing freely; the gear shift should be flexible and hand-sensitive obvious;
(2) Adjustment: put the watch flat, the pointer should point to zero, otherwise adjust to zero.
Measurement
1. Select the appropriate gear. The principles of file selection are:
(1) When the measured current range is known: select the gear that is larger than the measured value but closest to it.
(2) When the current range to be tested is not known: it can be placed in the highest current level for testing (or according to the cross-section of the wire, and its safe current carrying capacity is estimated, and the appropriate level is selected), and it is determined whether it is necessary to downgrade the measurement according to the test situation. In short, the deflection angle of the watch hands should be as large as possible.
2. The tester should wear gloves, put the meter on the flat end, open the jaws, let the wire under test enter the jaws and then close the jaws.
3. Reading: According to the gear used, read the reading on the corresponding scale line. (Note! The gear value is the full bias value).
4. If the measurement is at the lowest gear, the deflection angle of the hands is still very small (the small deflection angle of the hands means that the relative error of its measurement is large), it is allowed to wind the wire on the jaw core for several turns, after closing the jaws Take the reading. At this time, the current value on the wire = reading ÷ the number of turns (calculation of the number of turns: how many wires are inside the jaw, count as a few turns).
Safety issues that should be paid attention to in measurement
1. Fully check the watch before measuring, and select the gear correctly.
2. Gloves (insulated gloves or clean and dry wire gloves) should be worn during the test, and a monitor should be installed if necessary.
3. When changing gears for measurement, the wire should be withdrawn from the jaws first, and then clamped into the wire for measurement after shifting gears.
4. Can not measure the current on the bare conductor.
5. When measuring, pay attention to keep a safe distance from nearby charged objects. And care should be taken not to cause phase-to-phase short circuits and phase-to-ground short circuits.
6. After use, the gear should be set to the highest current level. If there is a watch cover, put it into the watch cover, and store it in a dry, dust-free, corrosive gas-free place and without vibration.
Current knowledge
1. The neutral current of the star connection circuit is equal to the phase current.
2. The current in the neutral line of the delta connection method is equal to the double phase current.
3. Calculate the rated current according to the power P of the equipment; Three-phase motor 1KW≈2A Single-phase power consumption 1KW≈4.5A
How to Measure AC Current Using a Clamp Meter
Schematic diagram of clamp ammeter operation
(A) The tester should wear gloves, hold the meter flat and open the jaws.
(B) Make the wire under test enter the jaws and then close the jaws.
(C) Clamp two wires at the same time, then the indicated current value should be the current of the third wire.
(D) If in a three-phase four-wire system, three phase wires are simultaneously clamped for measurement, the indicated current value should be the current value on the working zero line.
(E) If the current on the wire is too small, the deflection angle of the needle is still very small even if it is placed in the minimum current gear for measurement (so the reading is inaccurate), you can coil the wire on the clamp arm for several turns (four turns as shown in the figure) ) After measurement, divide the reading by the number of turns, which is the measured voltage of the wire under test.
