Using a clamp ammeter properly to measure AC current
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 (without disconnecting the current-carrying wire). (for 50HZ below 500V)
2. Selection: Its accuracy and maximum range should meet the needs of the test.
3. Inspection 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 free of rust, and the closure should be tight; The transformation should be flexible and the hand feeling should be obvious;
(2) Adjustment: put the watch flat, the pointer should point to zero, otherwise adjust to zero.
Measurement
1. Select the appropriate gear. The principle of file selection is: (1) When the measured current range is known: choose the file 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 current test first (or according to the cross-section of the wire, and estimate its ampacity, and select a suitable gear), and then decide whether 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. The wire to be tested should be located in the center of the space inside the jaws, and the jaws should be tightly closed;
4. After measuring a large current, before measuring a small current, the jaws should be opened and closed several times for demagnetization;
5. If the deflection angle of the needle is still small when measuring at the lowest gear when measuring a small current (a small deflection angle of the needle means that the relative error of its measurement is large), it is allowed to wind the wire on the jaw core for a few Turn, take the reading after closing the jaws. 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);
6. Reading: According to the gear used, read the reading on the corresponding scale line. (Note! The gear value is the full bias value);
7. After use, the gear should be set to the current gear.
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 it is necessary to change gears for measurement, the wire should be withdrawn from the jaws first, and then clamped into the wire for measurement after shifting gears;
4. Do not measure the current on the bare conductor;
5. When measuring, pay attention to keep a safe distance from nearby charged objects (not less than 0.1 meters, and be careful not to cause phase-to-phase short-circuit and phase-to-ground short-circuit to prevent personal electric shock;
6. It is not allowed to measure on the moving contact of the switch or on the fuse;
7. After use, the gear position should be at the beginning of the current zero, put it into the watch cover if there is one, and store it in a dry, dust-free, corrosive gas-free and vibration-free place.
