AC Current Measurement Proper Use of Clamp Meters
1. Usage: It can measure the AC current on low-voltage lines without interrupting the load operation (continuously opening the current conductor). (For 50 Hz and below 500 V)
2. Selection: Its accuracy and maximum range should meet the needs of testing.
3. Inspection before use: (1) Appearance inspection: all parts should be intact; Clamp handle operation should be flexible; Jaw core should be free of rust and closed tightly; Core insulation sheath should be intact; The pointer should be able to swing freely; Gear shift should be flexible and feel obvious;
(2) Adjustment: put the watch flat, and the pointer should be at the zero position, otherwise, adjust it to the zero position.
measure
1. Select the appropriate gear. The principles of gear selection are as follows: (1) When the measured current range is known, the gear that is larger than the measured value but closest to it is selected.
(2) When the range of the measured current is unknown, it can be placed in the first trial measurement of the current (or according to the cross section of the conductor, and the current carrying capacity is estimated, and the gear is selected appropriately), and whether the downshift measurement is needed can be decided according to the trial measurement. In a word, the deflection angle of the watch hand should be as large as possible.
2. Testers should wear gloves, flatten the surface, open the jaws, and then close the jaws after the tested wires enter the jaws.
3. The measured wire should be located in the center of the space in the jaw, and the jaw should be tightly closed;
4. After measuring the high current, before measuring the low current, the jaws should be opened and closed several times for demagnetization;
5. If the deflection angle of the watch hand is still small when measuring small current at the lowest gear (small deflection angle of the watch hand means large relative error in measurement), it is allowed to wind the wire around the jaw core for several turns and read the reading after closing the jaw. At this time, the current value on the wire = reading turns (calculation of turns: there are several wires inside the jaw, even if it is a few turns);
6. Reading: According to the gear used, read the reading on the corresponding scale line. (attention! The gear value is the full offset value);
7. After use, the gear position should be in the current gear position.
* * problems that should be paid attention to in measurement
1. Make a full inspection of the meter before measurement, and select files correctly;
2. Gloves (insulating gloves or clean and dry thread gloves) should be worn during the test, and guardianship should be set up when necessary;
3. When shifting measurement is needed, the wire should be withdrawn from the jaw first, and then clamped in after shifting;
4. Do not measure the current on the bare conductor;
5. When measuring, pay attention to keep a safe distance from the nearby charged body (not less than 0.1m), and pay attention not to cause interphase short circuit and relative short circuit to prevent personal electric shock;
6. It is not allowed to measure on the moving contact and safety tube of the switch;
7. After use, the gear should be set to zero current. If there is a meter sleeve, put it into the meter sleeve and store it in a dry, dust-free, corrosive gas-free and vibration-free place.
