How to use a clamp ammeter to measure AC current
1. Purpose: It can measure the AC current on low-voltage lines without interrupting load operation.
2. Selection: Its accuracy and maximum range should meet the testing needs.
3. Pre use inspection:
(1) Visual inspection: All parts should be intact and undamaged; The grip operation should be flexible; The clamp iron core should be rust free and tightly closed; The iron core insulation sheath should be intact; The pointer should be able to swing freely; Gear changes should be flexible and have clear hand sensing;
(2) Adjustment: Place the table flat, with the pointer pointing to the zero position. Otherwise, adjust to the zero position.
measure
1. Choose the appropriate gear. The principle of gear selection is:
(1) When the range of the measured current is known: choose the gear that is greater than the measured value but closest to it.
(2) When the range of the measured current is unknown, it is recommended to first place it at the highest current level for testing (or estimate its safe current carrying capacity based on the wire cross-section and select an appropriate gear), and decide whether to downshift the measurement based on the testing results. In short, the deflection angle of the watch needle should be maximized.
2. The tester should wear gloves, flatten the meter, open the jaws, and allow the tested wire to enter the jaws before closing the jaws.
3. Reading: According to the gear used, take a reading on the corresponding scale line. (Note! The gear value is the full offset value).
4. If the deviation angle of the pointer is still very small when measured at the lowest gear (the deviation angle of the pointer is small, which means that the relative error of its measurement is large), it is allowed to wrap the wire several turns around the clamp iron core, close the clamp, and take a reading. At this point, the current value on the wire is equal to the reading divided by the number of turns (calculation of turns: how many wires are inside the clamp, even if it is a few turns).
Safety issues to be noted in measurement
1. Before measurement, thoroughly check the table and select the correct gear.
2. Gloves (insulated gloves or clean and dry wire gloves) should be worn during testing, and supervision should be provided if necessary.
When shifting gears for measurement, the wire should be removed from the jaws first, and then clamped in for measurement after shifting gears.
4. The current on the bare conductor cannot be measured.
5. When measuring, pay attention to maintaining a safe distance from nearby charged objects. And attention should be paid 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 meter cover, it should be placed in the cover and stored in a dry, dust-free, non corrosive gas, and vibration free place.
Current knowledge
1. The neutral current in the star connection circuit is equal to the phase current.
2. The neutral current of the triangular connection method is equal to the phase current.
3. Calculate the rated current based on the power P of the device; Three phase motor 1KW ≈ 2A, single-phase power consumption 1KW ≈ 4.5A
