Clamp ammeter commonly used by electricians, referred to as clamp meter, is an instrument used to measure the current of a running electrical circuit. Current can be measured without interruption. The structure and principle of the meter: the clamp meter is essentially composed of a current transformer, a clamp wrench and a rectifying magnetoelectric system with a reaction force meter. Therefore, the clamp meter is actually a combination of a current transformer and an ammeter. Its closed iron core is opened, and the measured current-carrying wire is clamped into the iron core. This wire is equivalent to the primary winding of a current transformer with 1 turns. The iron core is wound with a secondary winding and connected to the measuring instrument, which can directly read the value of the measured current. There is no need to disconnect the circuit when measuring the current with the clamp meter, which is very convenient to use.
Instructions:
1. Before use, you should read the manual carefully to find out whether it is AC or AC and DC, and perform mechanical zero adjustment.
2. Select the appropriate range, first select the large range, then select the small range or look at the nameplate value for estimation, the voltage of the circuit under test cannot exceed the value indicated on the clamp meter, otherwise it is easy to cause a grounding accident. Or cause an electric shock hazard.
3. Only the current of one-phase wire can be measured at a time, the wire under test should be placed in the center of the clamp window, and multi-phase wires cannot be clamped in the window for measurement.
4. Before measuring the clamp meter, you should first estimate the magnitude of the measured current, and then decide which range to use. If it is impossible to estimate, you can use the maximum range block first and then change it to a smaller one for accurate reading. Do not use small currents to block large currents to prevent damage to the meter.
5. The jaws should be closed tightly during measurement, if there is any noise after closing. The jaws can be opened to overlap once. If the noise still cannot be eliminated, check whether the joint surfaces of the magnetic circuit are smooth and clean, and wipe it clean when there is dust.
6. Due to the low precision of the clamp ammeter itself, when measuring small currents. The following method can be used: firstly wind the wire of the circuit under test several times, and then put it into the jaw of the clamp meter for measurement. At this time, the current value indicated by the clamp meter is not the actual value being measured. The actual current should be the reading of the clamp meter divided by the number of turns of the wire. That is: reading = indicated value × range / full deviation × number of turns.
7. After the measurement, put the change-over switch at the leftmost range.
8. Do not operate with power on during maintenance. To prevent electric shock.
Because the secondary winding of the clamp meter cannot be opened. Otherwise, it may cause serious heating of the iron core, and may even damage the equipment and endanger the safety of the measuring personnel. So pay special attention when using it. In addition, it should also be noted that the voltage of the line under test should be lower than the rated voltage of the clamp meter; when measuring the current of the high-voltage line, you should wear insulating gloves and shoes, and stand on the insulating pad; Change the range with power.
