The structure, principle, and working principle of clamp watches
The working principle of a clamp watch is the same as that of a transformer. The primary coil is a wire that passes through a clamp type iron core, which is equivalent to the primary coil of a 1-turn transformer. This is a step-up transformer. The secondary coil and the ammeter used for measurement form the secondary circuit. When there is AC current passing through the wire, it is the alternating magnetic field generated by this coil, which induces current in the secondary circuit. The magnitude of the current is proportional to the proportion of the primary current, which is equivalent to the inverse ratio of the number of turns in the primary and secondary coils. A clamp type ammeter is used to measure large currents. If the current is not large enough, the number of turns of a wire passing through the clamp type ammeter can be increased, and the measured current can be divided by the number of turns.
The secondary winding of the through core current transformer of the clamp ammeter is wound around the iron core and connected to the AC ammeter. Its primary winding is the measured wire passing through the center of the transformer. The knob is actually a range selection switch, and the function of the wrench is to open and close the movable part of the core of the through core transformer, so as to clamp it onto the measured wire.
When measuring the current, press the wrench, open the pliers, and place the measured current carrying wire in the middle of the through type current transformer. When there is alternating current passing through the measured wire, the magnetic flux of the alternating current induces a current in the secondary winding of the transformer. This current passes through the coil of the electromagnetic ammeter, causing the pointer to deflect and indicating the measured current value on the dial scale.
The usage method is as follows:
1. Before use, carefully read the instruction manual to determine whether it is for AC or AC/DC dual use;
2. The voltage of the tested circuit should not exceed the value indicated on the clamp meter, otherwise it may cause grounding accidents or electric shock hazards;
3. Only one phase of the current can be measured at a time, and the measured wire should be placed in the center of the clamp window. It is not allowed to clamp all multiphase wires into the window for measurement;
4. Before measuring with a clamp meter, the magnitude of the measured current should be estimated before deciding which range to use. If it is impossible to estimate, you can first use the maximum range range range and then adjust it appropriately to obtain an accurate reading. Do not use low current range to measure high current to prevent damage to the instrument;
5. When measuring, the jaws should be tightly closed. If there is any noise after closing, the jaws can be opened and reset once. If the noise cannot be eliminated, the joint surfaces on the magnetic circuit should be checked for smoothness. If there is dust, it should be wiped clean;
6. Due to the low accuracy of the clamp ammeter itself, the following method can be used to measure small currents: first, wrap the wires of the tested circuit a few times, and then place them into the clamp of the clamp ammeter for measurement. At this point, 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 the wire is wound;
7. Do not operate with electricity during maintenance to prevent electric shock.
