What is the principle of a clamp type watch
A clamp meter is essentially composed of a current transformer, a clamp wrench, and a rectifier magneto electric system reactive force instrument.
The working principle of a clamp type meter 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 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 alternating current induces current in the secondary winding of the transformer, which passes through the coil of the electromagnetic ammeter, causing the pointer to deflect and indicating the measured current value on the dial scale.a fuel cut-off phenomenon, it is caused by a short circuit in the circuit connection; If the working current I is less than 4.5A, it indicates that there is a resistance or poor connection in the circuit, or the fuel tank is too dirty, and impurities are blocked in the oil filter screen, causing the oil pump to not be able to suck oil and forming a no-load current; If the working current I is greater than 4.5A, it indicates that the fuel filter may have been blocked or partially blocked, causing an increase in fuel pump load. In this situation, it is very easy to misjudge the oil pump, and attention should be paid during the inspection.
The voltage drop testing method is rarely used
For maintenance technicians, it is common to use a multimeter to detect voltage to diagnose faults, but it is not common to diagnose faults based on voltage drops. Cleverly using voltage drop testing to diagnose faults can play an irreplaceable diagnostic role in many cases. Experimental results have shown that in all circuits, the maximum voltage loss is 3% of the power supply voltage. Therefore, in vehicles using a 12V power supply, the maximum voltage drop should be 0.36V. If the voltage drop in the circuit exceeds 0.4V, it can be considered as an abnormality in the circuit, that is, the presence of high resistance.
