How to judge the quality of an ammeter
To judge the quality of an ammeter, the first thing to know is the working principle of an ammeter: an ammeter is made based on the magnetic field force acting on a conductor in a magnetic field. There is a permanent magnet inside the ammeter that generates a magnetic field between the poles. In the magnetic field, there is a coil with a wire spring at each end of the coil, which is connected to a terminal of the ammeter. The spring is connected to the coil by a shaft, and there is a pointer relative to the front end of the ammeter on the shaft. When there is current passing through, the current passes through the magnetic field along the spring and shaft, and the current cuts the magnetic induction line. Therefore, under the action of the magnetic field force, the coil deflects, driving the shaft and pointer to deflect. As the magnitude of magnetic field force increases with the increase of current, the magnitude of current can be observed by the degree of pointer deflection.
There are several methods to judge the quality of an ammeter:
1. Use a multimeter to measure whether the two terminals of the ammeter are open in the low resistance range. If there is an open circuit, it can be judged as faulty.
2. If there is a large error in the display of the ammeter wire, a multimeter can be used to connect the probe in series with the ammeter to measure the current deviation. This method is suitable for measuring in situations where the current is not too high.
3. The moving coil of the ammeter is broken, and even if the moving coil is broken, the meter needle will not move.
4. If the coil is not open, check whether the meter needle is blocked by foreign objects.
In addition to the above methods, some misjudgment factors should also be eliminated:
1. The range selection of the ammeter is inappropriate, as the range is too large and the current is relatively small.
2. Improper selection of ammeter, use a DC ammeter to measure AC current.
