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questions :What A hot wire ammeter measures
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[Visitor (111.8.*.*)]answers [Chinese ]Time :2020-02-08
The ammeter is made according to the effect of the magnetic field force on the conducting conductor in the magnetic field.
There is a permanent magnet inside the ammeter, which generates a magnetic field between the poles. There is a coil in the magnetic field. There is a coil spring at each end of the coil. Each spring is connected to a terminal of the ammeter. There is a pointer on the front of the ammeter.

When a current passes, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction line, so the force of the magnetic field causes the coil to deflect and drives the rotating shaft and pointer to deflect.

Because the magnitude of the magnetic field force increases with the increase of the current, the magnitude of the current can be observed by the degree of deflection of the pointer.
This is called a magnetoelectric ammeter, which is what we usually use in the laboratory.

AC ammeters can be used directly in small currents (generally below 5A), but the current electrical equipment in factories are relatively large, so they are mostly used with current transformers. Before selecting the ammeter, calculate the rated operating current of the device, then select the appropriate current transformer, and then select the ammeter. For example: the device is a 30KW motor with a rated current of about 60A, so we have to choose a 75 / 5A current transformer, then the ammeter must choose a current meter with a range of 0A-75A, 75 / 5A, so this is a large current The choice of equipment's ammeter!
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