Ammeter is used to measure current. It can measure the amount of current flowing in the circuit. It can use one of several different basic meter movements to achieve this. The most frequently used of the main meter movements darsonval type. Cm. Fig. 1-40. He uses permanent magnets and electromagnets for fault detection. A permanent magnet is used as a standard primary source of magnetism. As the current flows through the coil of wire, it creates a magnetic field around it. This magnetic field is strong or weak, depending on the amount of current flowing through it. The stronger the magnetic field generated by the moving coil, the more he shrank back from the permanent magnet. This reflection movement is calibrated to read current, mA (0.001), or MCA (0.000001).
Darsonval meter movement can also be used on the AC when the diode is placed in series with the moving coil winding. Diode changes AC / DC, and the device works as a constant current. Cm. Fig. 1-41. Dial or face the instrument is calibrated to indicate AC indications.
There are other types of ammeters AC.
They are not always accurate, darsonval, but they are effective. In some moving magnet meters, stationary coil and magnet moves. Although durable, this type is not as accurate as the d'arsonval type of meter.
Moving vane meter of useful measure AC power when in use. Cm. Fig. 1-42. Clamp-on ammeter already discussed. It has some limitations. However, he does have one advantage is that it can be used without the need ammeter must be connected in series with the loads. This means that the line should be broken or disconnected to insert the device in the chain.
Ampere reading can be used to determine if the device is drawing too much current or insufficient power. The correct current amount is usually printed on the nameplate of the motor. compressor. Opening and maintenance of amps can be checked when the engine is running when the load is too large or contact closure. Consumption of some pumps can be determined by reading the motor moves. The load on the entire line can be tested by inserting the ammeter in line. This is done by obtaining a fuse and a closed circuit with a meter. Be careful.
If the ammeter has more than one range, it is best to start at the highest ridge and work down. Reading must be within or near the center of the meter scale for more accurate readings. Make sure that you have some idea that the current in the circuit must be before the installation of the counter. Thus, the correct rangeor, in some cases, the correct metercan be selected.