How To Use the Ammeter in Detail?

Ammeter is also known as ammeter, its main purpose is to measure current, there are many types of ammeters, such as rotating coil ammeter, thermocouple ammeter and rotating iron ammeter and so on. So, do you know how to use an ammeter?

What is an ammeter

An ammeter is an instrument used to measure the current in AC and DC circuits. In the circuit diagram, the symbol of the ammeter is "circle A". Current values are in "amps" or "A" as standard units.

Ammeter classification

1. DC ammeter: mainly use magnetoelectric system or electric system measurement mechanism (see mechanical indicating meter measurement mechanism). The basic measurement of these measurement mechanisms is current, which can be used to directly measure small currents.

2. AC ammeter: It can use an electromagnetic system or electric system measuring mechanism. In order to make the magnetoelectric system measuring mechanism also used to measure the alternating current, the alternating current can be converted into direct current by using devices such as rectifiers or thermocouples. The electric meters composed of them are called rectifier ammeters (see rectifier ammeter) and thermoelectric ammeters respectively. In order to expand the range to measure large currents, rectifier ammeters also use shunts. The practice of electric ammeter is the same as before. The electromagnetic ammeter is to thicken the coil wire and reduces the number of turns. For larger measured current values, it needs to be used with current transformers.

How to use the ammeter:

1. Connect the meter: The ammeter must be connected in series in the circuit to be tested so that the current flows in from the "+" terminal of the ammeter and flows out from the "-" terminal. When using an ammeter, its two terminals must not be directly connected to the two poles of the power supply, otherwise, the ammeter will be burned out due to excessive current.

2. Select the range of the meter: the ammeter has three binding posts, as shown in the figure above, if the ammeter is connected to the two binding posts "+" and "0.6", its range is 0.6A, and the group of values below the dial is read. If it is connected to the two terminals "+" and "3", its range is 3A, and the above group of values on the dial is read. Before the experiment, if you do not know how to connect, you can first estimate the current value in the circuit. If the estimated current is less than 0.6A, the range should be selected. If the estimated current is greater than 0.6A but less than 3A, the range should be selected. If it cannot be estimated, it can be carried out by means of trial touch. Fix one terminal and quickly touch the terminal with the maximum range with the other wire end of the circuit. Then select the appropriate range according to the deflection angle of the ammeter pointer.

3. Trial circuit: After the physical diagram is connected according to the circuit diagram, a trial connection must be carried out. When trying to connect, carefully observe the deflection of the ammeter pointer. If the pointer does not deflect, it means that the circuit is broken somewhere. If the pointer is deflected in the opposite direction, it means that the positive and negative terminals of the watch are reversed. If the deflection angle of the pointer is too large, it means that the range selection is too small. If the deflection angle of the pointer is too small, the range is too large. Then, according to the situation observed during the test connection, make corresponding adjustments and then carry out the relevant experiments.

How to maintain the ammeter

1. Since the overload capacity of the magnetoelectric ammeter is very small, it is necessary to pay attention to the selection of the polarity and quantity limit of the connecting circuit when using it.

2. If the reverse deflection or forward deflection of the pointer is found to exceed the full-scale line on the scale during the measurement, the power should be cut off immediately to stop the measurement, and the measurement should be carried out after the correct connection or by re-selecting a larger current meter.

3. When the measurement work is completed, the power supply should be cut off first. Then remove the ammeter from the measuring circuit and place it in a dry, ventilated, and cool environment for microammeters and room-mounted meters with high sensitivity and accuracy. Use wires to connect the positive and negative terminal buttons to protect the measuring mechanism of the instrument.