Ammeter use precautions

Note the following when using an ammeter:

1) When connecting the ammeter, the "+" and "-" terminals must be connected correctly. The current must flow from the "+" terminal into the ammeter and out of the "-" terminal.

2) Since the ammeter is connected in series in the circuit, the resistance of the circuit is increased by the internal resistance, and the measured value is smaller than the true value. In order to make the measured value close to the true value, an ammeter with a small internal resistance should generally be used for measurement.

3) The measured current should not exceed the range of the ammeter. Otherwise, the current value cannot be measured, and the pointer of the ammeter will be bent and even burn the ammeter.

4) It is forbidden to connect the ammeter directly to the two poles of the power supply or to touch between the two poles. Since the external magnetic field can affect the deflection angle of the pointer, the influence of the external magnetic field should be avoided as much as possible to prevent the measurement from being accurate.

5) If the current to be measured cannot be estimated in advance, first take a line of the circuit and quickly touch the wiring of the ammeter to see if the deflection of the pointer is within the range. If the range is exceeded, use a larger range of ammeter. . In addition, the current meter can be connected in series with a variable resistor to connect to the circuit under test, and the variable resistor has a maximum value for the resistor and the maximum range for the ammeter. After the circuit is turned on, the resistance of the variable resistor is gradually reduced or even reduced to Zero to determine the range to be used.

6) For the DC ammeter, the scale is not uniform and the accuracy is low. It is necessary to measure the average value as the measured value.

7) After the ammeter is used, it should be stored in a clean and dry place to prevent moisture, prevent corrosive gas from eroding, prevent severe vibration and impact, and avoid the influence of strong magnetic field.