How to measure current with a multimeter
Select range: The multimeter's DC current range is marked with "mA" and has three ranges: 1mA, 10mA, and 100mA. The selection of the range should be based on the current in the circuit.
1. Select the range: The DC current range of the multimeter is marked with "mA" and has three ranges of 1mA, 10mA and 100mA. The selection of the range should be based on the current in the circuit. If the current size is unknown, the maximum range should be selected.
2. Measurement method: The multimeter should be connected in series with the circuit under test. After the corresponding part of the circuit should be disconnected, connect the multimeter test leads to both ends of the breakpoint. The red test lead should be connected to the breakpoint connected to the positive pole of the power supply, and the black test lead should be connected to the breakpoint connected to the negative pole of the power supply.
1) Connect the circuit to make the LED light normally.
2) Prepare the multimeter according to the requirements before use and set the selector switch to the mA range of 100mA.
3) Disconnect the lead between the middle point of the potentiometer and the negative terminal of the light-emitting diode to form a "breakpoint". At this time, the light-emitting diode goes out.
4) Connect the multimeter in series at the breakpoint. The red test lead is connected to the negative electrode of the light-emitting diode, and the black test lead is connected to the middle point lead of the potentiometer. At this time, the light-emitting diodes light up again. The scale value pointed by the pointer of the multimeter is the current value passing through the light-emitting diode.
5) Correctly read the current value through the LED.
Record: The current through the LED is xx mA.
6) Rotate the potentiometer handle to observe the change of the pointer of the multimeter and the change of the brightness of the light-emitting diode. It can be seen that: Record: The maximum current passing through the light-emitting diode is xx mA. The minimum current is xx mA.
Through the above operations, we can further understand the role of resistors in circuits.
7) After the measurement is completed, disconnect the power supply and store the multimeter as required.
