How to measure DC and AC currents with a multimeter
1、 How to Measure DC Current with a Digital Multimeter
When using a digital multimeter to measure DC current, the red lead is a positive lead, insert it into the "mA" or "A" socket, the black lead is a negative lead, insert it into the "COM" socket, rotate the measurement selection switch to the "DC A" position, and input it into the circuit under test to measure.
When measuring DC current below 200mA, the red lead should be inserted into the "mA" socket. When measuring DC current of 200mA and above, the red lead should be inserted into the "A" socket.
For example, to measure the working current of a DC relay K, first disconnect the current circuit of relay K as shown in the figure below, and then connect the positive lead to the battery positive pole and the negative lead to the relay. As shown in the figure below, the number displayed on the LCD is the working current of the tested relay.
If the positive and negative probes are reversed during the measurement of DC current using a digital multimeter, the measurement result will display as a negative value. When measuring DC current with a digital multimeter, it is not necessary to consider the direction of the current, which is particularly convenient when the direction of the current is not clear. At the same time, the direction and magnitude of the current are measured.
2、 Measuring DC Current with a Pointer Multimeter
When measuring DC current, the pointer multimeter should be connected in series to the tested circuit, as shown in the following figure. It can be connected between the positive pole of the power supply and the tested circuit, or between the tested circuit and the negative pole of the power supply.
When measuring DC currents of 500mA and below, the measurement selection switch should be selected as mA. When measuring DC currents of 0.5~5A, the "500mA" position should be selected and the positive probe should be inserted into the "5A" dedicated socket.
When measuring current, the reading method of a pointer multimeter is: the full scale value (to the far right of the scale line) is equal to the selected range gear, and the measurement result is converted based on the position indicated by the needle.
3、 Using a digital multimeter to measure AC current
Measuring AC current with a digital multimeter is similar to measuring DC current. Turn the measurement switch to the desired "AC" position, and connect the digital multimeter in series with the circuit being tested.
When measuring DC current below 200mA, the red lead should be inserted into the "mA" socket. When measuring DC current of 200mA and above, the red lead should be inserted into the "A" socket.
4、 Measuring AC Current with a Pointer Multimeter
A pointer type multimeter with AC current range must be used to directly measure AC current. Measuring DC current is similar, and the multimeter can be connected in series to the circuit being tested.
