How to measure DC current with a multimeter, four steps to remember
1. Mechanical zero adjustment
The multimeter can measure resistance as well as voltage. The multimeter must be mechanically zeroed before use.
The mechanical zero adjustment method is the same as the mechanical zero adjustment operation for measuring resistance and voltage. Generally speaking, if the multimeter is a frequently used multimeter, it is not necessary to perform mechanical zero adjustment every time.
Mechanical zero adjustment method: Separate the two test leads and use a flat-blade screwdriver of appropriate size to adjust the mechanical zero adjustment screw located in the middle of the dial until the pointer coincides with the zero scale line.
2. Select the measuring range
Estimate the size of the measured DC current based on the current of the power supply in the circuit to be measured, and select the range.
If you don't know the size of the current, first use the highest current level (500mA level) to measure, and gradually switch to the lower current level until you find the appropriate current level (the standard is the same as the measured voltage).
3. Measurement method
When using a multimeter current block to measure current, the multimeter should be connected in series in the circuit under test, because only a series connection can make the current flowing through the ammeter the same as the current in the branch being measured.
When measuring, the branch circuit under test should be disconnected, and the red and black test leads of the multimeter should be connected in series between the two disconnected points.
Note that the ammeter cannot be connected in parallel in the circuit under test. Doing so is very dangerous and can easily cause the multimeter to burn out. At the same time, pay attention to the polarity of the red and black meter rods. The red meter rod should be connected to the current inflow end of the circuit under test, and the black meter rod should be connected to the current outflow end of the circuit under test (same as the polarity selection of DC voltage).
4. Scale and reading
Correct use of scales and counting: When measuring DC current with a multimeter, select the dial scale line the same as when measuring voltage, which is the second line (there is the mA symbol on the right side of the second scale line). Other scale features and reading methods are the same as measuring voltage.
If the measured current is greater than 500mA, the 5A level can be selected.
Operation method: Set the transfer switch to the 500mA range, take out the red meter rod from the original "+" jack, and insert it into the jack marked 5A in the lower right corner of the multimeter to measure large currents below 5A.
