Illustration of the operation method of measuring DC current with a pointer multimeter

The pointer type is a multi-functional, multi-range measuring instrument. It is very common in life and industry. A few days ago we talked about the basic knowledge of using an analog multimeter to test DC voltage. Today we will introduce how to use an analog multimeter to test DC current.

When you usually use a multimeter to judge old dry batteries, in addition to measuring the voltage of the battery, you also need to measure the short-circuit current. The operation method is shown in Figure 1-13. Set the range switch of the multimeter to the maximum DC current range of the multimeter, such as 500ma or 1000ma, etc., which varies depending on the model of the multimeter. Use the red test lead to connect the positive electrode of the battery under test, and the black test lead to the negative electrode. The indicated current value is read at the moment when the test pen contacts the battery. For a battery that can provide normal power supply, its short-circuit current should be greater than 200ma. Otherwise, the battery under test is considered to be basically exhausted.

When measuring the short-circuit current of the battery, the time should be as short as possible. This not only helps protect the multimeter, but also reduces battery power consumption and prolongs the service life of the battery.

The following two points should be noted when using the DC current block for measurement.

(1) If you do not know the size of the current to be measured, you should select the largest current range for testing. After measuring the approximate range, select the appropriate range. If you do not know the direction of the current being measured, you can also use a test method to determine it. First, connect a test lead to one end of the circuit under test (either red or black pen can be used), and use another test lead to quickly touch the other end of the circuit under test. If the multimeter pointer does not hit back, it means the red or black The test leads are connected correctly. If the pointer appears to reverse, swap the red and black test leads and connect them to the terminal being measured. When testing the direction of the current, you should use the largest range and touch it for a very short time, otherwise the multimeter may be damaged.

(2) If the measured current is large and exceeds the range of the current block, you can insert the red test lead into the jack marked with a larger current (different models of meters have different sizes, such as 1.5, 5a, etc.). And set the range switch to the corresponding gear. For example, the mf47 multimeter is equipped with a 5a jack. When using it, set the range switch to the 500ma DC current m range, insert the red test lead into the 5a dedicated jack, and insert the black test lead into the negative jack.

The pointer multimeter is a relatively precise instrument. If used improperly, it will not only cause inaccurate DC current measurement but also be easily damaged. However, as long as we master the usage and precautions of the analog multimeter and work with caution, the analog multimeter will be durable and the measurement method will be easy to master.