How to Use an Analog Multimeter (MM) to Test Direct Current (DC)
A pointer multimeter is a multifunctional and multi range measuring instrument. It is common in both daily life and industry. A few days ago, we talked about the basic knowledge of using a pointer multimeter to test DC voltage. Today, we will introduce how to use a pointer multimeter to test DC current.
When using a multimeter to judge old dry batteries, in addition to measuring the battery voltage, it is also necessary to measure the short-circuit current.
Set the range switch of the multimeter to the maximum DC current range of the multimeter, such as 500mA or 1000mA, depending on the model of the multimeter. Use the red probe to receive the positive terminal of the test battery and the black probe to receive its negative terminal. At the moment when the probe contacts the battery, the indicated current value is read. For batteries that can supply power normally, their short-circuit current should be greater than 200mA, otherwise it is considered that the tested battery has been basically depleted.
When measuring the short-circuit current of a battery, the time should be as short as possible. This not only helps protect the multimeter, but also reduces battery consumption and extends the battery's service life.
When measuring with DC current mode, the following two points should be noted.
(1) If the magnitude of the measured current is unknown, the maximum current range should be selected for testing. After measuring the approximate range, the appropriate range should be selected. If the direction of the measured current is unknown, the method of trial testing can also be used for discrimination. Firstly, connect one probe to one end of the tested circuit (both red and black probes are acceptable), and quickly touch the other end of the tested circuit with the other probe. If the multimeter pointer does not reverse at this time, it indicates that the red and black probes are connected correctly. If the pointer is reversed, simply swap the red and black probes to the tested end. When attempting to measure the direction of current again, the maximum range gear should be selected, and the touch time should be extremely short, otherwise it may damage the multimeter.
(2) If the measured current is large and exceeds the range of the current gear, the red probe can be inserted into the socket marked with the larger current (different models of meters have different sizes, such as 1.5, 5A, etc.), and the range switch can be placed in the corresponding gear. If the MF47 multimeter is equipped with a 5A socket, when in use, place the range switch in the 500mA DC current M-range gear, insert the red probe into the 5A dedicated socket, and insert the black probe into the negative socket.
A pointer multimeter is a relatively precise instrument, and if used improperly, it can not only cause inaccurate measurement of DC current but also be easily damaged. However, as long as we master the usage method and precautions of the pointer multimeter, and proceed with caution, the pointer multimeter can be durable and the measurement method is also easy to master.
