What do the symbols on a multimeter mean? How to use a multimeter correctly?

Digital multimeters are divided into two types: compass and digital display. There are relatively many marks on the dial, and the marks on digital multimeters of different manufacturers and different models are also very different. However, in general, these marks have certain regularity and meaning. If you understand the marks on one digital multimeter, you can understand most of the others. Common marks on digital multimeters ①DCA→direct current→microampere (uA)→mAh (mA)→ampere (A). ②DCⅤ→alternating voltage→millivolt (mⅤ)→ampere (V). ③ACⅤ→alternating current→ampere (V). ④Ω→resistance measurement→ohm (Ω) →kiloohm (KΩ)→megaohm (MΩ) ⑤Channel beep→passive beep sounds when less than 10Ω. ⑥Capacitor measurement→C*0.1, C*1, C*10, C*100, C*1K, etc. ⑦hFE→ transistor DC amplification factor. ⑧dB→ audio pulse signal→-10dB~ 22dB, 0dB=1mw/600Ω. Let's introduce the markings on the digital multimeter and pointer multimeter respectively. 1. Markings on the digital multimeter The figure below shows the appearance design of the DT890B digital multimeter.

It consists of an LCD display, a main power switch, a precise measurement switch, a DC ammeter detection socket, a power capacitor socket and a transistor socket.

数字万用表上端为LCD显示屏，能够 立即表明三位半数字字符，小数位依据必须全自动挪动，减号“-”会依据精确测量結果全自动表明。显示器下边是操作面板，控制面板中间为精确测量切换开关，只需旋转一个旋纽就可以挑选各测量范围挡位，方便使用。精确测量切换开关标示盘依照精确测量类型各自用鲜红色、翠绿色、乳白色三种颜色间距印刷，那样就不容易弄混。

There are 4 test ammeter sockets under the control panel. The black one is the negative ammeter socket (also called the common terminal socket) "COM". The three red ones are the positive ammeter sockets, which are the voltage resistance measurement socket "VΩ", the mAh current measurement socket "mA", and the picoampere current measurement socket "A". As shown in the figure below. When in use, the black ammeter is usually plugged into the "COM" socket, and the red ammeter is plugged into the corresponding positive ammeter socket according to the measurement requirements. The upper left side of the control panel is equipped with the entire mechanical power switch (POWER). Press it to "on", and press it again to make it pop up to "off". The upper right side of the control panel is the transistor socket. The left side of the socket is marked "PNP". When testing the PNP transistor, plug it into this socket. The right side of the socket is marked "NPN". When testing the NPN transistor, plug it into this socket, as shown in the figure below.

2. Markings on a compass digital multimeter The following figure is an MF47 digital multimeter.

The appearance design of the MF47 digital multimeter is shown in the figure below. It consists of a handle, a meter head, a precision measurement switch, an ohmmeter zero adjustment knob, a DC ammeter socket, a transistor socket, etc.

The top of the digital multimeter control panel is the microampere meter. There is a mechanical zero adjuster in the middle below the meter to adjust the mechanical zero position of the meter stem. As shown in the figure below. There are 6 scale lines on the inner diameter scale below the meter stem, from top to bottom, they are the resistor scale line, the current and voltage scale line, the transistor value scale line, the capacitor scale line, the inductor scale line, and the pulse signal scale line. There is also a rearview mirror on the dial to eliminate parallax.

In the middle of the lower part of the control panel is the measurement switch. You can select each measurement range by simply turning a knob. The measurement switch dial matches the gauge on the meter head and is printed in three colors: AC red, transistor green, and other black. The MF47 digital multimeter has a total of four ammeter sockets. There are positive and negative ammeter sockets on the lower left side of the control panel. Generally, the red ammeter is plugged into the positive socket and the black ammeter is plugged into the negative socket. There are 2500V and 5A special sockets on the lower right side of the control panel. When measuring 2500V AC voltage, the positive ammeter should be plugged into the 2500V socket. When measuring 5A DC current, the positive ammeter should be plugged into the 5A socket.

On the upper right of the lower part of the control panel is the ohmmeter zero adjustment knob, which is used to calibrate the "0Ω" mark of the ohmmeter. On the upper left of the lower part of the control panel is the transistor socket. The left side of the socket is marked with "N". When testing the NPN transistor, insert it into this socket. The right side of the socket is marked with "P". When testing the PNP transistor, insert it into this socket, as shown in the figure below.