The structure and composition of a multimeter
The multimeter consists of three main parts: the meter head, measuring circuit, and conversion switch. A multimeter is the most basic tool in the field of electronic testing and is also a widely used testing instrument. Multimeters, also known as multi meters, three meters (A, V, Ω, also known as current, voltage, and resistance), multiplexers, and universal meters, are divided into pointer type multimeters and digital multimeters. There is also an oscilloscope function oscilloscope multimeter, which is a multifunctional and multi range measuring instrument. A general multimeter can measure DC current, DC voltage, AC voltage, resistance, audio level, etc. Some can also measure AC current, capacitance, inductance, temperature, and some parameters of semiconductors (diodes, transistors). Digital multimeter has become mainstream and has replaced analog instruments. Compared with analog instruments, digital instruments have high sensitivity, accuracy, clear display, strong overload capacity, and are easy to carry. They are also more convenient and simple to use.
Meter header
The head of a multimeter is a sensitive ammeter. The dial on the head is printed with various symbols, scale marks, and numerical values. The symbol A - V - Ω indicates that this meter is a multimeter that can measure current, voltage, and resistance. There are multiple scale lines printed on the dial, with the resistance scale line marked with "Ω" at the right end, zero at the right end, and ∞ at the left end. The distribution of scale values is uneven. The symbol "-" or "DC" represents direct current, "~" or "AC" represents alternating current, and "~" represents the scale line shared by alternating current and direct current. The few lines of numbers below the scale line are the scale values corresponding to the different gear positions of the selector switch.
There is also a mechanical zero adjustment knob on the meter head to correct the zero position of the pointer at the left end.
Selection switch
The selection switch of the multimeter is a rotary switch with multiple gears. Used to select measurement items and ranges. The general measurement items of a multimeter include: "mA"; DC current, "V (-)": DC voltage, "V (~)": AC voltage, "Ω": resistance. Each measurement item is divided into several different ranges for selection.
Pen and pen socket
The pens are divided into red and black. When using, the red probe should be inserted into the socket marked with "+", and the black probe should be inserted into the socket marked with "-".
Meter head (digital)
The head of a digital multimeter generally consists of an A/D (analog/digital) conversion chip, peripheral components, and LCD display. The accuracy of a multimeter is affected by the head. Due to the numbers converted by the A/D chip, a multimeter is commonly referred to as a 3 1/2 digit digital multimeter, a 4 1/2 digit digital multimeter, and so on. The most commonly used chips are ICL7106 (3 and a half LCD manual range classic chip, with subsequent versions of 7106A, 7106B, 72067240, etc.), ICL7129 (4 and a half LCD manual range classic chip), and ICL7107 (3 and a half LED manual range classic chip).
Measurement line
The measurement circuit is a circuit used to convert various measurements into small DC currents suitable for meter measurement. It is composed of resistors, semiconductor components, and batteries
It can convert various measured values (such as current, voltage, resistance, etc.), different ranges, and through a series of processes (such as rectification, shunting, voltage sharing, etc.) into a certain amount of small DC current and send it to the meter head for measurement.
Transfer switch
Its function is to select various measurement circuits to meet the measurement requirements of different types and ranges. The transfer switch is usually a circular dial with functions and ranges marked around it.
