Composition structure and description of multimeter
1, Header
1. Pointer type header
It is a highly sensitive magneto electric DC ammeter, and the main performance indicators of a multimeter depend largely on the performance of the meter head. The sensitivity of the meter head refers to the value of the direct current flowing through the meter head when the pointer deviates to full scale. The smaller this value, the higher the sensitivity of the meter head, and the greater the internal resistance during voltage measurement, resulting in better performance. There are four scale lines on the header, and their functions are as follows:
① The first line (from top to bottom) is marked with R or Ω, indicating the resistance value. When the switch is in the ohm range, this scale line is read;
② The second line is marked with ∽ and VA, indicating the values of AC/DC voltage and DC current. When the conversion switch is in the AC/DC voltage or DC current mode and the range is in other positions except for AC 10V, this scale line is read;
③ The third line is marked with 10V, indicating the AC voltage value of 10V. When the conversion switch is in the AC/DC voltage range and the measuring range is at 10V AC, this scale line is read;
④ The fourth item is marked with dB, indicating the audio level.
2. Digital meter head
The header of a digital multimeter is generally composed of an A/D (analog/digital) conversion chip, peripheral components, and a liquid crystal display. The accuracy of a multimeter is affected by the header. A multimeter, due to the number converted by the A/D chip, is generally also known as a 31/2-digit digital multimeter, 41/2-digit digital multimeter, and so on. The commonly used chips are ICL7106 (a classic 3-bit and a half LCD manual range chip, later versions include 7106A, 7106B, 7206, 7240, etc.), ICL7129 (a classic 4-bit and a half LCD manual range chip), and ICL7107 (a classic 3-bit and a half LED manual range chip).
2, Measurement line
A measurement circuit is a circuit used to convert various measured signals into small DC currents suitable for meter measurement. It consists of resistors, semiconductor components, and batteries. It can convert different measured signals (such as current, voltage, resistance, etc.) and different ranges into a certain limit of small DC currents through a series of processes (such as rectification, diversion, voltage division, etc.) and send them to the meter for measurement.
3, Conversion switch
Its function is to select various measurement circuits to meet the measurement requirements of different types and ranges. There are generally two conversion switches, each marked with different gears and ranges.
4, Pen and pen socket
There are two types of probes, red and black. When using, the red probe should be inserted into the socket marked with a "+" sign, and the black probe should be inserted into the socket marked with a "-" sign.
