Introduction and working principle of a multimeter
Meter header
The head of a multimeter is a sensitive ammeter. The dial on the meter head is printed with various symbols, scale lines, 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, which is zero at the right end and ∞ at the left end. The distribution of scale values is uneven. The symbol "-" or "DC" represents DC, "~" or "AC" represents AC, and "~" represents the scale line shared by AC and DC. The 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 pointer's zero position 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 Jack
The pen is divided into two types: red and black. When using, the red probe should be inserted into the socket marked with a "+" symbol, and the black probe should be inserted into the socket marked with a "-" symbol.
Meter head (pointer type)
It is a highly sensitive magneto electric direct current meter, and the main performance indicators of the multimeter basically depend on the performance of the meter head. The sensitivity of the meter head refers to the direct current value flowing through the meter head when the pointer of the meter head deviates from the full scale. The smaller this value, the higher the sensitivity of the meter head. The larger the internal resistance during voltage measurement, the better its performance. There are four scale lines on the meter head, and their functions are as follows: * * (from top to bottom) marked with R or Ω, indicating the resistance value. When the conversion switch is in the ohm gear, this scale line is read** The bars are marked with ǐ and VA, indicating the AC/DC voltage and DC current values. When the conversion switch is in the AC/DC voltage or DC current range, and the range is in positions other than AC 10V, this scale line is read. 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 AC voltage range is 10V, this scale line is read. The fourth item is marked with dB, indicating the audio level.
Meter head (digital)
The head of a digital multimeter generally consists of an A/D (analog/digital) conversion chip, peripheral components, and a LCD display,
