The internal structure of the multimeter is divided into three parts in principle: the meter head, the measurement circuit and the change switch.
(1) Header
The meter head is usually a DC microammeter, and its working principle can be summarized as: "The deflection point of view of the pointer of the meter head is proportional to the current flowing through the meter head". The main function of the multimeter basically depends on the function of the head. The sensitivity of the meter head refers to the DC current value flowing through the meter head when the pointer of the meter head is deflected at full scale. The smaller the value, the higher the sensitivity of the meter head. The greater the internal resistance when measuring the voltage, the better its function.
The meter can be connected with various measurement circuits to measure a variety of electricity. By changing the switch, the meter head and the measuring circuit can be formed into a multimeter.
(2) Measuring line
The measurement circuit of the multimeter is a circuit used to convert various measured values to fine DC currents suitable for measurement by the meter head. It consists of resistors, semiconductor components and batteries.
The measurement circuit of the multimeter is the basic part of the multimeter, which is composed of several measurement circuits such as a multi-range DC voltmeter, a multi-range DC ammeter, a multi-range ohmmeter, and a multi-range AC voltmeter. It can convert various measured (such as current, voltage, resistance, etc.) and different ranges into a certain amount of fine DC through a series of processes (such as rectification, shunt, voltage division, etc.) The current is fed into the meter for measurement.
(3) Change the switch
The effect of changing the switch is to select various measurement lines and complete the selection of measurement types and ranges. The changeover switches are marked with different gears and ranges.
