Structure of Analog Multimeter
There are many types of pointer multimeters, but their basic structures are similar. The structure of a pointer multimeter mainly consists of three parts: the meter head, the switch (also known as the selector switch), and the measuring circuit.
The meter head adopts a highly sensitive magneto electric mechanism, which is the display device for measurement; The header of a multimeter is actually 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 electric meter is a multimeter that can measure current, voltage, and resistance. There are multiple scale lines printed on the dial, among which the resistance scale line marked with "Ω" on the right end is zero, and the left end is ∞. The distribution of scale values is uneven. The symbol "-" or "DC" represents direct current, "~" or "AC" represents alternating current, and "~" represents the common scale line between alternating current and direct current. The lines below the scale line represent the scale values corresponding to the different gear positions of the selector switch. In addition, there are some symbols on the dial indicating the parameters of the meter head, such as DC 20K Ω/V, AC 9K Ω/V, etc. There is also a mechanical zero adjustment knob (screw) on the header to correct the pointer to zero on the left end.
The conversion switch is used to select the type and range (or magnification) of the measured electricity: The selection switch of the multimeter is a multi gear rotary switch. Used to select measurement items and ranges (or magnifications). The general measurement items of a multimeter include: "mA" for DC current, "V" for DC voltage, "V~" for AC voltage, and "Ω" for resistance. Each measurement item is divided into several different ranges (or magnifications) for selection.
The measurement circuit converts the measured electricity of different properties and sizes into a direct current that the meter can accept. Figure 1 shows the appearance of the MF-47 multimeter, which can measure various electrical quantities such as DC current, DC voltage, AC voltage, and resistance. When the conversion switch is turned to the DC current mode, it can be connected to 5 contact points respectively, used for DC current measurement in the ranges of 500mA, 50mA, 5mA, 0.5mA, and 50 μ A. Similarly, when the conversion switch is turned to the ohm range, the resistance can be measured at magnifications of x 1, x 10, x 100, x 1K Ω, and x 10K Ω, respectively; When the conversion switch is set to the DC voltage range, it can be used for DC voltage measurement in the ranges of 0.25V, 1V, 2.5V, 10V, 50V, 250V, 500V, and 1000V; When the conversion switch is set to AC voltage mode, it can be used for measuring AC voltage in the ranges of 10V, 50V, 250V, 500V, and 1000V.
