Description of Scale Plate Components for Analog Multimeter
A multimeter is mainly used for measuring various voltages and resistances. It consists of a dial, a calibration screw for the meter head, a function knob, a zero ohm calibration knob, a transistor detection socket, a probe socket, and a title; Because a multimeter has many functions, there are many scale lines and values on the dial of the multimeter. As shown in the following figure, the dial is composed of 5 concentric arcs, and each scale line also indicates the scale value corresponding to the range selection knob. Please refer to the following for specific instructions
1. Resistance Scale (Ω): The resistance scale is located at the top of the dial and is marked with "Ω" on both sides. Unlike other scale lines, its 0 position is on the right side, and the scale is not evenly distributed. It changes from sparse to dense from right to left. The final resistance measurement value of a pointer multimeter is: the reading of the dial pointer the range of the selected resistance measurement gear. For example, if the range of the selected resistance measurement gear is "* 100" gear and the pointer reading is "20", then the final measurement value is 20 * 100n=2000 Ω.
2. DC/AC voltage scale: The DC/AC voltage scale is located on the second line of the dial, with "DC/AC" markings on both sides. Its 0 position is on the left side, and the scale is evenly distributed. Below this scale line, there are three rows of scale values corresponding to its scale, which can respectively read the values of DC voltage and AC voltage.
The final DC/AC measurement value of a pointer multimeter is: the reading of the dial pointer multiplied by the selected gear range and the maximum value on the scale line where the dial pointer reading is located at this moment. For example, the selected measurement gear is DC voltage "100", and the pointer reading is the scale "6" on the reading "0~10", so its final reading is: 6 * (100/10) V=60V.
3. DC current scale (A): The DC current scale is located on the third line of the dial, with "DC A" markings on both sides. Its 0 position is on the left side, and the scale is evenly distributed, which can read the value of DC current. The final DC current measurement value of a pointer multimeter is the multiple of the dial pointer reading x the selected gear range and the maximum value on the scale where the dial pointer reading is located at this moment. For example, if the selected measurement gear is DC current flow "0.5mA" and the pointer reading is the scale "10" on the reading "0-50", its final reading is: 10 * (0.5/50) mA=0.1mA.
4. Decibel dial (dB): The decibel dial is located on the fourth line of the dial, with "dB" markings on both sides. Unlike other scale lines, its range is "-20~+22", and the scales are not evenly distributed. It is mainly used to measure the gain or attenuation value of amplifiers. If the lowest AC voltage is used during measurement, the dB value can be directly read on the decibel scale line; If using other gears, the reading should be added with additional decibels. If the load resistance is not the same as the standard resistance used on the scale, the reading should be obtained through conversion.
5. Transistor amplification factor scale (hFE): The transistor amplification factor is located on the fifth line at the bottom of the scale, with "hFE" markings on both sides. Its 0 position is on the left side, and the scale is not evenly distributed. The final measurement value is the reading indicated by the pointer.
