Pointer type multimeter structure and how to use it

1. Structure of the pointer multimeter

(l) The header is a high-sensitivity magneto-electric DC ammeter. The main performance of the multimeter depends on the performance of the meter. The sensitivity of the meter head refers to the value of the DC current flowing through the meter head when the meter pointer is deflected at full scale. The smaller the value, the higher the sensitivity of the meter head. The greater the internal resistance when measuring voltage, the better its performance. There are four tick marks on the meter head. Their functions are as follows: The first bar (from top to bottom) is marked with “R” or “Ω”, indicating the resistance value. When the switch is in the ohm range, the scale is read. line. The second bar is marked with “∽” and “VA”, indicating the AC, DC voltage and DC current values. When the transfer switch is in the AC, DC voltage or DC current range, the range is at a position other than 10 V AC, ie Read this tick. The third line is marked with “10V”, indicating the AC voltage value of 10V. When the transfer switch is in the AC and DC voltage range and the range is 10V AC, the scale line is read. The fourth bar is marked with "dB" and indicates the audio level.

(2) Measurement circuit The measurement circuit is a circuit for converting various measured DC currents suitable for meter measurement, and is composed of a resistor, a semiconductor element, and a battery. It can change various measured (such as current, voltage, resistance, etc.), different ranges, through a series of processing (such as rectification, shunt, voltage division, etc.) into a certain amount of small DC current feed The meter is measured.

(3) The function of the transfer switch is to select various measurement circuits to meet the measurement requirements of different types and different ranges. There are generally two transfer switches, each marked with a different gear position and range.

2. Symbolic meaning

l) “∽” means AC and DC.

2) “V-2.5KV 4000Ω/V” means the sensitivity is 4000Ω/V for AC voltage and 2.5KV DC voltage.

3) “A-V-Ω” means measurable current, voltage and resistance.

4) “45-65-l000Hz” means that the frequency range is below l000Hz, and the standard power frequency range is 45-65Hz.

5) “DC 2000Ω / V” means the sensitivity of the DC gear is 2000Ω / V. Figure 2-11 shows the outline of the MF-30 multimeter.

3. How to use the pointer multimeter

(l) Preparation Because there are many types of multimeters, it is necessary to prepare for measurement before use:

1) Familiar with the functions of the switch, knob, jack, etc., check the dial symbol, “∏” means horizontal placement, “⊥” means vertical use.

2) Understand the measured power corresponding to each tick mark on the dial.

3) Check if the position of the two red and black test leads is correct, the red pen is inserted into the “ten” jack, the black pen is inserted into the “one” jack, and some multimeters have the AC 2500V high voltage measuring end. When the black pen does not move, insert the red pen into the high voltage socket.

4) Mechanical zeroing. Rotate the mechanical zero adjustment screw on the universal surface plate so that the pointer points to the “O” position on the left end of the dial.

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