Usage and precautions of the hottest multimeter

2022-07-23
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Usage and precautions of multimeter

usage of multimeter

(1) be familiar with the meaning of each symbol on the dial and the main functions of each knob and selector switch

(2) perform mechanical zero adjustment

(3) select the gear and range of the change-over switch according to the type and size of the measured, and find out the corresponding scale line

(4) select the position of the probe socket

(5) measuring voltage: select a good range when measuring voltage (or current). If a small range is used to measure a large voltage, there will be a danger of burning the meter; If the experimental curve is drawn with a large range to measure a small voltage, the pointer deflection is too small to read. The range shall be selected so that the pointer deflects to about 2/3 of the full scale. If the size of the measured voltage is not known in advance, chairman Guo shall select the highest range gear first, and then gradually reduce to the appropriate range

a AC voltage measurement: place one change-over switch of the multimeter at the AC and DC voltage gear, and the other change-over switch at the appropriate range of AC voltage. The two probes of the multimeter can be connected in parallel with the circuit or load to be measured

b DC voltage measurement: put one change-over switch of the multimeter at the AC and DC voltage gear, and the other change-over switch at the appropriate range of DC voltage, and connect the "+" probe (red probe) to the high potential and the "-" probe (black probe) to the low potential, that is, let the current flow from the "+" probe and flow out from the "-" probe. If the probe is connected reversely, the pointer of the meter will deflect in the opposite direction, which is easy to bend the pointer

(6) current measurement: when measuring the DC current, set one change-over switch of the multimeter to the DC current gear and the other change-over switch to the appropriate range of 50ua to 500mA. The range selection and reading method of the current are the same as that of the voltage. When measuring, the circuit must be disconnected first, and then the multimeter shall be connected in series to the circuit to be measured according to the direction of current from "+" to "-", that is, the current flows in from the red probe and out from the black probe. If the multimeter is connected in parallel with the load by mistake, the internal resistance of the meter head is very small, which will cause a short circuit and burn the instrument. The reading method is as follows:

actual value = indicated value × Range/full scale deviation

(7) resistance measurement: when measuring resistance with a multimeter, the following methods shall be followed:

a mechanical zero adjustment. Before use until 2020, the pointer setting screw should be adjusted to make the current reading zero to avoid unnecessary errors

b select the appropriate magnification gear. The scale line of Ohm gear of multimeter is uneven, so the selection of magnification gear should make the pointer stay at the part with sparse scale line, and the closer the pointer is to the middle of the scale, the more accurate the reading is. Generally, the pointer shall be between 1/3 and 2/3 of the scale

c ohm zeroing. Before measuring the resistance, short circuit the two probes and adjust the "ohm (Electrical) zero adjustment knob" so that the pointer just points to the zero position on the right of the ohm scale line. If the pointer cannot be adjusted to the zero position, the battery voltage is insufficient or there is an internal problem with the instrument. In addition, ohmic zeroing shall be carried out again every time the multiplying gear is changed to ensure accurate measurement

d reading: the reading of the meter multiplied by the multiplying factor is the resistance value of the measured electric reducing cost resistance

(8) precautions

a when measuring current and voltage, do not change the range with power on

b when selecting the range, select the large one first and then the small one, try to make the measured value close to the range

c when measuring resistance, do not measure with power on. Because when measuring resistance, the multimeter is powered by the internal battery. If it is measured with electricity, it is equivalent to connecting an additional power supply, which may damage the meter

d after use, the transfer switch shall be at the maximum gear or neutral gear of AC voltage

e note that when the ohmmeter changes range, ohmic zero adjustment is required without mechanical zero adjustment

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