Measuring AC voltage with digital multimeter: connect the black stylus to-or ground (marked in the stylus jack), and connect the red stylus to AC (or add a hole below the V letter); Gear refers to the range of 750 (some are 1000) (if it is 220V) in the AC column. Then the two strokes touch the two holes of the power socket respectively, and the reading is the AC voltage value.
The pointer meter measures AC voltage: the black stylus is connected to negative or ground, the red stylus is connected to+,the gear is set to AC~500V, and two measurements are inserted with the digital multimeter. The number pointed by the pointer should be read corresponding to the maximum range on the right: that is, if the 500V gear is selected, the reading should be based on the row marked with 50 on the right side of the reading panel. If the pointer points to 20, the reading is 200V V.
Measuring DC voltage with digital multimeter: measure AC at the same time, only the red pen is connected to the+hole, and the red pen is also connected to the power supply+pole. The gear position is DC (or a short horizontal line under the letter V), and the range depends on the specific situation, from large to small. For example, if you measure a No.5 battery, then choose the 2V range. If the polarity test is reversed, there will be a negative electrode display before reading.
Measuring DC voltage with pointer multimeter: the same as measuring with digital multimeter, and the reading is the same as measuring AC voltage above; When you can't determine the positive and negative poles of DC voltage, you can measure it as AC first, but you don't care about the reading. You just switch the polarity of the stylus to see which one of the two measurements will deflect, so the stylus touches the correct positive and negative polarity. Then dial the gear to the appropriate range of DC voltage and re-measure the reading.
Digital multimeter has the advantages of accurate measurement, convenient value selection and complete functions, so it is very popular among radio enthusiasts. The most common digital square meter generally has resistance measurement, on-off sound detection and diode forward conduction voltage measurement. AC/DC voltage and current measurement, triode magnification and performance measurement, etc. Some digital multimeters add the functions of capacitance measurement, frequency measurement, temperature measurement, data memory and voice counting, which brings great convenience to the actual detection work. However, due to improper use of digital meter, it is easy to damage the components in the meter and cause faults in actual testing. According to the actual situation that causes the damage of digital multimeter, I summarize the matters needing attention in the use of digital square meter for the reference of beginners, so as to prevent the damage of digital multimeter as much as possible.
In most cases, the damage of digital multimeter is caused by the wrong measuring gear. For example, when measuring AC mains supply, the measuring gear is placed in the electric block. In this case, once the stylus touches the mains supply, the internal components of multimeter can be damaged instantly. Therefore, it is necessary to check whether the measuring gear is correct before measuring with multimeter. After use, place the measurement at 750V AC or 1000V DC, so that no matter what parameters are measured by mistake, the digital multimeter will not be damaged.
Some digital multimeters are damaged because the measured voltage and current exceed the range. If the commercial power is measured at the AC 20V gear, it is easy to damage the AC amplifier circuit of the digital multimeter and make the multimeter lose its AC measurement function. When measuring DC voltage, the measured voltage exceeds the measuring range, which is also easy to cause circuit failure in the meter. When measuring the current, if the actual current value exceeds the range, it will generally only cause the fuse in the multimeter to blow, and will not cause other damage. Therefore, when measuring voltage parameters, if you don't know the approximate range of the measured voltage, you should first put the measuring gear in the highest gear, and then shift the gear after measuring its value to get a more accurate value. If the voltage value to be measured is far beyond the maximum range that can be measured by multimeter, a high resistance measuring probe should be provided. Such as detecting the second anode high voltage and focusing high voltage of black and white color TV.
The upper range of DC voltage of most digital multimeters is 1000V, so when measuring DC voltage, the maximum voltage is below 1000V, which will not damage the multimeter generally. If it exceeds 1000V, it is likely to cause damage to the multimeter. However, the upper limit of measurable voltage of different digital multimeters may be different. If the measured voltage is out of range, it can be measured by reducing the voltage with resistance. In addition, when measuring the DC high voltage of 40o ~ 1000 V, the stylus must be in good contact with the measuring place without any jitter, otherwise, the multimeter may be damaged and the measurement may be inaccurate, and in severe cases, the multimeter may have no display.
