Tips for using a multimeter_Tips for using a multimeter
1,Before use, you must see clearly whether the function switch is in the corresponding position of the measured power, and whether the meter pen is in the corresponding jack.
2,According to the "ground" or "" arrow "" symbol on the head of the meter, the multimeter will be placed vertically or horizontally if the pointer does not point to the starting point of the scale should be adjusted to the mechanical zero position first. If the pointer does not point to the beginning of the scale, the mechanical zero position should be adjusted.
3, according to the size of the measured quantity of electricity to choose the appropriate range. Measurement of voltage, current should try to make the pointer deflection to more than 1/2 of the full degree, which can reduce the test error. If you do not know the size of the measurement, you can first use the maximum range measurement and then gradually reduce the range until the pointer has a larger deflection. But in the test of high voltage (more than 100 volts) or high current (more than 0.5A) should not be charged to change the range, otherwise, it is possible to make the changeover switch contact fire erosion.
4, DC voltage or DC current measurement should pay attention to the polarity of the measured. If you do not know the measured voltage of the two points of the high and low, the two pens can be briefly touch the two points, according to the direction of the pointer impact to determine the potential of the high and low, and then measured.
5, measure the AC voltage, to understand the AC voltage frequency in the multimeter operating frequency range, general multimeter operating frequency range of 45-1500Hz. 1500Hz beyond the measurement of the reading will be sharply lower. AC voltage scale is for sine wave RMS value to scale, so the multimeter can not be used to measure triangle wave, square wave sawtooth wave and other non-sinusoidal voltage. When the AC voltage superimposed on the DC voltage, should be strung with a voltage withstand value enough isolation capacitor and then measured.
6, when measuring the voltage on a load, we should consider whether the internal resistance of the multimeter is much larger than the load resistance, if not, due to the shunt effect of the multimeter, the reading value will be much lower than the actual value, then you can't test directly with the multimeter, should be changed to other methods. The internal resistance of the multimeter voltage file is equal to the voltage sensitivity multiplied by the full-scale voltage value, such as the MF-30 multimeter in DC100 volts voltage sensitivity of 5 kilo-ohms, the internal resistance of the file is 500 kilo-ohms. Generally speaking, low range gear internal resistance is small, high range gear internal resistance is large, when the low voltage gear test a voltage due to internal resistance is small resulting in a large shunt effect, it may be worthwhile to change to a high range test, so that, although the pointer deflection angle is small, but due to the shunt effect of the small, it is possible that, on the contrary, higher accuracy. Measurement of current has a similar situation, the multimeter as an ammeter, a large range of block resistance is less than the small range block resistance.
When measuring resistance, you have to adjust zero every time you change the gear. The value of the geometric centre of the multimeter resistance scale multiplied by the multiplication rate of the resistance file is the median resistance of the file, which is equal to the internal resistance of the multimeter in the file. The common centre scale values are 8, 10, 12, 13, 16, 20, 24, 25, 30, 60, 75 and so on. Resistance scale is non-linear, the use of the appropriate gear to make the pointer as far as possible to point in the centre of the nearby, usually in the 0.1Ro - 10Ro (Ro ----- value resistance) within the scope of the more accurate readings, outside the scope of the error is greater. For example, MF10 multimeter centre scale value of 13, in the Rx10 kilo-ohm block Ro = 130 kilo-ohm, the gear is suitable for measuring 13 kilo-ohm - 1.3 megohm resistance.
