Ten points of experience in the use of multimeters
Ten points of experience in the use of multimeters
Although digital multimeters have the characteristics of intuitive display, high accuracy, and complete functions, they are still widely used because they are not suitable for measuring continuously changing electricity and are more expensive than analog analog multimeters. This article introduces ten points of experience in the use of multimeters (analog) to beginners. Correct use can not only obtain accurate test data, but also make the digital multimeter have the characteristics of intuitive display, high accuracy, and complete functions, but because it is not suitable for measuring the continuous change of electricity and the price is more expensive than analog analog multimeters. Therefore, analog analog multimeters are still widely used. This article introduces ten points of experience in the use of multimeters (analog) to beginners. Correct use can not only obtain accurate test data, but also prevent damage to the multimeter. 1. Before use, you must see 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 requirements of the 'grounding' or 'arrow' symbol on the meter head, the multimeter should be placed vertically or horizontally. If the pointer does not point to the starting point of the scale, the mechanical zero position should be adjusted first. 3. Select the appropriate range according to the size of the measured electricity. When measuring voltage and current, try to make the pointer deflection to more than 1/2 of the full scale, so as to reduce the test error. If you do not know the size to be measured, you can use the maximum range to measure first and then gradually reduce the range until the pointer has a large deflection. However, when testing high voltage (above 100 volts) or large current (0. 5A and above 0), you should not change the range with electricity, otherwise, it may cause the switch contacts to ignite and burn candles. 4. Pay attention when measuring DC voltage or DC current The polarity to be measured. If you don’t know the voltage of the two points to be measured, you can briefly touch the two test leads to the two points, determine the level of the potential according to the direction of the pointer impact, and then measure it. 5. When measuring the AC voltage, Know whether the AC voltage frequency is within the working frequency range of the multimeter. Generally, the working frequency range of the multimeter is 45-1500Hz. If it exceeds 1500Hz, the measured reading value will be sharply lower. The AC voltage scale is based on the effective value of the sine wave, so the multimeter cannot be used For measuring triangle wave, square wave sawtooth wave and other sine wave voltage. When the AC voltage is superimposed with DC voltage, a DC blocking capacitor with sufficient withstand voltage should be connected in series to measure. 6. When measuring the voltage on a certain load, consider Whether the internal resistance of the multimeter is much greater than the load resistance, if it is not due to the shunt effect of the multimeter, the reading value will be much lower than the actual value. At this time, you cannot directly use the multimeter to test, and you should use other methods. The internal resistance of the multimeter voltage block is equal to the voltage sensitivity Multiply the full-scale voltage value. For example, the sensitivity of the MF-30 multimeter in the DC100V block is 5 kohms, and the internal resistance of this block is 500 kohms. Generally speaking, the low-range block has small internal resistance and the high-range block has large internal resistance. When using a low voltage block to test a certain voltage because the internal resistance is small and the shunting effect is greater, you may wish to switch to the high-range test. In this way, although the pointer deflection angle is small, the accuracy of the shunting effect may be higher due to the small shunting effect. There is also a similar situation. When the multimeter is used as an ammeter, the internal resistance of the large range block is small and the internal resistance is small. 7. When measuring resistance, each shift must be adjusted to zero. The value of the geometric center of the multimeter resistance scale is multiplied by the multiplier of the electrical barrier. It is the median resistance of the block, which is equal to the internal resistance of the multimeter in the block. Common center scale values u200bu200bare 184.108.40.206.220.127.116.11.30.60.75 and so on. Resistance The scale is non-linear. When using it, choose a suitable gear so that the pointer is as close to the center as possible. Usually, the reading is accurate in the range of 0.1Ro-10Ro (Ro-----median resistance), and the error is outside this range. Larger. For example, the center scale value of the MF10 multimeter is 13, when the Rx10 kiloohm block Ro u003d130 kiloohms, this block is suitable for measuring the resistance of 13 kiloohms-1. 3 megaohms. 8. When the multimeter is measuring resistance, the red test lead is connected The black test lead is connected to the positive electrode of the battery in the meter. The purpose of this is to make the multimeter test voltage, current or resistance, the current will be uniformly fed in by the red test lead, and the black test lead will exit, and the needles can be in normal forward direction. Deflection, will not be reversed. Remember that the red test lead is connected to the negative electrode of the battery, and the black test lead is connected to the positive electrode. It is useful to check polar components such as transistors, diodes, and electrolytic capacitors. 9. When checking large-capacity capacitors with electricity, you should Discharge the capacitor first to prevent its residual current voltage from damaging the multimeter. The resistance on the test circuit should be disconnected from one end of the resistance to avoid the influence of other resistances on the circuit. It is forbidden to use electricity to block the test when it is working. The resistance on the circuit. 10. After the measurement is completed, the range switch should be turned to the highest voltage gear to prevent accidental burning of the meter during the next use. If there is a “black dot” or “OFF” mark, turn the switch to this position to short-circuit the measuring mechanism.
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