The multimeter calculates the angle of deflection between the resistance and the resistance pointer.
When measuring resistance, pay attention to:
1. The measured resistance should be removed from the circuit before measurement.
2. Do not touch the two test leads together for a long time.
3. Two hands cannot touch the metal rods of the two test leads or the two pins of the measured resistance at the same time. It is better to hold the two test leads at the same time with the right hand
4. If the ohm range is not used for a long time, the battery in the meter should be taken out.
When the multimeter measures resistance, the measured value reflected on the meter head is actually the corresponding current passing through the measured resistance. The larger the measured resistance is, the smaller the current is, that is, the smaller the deflection angle. The relationship between the pointer deflection angle and the measured resistance is:
α=(RZθ)/(RX+RZ)
In the formula: α - pointer deflection angle;
RZ - the center resistance of the multimeter;
RX - the measured resistance;
θ———The angle when the pointer is fully deflected, this angle is mostly 90°
It can be seen from the ohm scale of the multimeter that the scale is an uneven reverse scale, and the smaller the deflection angle is, the greater the resistance value indicated. The resistance value between each scale line at the high-resistance end is very different. If you look at the pointer at an angle on this section of the scale line during measurement, it will cause a large error. Especially when measuring small resistance, the error is more obvious. Therefore, in order to ensure the accuracy of the measurement, when measuring a small resistance, the method of shifting gears should be used to keep the pointer near the center position as much as possible.
What file should the leakage multimeter display?
What is the gear of the leakage multimeter? How to measure the leakage with a digital multimeter
When the power is on, use the AC voltage file to measure the voltage of the equipment to the ground. In the case of power failure, measure the resistance to ground of the energized part with an electric barrier.
Severe leakage can be detected by the resistance of the multimeter, but if the leakage is not serious, the multimeter cannot measure it; there are special insulation resistance testers for measuring insulation, such as shaking meters, digital megohmmeters, etc., which can simulate real work Voltage, the test voltage of the multimeter is very low.
First ask the repairing user what is the fault phenomenon and what are the obvious features; secondly, observe whether there is an intuitive fault point from the surface, and then proceed to the next step of inspection.
1. First disconnect the main isolating switch of the user's power incoming line, and turn off all the user's electrical loads, such as unplugging the refrigerator, disconnecting the water pump switch, etc.
2. Put the gear of the digital multimeter on the 200M gear of the ohm range, place one test lead on one of the two outlets on the load side, and the other test lead touch the wall, preferably the ground wire or temporary Ground wire. After the number displayed on the multimeter is stable, the insulation resistance value of the main line is read. If the insulation resistance value is less than 0.5 megohm, then there is a problem with the main line. If the insulation resistance is above 0.5 megohm, it can be ruled out. It's a problem with the main line. Use the same method to measure another wire, and check the value to see if there is a problem with the main line.
3. Check the insulation resistance value of the shunt and each electrical appliance, and check one by one in the same way until the fault point is found.
