Can a bad contact on the utility zero wire be detected with a multimeter?
Look, in fact, many people think that only the zero line is broken, only to cause zero drift, in fact, not, in the not broken but the joints are false when it has been zero drift, (start a few hundred watts of electrical appliances), broken who will be measured, but when the false connection, surely someone will not be, in fact, simple, in your distribution room or distribution box, that is, your superior distribution (to have three-phase power Oh), to measure, with the 220v voltage gear measurement, measuring the voltage of each phase, the normal situation, each phase is the same (there can also be a small error), but in the zero line when the performance of the false connection for the three-phase different, know it? With the deterioration of the false connection, the voltage difference is the greater, but this method is almost disconnected when the performance.
There is another method is to see, in the zero line false connection is not real, whenever the use of power appliances, if you turn on the lights will see the lamps and lanterns of the light and dark, this is the performance of the early stage, but it is recommended that you check the line as often as possible, try to avoid such a problem, it will certainly cause damage.
Multimeter measurement of capacitance value is constantly changing
The digital multimeter display refreshes about 3 times per second, so it's normal for it to vary. But if it jumps randomly, it's not right, and it may be due to bad contact. Generally the meter pen and the line being measured, or the meter pen and the multimeter itself, there may be a multimeter jack welding is not good, multimeter transfer switch contact problems, battery shortage and so on.
With a digital multimeter to test the capacitance of good and bad steps are as follows:
1, determine the polarity, the first multimeter to 100 or 1K ohm gear, assuming that a positive pole, so that the black pen and it connected to the red pen and another pole connected to the resistance value, note down, and then the capacitor discharge, that is, let the two poles in contact, and then change the pen to measure the resistance, the resistance value of the large once the black pen connected to the positive pole of the capacitor.
2, the multimeter adjusted to the ohm gear appropriate gear, gear selection principle is: 1μF capacitance with 20K gear, 1-100μF capacitance with 2K gear, greater than 100,μF with 200 gear.
3, then use the red pen of the multimeter connected to the positive terminal of the capacitor, the black pen connected to the negative terminal of the capacitor, if the display slowly increases from 0, and finally shows the overflow symbol 1 is the capacitor is normal, if it is always displayed as 0, the capacitor is short-circuited internally, and if it is always displayed as 1, it is disconnected inside the capacitor.
