How to check if a line is shorted or grounded with a multimeter
1. How to use the multimeter to detect a short circuit in the line
(1) first power off, the multimeter function switch to the buzzer gear, the multimeter two pens on the two terminals to be measured bai test, if the short circuit will have a beeping sound, and show a very small value of the on-state voltage, this time between the two points to be measured short circuit.
(2) with a multimeter to measure the line insulation can know whether the line is short-circuited. For example, the measurement of single-phase ground insulation, if the insulation value is zero (metallic grounding) or very low (non-metallic grounding), you can judge this phase of the line grounded. If not grounded, the insulation value is very high. Then measure the insulation between phases, if the insulation between phases is zero, it means that this two-phase line is a short circuit between.
(3) to ensure that the line is not electrified, with a resistance file (pointer meter put RX10 file, digital meter will have a call of the on and off file), the two meter stick contact to measure the two points (or two lines), the pointer meter does not move is a circuit breaker, the fullness of the dump over is a short-circuit; digital meter circuit breaker digital did not change, there is no sound, a short-circuit will be called, or the number of zeros.
(4) will be separated from the two ends of the wire core, do not touch each other, and then the multimeter hit and above the position, the pen were hitched to the two different colors of the line, if the measured value is above 0.5 megohm, or show infinity, then the insulation of the line is not a problem, that is, the line does not have a leakage; if the measured value of the results is 0.5 megohm or less, then the line insulation is unqualified If the measurement result is below 0.5 megohm, then the line insulation is not qualified, and there is leakage. Find all the joints and junction boxes in the line after this air open, whether the joint insulation is not good, and then resistance measurement method at each joint and junction box with a multimeter check. The reason is that the short-circuit moment generates a high current air open automatically tripped, the line will not burn out how much general situation in the joints or junction boxes to resistance measurement method is able to determine the location of the short circuit. 2. how to detect a short circuit or a short-circuit?
2. how to detect a short circuit or grounding
But I still press in the absence of circuit breakers and leakage circuit breakers under the protection of the gate switch distribution line how to detect is a short circuit or grounding to answer the question; (in fact, the gate switch distribution if there is a short circuit phenomenon on the line, then; the consequences are either burned off the conductor is burned out of the gate switch, nonetheless; I'm still according to the principle of detection to answer the question).
(1) the power distribution line at the beginning of the power switch off, all the load switch on the line disconnected, including plugged in the socket plug load separation, with a multimeter resistance × 100 gear measurement of the power switch out of the end of the two wires out of the resistance, if it is measured to the multimeter resistance is very small (i.e., the pointer to the right swing almost the end of the end of the), then prove that there is a short-circuit phenomenon between the phase line and the zero line, or else there is no short-circuit. Otherwise, there is no short circuit. The same test method to measure the phase line to the protective ground (zero) line, zero line to the protective ground (zero) line whether there is a short-circuit phenomenon.
(2) If you exclude the phase line to the zero line, phase line to the protective grounding (zero) line, zero line to the protective grounding (zero) line no short-circuit phenomenon, you can test the phase line and the zero line whether the grounding phenomenon.
Detect grounding if you have a clamp meter on hand is best to use a clamp meter to detect grounding current. Detection method is: first disconnect the power switch, the distribution of zero line from the power switch from the end of the line removed (and mark), and then close the power switch, with a clamp meter clamp measurement of the phase line with or without grounding current (clamp meter first dialed to the 100A file such as the current can not be detected and then slowly dialed to the smaller current gear) if still not measured grounding current; can be excluded from the phase line grounding. After testing the phase line, disconnect the power switch to remove the phase line, the zero line to the power switch on the phase line out of the contact, close the power switch with the above clamp meter to measure the phase line method of testing the zero line.
If there is no clamp meter at hand; you can also find a chandelier head with about 25 watts of incandescent light bulbs and install the head, connect two 15 cm or so of wire backup. Detection method is; disconnect the power switch, remove the phase line and zero line, first of all, the lamp and the bulb in series in the phase line and the power switch between the phase line out of the contact point, do a good job of safety measures, close the power switch, at this time, if the bulb is bright to prove that there is a grounding phenomenon of the phase line, the higher the brightness of the bulb grounding current will be bigger, and vice versa, the smaller the grounding current, if the bulb does not light up to rule out the phase line grounding. After testing the phase line, disconnect the power switch, remove the phase line, the original light bulb in series in the zero line and the power switch out between the phase line junction, but also do a good job of safety measures, close the power switch to detect the zero line, the test results are the same as the above detection of the phase line.
