How to check short circuit with multimeter
A short circuit means that two lines that should not be connected are connected. A short circuit is between phases and phases, and between phases and ground. One is a phase-to-phase short circuit and the other is a ground short circuit. Grounding is relative grounding, and grounding is divided into dead grounding. The larger the resistance between the phase and the ground, the better, and the small resistance is called leakage.
When measuring with a multimeter, the larger the phase-to-phase resistance, the better. The small resistance between phases is called phase-to-phase leakage, and the resistance to zero is called phase-to-phase short circuit.
Use a multimeter to measure both ends of a line. If the resistance is zero, the line is connected. If the resistance is infinite, it is an open circuit. Sometimes the resistance is zero and sometimes it is not, indicating that the line is virtual.
Put a wire on the ground, with both ends guided without touching the ground, connect one end of the test lead to the wire, and the other test lead to the ground. The larger the resistance, the better, which means that the connection value is high, and the small resistance value means leakage, and the insulation performance is not good. Generally not less than 0.5 megohm, the state stipulates 1V1 ohm, low resistance wires should be scrapped.
Detailed use of mechanical multimeter
Mechanical multimeters, also known as analog multimeters and pointer multimeters, are the earliest three-purpose meters for testing electrical equipment. They are divided into resistance files, current files, and voltage files.
Among them, the current and voltage levels are divided into DC and AC levels. The AC voltage is not divided into positive and negative. For example, to detect 220v household AC power, you only need to switch the gear to 250v or 500v, and check the pointer swing. The second grid on the dial is For current and voltage files, the 250 file used for 220v should be placed between 250 and 200.
For the 500v range, check the 50 meter below. For 220v, it should be 2/3 more than the 20 digit, and then multiply by 10. It is not as accurate as the digital meter, but it can be confirmed that the voltage is normal. The 1000v file checks the 10th digit, the third one, 220v is a little behind 2, and the reading is multiplied by 100.
The DC voltage is divided into positive and negative, among which the red test lead is positive and the black test lead is negative. Don’t make a mistake, otherwise the hands of the watch will point backwards, which will damage the watch for a long time. The opposite is true for the detection of the second and third level tubes. At this time, the black test pen is positive and the red test pen is negative.
The current file is not used much, it can be connected in series to the circuit, skip it.
Resistance files are widely used, which is also the reason why digital meters are slightly inferior to pointer multimeters, but they need to be zeroed, which is the most annoying, and their durability is not as good as digital meters, which are fragile and fragile. However, the leakage detection of circuits and electronic components is stronger than that of digital meters, and the 10k level can basically solve most of the leakage problems of circuits.
The method of use is to set the resistance to a certain level and then zero it first, such as the 1k level, where the pointer is placed, multiply by 1k, and the same is true for other levels. If the pointer returns to zero, switch to 100 or 10 again. Most pointer meters do not have a buzzer gear, and you can judge whether the wire is on or off by selecting gear 1. It can also detect electronic components such as capacitors, transistors, power tubes, etc.
