Use a multimeter to measure the insulation resistance of a wire or piece of electrical equipment.
The so-called wire leakage, in fact, is to show that the insulation resistance of the wire or electrical equipment due to various reasons, so that it can not meet the conditions of normal operation, and cause the formation of insulated wires and the earth resistance value is very small resistance. For some insulation resistance value equal to zero, it is not a simple leakage, but the equivalent of a short circuit.
Here I popularize the concept of insulation resistance; the so-called insulation is the use of relatively non-conductive material will be charged body itself or with a different voltage level of the charged body between each other or wrapped up. The role of insulation; to ensure the safe operation of electrical equipment, power supply lines, to prevent the occurrence of personal electric shock accidents.
Insulation resistance is defined as the resistance value of the insulation layer of electrical equipment under the action of DC voltage. There is no absolute "insulating" material in the world, if the DC voltage is applied to both ends of the insulating material, the medium will always have a current through, just the voltage is high or low. Dielectric current is divided into leakage current (leakage current, polarization capacitance current).
Here simply put, the leakage of the wire ground current in the insulation material moisture and aging and so on have a relationship. The size of the leakage current is related to the applied voltage, the higher the voltage, the greater the leakage current. Their volt-ampere curve is not linear.
Whether it is a digital multimeter or pointer multimeter they are commonly used by electricians as an auxiliary measurement tool. Strictly speaking, the multimeter is unable to measure the leakage value of the wire. In fact, the multimeter can only be used to initially determine whether the household electrical equipment or motor is energized, whether there is a leakage of the case of the shell, the multimeter is equivalent to a test pen only.
For the wire line or electrical equipment whether there is leakage, should use megohmmeter for measurement. Commonly used megohmmeter 250v, 500v, 1000v several kinds. As long as the megohmmeter to shake at a speed of 120 revolutions per minute, its insulation resistance is greater than > 0.5MΩ, it is regarded as insulation resistance is basically qualified, you can rest assured that the use of electrical appliances.
Do not think that the multimeter is universal. General multimeter internal battery 1.5v and 9v stacked battery. It is for single-phase 220 Ⅴ or three-phase 380v alternating current lines or electrical equipment insulation resistance measurement is simply no way.
In the case of conditions do not allow, with the high resistance of the multimeter can be a preliminary judgment of the insulation resistance of the wire or electrical equipment, this method is not easy to recommend the use of. Using a multimeter to measure the line ground or measure the grounding resistance is also a preliminary judgment measurement. The real measurement of grounding resistance to use a single-arm or double-arm bridge to carry out.
