Precautions when using insulation resistance meter

The insulation resistance meter is also called the shake meter. It is mainly used to measure the insulation resistance of high-voltage or low-voltage electrical circuits and electrical equipment. It is easy to carry, does not require other auxiliary equipment when measuring, and can read the reading directly from the dial.
 　　Check before use
 　　Before using the insulation resistance meter, the ground resistance tester should first be placed in a horizontal position, the terminals "E" and "L" should be open, and the hand-cranked generator should be shaken at a rated speed of 120r/min or 150r/min to observe whether the pointer is at the infinite (∝) position, and then "E" and "L" should be short-circuited, and the generator should be hand-cranked at the rated speed to see if the pointer points to zero. At the same time, check whether the generator rotates flexibly and whether there is any jitter. Whether the pointer of the insulation resistance meter is stuck.
 　　Use
 　　First, select a suitable insulation resistance meter according to the measurement object and its rated voltage. That is, the rated voltage of the selected insulation resistance meter must be compatible with the working voltage of the electrical equipment or electrical circuit being measured. Example: To measure the insulation resistance of high-voltage equipment, an insulation resistance meter with a rated voltage below 500V cannot be used. The measurement result at this time cannot reflect the insulation resistance under the working voltage. Therefore, it should be noted that the insulation resistance of low-voltage electrical equipment cannot be measured with an insulation resistance meter with too high a voltage to prevent damage to its insulation. At the same time, the measurement range of the insulation resistance meter should not exceed the range of the insulation resistance to be measured.
 　　Precautions for use
 　　1? The insulation resistance measurement must be carried out when the electrical equipment or electrical circuit is powered off. Especially for equipment with large capacitance, it must be measured after complete discharge to prevent electric shock.
 　　2? In order to obtain accurate measurement results, the hand-cranked generator is required to work at the rated speed for one minute before reading.
 　　3? Before the insulation resistance meter stops rotating and the object to be measured is not discharged, the ground resistance tester cannot touch the measuring part of the object to be measured by hand. Especially when testing equipment with large capacitance, the object to be measured must be short-circuited to the ground for discharge, and then the insulation resistance meter must be stopped to prevent the capacitance from discharging and damaging the insulation resistance meter.
 
 　　Common faults and repairs
 　　1. When the terminals "E" and "L" are open, the pointer of the hand-cranked generator cannot point to "∝".
 　　First, remove the handle, unscrew the fastening screws, and use the electric soldering iron to solder the generator spring lead of the vibration meter to separate the measuring mechanism from the generator.
 　　1? Check the measuring mechanism: The measuring mechanism mainly consists of a cross coil (taking the ZC25 type meter as an example), a guide wire, voltage, and current loop resistance.
 　　① First, observe whether the guide wire is deformed. Due to the deformation of the guide wire, the residual torque increases, especially near the "∝". Due to the weak magnetic field, the positioning torque is small, which is easy to produce errors. If so, the guide wire should be readjusted or replaced. The replaced guide wire should meet the following requirements: the guide wire has no folds, and the upper, middle, and lower guide wires should be parallel and cannot be upturned or drooped. Move the pointer from "0" to "∝" by hand, and the guide wire cannot touch the shaft or other objects.
 　　② Use a multimeter to measure whether the voltage coil is open or short-circuited. If so, rewind or replace it.
 　　③ Check whether the voltage loop resistance increases. If so, readjust the voltage loop resistance.
 　　2? Check the generator: Digital anemometer ① Measure the output voltage of the generator: Hand-crank the generator, use an electrostatic voltmeter or a high-voltage digital voltmeter to measure its output voltage to see if it is consistent with its calibrated rated voltage, and an error of ±10% is allowed. If the output voltage of the generator is too low, check whether the generator winding is open or short-circuited. If so, replace or rewind.
 　　② Check whether the rectifier diode is short-circuited. If so, replace.
 　　③ Check whether the parallel capacitor of the generator is damaged. If so, replace.
 　　④ Check whether the screw spring of the speed regulator is too loose. If so, readjust the spring to tighten the spring.
 
 　　2. When "E" and "L" are short-circuited, the pointer cannot point to "0".
 　　① If the pointer cannot point to "0", you can use tweezers to move the pointer to adjust it.
 　　② Check whether the resistance of the current loop increases. If so, readjust the resistance.
 　　③ Check whether the current coil is short-circuited or open. If so, rewind or replace.
 　　④ Check whether the guide wire touches other objects or is greatly deformed. If so, replace it.
 
 　　3. The pointer does not rotate smoothly or is stuck when rotating.
 　　① Check whether the shaft tip is worn. If so, replace the shaft tip.
 　　② The jewel bearing and the shaft tip fit too tightly, resulting in a small gap. If so, the digital anemometer should readjust the gap between the bearing and the shaft tip.
 　　③ The movable coil of the instrument is deformed and collides with the internal iron core. If so, re-trim the wire frame.
 　　④ The guide wire is deformed, causing the pointer to collide with certain fixed parts when rotating. If so, readjust the guide wire.
 　　⑤ The movable coil collides with iron filings on the magnetic iron core. If so, insert a thin magnetic steel wire into the gap and use the principle of magnetization of the steel wire to suck out the iron filings.
 
 　　4. The position at the "∝" and "0" points is normal, but some scale points have large errors.
 　　① The mechanical balance is not good. If so, readjust the balance. The method is: unpower the instrument and keep it still at a certain position, and then tilt it 30° forward and backward and left and right to adjust the balance hammer.
 　　②Re-weld the guide wire, and extend or shorten the guide wire, and use its residual torque to change the scale characteristics of the instrument.
 　　③If the above adjustment method does not work, you can re-draw the scale line to solve the problem.