The Omega meter, commonly known as a rocking watch, is used to measure large resistance and insulation resistance. Its measurement unit is MΩ, so it is called MΩ. There are many types of megohmmeters, but their effects are roughly the same. Hand type Megohmmeter Electronic Megohmmeter 1, Megohmmeter selection The voltage level of the specified megger should be higher than the insulation voltage level of the measured object. Therefore, 500V or 1000V megohmmeter can be used to measure the insulation resistance of equipment or circuit with a rated voltage below 500V. When measuring the insulation resistance of a device or line with a rated voltage above 500V, a 1000~2500V megohmmeter should be used; when measuring the insulator, a 2500~5000V megohmmeter should be used. In general, a megohmmeter with a range of 0 to 200 MΩ can be used to measure the insulation resistance of low-voltage electrical equipment. 2. Insulation resistance measurement method The megohmmeter has three terminals. The two upper terminals are marked with "earth" (E) and "line" (L) respectively, and the lower one is marked with "protection ring" ( Or "shielded") (G). (1) Insulation resistance of line to ground The mezzanine "ground" terminal (ie, E terminal) is reliably grounded (generally connected to a grounding body), and the "line" terminal (ie, L terminal) is connected to the circuit under test, as follows Picture shows. After the connection is made, the megohmmeter is shaken clockwise, the speed is gradually increased, and it is shaken at a constant speed of about 120 rpm. When the speed is stable and the pointer of the watch is stable, the value indicated by the pointer is the insulation resistance of the measured object. value. In actual use, the two terminals E and L can also be connected arbitrarily. That is, E can be connected to the tested object, and L can be connected to the grounding body (ie, grounded). However, the G terminal can never be connected incorrectly. (a) Measuring the insulation resistance of the line (b) Measuring motor insulation resistance (c) Measuring cable insulation resistance (2) Measure the insulation resistance of the motor Connect the megohmmeter E terminal to the case (ground), and the L terminal to the winding of one phase of the motor. As shown in the above figure, the measured insulation resistance value is the insulation resistance value of a phase to ground. (3) Measure the insulation resistance of the cable When measuring the insulation resistance between the conductive core of the cable and the cable housing, the terminal E is connected to the cable housing, the terminal L is connected to the cable core, and the terminal G is connected to the insulating layer between the cable housing and the core. As shown in Figure c above. 3, use attention (1) Open and short circuit tests should be performed before use. Make L, E two terminals in the disconnected state, shake the megohmmeter, the pointer should point to "∞"; L and E two short posts, slowly rotate, the pointer should point at "0". Both of these meet the requirements, indicating that the Megohmmeter is good. (2) When measuring the insulation resistance of electrical equipment, it is necessary to cut off the power first and then discharge the equipment to ensure personal safety and accurate measurement. (3) The megohmmeter shall be placed in a horizontal position and the megohmmeter shall be pressed firmly to prevent shaking during shaking. The rotation speed shall be 120 rpm. (4) lead wire should be used more strands of flexible wire, and have good insulation properties, two leads should not be twisted together, so as not to cause inaccurate measurement data. (5) Immediately after the measurement, discharge the object to be measured. Before the crank of the shaking table does not stop rotating and the object to be measured is not discharged, do not touch the measuring part of the measured object or remove the wire by hand to prevent electric shock. Stainless Steel Drinkware, New Steel Drinkware, Metal Steel Drinkware Fucheng Metals Production Co., Ltd. of Jiangmen City , https://www.fcmp.com
October 19, 2022