How To Use a Megohmmeter

Also called megger, megohmmeter is an electrical tool used for measuring high insulation resistance in electrical items. The value is expressed in megohm (1 megohm = 1,000,000 ohms). Like any other electrical tool, a meghom is dangerous if not used properly. So for your safety, here are some tips on how to use a megohmmeter, whether yours is battery-operated or a hand-crank model.

  • Read your owner’s manual. Never use a megohmmeter without first going through the reader’s manual. Read it as you would read an important document. Know as much as you can about the parts, the functions, and the proper use.
  • Have an assistant. If you’ve never tried using a megohmmeter before, you need to observe caution all the more. To be on the safe side, ask someone to assist you. This person must have used a megohmmeter before and should be good at all things electrical.
  • Always inspect the megohmmeter. It is important to do a thorough inspection on the megohmmeter before you begin. This is to make sure that it is functioning properly and will work without compromising your safety. Check it for any broken parts. Dust it off. And address any moisture problems. If the megohmmeter doesn’t seem to be in a perfect condition, trace the problem and immediately fix it.
  • Check that all wirings are disconnected. Whether you are testing a circuit board or a device, remember to carefully disconnect all wires. The power source should also be cut off. This protects you from potential shock and electrical accidents. Double-check the wires and power source before you start.
  • Connect the leads properly. The megohmmeter has leads that should be connected to the items you are testing. For example, if you are testing the insulation resistance of conductors. You need to connect one lead to one conductor and the other lead to the other conductor. If you need to measure the insulation resistance between the ground and a circuit, you need to connect one lead to each. Make sure to avoid touching the lead while the megohmmeter is in operation.
  • Remember that temperature matters. Temperature has a bearing on the megohmmeter reading. This is because insulation resistance drops when there is a rise in temperature. So take note of the temperature whenever you use the megohmmeter. Always compare your readings with the previous readings and adjust them based on the temperature changes.
  • Record your readings. Make sure to have a paper and pen handy, so you can write down the megohmmeter readings. This is especially necessary if you are testing several items. Take note that a reading of above 1 megohm is a good indication. A reading of 100 megohms or above is even better.

You can pretty much predict how to use a megohmmeter by just looking at its structure and parts. But remember that it is never safe to do guesswork when using a megohmmeter. If you are unsure about how to use a specific feature of your model, it is best to refer to your owner’s manual. Better yet, consult an electrician.


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