A megohmmeter, commonly known as a megger, is an instrument used to measure the electrical resistance of insulation. Meggers measure resistance values by sending a high voltage signal into the object being tested which creates a small current through and over insulation surfaces.
Megger testing is most commonly performed as part of the commissioning process on new installations as a precursor to applying voltage, bump and check rotation, and functional testing. Though it is not common to find insulation anomalies on a quality electrical installation, performing megger testing is always a necessity in order to avoid having to stop commissioning and pull out wiring to find the source of a problem. Insulation can often be damaged in transit or during wiring installation when it is scraped or nicked on a sharp edge, or bent improperly in a panel or trough.
Megger testing is also used as a diagnostic tool in existing installations on wire, generators, and motor windings. With aging, insulation can develop pinholes and cracks, allowing moisture and foreign matter to penetrate, and mechanical damage, vibration, moisture, excessive heat or cold, dirt, oil, corrosives, and other factors can all cause insulation to fail.
About Omni
Omni Instrumentation & Electrical Services, Inc., located in New Jersey and Maryland, is a premier instrumentation and electrical contractor, providing superior total care solutions since 1986. Services include instrument installation, tubing installation, instrument calibration, control loop testing, startup and commissioning, power and lighting, process control wiring, BMS wiring, telecommunications and data wiring, fire alarm wiring, security wiring, process network wiring, and control panel fabrication. Omni Instrumentation & Electrical Services, Inc., is certified in Foundation Fieldbus, Profibus, DeviceNet and ASI-Bus installation.