Review on Insulation Resistance AP 6688B Megohmmeter 1MΩ 200GΩ by Tyler Cooley

This tool is not widely used but should be in every technician's toolbox for testing insulation resistance. In this case it was originally used to identify a faulty wire leading to a well pump motor. A multimeter can sometimes detect this error on an ohmic scale, but will not have enough voltage to actually test insulation resistance. This is a critical test, especially when powered by a variable speed motor.