SMG5 Fieldpiece Digital Megohm Meter - Evaluate Compressor Insulation. Helps to Predict Compressor Failure. The Fieldpiece Digital Megohm Meter, model SMG5, is a compact standalone meter designed for checking HVAC compressor insulation. The SMG5 provides a 1000V voltage source, monitors current, and displays the resistance between the test points. Maximum current output is <1mA. It can be used to determine the condition of insulation from winding to ground in a motor, compressor, or transformer. Includes a case, alligator clip lead tip and leads with removable tips.

To test resistance, a DMM supplies low voltage (<1V) to the test points and is capable of delivering only a few milliamps. It's not a high enough voltage to detect high resistance problems that might indicate moisture and other contaminants and it's not enough current to measure lower values of resistance.