M500 INSULATION TESTER MEGOHMMETER​ This reliable battery-powered tester, with LED indication, accurately measures insulation values up to 1000 megohms at 500 volts and indicates insulation condition by zone scale. ​FEATURES​ Full scale to 1000 megohms, Zone scale indicates insulation condition, Operates on 2 "C" size batteries (not included), Impact-resistant thermoplastic case, Operating instructions included, Test leads store in case Two-year warranty ​ APPLICATIONS​ Hermetic refrigeration and air conditioning compressors Motors and appliance wiring Distribution panels Relay control circuits ​ SPECIFICATIONS​ Parameter: Specification Scale Range: Up to 1000 megohms Applied Voltage: 500 volts DC Display: LED (light emitting diode) Case: Impact-resistant thermoplastic Dimensions: See physical unit or documentation Back Panel: Custom design Power: (2) "C" size batteries (not included) Test Leads: (2) 6"-long (store in case) Accessories: Zippered vinyl carrying case The M500 Megohmmeter is designed for the service engineer. It is a precise, rugged instrument requiring no calibration and engineered for years of dependable service. Use the M500 to keep an insulation history of new hermetic compressor units by recording the winding insulation value at each inspection. Even the slightest deterioration in insulation will show up as a declining megohm value while still in the "good" zone. As a diagnostic tool, the M500 confirms sound winding/heater insulation and warns of impending failure when overloaded windings risk failing during next high-load operation. ​APPLICATION NOTE: HERMETIC REFRIGERATION MOTORS​ Hermetic motors require special test parameters due to windings operating in oil/refrigerant environments. Normally high-resistance, these fluids show resistance changes when moisture-contaminated. New hermetic motors exceed 100 megohms. Readings ≤50 megohms indicate either: Deteriorating winding insulation, OR Contaminated oil/refrigerant Remedies include installing oversized driers or changing compressor oil. If megohm tests show even slight improvement, the remedy has checked the decline. ​OPERATION​ Install batteries (not included), Connect test leads to terminals, Press test button while applying leads:One lead to winding terminal, One lead to compressor shell (ground) Read LED zone scale: ▪ GOOD: >10 megohms ▪ FAIR: 2-10 megohms ▪ REPLACE: