UNI-T UT-521 Digital Earth Tester Earth Ground Insulation Resistance Meter Ohmmeter Voltmeter 2000&Omega; Digital Earth Tester Earth Ground Insulation Resistance Meter Ohmmeter Voltmeter 2000? Earth Resistance (): 20 (2%+10) ; 200 (2%+3) ; 2000 (2%+3) Double Insulation Protection LCD Backlight Auto Power Off Around 10 Minutes