Earth Resistance/Soil Resistivity Tester IEC61010-031, IEC61557-1 Ground Resistance Meter IEC61557-5 Soil Resistivity Meter - China Earth Resistance Tester Wikipedia and Megger Soil Resistivity Tester
An automatic exposure meter with a galvanometer and a CdS photoresistor. Photo 2005 by en:USER:Janke, released to; 3 October 2005 (original upload date); Transferred from en.wikipedia to Commons.; Janke at English Wikipedia