How to choose test current of our GDZC Transformer Winding Resistance Tester? The transformer DC resistance tester is subdivided into various specifications such as 1A, 3A, 5A, 10A, 20A, 40A, 50A, 100A, etc. The power supply of the instrument is divided into external power supply AC220V, internal power supply (battery power supply), AC and DC power supply, etc. At present, th