S470A 3 Terminal Earth Tester is a robust, compact, handheld automatic earth (ground) test instrument designed to measure earth electrode resistance. Not only it is simple and intuitive to use, but also it is accurate. The instrument is installed with Fast Fourier Transform (FFT) and Automatic Frequency Control (AFC) technology, which will automatically identify interference and select the appropriate measurement frequency, minimizing the effect of interference, and provide an accurate ground resistance value.