GEO Earth Ground Testers offer data storage and download capabilities via USB port 3- and 4-Pole Fall of Potential, using stakes 4-Pole Soil Resistivity testing, using stakes Selective testing, using 1 clamp and stakes Stakeless testing, using 2 clamps only Fluke 1625-2: Automatic Frequency Control (AFC) - identifies interferences and chooses a frequency for more accurate earth ground value Fluke 1625-2: R* measurement - calculates earth ground impedance at 55 Hz to more accurately reflect the earth ground resistance