The earth tester determine ground resistance for both specific and ohm resistances. The earth tester is powered by batteries and have a clock timer function (3 minutes), Data-Hold function, a 3 ½ positions LCD display and their dimensions are 163 x 100 x 50 mm. Resistance ranges come from 20, 200 to 2000 ohms. They have a resolution of 10 / 100 mΩ / 1 Ω. The earth tester measure resistance by means of a constant reverse current (approx. 800 Hz, 2 mA). To measure ground voltage a rectifier is used (5 kΩ/V aprox. 40...500 Hz). The earth tester PKT-2630 series have a small format as well as multiple functions.