You will find earth testers to determine ground resistance for both specific and ohm resistances. Earth testers are 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. Earth testers 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). Earth testers PKT-2630 series have a small format as well as multiple functions. Now, you can  see the difference between the ground conductor, phase conductor and the neutral one without any difficulty.