The BESANTEK BSTET52 Digital Ground Resistance Tester with Timer is used to measure the ohms (Ohm) of an earth grounding installation for buildings (residential, office, labs, hospitals), computer server rooms, military installations, cellular sites, radio and cable towers, etc. It is used to determine if the earth (or ground) is a good conductor of electricity. The included timer function operates automatically for about three to five minutes, when the "Push Button Switch" and "Timer on Button" are pressed simultaneously.