The Extech GRT350-NISTL 4-Wire Earth Ground Resistance/Resistivity Tester with Limited NIST is a 4-wire earth ground resistance and resistivity tester which measures earth ground resistance from 2 to 2000 Ohm and resistivity from 0.06 to 628 ohm-m. The GRT350 supports 4-wire, 3-wire, and 2-wire testing. This tester has a large dual line LCD, automatic spike check, test hold function, auto ranging, data hold and auto power off. The GRT350 can also store and recall up to 200 test results, has over-range and low battery indications. CE certified with a CAT IV 300V safety rating and features limited NIST Calibration.