Extech GRT300 4-Wire Earth Ground Resistance Tester
The Extech GRT300 is a precision 4-wire earth/ground resistance meter designed for measuring the resistivity of grounding systems. It supports 2-, 3-, and 4-wire testing modes, covers earth resistance ranges from 2 Ω to 2000 Ω, and includes features like automatic spike checks, data hold, and AC earth voltage measurement.
Description
The GRT300 is built for professionals tasked with verifying and diagnosing grounding and earthing systems, such as in electrical substations, utility installations, telecommunications towers, and building grounding. It uses a 4-terminal measurement technique (but can also operate in 3- or 2-wire modes) to minimize error caused by lead and contact resistances, leading to more accurate ground resistance readings.
It offers four selectable earth resistance ranges: 0–2 Ω, 0–20 Ω, 0–200 Ω, and 0–2000 Ω, with auto ranging and dual-line LCD display for clear readout. The instrument conducts automatic checks for current (I) and potential (P) spikes to validate proper test conditions before measurement. A Test/Hold function allows users to initiate and freeze readings without needing to keep the test button pressed. In addition, the meter measures AC earth voltage up to 300 V, so you can check whether stray potential on the ground system could affect test accuracy.
For convenience, it features automatic zero adjustment, data hold, autorange, auto power off, overrange and low battery indication. The GRT300 is supplied as a full kit, including test leads with alligator clips, four auxiliary earth bars (stakes), eight AA batteries, and a rugged carrying case. Safety design complies with relevant IEC/EN standards, and it is rated CAT IV 300 V for measurement safety.
Features
- 4-Wire / 3-Wire / 2-Wire Modes — Flexible connection options depending on test setup
- Earth Resistance Ranges: 0–2 Ω, 0–20 Ω, 0–200 Ω, 0–2000 Ω
- Automatic I & P Spike Checks — Verifies that test current and potential are stable before reading
- Dual-Line LCD Display — Shows both resistance and test voltage or auxiliary values
- AC Earth Voltage Measurement — Up to 300 V to catch stray voltage on the grounding system
- Test/Hold Function — Freeze measurement at the end of a test cycle
- Automatic Zero Adjustment & Autoranging — Helps simplify use and reduce operator error
- Data Hold, Auto Off, Overrange & Low Battery Indicators — Usability and safety aids
- Full Kit with Accessories — Comes with leads, earth bars, AA batteries, and carrying case
- Safety & Standards Compliance — Built to IEC/EN measuring safety and performance norms
Includes
- Alligator clips
- 4 auxiliary earth bars
- Hard carrying case
- Eight 1.5V AA batteries
