The AEMC Model 4620 is a digital ground resistance tester designed for evaluating grounding systems, ground rods, and bond continuity in industrial, commercial, and utility environments.
It uses the standard 3-Point (fall-of-potential) and 2-Point measurement methods, operating at 128 Hz to filter out background AC/DC noise and stray currents in energized substations or high-EMI industrial sites.
Measurement Range: $0.00\ \Omega$ to $1999\ \Omega$ across three auto-ranging scales ($20\ \Omega$, $200\ \Omega$, $2000\ \Omega$).
Testing Methods:
3-Point Test: Fall-of-potential test for individual rods and grounding grids.
2-Point Test: Direct resistance measurement for quick continuity checks.
Noise Immunity: High rejection of stray ground signals (up to $20\text{ V}_{\text{peak-to-peak}}$).
Diagnostic Indicators: Front-panel LEDs alert you to high lead resistance or open circuits on auxiliary rods (C and P stakes) before you record invalid data.
Power Source: Powered by six standard 1.5 V C-cell batteries.
Enclosure: Heavy-duty, IP54-rated field case.
When connecting the 4620 for a standard 3-Point fall-of-potential test:
Terminals X & Xv: Jumpered together and connected to the ground rod under test (Earth Electrode).
Terminal Y: Connected to the potential auxiliary stake (driven into the ground at roughly 62% of the total distance to the current stake).
Terminal Z: Connected to the current auxiliary stake (driven farthest out in a straight line).
