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This is a common question in electrical testing.
Although the names of these three instruments sound similar, their purposes, test objects, and methods are completely different:
1.Ground Resistance Tester
What it measures:
The resistance between a grounding device and the earth.
Ensures that lightning current or fault current can be safely discharged into the ground.
Applications:
Substation grounding grids
Power equipment grounding systems
Lightning rod grounding
Building grounding systems
What it measures:
The contact resistance of high-current circuits, such as switchgear, cable joints, and busbar connections (typically in the micro-ohm range).
Focuses on whether the contact points may overheat, ensuring reliable current transmission.
Applications:
Contact resistance of high-voltage circuit breakers
Busbar and cable joint testing
Electrical performance testing during factory inspection or maintenance of HV switchgear
What it measures:
The insulation resistance between electrical equipment and ground or between phases.
Evaluates the insulation condition to prevent leakage current or breakdown.
Applications:
Insulation testing of motors, transformers, and power cables
Control panels and wiring inspection
Household appliances insulation check
Key Differences
| Tester | Test Object | Test Purpose | Resistance Range | Test Voltage/Current |
|---|---|---|---|---|
| Ground Resistance Tester | Grounding system – Earth | Check grounding reliability | Ohms to tens of ohms | Low-frequency current, auxiliary electrode method |
| Loop Resistance Tester | Contacts, circuit connections | Check contact quality | Micro-ohm level | High current (tens to thousands of amperes) |
| Insulation Resistance Tester | Insulating materials | Check insulation quality | Mega-ohms to giga-ohms | High DC voltage (commonly 500V – 5kV) |
In simple terms:
Ground resistance: checks “how well you are connected to earth”
Loop resistance: checks “how good the circuit contact is”
Insulation resistance: checks “whether the insulation is reliable”
