Home / Blog / Iec 61557 5 Equipment For Testing Measuring Monitoring Of Protective Measures
14-09-2025
EN IEC 61557-5
The EN 61557-5 (officially IEC/EN 61557-5) is part of the EN 61557 series, which defines requirements for measuring equipment used in safety-related testing of low-voltage electrical installations (up to 1000 V AC and 1500 V DC).
Equipment for measuring earth resistance
EN 61557-5: “Equipment for measuring earth resistance”
This section sets out the requirements, measuring methods, and performance criteria for instruments used to measure the resistance of an earth electrode or earthing system with respect to earth.
It is especially relevant for installers, inspection authorities, and maintenance companies responsible for verifying earthing and protective systems.
Measuring principle
Instruments must use AC test current, typically in the range 15 Hz – 2 kHz.
This prevents errors due to DC components or interference from the mains frequency (50 Hz).
Accuracy & error limits
The standard defines the maximum permissible measurement error (e.g. ±30% of the reading under specified conditions).
Validity of accuracy is specified for certain operating conditions (temperature, supply voltage, external influences).
Safety requirements
Instruments must be safe to use in installations up to 1000 V AC / 1500 V DC.
Requirements include insulation, overvoltage category (often CAT IV up to 300 V), and mechanical robustness.
Measuring methods
The standard covers the main earth resistance test methods:
- 3-point method (voltage drop method) → using auxiliary current and voltage electrodes.
- 4-point method → improves accuracy by eliminating lead/contact resistance.
Clamp-based methods are possible, but are more explicitly covered in other standards.
Functional requirements
The instrument must, for example, warn if test voltage/current is insufficient to guarantee a valid reading.
It must remain safe even if connected incorrectly.
De systemen die IONIO levert en binnen de EN IEC 61557-5 vallen zijn de volgende toestellen:
The earth resistance meter EM4058
The earth resistance meter MTD20KWR
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