Rack-mount milliohmmeter 90 series

portablelow-resistance

Overview
Testing the protective earth (PE) connection on Class I equipment is essential for operator safety. Verifying the integrity of the PE path between the mains connection and all accessible conductive parts prevents hazardous touch voltages and ensures upstream protective devices can disconnect the equipment in case of enclosure fault.

Measurement principle
A PELV supply (typically 6 VAC or 12 VAC open-circuit) injects a test current from the PE terminal to all accessible metal parts. Resistance is calculated from the measured voltage drop and the test current. The low test voltage eliminates the need for additional safety measures during testing.

Variants / device groups

• Protective earth resistance testers 90-2A / 90-2B — Measurement range: 0–300 mΩ
• Protective earth resistance tester 90-4F — Measurement range: 350 mΩ
• Protective earth resistance tester 90-4G — Measurement range: 200 mΩ

Form factors
Units are available as a complete mobile enclosure for field use or as a plug-in module for integration into test cabinets, enabling modular and expandable test stations.

Applications
Typical application areas include household appliances, medical devices, consumer electronics and general machinery. The measurement documents the continuous connection of the protective conductor and is a key safety check before commissioning and after maintenance.

Important notes
Typical acceptance limits are often in the range of approx. 100–200 mΩ but may vary depending on product and standard requirements. When selecting a tester, consider required measurement range, test voltage and test current.

Technical specifications

• Test voltage (variant-dependent): 6 VAC / 10 VAC / 12 VAC
• Measurement range (variant-dependent): 0–300 mΩ / 200 mΩ / 350 mΩ
• Test current (variant-dependent): up to 25 A (e.g. 25 A or 10–25 A depending on model)
• Measurement principle: current injection (PE) → voltage drop measurement → resistance calculation
• Versions: mobile enclosure (complete) or rack-mount insertion for test cabinets
• Application areas: Class I equipment (household, medical, consumer, machinery)