Micro-Ohmmeters

Sonel & Hioki Low Resistance Testers – Precision Measurement for Electrical Reliability

Sonel and Hioki low resistance testers are designed for accurate measurement of electrical resistance in the micro-ohm and milliohm ranges. Utilizing four-wire (Kelvin) measurement technology, these instruments minimize lead resistance errors and enable reliable testing of electrical contacts, busbar connections, transformer and motor windings, and conductive components.

Offering both high-current field-testing instruments and high-precision resistance meters, they are ideal for hydropower plants, substations, power utilities, industrial maintenance, electrical manufacturing, and testing laboratories.

Key Features

  • High-Precision Measurement: Accurate resistance measurements with resolutions down to 0.1 µΩ and 1 nΩ on selected models.
  • Four-Wire Kelvin Technology: Minimizes test lead resistance errors for reliable low-resistance measurements.
  • Flexible Test Current: Measurement currents up to 100 A for resistive objects and up to 10 A for inductive objects on selected Sonel models.
  • Contact Resistance Testing: Suitable for circuit breaker contacts, busbar joints, terminals, and electrical connections with appropriate instruments.
  • Winding Resistance Measurement: Accurate testing of transformer, motor, and other inductive windings using compatible models.
  • Temperature Compensation: Corrects resistance measurements for temperature variations on supported models.
  • Advanced Measurement Functions: Comparator, automatic measurement, data recording, and diagnostic functions on selected instruments.
  • Portable & Benchtop Options: Rugged field-testing instruments and precision laboratory meters for different applications.
  • Data Connectivity: USB, LAN, Wi-Fi, and other communication options depending on the model.

Popular Models – Sonel

  • Sonel MMR-650 – 10 A winding resistance and low resistance meter for transformers, motors, and electrical connections, featuring temperature compensation and transformer core demagnetization.
  • Sonel MMR-6500 – High-current micro-ohmmeter with up to 100 A for resistive measurements and 10 A for inductive measurements, suitable for HV circuit breaker contacts, busbars, and transformer windings.

Popular Models – Hioki

  • Hioki RM3548-50 – Portable precision resistance meter with 0.1 µΩ resolution and up to 1 A test current for electrical maintenance, winding resistance, and connection testing.
  • Hioki RM3544 – Benchtop resistance meter for production-line testing of motors, transformers, relays, switches, and electrical components.
  • Hioki RM3545A – High-precision resistance meter with 1 nΩ resolution for component inspection, winding resistance, and automated production testing.
  • Hioki RM3546 – Ultra-high-resolution resistance meter designed for weld-quality inspection and electrical connection testing in EV and energy-storage battery manufacturing.

Applications

  • Power Substations: Circuit breaker contact resistance and busbar connection testing.
  • Hydropower Plants: Transformer and motor winding resistance measurement.
  • Industrial Maintenance: Inspection of electrical joints, contacts, terminals, and conductive connections.
  • Electrical Manufacturing: Quality control of motors, transformers, relays, switches, and electrical components.
  • Battery & EV Manufacturing: Resistance testing of welded connections, busbars, and battery assemblies.
  • Testing Laboratories: Precision resistance measurement, component evaluation, and research applications.

Sonel and Hioki low resistance testers deliver precise, dependable measurements for electrical maintenance, equipment diagnostics, and quality assurance—supporting reliable operation across power infrastructure and industrial applications.