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Index: WMGBMMR650
Winding Resistance and Low Resistance Meter
Technical Specification
  • Description

    Measure winding resistance and low resistance with MMR-650

    Ready to work even in extreme conditions, the winding resistance and small resistance meter Sonel MMR-650 has been created to accurately measure small resistances of resistive and inductive objects. The instrument can be used to measure the resistance of both transformer windings - including amorphous-core transformers - and resistive objects. The MMR-650 meter is dedicated to use in power plants, maintenance companies and railway industry, among others.

    Product features

    • measurement of winding resistance (inductive objects including amorphous core transformers)
    • measurement of very low resistance
    • transformer core demagnetization function
    • automatic temperature compensation function (temperature probe)
    • function of determining the temperature of a motor under load
    • high immunity to disturbances


    The MMR-650 winding resistance and low resistance meter is designed to measure very low very low resistance of both windings - including amorphous core transformers - and resistive objects. This product is made to be used in power plants, railways and maintenance companies to measure resistance of:

    • windings of power transformers and motors,
    • breakers, contacts,
    • earthing conductors, equipotential bondings,
    • welded and soldered connections,
    • bolted connections,
    • and other resistive and inductive objects.

    MMR-650 can be also utilized on production lines (eg. at the final production control stage).

    Device capabilities

    The MMR-650 winding resistance and low resistance meter provides an innovative combination of a high-performance measuring device with a modern user interface and advanced data management system. Wireless data transmission, enhanced system of 2D codes and ability to print labels to identify test items, all contribute to bringing new quality of work and allow the user to perform a wide range of measurements.

    Easy readout

    The MMR-650 winding resistance and low resistance meter is equipped with a readable colour touchscreen that, due to its 800 x 480 pixel resolution, provides both high comfort of interacting with the interface and high readability of the measurement results.

    Durable and practical casing

    In response to the customers needs the MMR-650 microohmmeter has been designed to operate in difficult environmental conditions. A unique casing with the IP67 ingress protection rating ensures that the device is both waterproof and dustproof.

  • Technical Specification

    Resistance measurement

    Range Resolution Test current Accuracy
    0…999.9 μΩ 0.1 μΩ 10 A ±(0.2% m.v. + 2 digits)
    1.0000…1.9999 mΩ 0.0001 mΩ 10 A ±(0.2% m.v. + 2 digits)
    2.000…19.999 mΩ 0.001 mΩ 10 A ±(0.2% m.v. + 2 digits)
    20.00…199.99 mΩ 0.01 mΩ 10 A / 1 A ±(0.2% m.v. + 2 digits)
    200.0…999.9 mΩ 0.1 mΩ 1 A / 0.1 A ±(0.2% m.v. + 2 digits)
    1.0000…1.9999 Ω 0.0001 Ω 1 A / 0.1 A ±(0.2% m.v. + 2 digits)
    2.000…19.999 Ω 0.001 Ω 0,1 A ±(0.2% m.v. + 2 digits)
    20.00…199.99 Ω 0.01 Ω 10 mA ±(0.2% m.v. + 2 digits)
    200.0…1999.9 Ω 0.1 Ω 1 mA ±(0.2% m.v. + 2 digits)

    „m.v.” - measured value.

    Other technical specification:

    • insulation typeaccording to EN 61010-1: double
    • measurement category: III 600 V acc. to EN 61010-2-030:2011
    • ingress protection according to EN 60529:
      • with closed housing: IP67
      • with open housing, powered from the battery pack, installed plugs: IP54
      • with open housing, powered from mains and/or without plugs: IP40
    • protection against external voltage: up to 600 V AC for 10 s
    • power supply to battery charger: 90 V…265 V/50 Hz…60 Hz, 2 A
    • battery charging time: approximately 3.5 hours
    • number of measurements (of resistive objects) with 10 A current performed when powered from the: 700…800 depending on the ambient temperature
    • maximum wire resistance for 10 A current: 300 mΩ
    • accuracy of measuring current setting: ± 10%
    • time of performing the resistance measurement:
      • with selected resistive object type and bidirectional current flow: 3 s
      • with selected inductive object type, dependent on the resistance and inductance of the object: 5 s or more
    • operating temperature: -10°C…+50°C / 14°F…122°F
    • charger operating temperature: 0°C…+45°C / 32°F…113°F
    • storage temperature: -20°C…+60°C / -4°F…+140°F
    • humidity: 20%…90%
    • reference temperature: +23°C ± 2°C / 73.4°F ± 3.6°F
    • reference humidity: 40%…60%
    • temperature coefficient: ±0.01% of d.v./°C ± 0.1 digit/°C (“d.v.” - displayed value)
    • time to AUTO-OFF: 5…45 minutes or option not active, depending on the setting
    • TFT graphic display: 800 x 480 pixels
    • interface standard: USB, LAN, Wi-F
    • quality standard: design and manufacturing are ISO 9001 compliant
    • the product meets the EMC requirements (emission for industrial environment) according to: PN-EN 61326-1 i PN-EN 61326-2-2
    • compliance with FCC Rules: Class A digital device

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