Friborg Hot Winding Ohmmeter

Model: 2950
Standard: IEC

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Measures temperature increase in AC windings in transformers and AC motors.
Tests to IEC standards

The Hot Winding Ohmmeter measures AC winding temperatures during AC operation. It can be used for AC motors, transformers and other AC coils. This instrument uses the resistance method, measuring DURING OPERATION. This equipment gives data logging of the test results. It is available with 1 to 3 measurement channels.

This equipment makes it possible to measure temperatures continuously during operation. The temperature time curve can be recorded, giving an early indication that temperatures are becoming too high or the temperature is stabilizing (which shortens the test).


  • Measures temperature rises during operation of motor windings and all types of AC coils.
  • 1 Channel Standard. Optional – can add up to 2 more channels.
  • Temperature rises are measured by the resistance method. Resistance of Copper windings change approximately 4.0 m W per degree Centigrade, measuring temperature change.
  • Four pole Kelvin connections are used. Current measurement terminal as well as voltage measurement terminals are isolated.
  • Cut-off capacitors are included to isolate mains from measurement current. Special capacitors are available, as an option, for higher voltages


  • Can measure products utilizing currents to 28A
  • Tests to IEC standards
  • Ranges 10-100-1000-10000 ohms
  • Accuracy ± 1%
  • Standard PC controls the measuring and logging results
  • Data logged in time and graph on PC
  • Data logging using optically isolated modem and logger
  • Data logging is controlled by a PC using an RS232 interface