DV Power RMO20T Winding Resistance OhmMeter

Sorry, this product is discontinued and is no longer available for purchase. Please call 1-877-766-5412 to find a suitable replacement.DV Power RMO40T Winding Resistance OhmMeter is a suggested replacement model.

The ohmmeter RMO20T is designed for resistance measurement of inductive test objects.  RMO20T generates true, filtered DC current. Both injection of current and discharge of energy from the inductance is automatically regulated.

RMO20T injects current with a voltage as high as 60V. This ensures that the duration of test is as short as possible, and that the desired test current is reached as soon as possible. Two independent channels enable testing of two series windings, or primary and secondary windings.  There is enough memory within RMO20T instrument to store 100 measurements. All measurements are time and date stamped.

The set is equipped with thermal and overcurrent protection. The RMO20T has very high ability to cancel electrostatic and electromagnetic interference in high HV electric fields. It is achieved by very efficient filtration. The filtration is made utilizing appropriate hardware and software. The RMO20T current output is rated at 20 A for 10 minutes, and 10 A continuously.

On Load Tap Changers

RMO20T can measure the winding resistance of the individual taps of a power transformer’s tap changer, and can check whether the on-load tap changer (OLTC) switches without an interruption.

In the moment the tap is changed from tap to tap, the device detects the sudden, very short drop of the current flow. A properly working of tap changer differs from a malfunctioning one, e.g., an interruption during the change, by the magnitude of the ripple and slope values. An interruption will result in much higher ripple and slope values than a properly functioning of tap changer.


Using RMOWin-T software a test can be operated from PC, and the results can be obtained directly in PC. Using RMOWin-T the result can be printed like an Excel table which later can be shown as a diagram and used for a report.

Typical application of RMO20T is measuring the resistance of:
  • transformers
  • On-Load Tap Changers
  • generators and electrical motors
  • high-current busbar joints
  • cable splices
The Good:

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The Bottom Line:

Full Review

  • Lightweight - only 7,5 kg
  • Test current 5mA - 20A DC
  • Measuring range 1μΩ - 2kΩ
  • Two voltage sense channels
  • Extremely quick measurement
  • Automatic discharge circuit

CURRENT RANGE5 mA - 10A5mA - 20A5mA - 30A5mA - 40A5mA - 50A
RESISTANCE RANGE0,1µΩ-2000Ω0,1µΩ-2000Ω 0,1µΩ-2000Ω0,1µΩ-2000Ω0,1µΩ-2000Ω
RESOLUTION0,1µΩ 0,1µΩ 0,1µΩ0,1µΩ0,1µΩ
ACCURACY 0,2%0,2%0,2%0,2%0,2%
Optional Optional Optional Optional Optional
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