The essential winding ohmmeter: three channels, 55 V output and only 8 kg
The RMO-TW series solves the winding resistance measurement of inductive objects with four models of 10, 20, 30 and 50 A — RMO10TW, RMO20TW, RMO30TW and RMO50TW — housed in a light metal case of just over 8 kg. The ripple-free DC current is injected with up to 55 V and discharged through an automatic circuit, and the three measuring channels get through a complete transformer in fewer passes.
Advantages
Three windings in a single measurement
The independent channels test primary, secondary and tertiary windings connected in series at once; saturating the core through the winding with the most turns shortens stabilisation and the whole test.
Tap changer verification
Resistance is measured at every tap position without discharging between taps: if the current is interrupted during switching, the device detects it and warns the operator.
De-energized taps too (DETC)
A dedicated mode walks through the positions of de-energized tap changers within the same test, with criteria separate from on-load tap changers.
Automatic discharge and demagnetization
The discharge circuit governs the stored energy at the end of the measurement, and demagnetization removes remanent magnetism by reversing polarity with decreasing magnitude.
Applications
- Winding resistance of power and distribution transformers and autotransformers.
- Verification of on-load and de-energized tap changers.
- Rotating machines: motor and generator stators through the three channels.
- Non-inductive resistive objects: busbars, splices and joints.
- Heat Run test with resistance and temperature extrapolation.
About the product
The measuring range spans 0.1 µΩ to 100 kΩ with a typical accuracy of ±(0.1% of reading + 0.1% of full scale) up to 2 kΩ and a best resolution of 0.1 µΩ; a Pt100 channel measures temperature from -50 to +180 °C. The memory keeps 1000 measurements (5000 optional) and the DV-Win software controls the test over USB and exports reports to Excel, PDF or Word.
Accessories: current and sense cables with TTA clamps, temperature probes, verification shunt, Bluetooth module, optional built-in thermal printer, bags and transport cases with or without wheels.
Technical specifications
| Models | RMO10TW, RMO20TW, RMO30TW and RMO50TW |
| Test current | 5 mA – 50 A DC depending on model |
| Output voltage | Up to 55 V DC |
| Measuring range | 0.1 µΩ – 100 kΩ |
| Typical accuracy | ±(0.1% rdg + 0.1% FS) up to 2 kΩ |
| OLTC verification | 4 ms sampling |
| Power supply | 90 – 264 V AC, 50/60 Hz; 2250 VA |
| Dimensions and weight | 198 × 250 × 350 mm; 8 – 8.5 kg |
Frequently asked questions
Which model should I choose?
It depends on the transformer size: the higher the power and the lower the winding resistance, the more current helps; the RMO50TW reaches 50 A with 1000 W of output and the RMO10TW covers small machines with 10 A.
How does it differ from the RMO-TD series?
The RMO-TW verifies the tap changer by detecting interruptions with 4 ms sampling, but it lacks the 0.1 ms DVtest dynamic analysis, the motor current channel and the OLTC control unit of the RMO-TD.
Does it measure rotating machines?
Yes. By connecting the three stator phases in series, the three channels measure the three resistances in one go.
How does it handle the energy stored in the winding?
The automatic discharge circuit dissipates it in a controlled way after each measurement, before the wiring is touched.
What PC interface does it offer?
USB as standard, with optional RS232 and Bluetooth; the included software plots the results and assembles the reports.
If you want to acquire Transformer winding resistance meters with quality, you can also consult prices of Transformer winding resistance meters.
If you have any doubts or need advice from our engineers, don't hesitate to contact us and we will be pleased to help you. You can also call us at (+34) 982 20 99 20.