Up to 600 A of true ripple-free DC current in a 7-8 kg device
The RMO-A series measures the contact resistance of medium- and high-voltage circuit breakers using Kelvin's four-point principle, with six models from 100 to 600 A. The current, with negligible ripple, rises and falls in automatically regulated ramps that remove magnetic transients from the measurement.
Advantages
Laboratory accuracy in the field
Typical accuracy of ±(0.1% of reading + 0.1% of full scale) and 0.1 µΩ resolution, with filtering that cancels the interference of high-voltage electric fields.
Three modes for every situation
SINGLE mode solves the spot measurement, CONTIN generates sustained current for longer tests and DTRtest saturates the current transformers of dead-tank breakers before measuring.
Power that gives margin
The high output voltage widens the measuring range at high currents and accepts long or thin cables: 20 m of only 16 mm² to test at 100 A.
Results in order
The internal memory stores 500 time- and date-stamped measurements, and an optional thermal printer prints the result right at the breaker.
Applications
- Contact resistance of medium- and high-voltage breakers, live tank and dead tank.
- Disconnectors, busbars and high-current joints.
- Cable splices, welded joints and fuses.
- Switchgear manufacturing, commissioning and maintenance.
- Pass/fail verification with Rmax limit.
About the product
The measuring range spans 0.1 µΩ to 999.9 mΩ, expandable to 6 Ω, and an optional high-precision module resolves 1 to 30 µΩ with 0.01 µΩ. The DV-Win software controls the test from the PC over USB or RS232, records at configurable intervals and generates reports with export to Excel.
Accessories: current cables of several cross-sections and lengths, sense cables with clamps, verification shunt, transport bag, optional thermal printer and Bluetooth.
Technical specifications
| Models | RMO100A to RMO600A (100 – 600 A DC) |
| Measuring range | 0.1 µΩ – 999.9 mΩ; expandable to 6 Ω |
| Typical accuracy | ±(0.1% rdg + 0.1% FS) |
| Current ripple | Below 1% |
| Memory | 500 time- and date-stamped measurements |
| Communication | USB; optional RS232 and Bluetooth |
| Operating temperature | -20 to +55 °C; IP50 |
| Dimensions and weight | 198 × 255 × 380 mm; 7 to 8 kg |
Frequently asked questions
Which model do I need?
It depends on the required test current: IEEE C37.09 and IEC 62271-100 call for high currents on breaker contacts, and the series goes from 100 to 600 A.
Why does the current ramp up?
Because abrupt current changes induce magnetic transients in the test object; the automatic ramp removes them and stabilises the reading.
Can it measure dead-tank breakers?
Yes. The DTRtest mode first saturates the breaker's current transformers and then measures, avoiding the magnetisation error.
How long can it hold the current?
At 100 A, continuously; at maximum current, 20 to 150 seconds depending on the model, with duty cycles that prevent overheating.
If you want to acquire Microhmmeters with quality, you can also consult prices of Microhmmeters.
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.