A 300 A micro-ohmmeter that fits in one hand: 0.95 kg
Measuring contact resistance at hard-to-reach points, such as from a bucket lift or on a high-voltage line, calls for a battery-powered handheld micro-ohmmeter that delivers a high, regulated current with no waiting between tests. RMO-H weighs 0.95 kg and its Li-Po battery generates a stable current selectable from 1 to 300 A DC, in an automatic ramp, to measure by Kelvin’s four-point method from 0.1 µΩ to 3000 mΩ with ±(0.1 % of reading + 0.1 % of full scale) typical accuracy up to 1 Ω, also with the breaker grounded on both sides.
RMO-H key data
- Six models: RMO-H1, RMO-H2 and RMO-H3 (1-cell battery, up to 4.2 V, 1.3 to 3 m leads) and RMO-H21, RMO-H22 and RMO-H23 (two cells, 8.4 V, leads of 5 m or longer); regulated current from 1 to 300 A DC depending on the model.
- Accuracy: up to 1 Ω, ±(0.1 % rdg + 0.1 % FS) typical and ±(0.2 % rdg + 0.2 % FS) guaranteed; from 1 to 3 Ω, ±(0.25 % rdg + 0.25 % FS) typical and ±(0.5 % rdg + 0.5 % FS) guaranteed; 0.1 µΩ resolution.
- Battery life: replaceable Li-Po battery for up to 3000 tests at 50 A, 1900 at 100 A or 600 at 300 A; 2 h recharge with the mains adapter or the car charger.
- Handling: 226 × 116 × 50 mm and 0.95 kg, keyboard designed for one-hand operation, one-click measurement and Kelvin probes with trigger button.
- Data: micro SD card with 10000 time- and date-stamped measurements, Bluetooth download to the PC software and an Rmax alert when the resistance exceeds the set limit.
- Applications: medium- and high-voltage breakers and switchgear per IEC 62271-100, including both sides grounded, disconnectors, busbar joints, welded joints, railway rails and lightning conductor bonding.
Advantages
One click to measure
The keyboard and menu are designed for one-hand operation: select the current, attach the clamps and the measurement starts with one click, even from a bucket lift.
Truly regulated current
The test value is chosen between 1 and 300 A and stays constant throughout the measurement, generated in an automatic ramp that avoids magnetic transients.
A full day of testing per charge
The user-replaceable Li-Po battery performs up to 3000 tests at 50 A, 1900 at 100 A or 600 at 300 A, and recharges in two hours with the mains adapter or the car charger.
Two sub-series to match the cabling
RMO-H1, RMO-H2 and RMO-H3 (up to 4.2 V) work with short 1.3 to 3 m leads; RMO-H21, RMO-H22 and RMO-H23 raise the output to 8.4 V for leads of 5 m or longer.
Applications
- Medium- and high-voltage breakers and switchgear per IEC 62271-100, including both sides grounded.
- Disconnectors, busbar joints and conductor terminals on HV power lines.
- Welded joints, cable splices and cable resistance in the factory.
- Railway joints and conductor rails, plus bonds in the aircraft industry.
- Off-line tap changer contacts and lightning conductor bonding.
About the product
The measuring range covers 0.1 µΩ to 3000 mΩ with a best resolution of 0.1 µΩ and a typical accuracy of ±(0.1% of reading + 0.1% of full scale) up to 1 Ω. The internal micro SD card stores up to 10000 time- and date-stamped measurements, which the PC software downloads over Bluetooth to analyse them and build customised reports.
Accessories: combined current and sense leads with TTA clamps, Kelvin probes with trigger button, cables with battery or alligator clamps, verification shunts, mains adapter, car charger, spare battery with fire-retardant bag and transport case.
Technical specifications
| Models | RMO-H1/-H2/-H3 and RMO-H21/-H22/-H23 |
| Test current | 1 – 300 A DC regulated, per model |
| Measuring range | 0.1 µΩ – 3000 mΩ |
| Typical accuracy | ±(0.1% rdg + 0.1% FS) up to 1 Ω |
| Memory | 10000 time- and date-stamped readings |
| Communication | Bluetooth to the PC |
| Battery | Replaceable Li-Po; 2 h recharge |
| Dimensions and weight | 226 × 116 × 50 mm; 0.95 kg |
| Typical accuracy from 1 to 3 Ω | ±(0.25 % rdg + 0.25 % FS) |
| Guaranteed accuracy | ±(0.2 % rdg + 0.2 % FS) up to 1 Ω; ±(0.5 % rdg + 0.5 % FS) from 1 to 3 Ω |
Frequently asked questions
Which portable micro-ohmmeter is suitable for measuring contacts from a bucket lift?
A battery-powered handheld unit designed for one-hand operation. RMO-H weighs 0.95 kg, measures with one click and generates a regulated current of 1 to 300 A DC from its Li-Po battery, enough for up to 600 tests at 300 A or 1900 at 100 A on a single charge.
How accurate is the RMO-H across its measuring range?
Up to 1 Ω, ±(0.1 % of reading + 0.1 % of full scale) typical and ±(0.2 % + 0.2 %) guaranteed; from 1 to 3 Ω, ±(0.25 % + 0.25 %) typical and ±(0.5 % + 0.5 %) guaranteed. Resolution reaches 0.1 µΩ over a range of 0.1 µΩ to 3000 mΩ.
How do the two sub-series differ?
In output voltage and cabling: RMO-H1/H2/H3 use a 1-cell battery (4.2 V) with short leads, while RMO-H21/H22/H23 use two cells (8.4 V) for leads of 5 m or longer. The lead sets are not interchangeable between sub-series.
What is the advantage of the Li-Po battery over an ultra-capacitor?
There is no waiting for a charge between tests and the current does not depend on the load: you select the exact value and it stays stable during the measurement.
Can it measure with the breaker grounded on both sides?
Yes. The BSG test uses the same connection as with one side grounded; bear in mind that part of the current flows through the groundings, so the reading may be slightly less accurate.
How are results transferred to the computer?
Over Bluetooth: the included PC software downloads the stored measurements, analyses them and exports reports in several formats.
