Micro Ohmmeters
RMO-A series
Micro Ohmmeters
- Lightweight – from 7 to 8 kg / 15.4 to 17.5 lbs
- Powerful – from 0 to 600 A DC
Measuring range 0 – 999,9 mΩ (up to 6 Ω)
- Resolution 0,1 μΩ
- Typical accuracy ± (0,1 % rdg + 0,1 % FS)
- SINGLE / CONTIN / DTRtest modes
Mechanical protection IP50
Description
RMO-A series of Micro Ohmmeters (hereafter referred to as “RMO-A”) contain 6 models: RMO100A, RMO200A, RMO300A, RMO400A, RMO500A and RMO600A.
All RMO-A models are based on a state of the art technology, using the most advanced switch mode technique available today. The main difference between these models is the maximum test current that can be generated (100 A for RMO100A, 200 A for RMO200A, up to 600 A for RMO600A model).
RMO-A generates a true DC ripple-free current with automatically regulated test ramps. During a test the RMO-A ramps with increasing current before measuring and decreasing current after the measurement. This significantly decreases magnetic transients.
Communication between the RMO-A and a PC is through an USB (as standard) or an RS232 cable (as an option). Bluetooth communication interface is also available as an option.
Using the DV-Win the result can be arranged as an Excel spread-sheet which can be later shown as a diagram and printed for a report.
The set is equipped with a thermal and an overcurrent protection. The RMO-A has a very high ability to cancel electrostatic and electro-magnetic interference in HV electric fields. It is achieved by very efÏcient filtration. The filtration is made utilizing a proprietary hardware and software.
The RMO-A instrument has three separate test modes:
The RMO-A instrument can store internally up to 500 measurements. All measurements are time and date stamped. Using the DV-Win soft-ware a test can be performed from a user’s PC, and the results can be obtained directly on the PC.
- SINGLE mode
- CONTIN mode
- DTRtest mode
Single Test
The RMO-A instrument generates a filtered (true ripplefree) DC current and output it in an automatically regulated current ramp. By sloping the current up and down, magnetic transients are virtually eliminated.
Below is an example of single test ramp for the 100 A current.
DTRtest
Presence of current transformers (CT) on the dead tank circuit breakers may introduce errors during contact resistance measurement due to CT magnetizing process. For this reason, it is necessary to saturate a CT prior to measurement.
DTRtest menu is specially designed for resistance measurement of the dead tank circuit breakers.
All calculations for detecting the saturated condition of CTs are done by internal algorithm. Accordingly, the process of measurement parameters setting and testing in this mode is very simple and does not differ much from live tank circuit breaker testing (in SINGLE / CONTIN test modes).
Application
Continuous Test
RMO-A can generate DC current continuously in predefined test durations, as presented in the table below.
Typical application is measuring resistance of noninductive test objects:
- High, middle and low voltage circuit breakers (live and dead tank)
- High, middle and low voltage disconnecting switches
C o n t i n u o u s T e s t
- High-current bus bar joints
- Cable splices
| Test current (A) | Maximum duration | Rest time (min) |
|---|---|---|
| Up to 100 A | Continuous | 0 |
| 200 A | 150 s | 2,5 min |
| 300 A | 90 or 150 s | 3 or 15 min |
| 400 A | 50 s | 2,5 min |
| 500 A | 30 s | 2 min |
| 600 A | 20 s | 2 min |
- Welding joints
- Fuses
*test duration at 100 A: test current can be up to
30 minutes depending on the request)
To avoid overheating, certain duty cycles are applied depending on the test current being used.
Connecting the Test Object to RMO-A
The connection diagram of our RMO-A devices corresponds to the Kelvin’s (four point) measurement principle. The measuring cables from the “Voltage Sense” sockets are attached as close as possible to Rx, and in between the current feeding cables. That way, a resistance of both cables and clamps is almost completely excluded from the resistance measurement.
Benefits and features
The main benefits and features of RMO-A devices are listed below:
- Very high output power (output voltage multiplied with output current) enables two main advantages:
- 1. Wide resistance measurement range even when very high currents are used..
e.g. The RMO600A can test up to 5.3 mΩ with a test current of 600 A when using the 5 m/50 mm2 current cables.
- 2. Use of thinner/longer test cables, depending of the customer requirement..
e.g. RMO100A can use 20 m current cables with crosssection of only 16 mm2 for testing circuit breakers with 100 A test current.
- The output current is filtered and has a ripple of less than 1 %.
- The instrument has a very high typical accuracy ± (0,1 % rdg + 0,1 % FS).
- The best resolution of RMO-A is 0,1 μΩ..
Several advanced features are available as standard/ optional accessories:
- Rmax feature (pass/fail criteria, enabled with the device and the DV-Win software)
- Built-in thermal printer (optional accessory)
- USB / RS232 communication port
- Bluetooth communication (optional)
- TRtest mode (a special mode for Dead Tank circuit breakers testing).
The connecting diagrams for the live tank and dead tank circuit breakers are presented in the figure below:
DV-Win Software
DV-Win software provides acquisition and analysis of the test results, as well as control of all the RMO functions from a PC. The DV-Win also provides several advanced features as a supplement to multiple functions of RMO devices. Testing in Continuous mode is upgraded with a sample time feature which allows user to record test results in specific time intervals set in seconds.
After performed measurements results can be saved in a various formats and test report can be generated and saved or printed. Result can also be downloaded from the device to the PC by use of several different search filters.
For the RMO form of DV-Win software there is Help menu available, with detailed instructions and explanations of all functions and features.
DV-Win Main Features
- Full control of the device in test
- Test reports *available in several formats
- Test plans
- Sampling time feature for CONTIN mode
- Several filters for results download to PC
Technical data
Mains power supply
- Connection according to IEC/EN60320-1; C320
- Mains supply: 90 V – 264 V AC
- Frequency: 50 / 60 Hz
- Power consumption
| Modelo | @ 230 V CA | @ 115 V CA |
|---|---|---|
| RMO100A | 1210 VA | 1150 VA |
| RMO200A | 1890 VA | 1880 VA |
| RMO300A | 2360 VA | 2170 VA |
| RMO400A | 3520 VA | 2650 VA |
| RMO500A | 3930 VA | 3850 VA |
| RMO600A | 4560 VA | 4040 VA |
| • Fuse: | Type F | |
| RMO100A & RMO200A | 12 A / 250 V | |
| RMO300A & RMO400A | 15 A / 250 V | |
| RMO500A & RMO600A | 20 A / 250 V |
| 0,1 μΩ - 999,9 μΩ | 0,1 μΩ |
|---|---|
| 1,000 mΩ - 9,999 mΩ | 1 μΩ |
| 10,00 mΩ - 99,99 mΩ | 10 μΩ |
| 100,0 mΩ - 999,9 mΩ | 0,1 mΩ |
| *1,000 Ω – 6,000 Ω | 1 mΩ |
- Typical accuracy ± (0,1 % rdg + 0,1 % FS)
Display
- LCD screen 20 characters by 4 lines;
- LCD display with backlight, visible in bright sunlight..
Interface
- RMO-A is equipped with an USB port
- optional: RS232 (connection to an external computer)
- optional: Bluetooth communication interfaceth
Test Result Storage
- RMO-A can store up to 500 measurements
Output data
- Test current ranges (from 0 to Imax) and load intervals at Imax:
| Model | Max. current | Test duration |
|---|---|---|
| RMO100A | 100 A | Continuous |
| RMO200A | 200 A | Up to 150 s |
| RMO300A | 300 A | Up to 150 s |
| RMO400A | 400 A | 60 s @300 A |
| RMO500A | 500 A | Up to 30 s |
| RMO600A | 600 A | Up to 20 s |
- Open circuit voltage: 9 V DC ± 2%
- Full Load Voltages at maximum current
| Model | @ 230 V CA | @ 115 V CA |
|---|---|---|
| RMO100A | 7,25 VA | 6,90 V |
| RMO200A | 7,10 VA | 6,10 V |
| RMO300A | 5,90 VA | 4,70 V |
| RMO400A | 6,60 VA | 4,30 V |
| RMO500A | 5,90 VA | 5,00 V |
| RMO600A | 5,70 V @600 A 7,2 V @300 A | 3,70 V |
Printer (optional)
- Thermal printer
- Paper width 80 mm / 3.2 in
- NOTE
The print density is guaranteed within the range 5°C to 40°C, 20 to 85% relative humidity, no condensation. The printer can operate from 0°C to 50°C..
Dimensions and weight
| Model | Dimensions (WxHXD) mm | Weight |
|---|---|---|
| RMO100A | 198 x 255 x 380 | 7 kg / 15.4 lbs |
| RMO200A | 198 x 255 x 380 | 7 kg / 15.4 lbs |
| RMO300A | 7.8 x 10 x 15 | 7,5 kg / 16.5 lbs |
| RMO400A | 7.8 x 10 x 15 | 7,5 kg / 16.5 lbs |
| RMO500A | 7.8 x 10 x 15 | 8 kg / 17.5 lbs |
| RMO600A | 7.8 x 10 x 15 | 8 kg / 17.5 lbs |
Measurement
- Resistance range: 0,1 μΩ – 999,9 mΩ*
Environmental protection
- *expandable from 0 Ω up to 6 Ω
- Ingress protection rating: IP50
- Resolution
Environmental conditions
- Operating temperature:
- 10 ºC - + 55 ºC / 14 ºF - +131 ºF
- Storage & transportation: 40 ºC - + 70 ºC / -40 ºF - +158 ºF
Humidity 5 % - 95 % relative humidity, non-condensing
Applicable Standards
- Installation/overvoltage: category II
- Pollution: degree 2
- Safety: Directive 2014/35/EU (CE conform) Applicable standards, for a class I instrument, pollution degree 2, Installation category II: IEC EN 61010-1
- EMC: Directive 2014/30/EU (CE conform), Applicable standard: EN 61326-1 Directive 2004/108/EC
- AN/CSA-C22.2 No. 61010-1, 2nd edition, including Amendment 1
Warranty
- 3 years
All specifications contained herein are valid at an ambient temperature of + 25 °C and with recommended accessories..
Specifications are subject to change without notice
Accessories
** Besides semi-isolated alligator (A1) clamps, sense cables are also available with isolated alligator (A2) clamps or with TTA clamps (as option)
Recommended cross-sections of the current cables for RMO-A models:
| CROSS SECTION/ LENGHT | 16 mm2 | 25 mm2 | *35 mm2 | 50 mm2 | 70 mm2 |
|---|---|---|---|---|---|
| 5 m | RMO100A | RMO200A | RMO300A & RMO400A | RMO500A & RMO600A | - |
| 10 m | RMO100A | RMO200A | RMO300A & RMO400A | RMO500A & RMO600A | - |
| 15 m | - | RMO100A | RMO200A | RMO300A & RMO400A | RMO500A & RMO600A |
*RMO500A and RMO600A devices can be provided with 2 x 5 m / 35 mm2 cables also
Order Info
| Instrument with included accessories | Article No. |
|---|---|
| Micro Ohmmeters RMO-A - DV-Win PC software including USB cable | RMO100A-N-00 |
| - DV-Win PC software including USB cable | RMO200A-N-00 |
| - DV-Win PC software including USB cable - Mains power cable - Ground (PE) cable | RMO200A-N-00 |
| - Ground (PE) cable | RMO300A-N-00 |
| RMO400A-N-00 | |
| RMO500A-N-00 | |
| RMO600A-N-00 | |
| Recommended accessories | Article No. |
| Current cables 2 x 5 m, *XX mm2 with battery clips | C2-05-XXYMBY |
| Sense cables 2 x 5 m with alligator clips | S2-05-02BPA2 |
| Transport case | HARD-CASE-ME |
| Optional accesories | Article No. |
| Cable bag | CABLE-BAG-00 |
| Device bag | DEVIC-BAG-00 |
| Test shunt 100 μΩ (600 A/60 mV) | SHUNT-600-MK |
| Current cables 2 x 10 m, *XX mm² with battery clips | C2-10-XXYMBY |
| Current cables 2 x 15 m, *XX mm² with battery clips | C2-15-XXYMBY |
| Current extension cable 2 x 10 m, *XX mm² | E2-10-XXYMYF |
| Sense cables, extension 2 x 10 m | E2-10-02BPBP |
| Sense cables 2 x 10 m with alligator clips | S2-10-02BPA2 |
| Sense cables 2 x 15 m with alligator clips | S2-15-02BPA2 |
| Bluetooth communication module | BLUET-MOD-00 |
| Built-in thermal printer | PRINT-080-00 |
*XX - Cross-section of current cables varies, depending on the output power of the model
**YMBY – For RMO100A and RMO200A: YMBY=LMB1; For other models: YMBY=VMB3 e.g. For RMO500A and RMO600A devices:
- the article number for current cables 2 x 5m/50 mm2 is C2-05-50VMB3,
- the article number for current cables 2 x 5m/35 mm2 is C2-05-35VMB3.