[+34] 982 20 99 20
Microhmmeters:
F.A.Q.
Frequently asked questions for Micro Ohmmeters
Q: Do you produce Micro-ohmmeter RMO50?
A: Yes, we produce Micro-ohmmeter RMO50. Maximum test current is 50A and the test voltage is up to 12V DC. This RMO50 device is designed for protective earth resistance tests in accordance with the IEC 61010-1 safety standard Annex F. The RMO50 device is not intended for winding resistance measurement of transformers nor test objects with high inductance.
Q: Do you produce Micro-ohmmeters with rechargeable battery and the test current up to 10A?
A: Unfortunately, we do not produce Micro-ohmmeters with the rechargeable battery and do not plan to produce it because of the following reason: In case of Circuit breakers contact resistances measurements, such a Micro-ohmmeter does not fulfil international standards. According to IEC 56 (now IEC62271-100) this resistance value should be measured using a test current between 50A and the breakers nominal current. According to ANSI C 37.09 the lowest test current is 100A. Other national and international standards specify similar regulations.
Q: Is RMO 300 adequate model to measure the contact resistance of lead-acid batteries in UPS?
A: Our experience is that the measurement of resistance values below 10μΩ to as high as 100μΩ should be performed with the test current higher than 50A. Using test current below 50A could not get good readings. The test current of micro-ohmmeter should be at least 100A or 200A to measure the contact resistances. We have experience with measurement of contact resistances of lead-acid batteries in a battery factory. There we have measured the contact resistance of battery with the test current of 300A. It proved that the RMO300 is adequate model for this task.
Q: Do your Micro-ohmmeters create magnetic transients that can inadvertently cause relays on a breaker under test to operate?
A: Previous generation of Micro-ohmmeters, which were designed 5 years ago or earlier, generate DC current which contains high level of AC component, 100Hz or 120Hz. Those devices had full wave rectification, but without additional filtration. Because of that, magnetic transients might induce current on a secondary of a CT and cause breaker control or a relay to operate. Modern Micro-ohmmeters (like our Micro-ohmmeters RMO series) generate a filtered (true) DC current which contains low level of AC component, lower than 1%. These devices do not create any transients. IBEKO devices RMO series and other modern Micro-ohmmeters
Q: Which current cables do you suggest for use with RMO 300 device?
A: We propose cables 2x10m 35mm2 instead of current cables 2x10m 50mm2. Cables of 35mm2 weigh less than cables of 50mm2 and they are sufficient for 300A. Our RMO300 is more powerful than other Micro-ohmmeters and there is no need for thick cables in order to generate 300A.
Q: What is the meaning of PFC? What are you referring with DC/DC and supply?
A:PFC (Power Factor Correction) is input electronic unit. It's function is to make our devices load power network with cos φ ≈ 1. It makes that our device takes from power network just active, but not reactive power. This unit is fitted only in modern devices, such as our. DC/DC is unit which transforms high input voltage to output voltage (5V, 600A). This enables galvanic isolation between input and output of the device. Supply is a short form of Supplier Unit. That is our small inter-unit that supplies our electronic components.
