Handheld Michro-ohmmeter DV Power RMO-H2

An essential part of power circuit breakers are its contacts. Mechanical wear and teat on circuit breaker contacts reduces the area of contact surface. Due to arcing, carbonized layers are built on the contact surface. This also reduces live contact area. Reduced contact surface leads to increased contact resistance which further leads to increased heating and losses.  At 10 kA a contact with resistance of 0,1 mΩ gives a power loss of 10 kW. This power loss at one point will cause a temperature rise, which may result in overheating and premature failure of the breaker and affect the power system's overall reliability.  To avoid this kind of problem, manufacturers specify reference values for each type of their circuit breakers. Prior to a circuit breaker commissioning of circuit breaker and during routine maintenance the value of primary circuit contact resistance (the resistance between two terminals of any pole a breaker) is measured. Standard IEC 62271-100 and ANSI C 37.09. 2010. specify conditions, methods and procedures of measurements.  For these purposes DV Power developed lightweight handheld micro-ohmmeters, RMO-H series:  

• RMO-H1 with test current up to 100 A and test leads up to 5 m  
• RMO-H2 with test current up to 220 A and test leads up to 5 m  
• RMO-H21 with test current up to 100 A and test leads up to 15 m  

Product Overview  

The RMO-H2 micro-ohmmeter is a handheld battery-operated micro-ohmmeter that is designed to measure the contact resistance of non-inductive test objects. The main applications are testing medium and high-voltage circuit breakers, disconnecting switches, high-current bus bar joints, and different high-current links.   High-induction fields impose no problem for the RMO-H series: the instrument is reliable and accurately performs measurements in both substations and factories. Its measuring range goes from 0,1 µΩ with up to 3000 mΩ. Additionally, it has a high accuracy of ± (0,1 % rdg + 0,1 % FS) which ensures that measurements are precise and consistent.  

Handheld ohmmeter design  

The RMO ohmmeters are designed to be portable and easy to use. They are manufactured by DV Power, a leading provider of high-quality test equipment for the electrical industry. Devices within this series meet the highest safety standards and are designed to be used in hazardous environments. They are also designed to be easy to use and can be operated with just one hand, which reduces the risk of accidents.  Unlike many other handheld micro-ohmmeters available on the market, RMO-H instruments have regulated and user-selectable test currents. Therefore, they can generate an automatically regulated test ramp with stable and ripple-free test current during measurement. These characteristics in small and portable micro-ohmmeter are enabled by using sophisticated Li-Po batteries. Consequently, modern battery technology enables you to do multiple measurements, and a full day of testing without recharging the battery. Moreover, no rest time is needed between tests since there is no ultra-capacitor charging.  For RMO-H1 and RMO-H2, the 1-cell Li-Po battery with 8800 mAh capacity provides an output voltage up to 4,2 V DC.   For RMO-H21, the high output voltage (up to 8,4 V DC) is provided by 2-cell 4400 mAh LiPo battery.  The test current is regulated and can be selected in a range of 1 A to a maximum of 100 A for RMO-H1 and RMO-H21, and from 1 A to a 220 A for RMO-H2.  The instrument can store up to 1000 measurements on its internal micro-SD card, and the free DV Win software enables wireless Bluetooth communication for downloading, analyzing, and generating fully configurable test reports.  

Testing both sides grounded circuit breaker  

Any substation testing can be dangerous due to the risk of high electric potential presence. Regulations and laws impose grounding on both sides of a test object before any maintenance work is performed on the test object.  Grounding of both sides increases safety for the user and other personnel nearby.   With RMO-H instruments it is possible to perform tests with grounded both sides of the test object (Both Sides Grounded Test). The user-friendly interface of RMO-H series with one click measurement speeds up testing and even more enhances safety.   In conclusion, RMO-H micro-ohmmeters are reliable, portable, and lightweight test devices that are suitable for a wide range of applications. They are designed to be easy to use and provide accurate and reliable measurements. Additionally, they are a part of a range of electrical test equipment that are designed to meet the needs of the electrical industry.