Dual Canopy Mechanic Electrical Engineering Co., Ltd. is one of the leading manufacturers and suppliers of Micro-Ohmmeter in China. Please feel free to wholesale discount products for sale here and get quotation from our factory. Customized orders are welcome.
What is a Micro-Ohmmeter?
The Micro-Ohmmeter(also known as a Contact Resistance Tester or Loop Resistance Tester) is a specialized instrument designed to measure the electrical resistance of switching devices and their connections. Unlike general-purpose ohmmeters or winding resistance testers, this device is specifically engineered to test the contact resistance of high-voltage circuit breakers, disconnectors (isolators), and busbar joints.
The measurement of contact resistance is critical because excessive resistance at contact points leads to localized overheating (hot spots), accelerated aging, and potential catastrophic failure of switchgear. To accurately measure these very low resistances (often in the micro-ohm range) and to break through surface oxidation films on contacts, the tester injects a high DC test current, typically ranging from 100A to 600A (or higher), in accordance with international standards such as IEC 62271-1.
What are the main points to pay attention to during use?
1. **Mandatory Power Disconnection and Reliable Isolation:** Verify that the circuit under test is disconnected from the active power system; live testing is strictly prohibited.
2. **Circuit Breaker Testing Requires "Closed" State:** Circuit resistance testing typically requires the main circuit to be closed; otherwise, a valid measurement cannot be obtained.
3. **Ensure Secure Fixture Contact:** Unstable clamping can lead to fluctuating or artificially high readings; it is recommended to clean the contact surfaces and ensure the fixtures are securely clamped.
4. **Do Not Disconnect Cables While Output Current Is Active:** Avoid arcing and potential damage to the terminals.
5. **Avoid Prolonged High-Current Output:** For connection points with small cross-sections or components sensitive to temperature rise, adhere to established procedures regarding test duration; perform intermittent testing if necessary.
6. **Maintain Consistency in Test Points:** When performing trend analysis on the same device, ensure consistency in fixture placement, test current, and operating procedures; otherwise, the data will not be comparable.
7. **Verify Results in High-Interference Environments:** High-current operations or strong magnetic fields in the vicinity may compromise measurement stability; perform multiple measurements to confirm consistent results.
**Model Selection Guidance:** We assist in selecting the appropriate model based on the specific application (circuit breakers, disconnectors, or busbars), desired test current, target resolution, and data export requirements.
**Accessory Matching:** We recommend suitable high-current clamps, extension cables, specialized adapters, and carrying cases to minimize the need for improvised field modifications.
**Documentation Support:** We provide technical specifications, wiring diagrams, typical testing procedures, and-within the scope of available resources-documentation required for tender submissions.
**Remote Technical Support:** We assist in troubleshooting common issues, such as unstable readings, anomalously high values, or abnormal phase-to-phase discrepancies.
**Spare Parts Supply:** Clamps, test leads, fuses, power adapters, and other spare parts are available for long-term supply.
**Repair and Calibration:** We offer factory-based inspection, repair, and calibration services to ensure compliance with project acceptance and auditing requirements.
**Refresher Training:** Upon personnel turnover, we provide remote training to ensure consistency in testing methodologies and data recording standards.
FAQ
Q:Does it support data storage and export?
A:Depending on the specific configuration, it supports internal storage, USB export, printing, or wireless transmission, facilitating the generation of acceptance reports and maintenance logs.
Q:How often is calibration required?
A:Generally, it is recommended to perform calibration once every 12 months, or in accordance with internal corporate control policies. For acceptance testing projects, it is advisable to retain the calibration or metrology certificates.
Q:Can it be used to identify overheating risks at busbar connection points?
A:Yes. By comparing the resistance values of similar connection points, it assists in pinpointing potential high-resistance hotspots that could lead to overheating.
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