The UNI-T UT625A and UT625B High Current Low Resistance Ohmmeters are professional test instruments designed for accurate contact resistance, loop resistance and high-current connection resistance measurement in substations, switchgear, rail networks, renewable energy systems and industrial electrical installations.
Available in 100A (UT625A) and 200A (UT625B) versions, these instruments inject a controlled high DC test current through the device under test and use a 4-wire Kelvin measurement method to accurately determine very low resistance values down to 0.1μΩ resolution.
They are particularly suited for testing low , medium- and high-voltage circuit breakers, switchgear contacts, busbar joints, cable connections and other high-current electrical connections where even a small increase in resistance can indicate deterioration, contamination, loose connections or contact damage.
With a 7-inch colour display, built in thermal printer, PASS/FAIL comparison testing, 200-record storage and PC software connectivity, the UT625 series provides a complete field solution for commissioning, preventative maintenance and asset-condition testing.
Designed for Circuit Breaker Contact Resistance Testing
Electrical contacts within circuit breakers and switchgear carry very high currents during normal operation.
Over time, contact resistance can increase due to:
- Contact wear
- Oxidation
- Contamination
- Mechanical deterioration
- Loose connections
- Contact misalignment
- Arcing damage
- Poor installation or assembly
An increase in resistance can cause localised heating, power loss and potentially premature equipment failure.
The UT625A/UT625B injects a controlled high DC current through the contact and measures the resulting voltage drop to accurately calculate the contact resistance.
This provides maintenance teams with a practical way to assess the condition of critical high-current electrical connections.