The contact resistance meter comes in a variety of sizes, including micro, mega, and milli-ohmmeters. Resistance is measured in a variety of electrical testing applications. The test measures resistance at the micro- or milli-ohm level and is used largely to check that electrical connections are formed correctly. It can detect the following problems:
- Loose connections
- Adequate tension on bolted joints.
- Eroded contact surfaces.
- Contaminated or corroded connections.
Contact resistance is the resistance to current flow caused by surface conditions and other factors when contacts come into contact (in the device’s closed state). This can happen between contacts of electrical components including:
- Breakers
- Contactors
- Relays
- Switches
- Connectors
- Other switching devices
Contact resistance testing, also known as ductor testing, is used to evaluate the resistance of electrical connections such as terminations, joints, connectors, busbar sections, and cable connections. These are connections between any two conductors, such as cable connectors or busbar sections. The device used to perform the contact resistance test is called an Ohmmeter, and because it only does the ductor test, it is also known as a contact resistance meter.
Why Do You Need a Contact Resistance Meter?
The circuit breaker’s contacts must be tested regularly to ensure it is in good working order. Poorly maintained or broken contacts can result in arcing, phase loss, and even fire.
This test is especially critical for connections that carry a lot of current (such as switchgear busbars) because increased contact resistance can lead to decreased current-carrying capability and higher losses. This testing is often done with a contact resistance meter, micro/milli-ohmmeter, or a low ohmmeter.
The measurement of contact resistance aids in the identification of fretting corrosion of contacts and permits contact corrosion to be identified and avoided. Increased contact resistance might result in a significant voltage drop in the system, which must be managed.
What happens during contact resistance testing?
The two most typical inspections performed on circuit breaker contacts are visual examination and contact resistance.
- The visual inspection check entails inspecting the circuit breaker contacts for pitting marks caused by arcing, as well as damaged or deformed contacts.
- The second check is to assess contact resistance. This includes pumping a set current, often 100A, 200A, or 300A, through the contacts and monitoring the voltage drop between them. This test is performed with a specialized contact resistance measuring device. The resistance value is then computed according to Ohm’s law. The resistance value should be compared to the value specified by the manufacturer. Additionally, the value should be compared to previous records.
Both of these tests must be performed simultaneously. There have been occasions where contacts have adequate contact resistance yet are damaged. Thus, to be certified healthy, a contact must have a strong contact resistance and pass the visual inspection test.
Conclusion
Thermal conductivity measurements are affected by contact resistance, which is especially important when transporting heat via a granular medium. When fluid flow moves from one channel to another, there is a reduction in hydrostatic pressure, similar to an electrical voltage.
You need a contact resistance meter to perform contact resistance tests to indicate how healthy the contacts are and their capacity to handle the rated current. The maximum contact resistance should be confirmed against the manufacturer’s requirements. The rated current should not be exceeded, and testing at 10% is advised.
S.B.ELECTROTECH
S.B. Electrotech is a company that specializes in manufacturing of electrical and electronic testing and measuring instruments. With years of expertise in this field, we ensure to provide high quality, safe, and sustainable products.
