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What is Contact Resistance

Contact resistance is the resistance to current flow, due to surface conditions and other causes, when contacts are touching one another (in the closed condition of the device). This can occur between contacts of: 

• Breakers 
• Cont actors 
• Relays 
• Switches 
• Connectors 
• Other switching devices 

Contact resistance testing also known as Ductor testing, measures the resistance of electrical connections – terminations, joints, connectors, bus bar sections or cable connections and so on. These can be connections between any two conductors, for example, cable connections or busbar sections. The instrument which is used to perform the ductor test is called an Ohmmeter, and since its function is to perform the ductor test, the ohmmeter is also known as a ductor tester.  

The ductor tester can be found in many variations such as Micro, Mega and Milli- Ohmmeters, static resistance tester or DLRO which stands for Digital Low Resistance Ohm Meter. Is used to measure resistance in different applications of electrical testing. This tester consists of a DC ammeter and a few other components. The test measures the resistance at the micro- or milli-ohm level and is used primarily to verify that electrical connections are made properly, and can detect the following problems: 

• Loose connections 
• Adequate tension on bolted joints 
• Eroded contact surfaces 
• Contaminated or corroded contacts 

The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance, which is an inherent property, independent of the measurement method. This effect is often described by the term Electrical Contact Resistance or ECR and may vary with time, most often decreasing, in a process known as resistance creep. The idea of potential drop on the injection electrode was introduced by William Shockley to explain the difference between the experimental results and the model of gradual channel approximation. 

Product Description

Intelligent loop/contact resistance tester is based on the new power standard IEC62271, the use of high frequency switching power supply technology and digital circuit technology combined design.

It is suitable for the measurement of circuit resistance of switching control equipment.

The circuit resistance can be directly measured at the current of 100A, 200A, 400A and 600A, and the final test results are displayed digitally.

The instrument is accurate in measurement and stable in performance, and meets the requirements of on-site maintenance of high-voltage switches in power and power supply departments and circuit resistance test in high-voltage switchgear factories.

Specification