Contact Resistance Test

[PH927]

I have to do a contact resistance test on a bus we have installed. The meter I have is a DRM-100 made by Adwel. Does anyone have any advice, tips, tricks, dos or don’ts? Sorry I’m so vague but this is the best I can do with the nature of the customer.

Thanks

 

[Zogzog]

You mean on a bus connection right?

You should have a 100A output for bus connections, and you simply compare the phases to each other and make sure they are within 5% of each other. Bus connections may also be checked with a calibrated torque wrench or a IR scan under load.

 

[hightime]

It is a very simple test. Remember the Ohms law, your applying dc voltage /injecting current and measuring the resistance. your meter will read resistance in milli or micro ohms.Record this value for future use if this is a new equipment. If you are conducting this test on a existing equipment compare the test values with old readings. As I wrote before this value will be very less. If you get a higher reading make sure to inspect the contact for dirt, worn out are any other possible reasons. Hope this will help you.
regards

 

[DanDel]

Key Point: Make sure the bus is de-energized before you attempt this test.

 

[busbar]

It may be helpful to note that, for accuracy’s sake, milliohm and microohm measurements are made using 4 leads {a Kelvin measurement}. The two current connections are made “outside” of the potential points of contact, while the two potential leads are connected (or “spiked”) exactly at the measurement point of interest.

 

[Zogzog]

Actually it is a Wheatstone Bridge, not a Kelvin Bridge. Same basic idea. Goes back to my favorite saying "You cant measure resistance", you can only calculate it.