Why Does My NI Switch Card Say It Is Not Recommended for 2-Wire Measurements?

Updated Jun 6, 2018

Reported In


  • PXIe-2526

Issue Details

I am planning on buying NI Switches (like the PXIe-2526) and will be using them for some resistance measurements. I noticed in the spec sheet that there is a note that says "The NI 2526 is not recommended for 2-wire resistance measurements." Why is this the case?


The has to do with the fact that some of our switches, like the PXIe-2526, use armature relays. These switches have a minimum switch load (ex. 20 mV/1mA). If you can guarantee that this spec is met, than you can use them for resistance measurements. However, it this is not met than the oxidation on the switch will cause a higher resistance. Therefore, this is the reason why it is not recommended for resistance measurements. Our document on Armature Relay Contact Stability talks about this more in depth, and even item 4 talks specifically about Resistance measurements. 

Additional Information

You may want to look at some of our Reed relay devices for 2-wire resistance measurements. 


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