Solution
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.
If you are application require you to use 2-wire resistance measurements, a reed relay option will be a good option.