NI-9216 Datasheet Question

[MrGosack]

I have a question regarding a line in the NI-9216 (RTD) module Getting Started guide, but I'll start with a little context.

I am assembling a system with 70, 10-Ohm Copper RTDs wired in a 3-wire configuration. There are 100 ft wire runs between the location of the DAQ and the RTDs.

I was confident that the NI-9216 was the correct module for the application until I read the following line in the Getting Started guide (just below figure 1):

"For the best measurement results when using the NI-9216 with a 3-wire RTD, use equal-length wires between the RTD+ terminal and the RTD and between the COM terminal and the RTD. Also, keep the lead resistance within 5% of the nominal RTD value. The NI-9216 accuracy specifications account for this lead error."

I was hoping to get an Applications Engineer to weigh in on this statement.

If I am understanding this correctly, if I have a 10 Ohm RTD connected, my lead resistance must be 0.5 Ohm or the accuracy suffers?

I took some lead resistance measurements, and each 3-wire run has something in the neighborhood of 1 Ohm per lead of resistance.

I'm afraid there is nothing practical I can do to reduce lead resistance.

Is there a best-practice for accommodating the additional lead resistance? (Signal Buffering? Software compensation?)

Thank you, I'm really trying to understand the implications of exceeding this limit.