Gurus,
I am having a custom test apparatus built by an outside contractor that is to include an NI cRIO with a few different DAQ modules; including the NI 9216 and NI 9217 RTD modules. Our uncertainty (accuracy) requirements for air and liquid temperature measurements (RTDs) are 0.15°C and 0.2°C, respectively. After looking at the data sheets for these modules, I am concerned in that they show temperature accuracies of 0.15°C for the module alone (4-wire mode). This appears to leave no room left for uncertainty in the RTD itself. I assume that we need to account for error-stacking between the sensor itself and the DAQ module. Am I incorrect in my reasoning, is there a more accurate DAQ card that can be specified, or are we simply not going to be able to meet the specified accuracy requirement? Thank you in advance for any insight that you all may have.