Contents
SCXI-1581 User Manual
vi
ni.com
Appendix B
Measuring Temperature with Resistive Transducers
RTDs.............................................................................................................................. B-1
The Relationship Between Resistance and Temperature in RTDs ................. B-2
RTD Measurement Errors ............................................................................... B-6
Thermistors.................................................................................................................... B-7
Resistance/Temperature Characteristic of Thermistors .................................. B-9
Thermistor Measurement Circuits .................................................................. B-10
Connecting Resistive Devices to the SCXI-1581.......................................................... B-11
4-Wire Configuration ...................................................................................... B-12
2-Wire Configuration ...................................................................................... B-13
3-Wire Resistive Sensor Connected in a 2-Wire Configuration ..................... B-14
Lead-Resistance Compensation Using a 3-Wire Resistive Sensor
and Two Matched Current Sources.............................................................. B-15
Lead-Resistance Compensation Using a 3-Wire Resistive Sensor
and Two Differential Amplifiers.................................................................. B-16
Appendix C
Common Questions
Glossary
Index
Figures
Figure 1-1.
Installing the SCXI-1581 Module......................................................... 1-4
Figure 1-2.
Connecting an SCXI Chassis to an E Series DAQ Device ................... 1-6
Figure 1-3.
Removing the SCXI-1581..................................................................... 1-15
Figure 2-1.
Rear Signal Connector Pin Assignments .............................................. 2-4
Figure B-1.
Resistance-Temperature Curve for a 100
Ω
Platinum RTD,
α
= 0.00385........................................................................................... B-2
Figure B-2.
2-Wire RTD Measurement ................................................................... B-5
Figure B-3.
Resistance-Temperature Curve for a 2,252
Ω
Thermistor.................... B-7
Figure B-4.
Thermistor Measurement with Constant Current Excitation,
I
EX
......... B-9
Figure B-5.
4-Wire Resistive Sensor Connected in a 4-Wire Configuration ........... B-11
Figure B-6.
2-Wire Resistive Sensor Connected in a 2-Wire Configuration ........... B-12
Figure B-7.
3-Wire Resistive Sensor Connected in a 2-Wire Configuration ........... B-13
Figure B-8.
3-Wire Configuration Using Matched Current Sources ....................... B-14
Figure B-9.
3-Wire Configuration Using Two Differential Amplifiers ................... B-16