Rockwell Automation 1771-IR , D17716.5.76 RTD INPUT MODULE - Manual (Page 15)

Installing the RTD Input Module
Chapter 3
3Ć4
Figure 3.2
Connection Diagram for RTDs
18
16
14
12
10
8
6
4
2
C
B
A
C
B
A
C
B
A
C
B
A
C
B
A
C
B
A
12935
RTD
Ground
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Terminal
Identification
Chassis
Most importantly, you must ground the shield at the chassis end only. We
recommend connecting each input cable’s shield to a properly grounded
common bus.
Refer to Appendix E for 2–wire and 4–wire RTD connections.
Cable impedance –– Since the operating principle of the RTD module is based
on the measurement of resistance, you must take special care in selecting your
input cables. Select a cable that has a consistent impedance throughout its entire
length. We recommend Belden 9533 or equivalent. As cable length is directly
related to overall cable impedance, keep input cables as short as possible by
locating your I/O chassis as near the RTD sensors as I/O module considerations
permit. Keep the cable free of kinks and nicks to the shielding material.
Maximum cable length is limited by an overall cable impedance of 10 ohms on
a single wire. This recommendation is based on considerations of signal
degradation due to resistance mismatch between the three conductors within the
cable.