Rockwell Automation 1790-XXXX CompactBlock LDX I/O DeviceNet RTD and Thermocouple - Manual (Page 11)

11
Publication 1790-IN011B-EN-P - April 2003
To ensure that the lead values match as closely as
possible:
• keep lead resistance as small as possible and less than
25 ohms
• use quality cable that has a small tolerance impedance
rating
• use a heavy-gauge lead wire which has less resistance
per foot
RTD Wiring Configurations
Three configurations of RTDs can be connected to the
blocks:
• 2-wire RTD, which is composed of an RTD EXC
(excitation) lead wire and a RTN (return) wire
• 3-wire RTD, which is composed of a Sense and 2 RTD
lead wires (RTD EXC and RTN)
• 4-wire RTD, which is composed of a Sense and 2 RTD
lead wires (RTD EXC and RTN). The second sense
wire of a 4-wire RTD is left open.
2-Wire RTD Configuration
CH0_A
CH0_B
COM
Add Jumper Cable Shield (to Ground)
RTD EXC RTD EXC
Return Return