Technical data
Publication 1794-2.1 - January 2000
FLEX I/O and FLEX Integra Product Data
24V dc RTD Input Module Cat. No. 1794-IR8 123
24V dc RTD Input Module Cat. No. 1794-IR8
Wiring
1. Connect the individual high and low signal wiring to numbered
terminals on the 0-15 row (A) on the terminal base unit as
indicated in the table below.
2. Connect 24V dc common to terminal 16 on row (B).
3. Connect individual channel signal returns to the associated terminal
on row (B) as shown in the table below.
4. Connect individual channel shield returns to the associated
terminal on row (B) for 1794-TB3 or row (C) for the 1794-TB3T as
shown in the table below.
5. Connect +24V dc to terminal 34 on the 34-51 row (C).
6. If daisy-chaining 24V dc common, connect jumper from terminal 33
to terminal 16 on the next terminal base unit.
7. If daisy-chaining +24V dc, connect jumper from terminal 51 to
terminal 34 on the next terminal base unit.
8. Connect the shield to functional earth ground as near as possible to
the module.
Recommended
Terminal Base
Compatible
Terminal Base(s)
1794-IR8
3 WIRE RTD INPUT 8 CHANNEL
-++-+
-
+-
3
-++-+
-
+-
INPUT 0 INPUT 1 INPUT 2 INPUT 3
INPUT 4 INPUT 5 INPUT 6 INPUT 7
OK
40147
TB3
TB2
TB3S TB3T TB3TS
40148
Simplified Schematic of Channel 0 Using a 3- or 4-wire RTD
TB3, TB3S, or TB2 shown
Input Device
Shielded
Twisted Pair
Cable
24V
Power Supply
A-0
B-17
A-1
C-34
B-16
dc/dc
Converter
+5V
-5V
+15V
-15V
V
ref
V
ref
I
V
ref
Voltage
Reference
A/D
Converter
Micro
Processor
Flexbus
Interface
Voltage
Reference
+5V +5V
+5V +5V
ATTENTION
!
Use the following Belden cables for connecting the
RTD to the terminal base unit.
RTD Type Length of Run/Humidity Level Belden Cable
Number
2-wire Not applicable 9501
3-wire Less than 100ft (30.5m) with normal
humidity
9533
Over 100ft (30.5m) or high humidity
1
83503
1 Greater than 55% for more than 8 hours
ATTENTION
!
To reduce susceptibility to noise, power analog
modules and digital modules from separate power
supplies. Do not exceed a length of 33ft (10m) for dc
power cabling.
Do not daisy chain power or ground from the RTD
terminal base unit to any ac or dc digital module
terminal base units.