Allen-Bradley 1794-IT8 User manual

English
FLEX I/O is a trademark of Rockwell Automation
Publication 1794-5.21 – May 1999
24V dc FLEX I/O
Thermocouple/mV Input Module
(Cat. No. 1794-IT8)
4
1
3
2
5
6
7
Module Installation
This module mounts on a 1794 terminal base unit.
1.Rotate keyswitch (1) on terminal base unit (2) clockwise to position 3
as required for this type of module.
2.Make certain the flexbus connector (3) is pushed all the way to the left
to connect with the neighboring terminal base/adapter. You cannot
install the module unless the connector is fully extended.
3.Make sure that the pins on the bottom of the module are straight so
they will align properly with the connector in the terminal base unit.
4.Position the module (4) with its alignment bar (5) aligned with the
groove (6) on the terminal base.
5.Press firmly and evenly to seat the module in the terminal base unit.
The module is seated when the latching mechanism (7) is locked into
the module.
Installation Instructions
Allen-Bradley Parts

24V dc FLEX I/O Thermocouple/mV Input Module2
Publication 1794-5.21 – May 1999
!ATTENTION: Remove field-side power before
removing or inserting this module. This module is
designed so you can remove and insert it under
backplane power. When you remove or insert a module
with field-side power applied, an electrical arc may
occur. An electrical arc can cause personal injury or
property damage by:
•sending an erroneous signal to your system’s field
devices causing unintended machine motion
•causing an explosion in a hazardous environment
Repeated electrical arcing causes excessive wear to
contacts on both the module and its mating connector.
Worn contacts may create electrical resistance.
European Union Directive Compliance
If this product has the CE mark it is approved for installation within the
European Union and EEA regions. It has been designed and tested to meet
the following directives.
EMC Directive
This product is tested to meet Council Directive 89/336/EEC
Electromagnetic Compatibility (EMC) and the following standards, in
whole or in part, documented in a technical construction file:
•EN 50081-2 EMC – Generic Emission Standard, Part 2 – Industrial
Environment
•EN 50082-2 EMC – Generic Immunity Standard, Part 2 – Industrial
Environment
This product is intended for use in an industrial environment.
Low Voltage Directive
This product is tested to meet Council Directive 73/23/EEC Low Voltage,
by applying the safety requirements of EN 61131–2 Programmable
Controllers, Part 2 – Equipment Requirements and Tests.
For specific information required by EN 61131-2, see the appropriate
sections in this publication, as well as the following Allen-Bradley
publications:
•Industrial Automation Wiring and Grounding Guidelines For Noise
Immunity, publication 1770-4.1
•Automation Systems Catalog, publication B111
This equipment is classified as open equipment and must be mounted in
an enclosure during operation to provide safety protection.

24V dc FLEX I/O Thermocouple/mV Input Module 3
Publication 1794-5.21 – May 1999
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 wiring table.
2. Connect 24V dc common to terminal 16 on row (B).
!ATTENTION: You must power this module from the same
power supply that supplies the adapter module so they both
power up or down together. You must cycle power for the
adapter to recognize this module.
3. Connect individual channel shield returns to the associated terminal
on row (B) for 1794-TB3 and -TB3S or row (C) for the 1794-TB3T or
-TB3TS as shown in the wiring table.
4. Connect +24V dc to terminal 34 on the 34-51 row (C).
ATTENTION: To reduce susceptibility to noise, power
analog modules and digital modules from separate power
supplies. Do not exceed a length of 33 ft (10m) for dc
power cabling.
!ATTENTION: Do not daisy chain power or ground from the
thermocouple terminal base unit to any ac or dc discrete
module terminal base units.
5. On 1794–TB3T or –TB3TS terminal bases, connect cold junction
compensation (CJC) wiring to terminals 36, 37 and 38 for inputs 0–3,
and terminals 47, 48 and 49 for inputs 4–7.
Connect the tail of the cold junction compensator to any of the
associated thermocouple input terminals: 0 through 7 for CJC
connected to terminals 37, 38 and 39; or 8 through 15 for CJC
connected to terminals 47, 48 and 49. The tail of the cold junction
compensator shares a terminal with an input.
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.
Allen-Bradley Parts

24V dc FLEX I/O Thermocouple/mV Input Module4
Publication 1794-5.21 – May 1999
8. Connect the shield to functional earth ground as near as possible to
the module.
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
16
1234567891011121314150
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
34
1794-TB2, TB3, -TB3T
0 –15
34–51
16–33 A
B
C
Shaded terminals not included on 1794-TB2 terminal base unit.
Note: Use 1794-TB3T or -TB3TS base units for thermocouple or millivolt inputs
.
Use 1794-TB2 or -TB3 base units for millivolt inputs only.
ATTENTION: Total current draw through the terminal
base unit is limited to 10A. Separate power connections to
the terminal base unit may be necessary.
Millivolt Mode
1794-TB2, -TB3, -TB3S T erminal Base Units
Millivolt Mode
Channel High Signal
T
erm. (+)
Low Signal
T
erm. (–)
Shield Return Not Used
0 0 1 17 18
1 2 3 19 20
2 4 5 21 22
3 6 7 23 24
4 8 9 25 26
5 10 11 27 28
6 12 13 29 30
7 14 15 31 32
24V dc Common 16 thru 33
+24V dc power 34 and 51 on 1794-TB2; 34 thru 51 on 1794-TB3

24V dc FLEX I/O Thermocouple/mV Input Module 5
Publication 1794-5.21 – May 1999
Thermocouple
1794-TB3T or -TB3TS T erminal Base Unit
Thermocouple
Channel High Signal
T
erm. (+)
Low Signal
T
erm. (–)
Not Used
Shield
Return
0 0 1 17(C) 39
1 2 3 19(C) 40
2 4 5 21(C) 41
3 6 7 23(C) 42
4 8 9 25(C) 43
5 10 11 27(C) 44
6 12 13 29(C) 45
7 14 15 31(C) 46
24V dc Common 16, 17, 19, 21, 23, 25, 27, 29, 31 and 33
+24V dc power 34, 35, 50 and 51
*T erminals 39 to 46 are chassis ground.
T erminals 36, 37, 38 and 47, 48, 49 are for cold junction compensators only .
Example of Thermocouple W iring to 1794-TB3T Base Unit
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 150
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
34
1794-TB3T
0 –15
34–51
16–33
+
–
Channel 0 (T erminals 0 and 1 with shield to 39)
CJC CJC
CJC kit Cat. No. 1794–CJC2/A
(contains 2 CJCs)
Allen-Bradley Parts

24V dc FLEX I/O Thermocouple/mV Input Module6
Publication 1794-5.21 – May 1999
Example of Millivolt Input W iring to a 1794-TB3 or -TB3T Base Unit
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 150
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
34
1794-TB3
0 –15
34–51
16–33
+
–
Millivolt input
Channel 1
Millivolt
Source
Channel 0 (T erminals 0, 1 and 17)
Indicators
INPUT 0 INPUT 2 INPUT 4 INPUT 6INPUT 1 INPUT 3 INPUT 5 INPUT 7
THERMOCOUPLE INPUT 8 CHANNEL
3
1794–IT8
Allen-Bradley
AB
+– +– +– +–+– +–+–+–
OK
A= Status Indicator – indicates diagnostics results and
configuration status.
B= Insertable label for writing individual input designations.

24V dc FLEX I/O Thermocouple/mV Input Module 7
Publication 1794-5.21 – May 1999
Block T ransfer Read and W rite
The following block transfer read and write word bit information is
presented for experienced users only. Refer to the user manual
(publication 1794-6.5.7)for this product for complete information on
programming and configuring your module.
Input Mapping
Bit⇒1
514 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Word
⇓Read
0 Reserved
1 Channel 0 Input Data
2 Channel 1 Input Data
3 Channel 2 Input Data
4 Channel 3 Input Data
5 Channel 4 Input Data
6 Channel 5 Input Data
7 Channel 6 Input Data
8 Channel 7 Input Data
9 Overrange Bits Underrange Bits
10 0 0 0 0 0 Bad
Cal Cal Done Cal
Rn
gRIUP Diagnostic
Status Bits
Pwr
Up Bad Struct CJC over CJC Under
Output Mapping
Bit⇒15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Word⇓Write
0 8-bit Calibration Mask
Cal
Clk Cal Hi/Lo
Filter Cutof f FDF Module
Data
Type
1 Thermocouple 3 T ype Tfhermocouple 2 T ype Thermocouple 1 T ype Thermocouple 0 T ype
2 Thermocouple 7 T ype Thermocouple 6 T ype Thermocouple 5 T ype Thermcouple 4 T ype
3 Reserved
Where: FDF = fixed digital filter
Allen-Bradley Parts

24V dc FLEX I/O Thermocouple/mV Input Module8
Publication 1794-5.21 – May 1999
Thermocouple T ype
Word Description
Thermocouple T ype – Range
Write
W ord 1
Bit 03 02 01 00 Channel 0
W ord 1
Bit 07 06 05 04 Channel 1
Bit 11 10 09 08 Channel 2
Bit 15 14 13 12 Channel 3
Write
W ord 2
Bit 03 02 01 00 Channel 4
W ord 2
Bit 07 06 05 04 Channel 5
Bit 11 10 09 08 Channel 6
Bit 15 14 13 12 Channel 7
0 0 0 0 Millivolts (default)
0 0 0 1 B 300 to 1800
oC
(572 to 3272
oF)
0 0 1 0 E –270 to 1000
oC
(–454 to 1832
oF)
0 0 1 1 J –210 to 1200
oC
(–346 to 2192
oF)
0 1 0 0 K –270 to 1372
oC
(–454 to 2502
oF)
0 1 0 1 R –50 to 1768
oC
(–58 to 3214
oF)
0 1 1 0 S –50 to 1768
oC
(–58 to 3214
oF)
0 1 1 1 T –270 to 400
oC
(–454 to 752
oF)
1 0 0 0 C 0 to 2315
oC
(32 to 4199
oF)
1 0 0 1 N –270 to 1300
oC
(–454 to 2372
oF)
1 0 1 0 TXK/XK (L) –200 to 800
o
C (–328 to 1472
oF)
1 0 1 1 Reserved
1 1 0 0 Module reports cold junction temperature for
channels 00–03
1 1 0 1 Module reports cold junction temperature for
channels 04–07
1 1 1 0 Reserved
1 1 1 1 No sensor connected (do not scan)

24V dc FLEX I/O Thermocouple/mV Input Module 9
Publication 1794-5.21 – May 1999
Data T ype
Word Description
Write
Word 0
Module Data T ype
W ord 0
Bit 01 00 Definition
0 0 o C (default)
0 1 oF
1 0 Bipolar counts scaled between –32768 and
+32767 (default)
1 1 Unipolar counts scaled between 0 and 65535
Allen-Bradley Parts

24V dc FLEX I/O Thermocouple/mV Input Module10
Publication 1794-5.21 – May 1999
CSA Hazardous Location Approval
CSA certifies products for general use as well as for use in hazardous locations. Actual
CSA certification is indicated by the product label as shown below , and not by
statements in any user documentation.
Example of the CSA certification product label
I
To comply with CSA certification for use in hazardous locations, the following information
becomes a part of the product literature for CSA-certified Allen-Bradley industrial control
products.
•This equipment is suitable for use in Class I, Division 2,
Groups A, B, C, D, or non-hazardous locations only .
•
The products having the appropriate CSA markings (that is, Class I Division 2, Groups
A, B, C, D), are certified for use in other equipment where the suitability of combination
(that is, application or use) is determined by the CSA or the local inspection of fice
having jurisdiction.
Important: Due to the modular nature of a PLC

control system, the product with the
highest temperature rating determines the overall temperature code rating of a PLC
control system in a Class I, Division 2 location. The temperature code rating is marked on
the product label as shown.
T
em
p
erature code rating
Look for temperature code
rating here
I
The following warnings apply to products having CSA certification for use in hazardous
locations.