Allen-Bradley SLC 500 1746-NT8 User manual

Publication 1746-5.23
SLC 500 Thermocouple/mV Analog
Input Module
(Catalog Number 1746-NT8)
Installation Instructions
Inside...
Important User Information . . . . . . . . . . . . . . . . . . . . . . . . . 2
For More Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Module Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Input Ranges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Hardware Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Installing And Wiring Your Module . . . . . . . . . . . . . . . . . . . 8
Electrostatic Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Required Tools and Equipment. . . . . . . . . . . . . . . . . . . . . . 9
Power Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Considerations for a Modular System. . . . . . . . . . . . . . . . . 10
Considerations for a Fixed Controller . . . . . . . . . . . . . . . . . 10
Selecting A Rack Slot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Module Installation and Removal . . . . . . . . . . . . . . . . . . . . 11
Terminal Block Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Cold Junction Compensation (CJC) . . . . . . . . . . . . . . . . . . 13
Wiring Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Thermocouple Junctions. . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Preparing and Wiring the Cables . . . . . . . . . . . . . . . . . . . . 18
Module Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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2SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-5.23
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Because of the variety of uses for the products described in this publication, those
responsible for the application and use of this control equipment must satisfy
themselves that all necessary steps have been taken to assure that each
application and use meets all performance and safety requirements, including any
applicable laws, regulations, codes and standards.
The illustrations, charts, sample programs and layout examples shown in this
guide are intended solely for purposes of example. Since there are many
variables and requirements associated with any particular installation,
Allen-Bradley does not assume responsibility or liability (to include intellectual
property liability) for actual use based upon the examples shown in this
publication.
Allen-Bradley publication SGI-1.1, Safety Guidelines for the Application,
Installation, and Maintenance of Solid-State Control (available from your local
Allen-Bradley office), describes some important differences between solid–state
equipment and electromechanical devices that should be taken into consideration
when applying products such as those described in this publication.
Reproduction of the contents of this copyrighted publication, in whole or in part,
without written permission of Allen-Bradley Company, Inc., is prohibited.
Throughout these installation instructions we use notes to make you aware of
safety considerations:
Attention statements help you to:
• identify a hazard
• avoid the hazard
• recognize the consequences
!ATTENTION: Identifies information about practices or
circumstances that can lead to personal injury or death, property
damage or economic loss.
Important: Identifies information that is critical for successful application and
understanding of the product.

SLC 500 Thermocouple/mV Analog Input Module 3
Publication 1746-5.23
For More Information
As part of our effort to preserve, protect, and improve our environment, Allen-
Bradley is reducing the amount of paper we use. Less paper means more options
for you. In addition to traditional printed publications and CD-ROM versions, we
now offer on-line manuals with the most up-to-date information you can get. We
recommend that you read the related publications listed below before starting up
your control system.
Related Publications
How to Get More Information
If you would like a manual, you can:
• download a free electronic version from the internet at
www.theautomationbookstore.com
• purchase a manual by:
— contacting your local distributor or Rockwell Automation
representative
— visiting www.theautomationbookstore.com and placing your order
— calling 1.800.963.9548 (USA/Canada) or 001.330.725.1574 (Outside
USA/Canada)
For Refer to this Document Pub. No.
A more detailed description on how to install
and use your SLC 500™ Thermocouple/mV
Input Module
SLC 500™ Thermocouple/
mV Analog Input Module
User Manual 1746-6.22
A more detailed description on how to install
and use your SLC 500™ Modular Hardware
Style Control System.
SLC 500™ Modular
Hardware Style Installation
and Operation Manual 1747-6.2
More information on proper wiring and
grounding techniques. Automation Wiring and Grounding Guidelines 1770-4.1
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4SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-5.23
Module Overview
The module communicates with the SLC 500 processor and receives +5V dc and
+24V dc power from the system power supply through the parallel backplane
interface. No external power supply is required. You may install as many
thermocouple modules in the system as the power supply can support.
Each module channel can receive input signals from a thermocouple or a
millivolt analog input device. You configure each channel to accept either one.
The module converts analog input voltages when it is configured for
thermocouple input types. The analog input voltages are converted into cold-
junction compensated, digital temperature readings. The module uses the
National Institute of Standards and Technology (NIST) based on ITS-90 for
thermocouple linearization.
When configured for millivolt analog inputs, the module converts analog values
directly into digital counts. The module assumes that the mV input signal is
linear prior to input to the module.

SLC 500 Thermocouple/mV Analog Input Module 5
Publication 1746-5.23
Input Ranges
The following tables define thermocouple types and associated temperature
ranges and the millivolt analog input signal ranges that each of the module’s
input channels will support. To determine the practical temperature range of your
thermocouple, refer to the specifications in Appendix A of the SLC 500
Thermocouple/mV Analog Input Module User Manual, publication 1746-6.22.
Thermocouple Temperature Ranges
Millivolt Input Ranges
Each input channel is individually configured for a specific input device. Each
channel detects and indicates:
• open-circuit
• over-range
• under-range
Type °C Temperature Range °F Temperature Range
J-210 °C to 760 °C -346 °F to 1400 °F
K -270 °C to 1370 °C -454 °F to 2498 °F
T -270 °C to 400 °C -454 °F to 752 °F
B 300 °C to 1820 °C 572 °C to 3308 °F
E -270 °C to 1000 °C -454 °F to 1832 °F
R 0 °C to 1768 °C 32 °F to 3214 °F
S 0 °C to 1768 °C 32 °F to 3214 °F
N 0 °C to 1300 °C 32 °F to 2372 °F
CJC Sensor -25 °C to 105 °C -13 °F to 221 °F
-50 to +50 mV
-100 to +100 mV
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6SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-5.23
Hardware Features
The module fits into any single slot (other than slot 0) for I/O modules in either
an SLC 500 modular system or an SLC 500 fixed system expansion chassis
(1746-A2). It is a Class 11module (uses 8 input words and 8 output words).
The module contains a removable terminal block providing connections for eight
thermocouple and/or analog input devices. On the terminal block are two cold-
junction compensation (CJC) sensors that compensate for the cold junction at
ambient temperature. It should also be noted there are no output channels on the
module. Configure the module with software rather than with jumpers or
switches.
1. Requires use of a Block Transfer in a remote configuration.
Important: There is a jumper (JP1) on the circuit board. The module is
shipped with the jumper in the up position as illustrated below. Do
not change the position of JP1. The jumper is used for test
purposes only.
JP1
Jumper - Do Not move.

SLC 500 Thermocouple/mV Analog Input Module 7
Publication 1746-5.23
1746-NT8 Features
Hardware Function
Channel Status LED Indicators Display operating and fault status of channels 0-7
Module Status LED Displays operating and fault status of the module
Side Label (Nameplate) Provides module information
Removable Terminal Block Provides electrical connection to input devices
Door Label Permits easy terminal identification
Self Locking Tabs Secure module in chassis slot
MODULE
0
14 5
2
12 3
CHANNEL
STATUS
THERMOCOUPLE/mV
INPUT
CJC A+
CJC A-
CHL 0+
CHL 0-
SHIELD
CHL 1+
CHL 1-
CHL 2+
CHL 2-
SHIELD
CHL 3+
CHL 3-
CHL 4+
CHL 4-
SHIELD
CHL 5+
CHL 5-
CHL 6+
CHL 6-
SHIELD
CHL 7+
CHL 7-
CJC B+
CJC B-
1746-NT8
Door Label
Channel Status
LEDs (Green)
Module Status
LED (Green)
Removable
Terminal Block
CJC Sensors
Cable Tie Slots
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8SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-5.23
Installing And Wiring Your Module
Read this section to install and wire your module. This section covers:
• avoiding electrostatic damage
• determining power requirements
• installing the module
• wiring signal cables to the module’s terminal block
Electrostatic Damage
Electrostatic discharge can damage semiconductor devices inside this module if
you touch backplane connector pins. Guard against electrostatic damage by
observing the following precautions:
!ATTENTION: ELECTROSTATICALLY SENSITIVE
COMPONENTS
• Before handling the module, touch a grounded object to rid
yourself of electrostatic charge.
• Handle the module from the front, away from the backplane
connector. Do not touch backplane connector pins.
• Keep the module in its static-shield container when not in
use or during shipment.
Failure to observe these precautions can degrade the module’s
performance or cause permanent damage.

SLC 500 Thermocouple/mV Analog Input Module 9
Publication 1746-5.23
Required Tools and Equipment
Have the following tools and equipment ready:
• 2.5 mm (0.1 in.) slot-head screwdriver
• thermocouple or millivolt sensor
• appropriate thermocouple extension wire (if needed)
• thermocouple/mV input module (1746-NT8)
• programming equipment
Power Requirements
The module receives its power through the SLC 500 chassis backplane from the
fixed or modular +5V dc/+24V dc chassis power supply. The maximum current
drawn by the module is shown in the following table.
Maximum Current Drawn By the Module
5VDC Amps 24VDC Amps
0.120 0.070
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10 SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-5.23
Considerations for a Modular System
Place your module in any slot of an SLC 500 modular, or modular expansion
chassis, except for the left-most slot (slot 0) reserved for the SLC processor or
adapter modules.
Considerations for a Fixed Controller
The power supply in the 2-slot SLC 500 fixed I/O chassis (1746-A2) can support
only specific combinations of modules. Make sure the chassis power supply can
support the 1746-NT8 and additional module power requirements.
Selecting A Rack Slot
Two factors determine where you should install your module in the rack: ambient
temperature and electrical noise. When selecting a slot for your module, try to
position your module:
• in a rack close to the bottom of the enclosure (where the air is cooler)
• away from modules that generate significant heat, such as the 1746-OA16
or the 1746-IA16
• in a slot away from ac or high-voltage dc modules, hard contact switches,
relays, and ac motor drives
• away from the rack power supply (if using a modular system)
Remember that in a modular system, a processor or adapter always occupies the
first slot of the rack.