Allen-Bradley SLC 500 Series User manual

Publication 1746-IN015C-EN-P - July 2001
Installation Instructions
SLC 500 Thermocouple/mV Analog Input Module
(Catalog Number 1746-NT8)
Inside...
Hazardous Location Considerations ........................................................ 2
Environnements dangereux ..................................................................... 2
Module Overview..................................................................................... 3
Input Ranges ............................................................................................ 3
Hardware Features .................................................................................. 4
Installing And Wiring Your Module ......................................................... 5
Electrostatic Damage............................................................................... 6
Required Tools and Equipment................................................................ 6
Power Requirements................................................................................ 6
Considerations for a Modular System ..................................................... 7
Considerations for a Fixed Controller ...................................................... 7
Selecting A Chassis Slot.......................................................................... 7
Module Installation and Removal............................................................ 8
Terminal Block Removal........................................................................... 9
Cold Junction Compensation (CJC) ....................................................... 10
Wiring Guidelines .................................................................................. 10
Thermocouple Junctions........................................................................ 11
Preparing and Wiring the Cables........................................................... 14
Module Specifications........................................................................... 17
For More Information ............................................................................. 20

2SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-IN015C-EN-P - July 2001
Hazardous Location Considerations
This equipment is suitable for use in Class I, Division 2, Groups A, B, C, D or
non-hazardous locations only. The following WARNING statement applies to use in
hazardous locations.
Environnements dangereux
Cet équipement est conçu pour être utilisé dans des environnements de Classe I,
Division 2, Groupes A, B, C, D ou non dangereux. La mise en garde suivante
s’applique à une utilisation dans des environnements dangereux.
WARNING
!
EXPLOSION HAZARD
•Substitution of components may impair suitability for Class
I, Division 2.
•Do not replace components or disconnect equipment
unless power has been switched off or the area is known to
be non-hazardous.
•Do not connect or disconnect components unless power
has been switched off or the area is known to be
non-hazardous.
•All wiring must comply with N.E.C. article 501-4(b).
AVERTISSEMENT
!
DANGER D’EXPLOSION
•La substitution de composants peut rendre cet équipement
impropre à une utilisation en environnement de Classe I,
Division 2.
•Ne pas remplacer de composants ou déconnecter
l'équipement sans s'être assuré que l'alimentation est
coupée.
•Ne pas connecter ou déconnecter des composants sans
s'être assuré que l'alimentation est coupée.

SLC 500 Thermocouple/mV Analog Input Module 3
Publication 1746-IN015C-EN-P - July 2001
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.
Input Ranges
The following two 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.
Table A Thermocouple Temperature Ranges
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
Table B Millivolt Input Ranges(1)
(1) Output impedance of input device must be less than 100 Ω to meet accuracy specifications.
-50 to +50 mV -100 to +100 mV

4SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-IN015C-EN-P - July 2001
Each input channel is individually configured for a specific input device. Each
channel detects and indicates:
•open-circuit
•over-range
•under-range
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 1(1) module (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 BlockTransfer 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 5
Publication 1746-IN015C-EN-P - July 2001
1746-NT8 Features
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
Hardware Function
Channel Status LED Indicators Display operating and fault status of channels 0 through 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

6SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-IN015C-EN-P - July 2001
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:
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.
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.
Table C Maximum Current Drawn By the Module
5VDC Amps 24VDC Amps
0.120 0.070

SLC 500 Thermocouple/mV Analog Input Module 7
Publication 1746-IN015C-EN-P - July 2001
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 Chassis Slot
Two factors determine where you should install your module in the chassis:
ambient temperature and electrical noise. When selecting a slot for your module,
try to position your module:
•in a chassis 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 chassis power supply (if using a modular system)
Remember that in a modular system, a processor or adapter always occupies the
first slot of the chassis.

8SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-IN015C-EN-P - July 2001
Module Installation and Removal
To insert your module into the chassis, follow these steps:
1. Before installing the module, connect ground wire to TB1. See page 15.
2. Align the circuit board of your module with the card guides at the top and
bottom of the chassis.
3. Slide your module into the chassis until both top and bottom retaining clips
are secure. Apply firm even pressure on your module to attach it to its
backplane connector. Never force your module into the slot.
4. Cover all unused slots with the Card Slot Filler, Allen-Bradley part number
1746-N2.
ATTENTION
!
Before installing or removing your module, always disconnect:
•power from the SLC 500 system
•any other power sources to the module
•any devices wired to the module
Failure to observe this precaution can cause unintended
equipment operation and damage.
Top and Bottom Module
Release(s)
Card Guide

SLC 500 Thermocouple/mV Analog Input Module 9
Publication 1746-IN015C-EN-P - July 2001
Terminal Block Removal
To remove the terminal block:
1. Loosen the two terminal block release screws. To avoid cracking the
terminal block, alternate between screws as you remove them.
2. Using a screwdriver or needle-nose pliers, carefully pry the terminal block
loose. When removing or installing the terminal block be careful not to
damage the CJC sensors.
Terminal Block Diagram with CJC Sensors
ATTENTION
!
POSSIBLE EQUIPMENT OPERATION
Before wiring your module, always disconnect power from the
SLC 500 system and from any other source to the module.
Failure to observe this precaution can cause unintended
equipment operation and damage.
Terminal Block Release Screws
CJC Sensors
CJC Sensors
Terminal Block Release Screws

10 SLC 500 Thermocouple/mV Analog Input Module
Publication 1746-IN015C-EN-P - July 2001
Cold Junction Compensation (CJC)
To obtain accurate readings from each of the channels, the cold-junction
temperature (temperature at the module’s terminal junction between the
thermocouple wire and the input channel) must be compensated for. Two cold
junction compensating sensors are integrated in the removable terminal block.
They must remain installed to retain accuracy.
Wiring Guidelines
Isolation
The 1746-NT8 module provides the following electrical isolation:
•12.5V dc electrical isolation channel to channel
•500V dc for 1 minute electrical isolation channel to chassis ground
•500V dc for 1 minute electrical isolation channel to backplane
Care must be taken when choosing a thermocouple type and connecting it to the
1746-NT8 module from the environment being measured. If adequate precautions
are not taken for a given thermocouple type, the electrical isolation of the 1746-NT8
module may be compromised.
ATTENTION
!
Do not remove or loosen the cold junction compensating
temperature transducers located on the terminal block. Both
CJCs are critical to ensure accurate thermocouple input readings
at each channel. The module will not operate in thermocouple
mode if a CJC is not connected.
Failure to observe this precaution can cause unintended
equipment operation and damage.