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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

Spare Allen-Bradley Parts

Summary of Contents for SLC 500 1746-NT8

Page 1: ...res 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 M...

Page 2: ...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 pu...

Page 3: ... 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...

Page 4: ...gnals 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 thermo...

Page 5: ...t 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 18...

Page 6: ...couple 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 ...

Page 7: ...n 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 1 4 5 2 1 2 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 C...

Page 8: ...ductor 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 ...

Page 9: ... 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 ...

Page 10: ...rt 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 o...

Page 11: ...sis 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 an...

Page 12: ...s 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 an...

Page 13: ... for Two cold junction compensating sensors are integrated in the removable terminal block They must remain installed to retain accuracy 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 ...

Page 14: ... NT8 module may be compromised Thermocouple Junctions There are three types of thermocouple junctions Grounded Junction The measuring junction is physically connected to the protective metal sheath providing electrical continuity between junction and sheath Ungrounded Junction The measuring junction is electrically isolated from the protective metal sheath Ungrounded Junction can also be called In...

Page 15: ...d even if the sheaths are connected to chassis ground at a location other than the module since the module is connected to chassis ground As shown in the above wiring diagram it is recommended that grounded junction thermocouples have either protective sheaths made of electrically insulated material e g ceramic or that the metal protective sheaths be floated The metal sheaths would need to be floa...

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Page 17: ... cross at right angles To limit the pickup of electrical noise keep thermocouple and millivolt signal wires as far from power and load lines as possible For high immunity to electrical noise use Belden 8761 shielded twisted pair or equivalent wire for millivolt sensors you can also use shielded twisted pair thermocouple extension lead wire specified by the thermocouple manufacturer Using the incor...

Page 18: ... wires remove the foil shield bundle the input cables with a cable strap 4 Connect the following pairs of drain wires together Channels 0 and 1 Channels 2 and 3 Channels 4 and 5 Channels 6 and 7 Keep drain wires as short as possible 5 Connect the drain wires to the shield inputs of the terminal block if appropriate for thermocouple used See Wiring Guidelines on page 14 for more information Channel...

Page 19: ...rimary side of the PCB 8 At the sensor end of cables from thermocouple mV devices remove the drain wire and foil shield apply shrink wrap as an option connect to thermocouple mV devices keeping the leads short Important Only after verifying that your connections are correct for each channel trim the lengths to keep them short Avoid cutting leads too short Important If noise persists try grounding ...

Page 20: ...le Thermocouple or mV Cable CJC A CJC A Channel 0 Channel 0 Shield for CH0 and CH1 Channel 1 Channel 1 Channel 2 Channel 2 Shield for CH2 and CH3 Channel 3 Channel 3 Channel 4 Channel 4 Shield for CH4 and CH5 Channel 5 Channel 5 Channel 6 Channel 6 Shield for CH6 and CH7 Channel 7 Channel 7 CJC B CJC B TB1 ...

Page 21: ...filter frequencies Normal Mode Rejection between input and input Greater than 100 dB at 50 60 Hz Common Mode Rejection between input and ground Greater than 100 dB at 50 60 Hz Input Filter Cut Off Frequencies 2 6 Hz at 10 Hz filter frequency 13 1 Hz at 50 Hz filter frequency 15 72 Hz at 60 Hz filter frequency 65 5 Hz at 250 Hz filter frequency Greater than 100 dB at 50 60 Hz Calibration Module aut...

Page 22: ...nd one for module status Module ID Code 3533 Maximum Wire Size One 14 AWG wire or two 22 AWG wires per terminal Operating Temperature 0 C to 60 C 32 F to 140 F Storage Temperature 40 C to 85 C 40 F to 185 F Relative Humidity 5 to 95 without condensation Certification UL CUL approved Hazardous Environment Classification Class I Division 2 Hazardous Environment Groups A B C D EMC CE compliant ...

Page 23: ...ectable 0 1 mV or 0 01 mV Open Circuit Detection Selectable Upscale Downscale Zero or Disabled Time to Detect Open Circuit One channel cycle time Input Step Response 0 to 95 in 400 msec 10 Hz Display Resolution See Channel Data Word Resolution table in Chapter 4 of the SLC 500 Thermocouple mV Analog Input Module manual publication 1746 6 22 Overall Module Accuracy at 25 C 77 F See Module Accuracy ...

Page 24: ...Publication 1746 5 23 June 1999 40071 064 01 A 1999 Rockwell International All Rights Reserved Printed in USA ...

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