500Thermocouple/mV Analog Input Module (Catalog Number 1746-NT8)
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Allen-Bradley
500Thermocouple/mV Analog Input Module
(Catalog Number 1746-NT8)
Important User Information
Because variety uses products described this publication, those responsible application this control equipment must satisfy themselves that necessary steps have been taken assure that each application meets performance safety requirements, including applicable laws, regulations, codes standards. illustrations, charts, sample programs layout examples shown this guide intended solely purposes example. Since there many variables requirements associated with particular installation, Allen-Bradley does assume responsibility liability include intellectual property liability) actual based upon examples shown this publication. Allen-Bradley publication SGI-1.1, Safety Guidelines Application, Installation Maintenance Solid-State Control (available from your local Allen-Bradley office), describes some important differences between solid-state equipment electromechanical devices that should taken into consideration when applying products such those described this publication. Reproduction contents this copyrighted publication, whole part, without written permission Rockwell Automation, prohibited. Throughout this manual notes make aware safety considerations: ATTENTION: Identifies information about practices circumstances that lead personal injury death, property damage economic loss
Attention statements help identify hazard avoid hazard recognize consequences Important: Identifies information that critical successful application understanding product.
PLC, PLC-2, PLC-3, PLC-5 registered trademarks Rockwell Automation. SLC, 500, 5/01, 5/02, 5/03, 5/04, 5/05 registered trademarks Rockwell Automation. Belden trademark Belden, Inc.
Table Contents
Preface
Should This Manual What This Manual Covers Related Allen-Bradley Documents Common Techniques Used this Manual Allen-Bradley Support Local Product Support Technical Product Assistance Your Questions Comments this Manual
Module Overview
Chapter
General Description Input Ranges Hardware Features Diagnostic LEDs System Overview System Operation Module Operation Module Addressing Block Diagram Linear Millivolt Device Compatibility.
Installing Wiring Your Module
Chapter
Electrostatic Damage Power Requirements Considerations Modular System. Fixed Chassis Module Compatibility General Considerations Module Installation Removal Terminal Block Removal Wiring Your Module Preparing Wiring Cables Cold-Junction Compensation (CJC). 2-10
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Table Contents
Things Consider Before Using Your Module
Chapter
Module Code Module Addressing Output Image Configuration Words Input Image Data Words Status Words. Channel Filter Frequency Selection Channel Cut-Off Frequency Channel Step Response Update Time Update Time Calculation Example. Channel Turn-On, Turn-Off, Reconfiguration Times Auto-Calibration Response Slot Disabling Input Response Output Response
Channel Configuration, Data, Status
Chapter
Channel Configuration Channel Configuration Procedure Select Channel Enable (Bit Select Input Types (Bits through Select Data Format (Bits Using Scaled-for-PID Proportional Counts Effective Resolutions Scaling Examples Select Open-Circuit State (Bits Select Temperature Units (Bit 4-10 Select Channel Filter Frequency (Bits 4-10 Unused Bits (Bits through 4-11 Select Input Image Type (Bit 4-11 Channel Data/Status Word 4-12 Channel Status Checking 4-12 Channel Status (Bit 4-14 Input Type Status (Bits through 4-14 Data Format Type Status (Bits 4-14 Open-Circuit Type Status (Bits 4-14 Temperature Units Type Status (Bit 4-14
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Table Contents
Channel Filter Frequency (Bits 4-14 Open-Circuit Error (Bit 4-14 Under-Range Error (Bit 4-15 Over-Range Error (Bit 4-15 Channel Error (Bit 4-15
Programming Examples
Chapter
Basic Example Procedure Automatic Monitoring Thermocouples Sensors Verifying Channel Configuration Changes Interfacing Instruction Monitoring Channel Status Bits Example with Remote Rack 5-14
Troubleshooting Your Module
Chapter
Module Channel Diagnostics Module Diagnostics Powerup Channel Diagnostics Indicators Troubleshooting Tables. Channel-status LEDs (Green) Open-circuit Detection (Bit Out-of-Range Detection (Bit Under Range, Over Range) Channel Error (Bit Module Status (Green) Interpreting Error Codes
Maintaining Your Module Safety Considerations
Chapter
Preventive Maintenance Safety Considerations
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Table Contents
Module Specifications
Appendix
Electrical Specifications .A-1 Physical Specifications .A-1 Environmental Specifications .A-2 Input Specifications .A-2 Overall Accuracy .A-2 Millivolt .A-3 Thermocouple .A-5
Using Grounded Junction, Ungrounded Junction, Exposed Junction Thermocouples Appendix
Thermocouple Types .B-1 Grounded Junction .B-2 Ungrounded (Insulated) Junction .B-2 Exposed Junction .B-2 Isolation .B-2 Grounded Junction Thermocouples. .B-3 Exposed Junction Thermocouples. .B-4
Glossary
Index
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Preface
Read this preface familiarize yourself with this user manual. This preface covers: should this manual what this manual provides related Allen-Bradley documents common techniques used this manual Allen-Bradley support
Should This Manual
this manual design, install, program, maintain control system that uses Allen-Bradley Small Logic Controllers (SLC). should have basic understanding products. should also understand electronic process control ladder program instructions required generate electronic signals that control your application. not, contact your local AllenBradley representative proper training before using these products.
What This Manual Covers
This manual covers 1746-NT8 thermocouple/millivolt analog input module. contains information need install, wire, use, maintain these modules. also provides diagnostic troubleshooting help should need arise.
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Preface
Related Allen-Bradley Documents
following table lists several Allen-Bradley documents that help these products.
Publication Number 1747-2.30 SGI-1.1 1770-4.1 1747-6.2 1747-6.21 1747-6.15 ABT-1747-TSG001 1747-NP002 1747-NM009 SD499 AG-7.1 System Overview Application Considerations Solid State Controls Allen-Bradley Programmable Controller Grounding Wiring Guidelines Installation Operation Manual Modular Hardware Style Programmable Controllers Installation Operation Manual Fixed Hardware Style Programmable Controllers Instruction Reference Manual Software Programmers's Quick Reference Guide Allen-Bradley (Hand-Held Terminal) User Manual Getting Started Guide (Hand-Held Terminal) Allen-Bradley Publication Index Allen-Bradley Industrial Automation Glossary Title
obtain copy Allen-Bradley documents listed, contact your local Allen-Bradley office distributor.
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Preface
Common Techniques Used this Manual
following conventions used throughout this manual: Bulleted lists such this provide information, procedural steps. Numbered lists provide sequential steps hierarchical information. Text this font indicates words phrases should type. names appear bold, capital letters within brackets (for example, [ENTER]).
Allen-Bradley Support
Allen-Bradley offers support services worldwide, with over Sales/ Support Offices, authorized Distributors authorized Systems Integrators located throughout United States alone, plus Allen-Bradley representatives every major country world.
Local Product Support
Contact your local Allen-Bradley representative for: sales order support product technical training warranty support support service agreements
Technical Product Assistance
need contact Allen-Bradley technical assistance, please review information Troubleshooting chapter first. Then call your local Allen-Bradley representative.
Your Questions Comments this Manual
find problem with this manual, please notify enclosed Publication Problem Report. have suggestions this manual could made more useful you, please contact address below: Allen-Bradley Control Information Group Technical Communication, Dept. A602V, T122 P.O. 2086 Milwaukee, 53201-2086
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Chapter
Module Overview
This chapter describes thermocouple/mv input module explains processor reads thermocouple millivolt analog input data from module. Read this chapter familiarize yourself further with your thermocouple/mV analog input module. This chapter covers: general description hardware features overview system module operation block diagram channel input circuits
General Description
This module designed exclusively mount into 1746 racks with fixed modular systems. module stores digitally converted thermocouple/mV analog data image table retrieval fixed modular processors. module supports connections from combination eight thermocouple/mV analog sensors.
Input Ranges
following tables define thermocouple types associated temperature ranges millivolt analog input signal ranges that each module's input channels support. determine practical temperature range your thermocouple, refer specifications appendix
Thermocouple Temperature Ranges Type Sensor Millivolt Input Ranges -100 +100 Temperature Range -210°C +760°C -270°C +1370°C -270°C +400°C +300°C +1820°C -270°C +1000°C +1768°C +1768°C +1300°C -25°C +105°C Temperature Range -346°F +1400°F -454°F +2498°F -454°F +752°F +572°C +3308°F -454°F +1832°F +3214°F +32°F +3214°F +32°F +2372°F -13°F +221
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Module Overview
Each input channel individually configured specific input device, provides open-circuit, over-range, under-range detection indication.
Hardware Features
module fits into single slot modules either modular system fixed system expansion chassis (1746-A2), except zero slot which reserved processor. Class module using input words output words.1 module contains removable terminal block providing connections eight thermocouple and/or analog input devices. terminal block cold-junction compensation (CJC) sensors that compensate cold junction ambient temperature. should also noted there output channels module. Configure module with software rather than with jumpers switches. Important: There jumper (JP1) circuit board. module shipped with jumper position illustrated below. change position JP1. jumper used test purposes only.
Side Label Channel Status LEDs (Green) Module Status (Green) Removable Terminal Block Sensors Cable Slots
INPUT CHANNEL STATUS MODULE
Door Label
OPERATING LISTED IND. CONT. TEMPERATURE VOLTAGE: 1746 HAZ. LOC. A196 CODE ±50mVDC +50mVDC ±100mVDC +100mVDC CLASS GROUPS DIV.2 SERIAL MADE NT4±xxx
THERMOCOUPLE/mV INPUT MODULE
THERMOCOUPLE/mV
1746-NT8 ACHL 0SHIELD 1CHL 2SHIELD 3CHL 4SHIELD 5CHL 6SHIELD 7CJC
THERMOCOUPLE TYPES:
INPUT SIGNAL RANGES
Jumper Move.
Self-Locking Tabs
Requires Block Transfer when used remote rack with 1747-ASB.
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Module Overview
Hardware Features Hardware Channel Status Indicators Module Status Side Label (Nameplate) Removable Terminal Block Door Label Cable Slots Self Locking Tabs Function Display operating fault status channels Displays operating fault status module Provides module information Provides electrical connection input devices Permits easy terminal identification Secure route wiring from module Secure module chassis slot
Diagnostic LEDs
module contains diagnostic LEDs that help identify source problems that occur during power-up during normal operation. Power-up channel diagnostics explained Chapter Testing Your Module.
System Overview
module communicates with processor receives +24V power from system power supply through parallel backplane interface. external power supply required. install many thermocouple modules system power supply support. Each module channel receive input signals from thermocouple analog input device. configure each channel accept either one. When configured thermocouple input types, module converts analog input voltages into cold-junction compensated linearized, digital temperature readings. module uses National Institute Standards Technology (NIST) ITS-90 thermocouple linearization. When configured millivolt analog inputs, module converts analog values directly into digital counts. module assumes that input signal linear.
System Operation
power-up, module checks internal circuits, memory, basic functions. During this time module status remains off. module finds faults, turns module status LED.
Channel Data Word Channel Status Word Thermocouple Analog Signals Thermocouple Input Module Channel Configuration Word Processor
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Module Overview
After completing power-up checks, module waits valid channel configuration data from your ladder logic program (channel status LEDs off). After channel configuration data transferred channel enable bits set, enabled channel status LEDs turn Then channel continuously converts thermocouple millivolt input value within range selected channel. Each time module reads input channel, module tests that data fault, i.e. over-range under-range condition. opencircuit detection enabled, module tests open-circuit condition. detects open-circuit, over-range, under-range condition, module sets unique channel status word causes channel status flash. processor reads converted thermocouple millivolt data from module program scan, when commanded ladder program. After processor module determine that data transfer made without error, data used your ladder program.
Module Operation
module's input circuitry consists eight differential analog inputs, multiplexed into convertor. convertor reads analog input signals converts them digital value. input circuitry also continuously samples sensors compensates temperature changes cold junction (terminal block).
Module Addressing
module requires eight words each processor's input output image tables. Addresses module slot follows: I:e.0-7 thermocouple/mV status data channels 0-7, respectively (dependent configuration word). O:e.0-7 configuration data channels 0-7, respectively. "Module Addressing" page module's image table.
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Module Overview
Block Diagram
Terminal Block CJCA Sensor Module Circuitry
ungrounded thermocouple
Shield
Within 12.5V Shield grounded thermocouple Shield
multiplexer User Selected Filter Frequency
Analog Digital Converter Analog Ground
Digital Filter
Digital Value
Shield
CJCB Sensor
Important: When using multiple thermocouples, potential between channels cannot exceed channel-tochannel differential voltage (12.5 volts). more information, Appendix
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Module Overview
Linear Millivolt Device Compatibility large number millivolt devices used with 1746-NT8 module. this reason specify compatibility with particular device. However, millivolt applications often strain gage bridges. resistive voltage divider using fixed resistors recommended this application. circuit diagram below shows this connection made.
Strain Gage Bridge
1746-NT8 Channel Input
variable fixed
fixed fixed
Note:
resistors should selected ensure that differential input voltage less than equal ±100
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Chapter
Installing Wiring Your Module
Read this chapter install wire your module. This chapter covers: avoiding electrostatic damage determining power requirements installing module wiring signal cables module's terminal block
Electrostatic Damage
Electrostatic discharge damage semiconductor devices inside this module touch backplane connector pins. Guard against electrostatic damage observing following precautions: ATTENTION: Electrostatically Sensitive Components Before handling module, touch grounded object yourself electrostatic charge. Handle module from front, away from backplane connector. touch backplane connector pins. Keep module static-shield container when during shipment. Failure observe these precautions degrade module's performance cause permanent damage.
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Installing Wiring Your Module
Power Requirements
module receives power through chassis backplane from fixed modular VDC/+24 chassis power supply. maximum current drawn module shown table below.
Maximum Current Drawn Module
5VDC Amps 0.120
24VDC Amps 0.070
Considerations Modular System Place your module slot modular, modular expansion chassis, except left-most slot (slot reserved processor adapter modules. When using module with modular system, values shown above requirements other modules prevent overloading chassis power supply. Refer Modular Hardware Style Instruction Operating Manual, publication 17476.2.
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Installing Wiring Your Module
Fixed Chassis Module Compatibility following chart depicts range current combinations supported fixed expansion chassis. find backplane current draw operating voltage both modules being used chassis. These specifications found table alongside chart. Next, plot each currents chart below. point intersection falls within operating region, combination valid. not, combination cannot used 2-slot, fixed chassis.
Module Current Draw Power Supply Loading Module BASn
OA16 455)
.150 .150 .360 .055 .055 .300 .200 .035 .050 .085 .050 .085 .106 .085 .140 .085 .035 .050 .085 .085 .030 .060 .090 .085 .085 .050 .085 .106
.040 .125 .000 .150 .120 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .025 .045 .070 .000 .000 .000 .000 .000
Module NIO4I NIO4V NO4I NO4V OA16 OAP12 OB16 OB16E OB32 OBP8 OBP16 OG16 OV16 OV32 OVP16 OW16
.150 .150 .025 .200 .055 .055 .055 .055 .050 .060 .370 .185 .370 .135 .280 .135 .452 .135 .250 .180 .135 .270 .452 .250 .170 .045 .085 .085
.040 .125 .085 .100 .145 .115 .195 .145 .050 .040 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .180 .045 .090 .090
Current (mA)
FIO4I FIO4V HSTP1 IA16
OW16 IA16 (180, 255)
Valid Operating Region
IB16 IB32 IC16
Plotted from Example Shown Below
IG16 IH16 IM16 IN16
IO12 ITB16 ITV16 IV16 IV32
Current (mA)
Example: Plot IN16 NIO4V IN16 0.085 NIO4V 0.055A 0.115A current draws both modules 0.14 (140mA) Plot this point chart above (140mA dc). current draws both modules 0.115A (115mA) Plot current draw (115mA Note point intersection chart above (marked This combination falls within valid operating region fixed chassis. Important: The1746-NO4I 1746-NO4V analog output modules require external power supply.
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Installing Wiring Your Module
When using module supply power 1747-AIC Link Coupler, link coupler draws power through module. higher current drawn shown table BASn (BAS networked) networked). sure these current draw values application uses module this way.
General Considerations
Most applications require installation industrial enclosure reduce effects electrical interference. Thermocouple inputs highly susceptible electrical noises small amplitudes their signal (microvolt/°C). Group your modules minimize adverse effects from radiated electrical noise heat. Consider following conditions when selecting slot thermocouple module. Position module: slot away from sources electrical noise such hardcontact switches, relays, motor drives away from modules which generate significant radiated heat, such 32-point modules addition, route shielded twisted pair thermocouple millivolt input wiring away from high voltage wiring. Remember that modular system, processor communications adapter always occupies first slot rack.
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Module Installation Removal
ATTENTION: Possible Equipment Operation
Before installing removing your module, always disconnect power from system from other source module other words, "hot swap" your module), disconnect devices wired module. Failure observe this precaution cause unintended equipment operation damage.
Bottom Module Release(s)
Card Guide
insert your module into rack, follow these steps: Before installing module, connect ground wire TB1. figure page 2-9. Align circuit board your module with card guides bottom chassis. Slide your module into chassis until both bottom retaining clips secure. Apply firm even pressure your module attach backplane connector. Never force your module into slot. Cover unused slots with Card Slot Filler, Allen-Bradley part number 1746-N2.
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Terminal Block Removal remove terminal block: Loosen terminal block release screws. avoid cracking terminal block, alternate between screws remove them. Using screwdriver needle-nose pliers, carefully terminal block loose. When removing installing terminal block careful damage sensors.
Terminal block diagram with sensors
Terminal Block Release Screws Sensors
Recommended Torque: wiring screws: 0.25 (2.2 in-lb) release screws: 0.25 (2.2 in-lb)
Sensors Terminal Block Release Screws
ATTENTION: Possible Equipment Operation
Before wiring your module, always disconnect power from system from other source module. Failure observe this precaution cause unintended equipment operation damage.
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Wiring Your Module
Follow these guidelines wire your input signal cables: Power, input, output (I/O) wiring must accordance with Class Division wiring methods [Article 501-4(b) National Electrical Code, NFPA accordance with authority having jurisdiction. Route thermocouple millivolt signal wires possible from sources electrical noise, such motors, transformers, contactors, devices. general rule, allow least (about 15.2 separation every 120V power. Routing field wiring grounded conduit reduce electrical noise further. field wiring must cross power cables, ensure that they cross right angles. high immunity electrical noise, Belden8761 (shielded, twisted pair) equivalent wire millivolt sensors; shielded, twisted pair thermocouple extension lead wire specified thermocouple manufacturer. Using incorrect type convention thermocouple extension wire following correct polarity cause invalid readings. Ground shield drain wire only cable. preferred location shield connections terminal block. (Refer IEEE Std. 518, Section 6.4.2.7 contact your sensor manufacturer additional details.) Keep unshielded wires short possible. Excessive tightening strip screw. Tighten screws 0.25 (2.2 in-lb) less, based 1059, C22.2 158, 0110B 2.79 standards. Follow system grounding wiring guidelines found your Modular Installation Operation Manual, publication 1747-6.2 (modular) 1747-6.21 (fixed).
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Preparing Wiring Cables prepare connect cable leads drain wires, follow these steps:
Cable Signal Wires (Remove foil shield drain wire from sensor cable.)
Drain Wire
Signal Wires
each cable, strip some casing expose individual wires. Trim signal wires 5-inch lengths beyond cable casing. Strip about 3/16 inch (4.76 insulation expose ends wires. module cables: extract drain wire signal wires remove foil shield bundle input cables with cable strap Connect pairs drain wires together: Channels Channels Channels Channels Keep drain wires short possible. Connect drain wires shield inputs terminal block appropriate thermocouple used. Channel drain wires Channel drain wires Channel drain wires Channel drain wires Connect signal wires each channel terminal block. Important: Only after verifying that your connections correct each channel, trim lengths keep them short. Avoid cutting leads short.
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Connect chassis ground connector nearest chassis mounting bolt with gauge wire. (Looking face module, near lower part terminal block primary side PCB.)
Connect ground wire before installing module.
sensor cables from thermocouple/mV devices: remove drain wire foil shield apply shrink wrap option connect devices keeping leads short Important: noise persists, grounding opposite cable. Ground only.
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2-10
Installing Wiring Your Module
Terminal Block Diagram with Input Cable
AChannel Channel 0Shield Channel Channel 1Channel Channel 2Shield Channel Channel 3Channel Channel 4Shield Channel Channel 5Channel Channel 6Shield Channel Channel 7CJC BRecommended Torque: (2.5 in-lb)
Thermocouple Cable
module also ground terminal TB1, which should grounded chassis mounting bolt with 14-gauge wire.
Cold-Junction Compensation (CJC)
ATTENTION: Possible Equipment Operation
remove loosen cold-junction compensating temperature transducers located terminal block. Both CJCs required ensure accurate thermocouple input readings each channel. module will operate thermocouple mode connected. Failure observe this precaution cause unintended equipment operation damage.
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2-11
obtain accurate readings from each channels, coldjunction temperature (temperature module's terminal junction between thermocouple wire input channel) must compensated for. cold-junction compensating sensors have been integrated removable terminal block. They must remain installed.
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Chapter
Things Consider Before Using Your Module
This chapter explains module processor communicate through processor's image tables. also describes module's input filter characteristics. Topics discussed include: module code module addressing channel filter frequency selection channel turn-on, turn-off, reconfiguration times response slot disabling
Module Code
module code unique number assigned each 1746 module. code defines processor type module number words used processor's image table. module code 1746-NT8 module 3533. special configuration required. module automatically assigns correct number input output words.
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Module Addressing
following memory shows processor's output input tables defined module.
Image Table
Channel Configuration Word Channel Configuration Word Channel Configuration Word Channel Configuration Word Channel Configuration Word Channel Configuration Word Channel Configuration Word Channel Configuration Word Word Word Word Word Word Word Word Word Address O:e.0 O:e.1 O:e.2 O:e.3 O:e.4 O:e.5 O:e.6 O:e.7
5/0X Data Files Slot Output Image Input Scan Output Scan
Thermocouple Module Image Table
Output Image Words
Slot Input Image
Input Image Words
Channel Data Status Word Channel Data Status Word Channel Data Status Word Channel Data Status Word Channel Data Status Word Channel Data Status Word Channel Data Status Word Channel Data Status Word
Word Word Word Word Word Word Word Word
I:e.0 I:e.1 I:e.2 I:e.3 I:e.4 I:e.5 I:e.6 I:e.7 Address
Output Image Configuration Words
Eight words processor's output image table reserved module. Output image words used configure module's input channels 0-7. Each output image word configures single channel referred configuration word. Each word unique address based slot number assigned module. Example Address want configure channel module located slot chassis, your address would O:4.2.
Slot File Type Word
O:4.2
Element Delimiter Word Delimiter
Chapter Channel Configuration, Data, Status, gives detailed information about data content configuration word.
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Input Image Data Words Status Words
Eight words processor's input image table reserved module. Input image words multiplexed since each channel data word status word. corresponding configuration word selects whether channel status channel data input image word. Status bits particular channel reflect configuration settings that entered into configuration (output image) word that channel. receive valid status, channel must enabled module must have stored valid configuration word that channel. Each input image word unique address based slot number assigned module. Example Address obtain status/data word channel (input word module located slot chassis address I:4:2.
File Type Slot Word
I:4.2
Element Delimiter Word Delimiter
Chapter Channel Configuration, Data, Status, gives detailed information about content data word status word.
Channel Filter Frequency Selection
thermocouple module uses digital filter that provides highfrequency noise rejection input signals. digital filter programmable, allowing select from four filter frequencies each channel. digital filter provides highest noise rejection selected filter frequency. graphs follow show input channel frequency response each filter frequency selection. Selecting value (i.e. channel filter frequency provides best noise rejection channel, also increases channel update time. Selecting high value channel filter frequency provides lower noise rejection, decreases channel update time. following table shows available filter frequencies, cut-off frequency, step response, effective resolution each filter frequency.
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Cut-off frequency, Step Response Time, Effective Resolution (Based Filter Frequency) Filter Frequency Cut-Off Frequency 2.62 13.1 15.72 65.5 Step Response 66.7 Effective Resolution 20.5 19.0 19.0 15.5
step response calculated (1/filter frequency) settling time.
Channel Cut-Off Frequency
channel filter frequency selection determines channel's cut-off frequency, also called frequency. cut-off frequency defined point input channel frequency response curve where frequency components input signal passed with attenuation. frequency components below cut-off frequency passed digital filter with less than attenuation. frequency components above cut-off frequency increasingly attenuated, shown graphs page 3-5. cut-off frequency each input channel defined filter frequency selection. table above shows input channel cut-off frequency each filter frequency. Choose filter frequency that your fastest changing signal below that filter's cut-off frequency. cut-off frequency should confused with update time. cut-off frequency relates digital filter attenuates frequency components input signal. update time defines rate which input channel scanned channel data word updated.
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Signal Attenuation with Input Filter
Amplitude
-100 -120 -140 -160 -180 -200
2.62
Signal Frequency
Signal Attenuation with Input Filter
Amplitude -100
-120 -140 -160 -180 -200
13.1
Signal Frequency
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Signal Attenuation with Input Filter
-100 Amplitude -120 -140 -160 -180 -200
15.7
Signal Frequency
Signal Attenuation with Input Filter
-100 -120 -140 -160 -180 -200
65.5
Amplitude
1000
1250
1500
Signal Frequency
Channel Step Response
channel filter frequency determines channel's step response. step response time required analog input signal reach expected, final value given full-scale step change input signal. This means that input signal changes faster than channel step response, portion that signal will attenuated channel filter. table page shows step response each filter frequency.
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Update Time
thermocouple module update time defined time required module sample convert input signals enabled input channels make resulting data values available processor. calculated adding enabled sample times, plus update time.
Channel Disabled Enabled Sample Channel Sample Channel Channel Disabled Enabled Sample Channel Channel Disabled Enabled Sample Channel Sample Channel Calculate Previous
Channel Disabled Enabled
Update
Calculate Previous
Calculate Previous
Calculate Previous
following table shows channel sampling time each filter frequency. also gives update time.
Channel Sampling Time Channel Sampling Time Each Filter Frequency (all values msec) Channel Sampling Time Update Time msec Filter msec Filter msec Filter msec Filter msec
times above include settling time necessary between input channel readings. sampling times filter frequencies listed include msec open-circuit detection time utilized when channel configured open-circuit detection. open-circuit detection does require additional msec settling time. fastest module update time occurs when only channel with filter frequency enabled. Module update time msec msec msec slowest module update time occurs when eight channels, each using filter frequency, enabled. Module update time msec msec msec msec msec msec msec msec msec 4.05
Update Time Calculation Example
following example shows calculate module update time given configuration:
Channel configured filter frequency, enabled Channel configured filter frequency, enabled Channel configured filter frequency, enabled Channel through disabled
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Using values from table page 3-7, enabled channel sample times, plus update time.
Channel sampling time Channel sampling time Channel sampling time update time Module update time msec msec msec msec msec
Channel Turn-On, Turn-Off, Reconfiguration Times
time required module recognize configuration channel generally module update time plus µsec newly configured channel. filter frequency selected newly enabled, configured channel module, then autocalibration performed following configuration recognition. Turn-off time requires module update time. Reconfiguration time same turn-on time.
Auto-Calibration
Auto-calibration performed module correct drift errors over temperature. Auto-calibration occurs immediately following configuration previously unselected filter frequency, generally every minutes selected filter frequencies system. time required perform auto-calibration defined follows:
Auto-calibration Time Filter msec Filter msec Filter msec Filter 1.975
sensors acquired maximize trade-offs between resolution update rate. example, some channels acquired some acquired then total auto-calibration time would
Frequency Auto-Calibration msec msec msec 1.435 Total
During auto-calibration, input values updated.
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Response Slot Disabling
writing status file modular processor, disable chassis slot. Refer your programming manual slot disable/enable procedure. ATTENTION: POSSIBLE EQUIPMENT OPERATION Always understand implications disabling module before using slot disable feature. Failure observe this precaution cause unintended equipment operation.
Input Response
When thermocouple slot disabled, thermocouple module continues update input image table. However, processor does read input from module that disabled. Therefore, when processor disables thermocouple module slot, module inputs appearing processor image table remain their last state, module's updated image table read. When processor re-enables module slot, current state module inputs read processor during subsequent scan.
Output Response
processor change thermocouple module output data (configuration) appears processor output image. However, this data transferred thermocouple module. outputs held their last state. When slot re-enabled, data processor image transferred thermocouple module.
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Chapter
Channel Configuration, Data, Status
Read this chapter configure each input channel check each input channel's configuration status
Channel Configuration
Channel configuration words appear processor's output image table shown below. Words correspond module channels 0-7. After module installation, configure each channel establish channel operates (e.g., thermocouple type, temperature units, etc.). Configure channel setting bits configuration word using your programming device. configuration words shown below.
Output Image (Configuration) Words
O:e.0 O:e.1 O:e.2 O:e.3 O:e.4 O:e.5 O:e.6 O:e.7 Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word Channel Channel Configuration Word
slot number module
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Channel Configuration, Data, Status
configuration word default settings zero. Next, describe configuration bits channel configuration word following channel parameters: data format such engineering units, counts, scaled channel should respond detected open-input circuit filter frequency selection temperature units whether channel enabled disabled whether status data information selected module's input image table.
Channel Configuration Procedure
channel configuration word consists fields, settings which determine channel operates. This procedure looks each field separately helps configure channel operation. Refer chart page field descriptions that follow complete configuration information. Determine which channels used your program enable them. Place channel enabled. Place zero channel disabled. Determine input device type etc. thermocouple) channel enter respective four-digit binary code field through channel configuration word. Select data format data word. Your selection determines analog input value from converter will expressed data word. Enter your two-digit binary code field channel configuration word. Determine desired state channel data word opencircuit condition enabled detected that channel. Enter two-digit binary code field channel configuration word. channel configured thermocouple inputs, determine channel data word should read degrees Fahrenheit degrees Celsius enter zero configuration word. channel configured analog sensor, enter zero Determine desired input filter frequency channel enter two-digit binary code bits channel configuration word. lower filter frequency increases channel update time, also increases noise rejection channel resolution. higher filter frequency decreases channel update time, also decreases noise rejection effective resolution.
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Channel Configuration, Data, Status
Ensure that bits through contain zeros. Determine whether channel input image word should contain data status. Place channel data desired. Place zero status desired. Build channel configuration word every channel each thermocouple/mV module repeating procedures given steps through Enter this configuration into your ladder program download thermocouple module.
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detailed explanation appears following table:
Channel Configuration Word (O:e.0 through O:e.7) Definitions
Channel Enable Channel Disable Channel Enable Thermocouple Type Thermocouple Type Thermocouple Type Thermocouple TypeE Thermocouple Type Thermocouple TypeS Thermocouple Type Input Type Thermocouple Type ±100 Invalid Invalid Invalid Invalid Invalid temperature Engineering Units Data Format Engineering Units Scaled Proportional counts Zero open circuit Open Circuit Max. open circuit Min. open circuit Disabled Temperature Units Channel filter freq. Unused Input Image Type Degrees Degrees input filter input filter input filter input filter Unused3 Invalid Status Word Data Word
engineering units values expressed degrees 0.01 engineering units x10, values expressed degree When millivolt input type selected, setting temperature units ignored. Ensure unused bits through always zero.
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Select Channel Enable (Bit
channel enable enable channel. thermocouple module only scans enabled channels. optimize module operation minimize throughput times, unused channels should disabled setting channel enable zero (default value). When channel enable used module read configuration word information selected. While enable set, modification configuration word lengthen module update time cycle. change made configuration word, change reflected status word before data valid (described page 4-11). While channel enable cleared (0), associated channel data/status word values cleared. After channel enable (1), associated channel data/status word remains cleared until thermocouple module sets channel status (bit channel status word.
Select Input Types (Bits through
input type field lets configure channel type input device have connected module. Valid input devices types thermocouple sensors ±100mV analog input signals. channel also configured read cold-junction temperature calculated that specific channel. When cold-junction compensation (CJC) temperature selected, channel ignores physical input signal.
Select Data Format (Bits
data format field lets define expressed format channel data word contained module input image. data types engineering units, scaled-for-PID, proportional counts. engineering units allow select from resolutions, x10. engineering units values expressed degrees 0.01mV. engineering units x10, values expressed degrees 0.1mV. (Use setting produce temperature readings whole degrees Celsius Fahrenheit.) scaled-for-PID value same millivolt, thermocouple, input types. input signal range proportional your selected input type scaled into through 16,383 range, which standard algorithm. proportional counts scaled defined temperature voltage range. input signal range proportional your selected input scaled into -32,768 32,767 range.
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Using Scaled-for-PID Proportional Counts
thermocouple module provides eight options displaying input channel data. These 0.1°F, 0.1°C, 1°F, 1°C, 0.01 Scaled-for-PID, Proportional Counts. first options represent real Engineering Units displayed 1746-NT8 require explanation. Scaled-for-PID Proportional Counts selections provide highest display resolution, also require manually convert channel data real Engineering Units. equations below show convert from Scaled-for-PID Engineering Units, Engineering Units Scaled-for-PID, Proportional Counts Engineering Units, Engineering Units Proportional Counts. perform conversions, defined temperature millivolt range channel's input type. Channel Data Word Format table page 4-7. lowest possible value input type SLOW, highest possible value SHIGH. Effective Resolutions effective resolution input channel depends upon filter frequency selected that channel.
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Scaling Examples
Scaled-for-PID Engineering Units Equation: Engineering Units Equivalent SLOW [(SHIGH-SLOW) (Scaled-for-PID value displayed/16384)] Assume type input type, scaled-for-PID display type, channel data 3421. Want calculate equivalent. From Channel Data Word Format table, SLOW -210°C SHIGH 760°C. Solution: Engineering Units Equivalent -210°C [(760°C-(-210°C)) (3421/16384)] -7.46°C. Engineering Units Scaled-for-PID Equation: Scaled-for-PID Equivalent 16384 [(Engineering Units desired -SLOW)/(SHIGH-SLOW)] Assume type input type, scaled-for-PID display type, desired channel temp. 344°C. Want calculate Scaled-for-PID equivalent. From Channel Data Word Format table, SLOW -210°C SHIGH 760°C. Solution: Scaled-for-PID Equivalent 16384 [(344°C (-210°C))/(760°C (-210°C))] 9357 Proportional Counts Engineering Units Equation: Engineering Units Equivalent SLOW {(SHIGH-SLOW) [(Proportional Counts value displayed 32768)/ 65536]} Assume type input type, proportional counts display type, channel data 21567. Want calculate equivalent. From Channel Data Word Format table, SLOW -454°F SHIGH =1832°F Solution: Engineering Units Equivalent -454°F {[1832°F -(-454°F)] [(21567 32768)/65536]} 1441.3°F Engineering Units Proportional Counts Equation: Proportional Counts Equivalent {65536 x[(Engineering Units desired SLOW)/(SHIGH-SLOW)]} -32768 Assume type input type, proportional counts display type, desired channel temp. 1000°F. Want calculate Proportional Counts equivalent. From Channel Data Word Format table, SLOW -454°F SHIGH 1832°F. Solution: Proportional Counts Equivalent {65536 x[{1000°F (-454°F))/(1832°F (-454°F))]} 32768 8916.
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1746-NT8 Thermocouple Module Channel Data Word Format Data Format Input Type ±100 Sensor Engineering Units Celsius -210 +760 -270 +1370 -270 +400 -270 +1000 +1768 +1768 +300 +1820 +1300 -500 +500 -1000 +1000 +105 Fahrenheit -346 +1400 -454 +2498 -454 +752 -454 +1832 +3214 +2372 +572 +3308 +2372 -500 +500 -1000 +1000 +221 Engineering Units Celsius -2100 +7600 -2700 +13700 -2700 +4000 -2700 +10000 +17680 +17680 +3000 +18200 +13000 -5000 +5000 -10000 +1000 -250 +1050 Fahrenheit -3460 +14000 -4540 +24980 -4540 +7520 -4540 +18320 +320 to+32140 +320 +32140 +5720 +3276.7 +320 +23720 -5000 +5000 -10000 +10000 -130 +2210 Scaled-forPID +16383 +16383 +16383 +16383 +16383 +16383 +16383 +16383 +16383 +16383 +16383 Proportional Counts -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767 -32768 +32767
Type thermocouple cannot represented engineering units (°F) above 3276.7°F. Software treats over range error. When millivolts selected, temperature setting ignored. Analog input data same either selection.
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1746-NT8 Thermocouple Module Channel Data Word Resolution
Data Format Input Type
Engineering Units Celsius 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 0.1mV/step 0.1mV/step 1°C/step
Engineering Units Celsius 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 1°C/step 0.01mV/step 0.01mV/step 1°C/step Fahrenheit 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 0.01mV/step 0.01mV/step 1°F/step
Scaled-for-PID Celsius 0.0592°C/step 0.1001°C/step 0.0409°C/step 0.0775°C/step 0.1079°C/step 0.1079°C/step 0.0928°C/step 0.0793°C/step 6.104µV/step 12.21µV/step 0.0079°C/step Fahrenheit 0.1066°F/step 0.1802°F/step 0.0736°F/step 0.1395°F/step 0.1942°F/step 0.1942°F/step 0.1670°F/step 0.1428°F/step 6.104µV/step 12.21µV/step 0.0143°F/step
Proportional Counts Celsius 0.0148°C/step 0.0250°C/step 0.0102°C/step 0.0194°C/step 0.0270°C/step 0.0270°C/step 0.0232°C/step 0.0198°C/step 1.526µV/step 3.052µV/step 0.0020°C/step Fahrenheit 0.0266°F/step 0.0450°F/step 0.0184°F/step 0.0349°F/step 0.0486°F/step 0.0486°F/step 0.0417°F/step 0.0357°F/step 1.526µV/step 3.052µV/step 0.0036°F/step
Fahrenheit 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 1°F/step 0.1mV/step 0.1mV/step 1°F/step
±100
Sensor
When millivolts selected, temperature setting ignored. Analog input data same either selection.
Important: Data resolution equivalent data accuracy. Input accuracy span multiple steps Proportional Counts data types. example, Type thermocouple temperature range 1820°C provides voltage input range 13.82mV 1746-NT8. This very small input range and, when scaled proportional counts ranges, small input change results many counts being changed.
Select Open-Circuit State (Bits
open-circuit field lets define state channel data word when open-circuit condition detected that channel. This feature disabled selecting disable option. open-circuit condition occurs when thermocouple itself extension wire physically separated open. This happen wire gets disconnected from terminal block. either devices removed from terminal block, input channel configured either thermocouple temperature input placed open-circuit condition. input channel configured millivolt input affected opencircuit conditions. results data word open-circuit condition depend upon selection bits zero selected (00), channel data word forced during open-circuit condition.
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Channel Configuration, Data, Status
Selecting maximum forces (01) channel data word value full scale value during open-circuit condition. full scale value determined selected input type data format. Selecting minimum forces (10) channel data word value scale value during open-circuit condition. scale value determined selected input type data format. Disabling open-circuit selection (11) result unintended operation failure. Generally, with open-circuit option disabled, data word remains unchanged. open-circuit error channel flags condition until error resolved. example, channel configured thermocouple type when breaks open-circuit condition, open-circuit detection disabled, data word remains unchanged. circuit selection minimum, data word scale value range format. Important: Enabling open-circuit function adds approximately msec channel update time. Disabling opencircuit detection removes time adder. sensors require additional time; thus recommended that when using channel sensor acquisition, open-circuit selection enabled.
Select Temperature Units (Bit
temperature units lets select temperature engineering units thermocouple input types. Units either degrees Celsius (°C) degrees Fahrenheit (°F). This field only active thermocouple input types. ignored when millivolt inputs types selected. Important: using engineering units mode) Fahrenheit temperature units (i.e. 0.1°F), full scale temperature thermocouple type achievable with 16-bit signed numerical representation. overrange error occurs that channel tries represent full scale value. maximum representable temperature 3276.7°F (instead 3308°F).
Select Channel Filter Frequency (Bits
channel filter frequency field lets select four filters available channel. filter frequency affects channel update time noise rejection characteristics. smaller filter frequency increases channel update time, also increases noise rejection channel resolution. larger filter frequency decreases noise rejection, also decreases channel update time channel resolution. Guidelines filter frequency listed below.
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4-11
setting provides minimal noise filtering. setting provides line noise filtering. setting provides line noise filtering. setting provides both line noise filtering. When input type selected, filter frequency ignored. maximize speed versus resolution trade-off, inputs sampled Unused Bits (Bits through Bits 12-14 defined. Ensure these bits always cleared (0). Select Input Image Type (Bit input image type allows select data status information channel's input image word. When (1), module places channel data corresponding input image word. When cleared module places channel status corresponding input image word.
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Channel Configuration, Data, Status
Channel Data/Status Word
actual thermocouple millivolt input data values channel status reside I:e.0 through I:e.7 thermocouple module input image file. data values present depend input type data formats have selected. When input channel disabled, data word reset (0).
Module Input Image (Data/Status) Word I:e.0 I:e.1 I:e.2 I:e.3 I:e.4 I:e.5 I:e.6 I:e.7
Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word Channel Channel Data/Status Word
Channel Status Checking
information provided status word determine input configuration data channel valid your configuration O:e.0 through O:e.7. channel status analyzed bit. addition providing information about enabled disabled channel, each bit's status tells input data from thermocouple millivolt analog sensor connected specific channel will translated your application. status also informs error condition tell what type error occurred. bit-by-bit examination status word provided chart following page.
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Channel Status Word (I:e.0 through I:e.7) Definitions
Channel Status Channel Disable Channel Enable Thermocouple Type Thermocouple Type Thermocouple Type Thermocouple TypeE Thermocouple Type Thermocouple TypeS Thermocouple Type Input Type Thermocouple Type ±100 Invalid Invalid Invalid Invalid Invalid temperature Engineering Units Data Format Engineering Units Scaled Proportional counts Zero open circuit Open Circuit Max. open circuit Min. open circuit Disabled Temperature Units Channel filter frequency Open-circuit error Under-range error Over-range error Channel error Degrees Degrees input filter input filter input filter input filter error Open circuit detected error Under range condition error Over range condition error Channel error
Note:
takes timing cycle complete update. (Refer Chapter module update times.)
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Channel Configuration, Data, Status
Important: channel which seeking status disabled, fields cleared. status word disabled channel always 0000 0000 0000 0000 regardless previous setting that have been made configuration word. Explanations status conditions follow. Channel Status (Bit channel status indicates operational state channel. When channel enable configuration word, thermocouple module configures selected channel takes data sample channel data word before setting this status word. Input Type Status (Bits through input type field indicates what type input signal have configured channel. This field reflects input type defined channel configuration word. Data Format Type Status (Bits data format field indicates data format have defined channel. This field reflects data type selected bits channel configuration word. Open-Circuit Type Status (Bits open-circuit field indicates have defined opencircuit bits configuration word, therefore, response thermocouple module open-circuit condition. This feature active input types, including temperature input. Temperature Units Type Status (Bit temperature units field indicates state temperature units configuration word (bit Channel Filter Frequency (Bits channel filter frequency field reflects filter frequency selected configuration word. Open-Circuit Error (Bit This whenever configured channel detects opencircuit condition input. open-circuit sensor also flags this error channel input type either thermocouple temperature. range error sensor also flags this input type thermocouple.
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4-15
Under-Range Error (Bit This whenever configured channel detects underrange condition channel data. under-range condition exists when input value equal below specified lower limit particular sensor connected that channel. Over-Range Error (Bit This whenever configured channel detects overrange condition channel data. over-range condition exists when input value equal above specified upper limit particular sensor connected that channel. Channel Error (Bit This whenever configured channel detects error configuration word, error occurred while acquiring data value. during auto-calibration process, module detects out-of-range condition filter frequency selected channel, channel error set. out-of-range condition occurring during auto-calibration would result overly noisy environment, whereby module cannot maintain accuracy specifications, thus flagging error. error cleared when error condition resolved. channel data word updated during period auto-calibration filter frequency tolerance errors.
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Chapter
Programming Examples
Earlier chapters explained configuration word defines channel operates. This chapter shows programming required configure module. also provides with segments ladder logic specific unique situations that might apply your programming requirements. example segments include: basic example automatic monitoring thermocouples sensors verifying channel configuration changes interfacing instruction monitoring channel status bits example with remote rack
Basic Example
enter data into channel configuration word (O:e.0 through O:e.7) when channel disabled (bit follow these steps. Refer table page specific configuration details. Example Configure eight channels thermocouple module residing slot 1746 chassis. Configure each channel with same parameters.
Channel Configuration
Configure Channel for: Channel Enable Type Thermocouple Input Engineering Units Zero Open Circuit Fahrenheit Filter Frequency Used Data Word
following procedure transfers configuration data sets channel enable bits eight channels with single File Copy instruction.
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Procedure
Create integer file N10. Integer file should contain eight elements (N10:0 through N10:7). Using programming software, enter configuration parameters eight thermocouple channels into data file locations N10:0 through N10:7.
Data table initial programming
address N10:0 N10:1 N10:2 N10:3 N10:4 N10:5 N10:6 N10:7
1000 1000 1000 1000 1000 1000 1000 1000
data 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010
0011 0011 0011 0011 0011 0011 0011 0011
address
data
Press enter value N10:3/0 offline forces CHANGE RADIX
binary data SPECIFY ADDRESS
decimal addr NEXT FILE PREV FILE
File EXMPL
Program rung your ladder logic copy contents integer file eight consecutive output words thermocouple module beginning with O:3.0.
Initial programming example
During first pass, send channel configuration data thermocouple module. First Pass
0000
#NT8_CONFIGURATION Copy File Source #N10:0 Dest #O:3.0 Length
0001
power S:1/15 first program scan. During first program scan, configuration data N10:0 through N10:7 will sent 1746-NT8 channel configuration words.
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Programming Examples
Automatic Monitoring Thermocouples Sensors
following example explains change data channel configuration word when channel currently enabled. Example Execute dynamic configuration change channel thermocouple module located slot 1746 chassis. Periodically (e.g., every seconds) change from monitoring external type thermocouple monitoring sensors mounted terminal block. reading gives good indication what temperature inside control cabinet. Finally, channel back type thermocouple. Important: During configuration alteration, state each modified channel determined until after module update time. Note: N10:2/1 through N10:2/4 have input type type Thermocouple (0001). N10:8/1 through N10:8/4 have input type Temperature Sensor (1111).
Verifying Channel Configuration Changes
When executing dynamic channel configuration change, there always delay from time ladder program makes change time 1746-NT8 supplies data word using that configuration information. Also, ladder program should thermocouple temperature data location N10:20 thermocouple temperature readings data location N10:12 temperature readings.
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0000
During first pass, send channel configuration data thermocouple module. #NT8_CONFIGURATION First Pass Copy File Source #N10:0 Dest #O:1.0 Length
CHECKING_CJC B3:6
Checking CJC, copy Channel temperature data into data location use. Temperature control logic should N10:20 rather than input image (I:1.0) eliminate problems during checking. CHECKING_CJC CH0_TEMP B3:6 0001 Move Source I:1.0 3744< Dest N10:20 3744<
Copy temperature data from Channels data registers use. 0002
Copy File Source Dest Length
#I:1.1 #N10:21
0003
Repeating seconds timer (T11:0) which starts check cycle. CJC_CYCLE_TMR CJC_CYCLE_TMR/DN T11:0 Timer Delay Timer T11:0 Time Base Preset Accum
0004
Every seconds, start check cycle changing Channel configuration word latching Checking (B3/ 100). CJC_CYCLE_TMR/DN NT8_CONFIGURATION T11:0 Move Source N10:8 -32737< Dest O:1.0 -32767<
CHECKING_CJC B3:6
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0005
Wait seconds Channel accept configuration provide data value (time depends module configuration). CHECKING_CJC CJC_CFG_TMR B3:6 Timer Delay Timer T11:1 Time Base Preset Accum Copy Temperature (I:1.0) into register (N10:12) CJC_CFG_TMR/DN B3:0 T11:1
0006
CJC_TEMP Move Source Dest
I:1.0 3744< N10:12 329<
0007
Move Channel regular configuration word into Channel configuration word start timer ensure word been accepted prior taking thermocouple temperature readings. CJC_CFG_TMR/DN NT8_CONFIGURATION T11:1 Move Source N10:0 -32767< Dest O:1.0 -32767<
REG_CFG_TMR Timer Delay Timer T11:2 Time Base Preset Accum
When check cycle completed (T11:2/DN set), reset Checking (B3/100).
REG_CFG_TMR/DN T11:2 CHECKING_CJC B3:6
0008
0009
Data Table Configuration Changes
address N10:0 N10:1 N10:2 N10:3 N10:4 N10:5 N10:6 N10:7
0000 0000 0000 0000 0000 0000 0000 0000
data 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010
0011 0011 0011 0011 0011 0011 0011 0011
address N10:8
data 0000 0010 0011 1111
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Update Time Calculation Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Update Time Open Circuit Check Checking Update Time Autocalibration Time Calculation Auto-Calibration Auto-Calibration Total Auto-Calibration Time Between Updates 1.975 0.525 2.500 6.910 0.470 0.045 0.470 0.045 0.470 0.045 0.470 0.045 0.470 0.045 0.470 0.045 0.470 0.045 0.470 0.045 0.290 4.410
After channel configuration word changed ladder logic, module update processor's input image until update time later. order ensure that program using proper input data, ladder logic should wait update time plus calibration time ensure that input data matches channel configuration requested. above table shows calculate update time autocalibration time channel configuration being used.
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Interfacing Instruction
thermocouple module designed interface directly 5/02or later processor instruction without need intermediate scale operation. Example 1746-NT8 channel data process variable instruction. Select scaled-for-PID data type channel configuration word. Specify thermocouple channel data word process variable instruction. this example, value -32701 (8043 numeric equivalent configuration word N10:0 channel configured type thermocouple, scaled-for-PID, zero signal open-circuit, channel enabled.
Programming Control Example
Program Listing First Pass Initialize Channel
N10:0 -32701 O:3.0
Rung
MOVE Source Dest
Rung
Control Process Control Control
Block N11:0 Variable I:3.0 Variable N11:23 Block Length
Rung
SCALE Source
N11:23
Rate [/10000] Offset Dest
Rate Offset parameters should your application. Destination will typically analog output channel.
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Monitoring Channel Status Bits
following example shows monitor open-circuit error bits each channel alarm processor thermocouples opens. open-circuit error occur thermocouple breaks, thermocouple wires gets disconnected from terminal block, sensors installed damaged. Important: input installed damaged, enabled thermocouple alarms set, enabled thermocouple channel LEDs flash. example shows automatically switch between reading channel status words channel sensor data words. Specifically, this example shows simple method utilizing timer periodically switch between reading channel status data words. program utilizes timer accumulator value determine when configuration words when read channel status channel data information. channel status information copied from I:2.0 I:2.7 registers into registers N7:10 N7:17. channel data information copied from I:2.0 I:2.7 into registers N7:0 N7:7. This allows sensor data channel status information accessed time from these registers. However, when module channels configured read sensor data, channel status words reflected N7:10 N7:17) being dynamically updated, vice-versa.
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Monitoring Channel Status Bits Example
During program scan, copy thermocouple channel configuration words (N10:0 N10:7) NT8. addition, initialize channel error registers (N10:20 N10:27) Error Flags (B3/112 B3/119). 0000
#NT8_CH_CNF Copy File Source #N10:0 Dest #O:1.0 Length #NT8_CH0_STS_FLAGS Fill File Source Dest #N10:20 Length Clear Dest B3:7 0000000000000001<
checking channel status, store thermocouple readings last channel reading registers (N10:37). These registers should used remainder program (e.g. temperature control) instead image location. 0001
NT8_CHECKING_STS B3:6 #NT8_LAST_TEMP_READ Copy File Source #I:1.0 Dest #N10:30 Length
T11:0 repeating 60-second timer which initiates channel status check. 0002
NT8_STS_CHECK_TMR/DN T11:0 NT8_STS_CHECK_TMR Timer Delay Timer T11:0 Time Base Preset Accum
Every seconds, initiate channel status check latching channel status checking copying "Status check" configuration words (N10:10 N10:7) configuration words. 0003
NT8_STS_CHECK_TMR/DN T11:0 NT8_CHECKING_STS B3:6 #NT8_CH_CNF Copy File Source #N10:10 Dest #O:1.0 Length
After copying "Status Check configuration words" start 7-second timer (T11:1) allow update image channel status words. time required update image dependent configuration. Note, time required greater than channel update time including autocalibration time.
NT8_CHECKING_STS B3:6
0004
NT8_STS_CNF_TMR Timer Delay Timer T11:1 Time Base Preset Accum
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Programming Examples
After waiting update image, check each channel's status error bits masking appropriate bits checking these bits (non-zero). error detected, appropriate channel status error bits (B3:112 B3/119). Rung checks channels 0-3). 0005
NT8_STS_CNF_TMR/DN T11:1 NT8_CHECK_FLAGS B3:6 Move Source
Dest B3:7 0000000000000001<
NT8_CH0_STS_FLAGS Masked Move Source I:1.0 Mask 0F000h -4096< Dest N10:20 4096<
NT8_CH0_STS_FLAGS Equal Source N10:20 4096< Source
NT8_CH0_ERROR B3:7
NT8_CH1_STS_FLAGS Masked Move Source I:1.1 Mask 0F000h -4096< Dest N10:21
NT8_CH1_STS_FLAGS Equal Source N10:21 Source
NT8_CH1_ERROR B3:7
NT8_CH2_STS_FLAGS Masked Move Source I:1.2 Mask 0F000h -4096< Dest N10:22
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NT8_CH2_STS_FLAGS Equal Source N10:22 Source
NT8_CH2_ERROR B3:7
NT8_CH3_STS_FLAGS Masked Move Source I:1.3 Mask 0F000h -4096< Dest N10:23
NT8_CH3_STS_FLAGS Equal Source N10:23 Source
NT8_CH3_ERROR B3:7
After waiting update image, check each channel's status error bits masking appropriate bits checking these bits (non-zero). error detected, appropriate channel status error bits (B3:112 B3/119). Rung checks channels
NT8_STS_CNF_TMR/DN T11:1
NT8_CHECK_FLAGS2 B3:6
0006
NT8_CH4_STS_FLAGS Masked Move Source I:1.4 Mask 0F000h -4096< Dest N10:24
NT8_CH4_STS_FLAGS Equal Source N10:24 Source
NT8_CH4_ERROR B3:7
NT8_CH5_STS_FLAGS Masked Move Source I:1.5 Mask 0F000h -4096< Dest N10:25
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NT8_CH5_STS_FLAGS Equal Source N10:25 Source
NT8_CH5_ERROR B3:7
NT8_CH6_STS_FLAGS Masked Move Source I:1.6 Mask 0F000h -4096< Dest N10:26
NT8_CH6_STS_FLAGS Equal Source N10:26 Source
NT8_CH6_ERROR B3:7
NT8_CH7_STS_FLAGS Masked Move Source I:1.7 Mask 0F000h -4096< Dest N10:27
NT8_CH7_STS_FLAGS Equal Source N10:27 Source
NT8_CH7_ERROR B3:7
After updating error status registers flags, copy "regular" channel configuration words into image. Begin 7-second timer wait change image back regular channel configuration. Again, time required change image dependent configuration. 0007
NT8_STS_CNF_TMR/DN T11:1 #NT8_CH_CNF Copy File Source #N10:0 Dest #O:1.0 Length
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NT8_REG_CNF_TMR Timer Delay Timer T11:2 Time Base Preset Accum
After restored normal image, clear checking status (B3/100). 0008
NT8_REG_CNF_TMR/DN T11:2 NT8_CHECKING_STS B3:6
0009
Example with Remote Rack
following example shows sample ladder logic when using PLC/ controller control module remote rack across Remote network. PLC/5 must Block transfer reads writes communicate with 1746-NT8 module remote rack. Note, example provides code which will reconfigure module PLC/ senses remote rack fault. Also, PLC/5 processor uses exact same configuration words processors.
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Programming Examples
During first scan, clear Configurated (B3/4) initiate configuration process. First scan step NT8_CONFIGURED B3:0 configured rack fault occurs, clear Configured (B3/4) initiate configuration process.
NT8_CONFIGURED B3:0
RIO_RACK1_FLT Masked Move Source N30:2 256< Mask Dest N11:3 RIO_RACK1_FLT Equal Source N11:3 Source NT8_CONFIGURED B3:0
Until configured, send configuration words (N12:10-17) using repeating BTW's.
NT8_CONFIGURED B3:0
NT8_BTW/EN BT20:1
NT8_BTW Block Transfer Write Module Type Generic Block Transfer Rack Group Module Control Block BT20:1 Data File N12:10 Length Continuous
When configured latch Configured (B3/4).
BTW_DONE BT20:1
configured, read input words into N12:0 N12:7 using repeating BTR's.
NT8_CONFIGURED B3:0
NT8_CONFIGURED B3:0
BTR_TRIGGER BT20:0
Block Transfer Read Module Type Generic Block Transfer Rack Group Module Control Block BT20:0 Data File N12:0 Length Continuous
Publication 1746-6.22
Chapter
Troubleshooting Your Module
This chapter describes troubleshooting with channel-status module-status LEDs. explains types conditions that might cause module flag error suggests what corrective action could take. Topics include: module channel diagnostics indicators Interpreting error codes troubleshooting flowchart
Module Channel Diagnostics
module operates levels: module level channel level Module-level operation includes functions such powerup, configuration, communication with processor. Channellevel operation includes functions such data conversion opencircuit detection. module performs internal diagnostics both levels immediately indicates detected error conditions with either status LEDs. troubleshooting tables page operation.
Module Diagnostics Powerup
module powerup, module performs series internal diagnostic tests. module detects failure, module status remains off.
Channel Diagnostics
When channel enabled, module checks valid configuration. Then each scan inputs, module checks out-of-range open-circuit fault conditions inputs including input. When module detects failure channel diagnostic test, causes channel status blink sets corresponding channel fault (bits 12-15 channel status word). Channel fault bits LEDs self-clearing when fault conditions corrected.
Publication 1746-6.22
Troubleshooting Your Module
Important: clear channel enable bit, channel status bits reset.
Indicators
module nine LEDs; shown below. eight channel-status LEDs, numbered correspond with each channel module-status
INPUT
Channel Status Module
Module Status
LEDs Channels
Thermocouple/mV
Troubleshooting Tables
Module-status Module Status
Then: module operating properly. module turned off, detected module fault. Jumper wrong position
Take this Corrective Action:
Flashing
action required. Cycle power. condition persists, call your local Allen-Bradley distributor assistance. Check jumper 1position.
Module-status Channel-status Module Status Channel Status
Then: channel enabled module detected: opencircuit condition, under-range condition, overrange condition module power channel disabled.
Take this Corrective Action:
action required. Examine error bits status word 12=1, input open circuit 13=1, input value under range 14=1, input value over range 15=1, channel diagnostic channel error action required.
Flashing
Publication 1746-6.22
Troubleshooting Your Module
Channel-status LEDs (Green)
channel-status operates with status bits channel status word indicate following faults detected module: invalid channel configuration open-circuit input out-of-range errors selected filter frequency data acquisition auto-calibration errors When module detects following fault conditions, causes channel-status flash sets corresponding fault channel status word. Channel fault bits (bits through channel-status LEDs self-clearing when fault conditions corrected.
Open-circuit Detection (Bit
open-circuit detection enabled input channel, module tests channel open-circuit condition each time scans input. Open-circuit detection always performed inputs. Possible causes open circuit include: broken thermocouple sensor thermocouple sensor wire disconnected millivolt input wire disconnected
Out-of-Range Detection (Bit Under Range, Over Range)
module tests enabled channels out-of-range condition each time scans inputs. Possible causes out-of-range condition include: temperature cold thermocouple being used type thermocouple registering value Engineering Units beyond range allowed processor (beyond 32,767) data word sensor damaged temperature being detected outside sensor range limits
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Troubleshooting Your Module
Channel Error (Bit
module sets this fault when detects following: Configuration errors: configuration bits through invalid input type 1010, 1011, 1100, 1101, 1110 configuration bits through invalid non-zero setting invalid data acquisition input channel filter frequency selected valid channel currently fails auto-calibration range checks
Module Status (Green)
module-status indicates when module detects nonrecoverable fault power during operation. this type fault, module: longer communicates with processor disables channels clears data status words module failure non-recoverable requires assistance your local Allen-Bradley distributor.
Interpreting Error Codes
error codes appear word processor status file. first digits error code identify slot hexadecimal) with error. last digits identify error code hexadecimal). error codes that apply your module include hexadecimal): through (watchdog error) through description error codes, refer Instruction Reference Manual, publication 1746-6.15.
Publication 1746-6.22
Troubleshooting Your Module
Troubleshooting Flowchart
Check LEDs module.
Module Status LED(s) off.
Module Status LED(s)
Channel Status LED(s) flashing.
Channel Status LED(s) off.
Channel Status LED(s)
Module fault condition.
Normal module operation. End.
Fault condition.
Channel enabled.
Channel enabled working.
Check that module seated properly chassis. Cycle power.
faulted channel(s) configured thermocouple input? Thermocouple more than blinking? fault probably occurred
Enable channel desired setting channel config. word (bit 0=1). Retry. End.
Check channel status word bits through Channel error. Check configuration word bits through valid input type configuration ensure bits through zero. Retry.
Check that wiring secure both CJCs that temperature within enclosure range limits sensor. problem corrected? End. problem corrected?
Over-range condition exists. input signal greater than high scale limit channel connections. Correct retry.
problem corrected?
Contact your local Allen-Bradley distributor Contact your local Allen-Bradley distributor.
Under-range condition exists. input signal less than scale limit channel connections. Correct retry. open-circuit condition present. Check channel wiring open loose connections. Retry.
Contact your local Allen-Bradley distributor.
Publication 1746-6.22
Chapter
Maintaining Your Module Safety Considerations
Read this chapter familiarize yourself with: preventive maintenance safety considerations National Fire Protection Association (NFPA) recommends maintenance procedures electrical equipment. Refer article NFPA general safety-related work practices.
Preventive Maintenance
printed circuit boards your module must protected from dirt, oil, moisture, other airborne contaminants. protect these boards, install system enclosure suitable operating environment. Keep interior enclosure clean, whenever possible, keep enclosure door closed. Also, regularly inspect terminal connections tightness. Loose connections cause malfunctioning system damage components. ATTENTION: Possible Loose Connections
Before inspecting connections, always ensure that incoming power OFF. Failure observe this precaution cause personal injury equipment damage.
Safety Considerations
Safety always most important consideration. Actively think about safety yourself others, well condition your equipment. following some things consider: Indicator Lights When module status your module illuminated, your module receiving power. Activating Devices When Troubleshooting Never reach into machine activate device; machine move unexpectedly. wooden stick.
Publication 1746-6.22
Maintaining Your Module Safety Considerations
Standing Clear Machinery When troubleshooting problem with system, have personnel remain clear machinery. problem intermittent, machine move unexpectedly. Have someone ready operate emergency stop switch. ATTENTION: Possible Equipment Operation
Never reach into machine actuate switch. Also, remove electrical power main power disconnect switches before checking electrical connections inputs/outputs causing machine motion. Failure observe these precautions cause personal injury equipment damage.
Safety Circuits Circuits installed machinery safety reasons (like over-travel limit switches, stop push-buttons, interlocks) should always hard-wired master control relay. These circuits should also wired series that when circuit opens, master control relay de-energized, thereby removing power. Never modify these circuits defeat their function. Serious injury equipment damage result. ATTENTION: Explosion Hazard
Substitution components impair suitability Class Division disconnect equipment unless power been switched area known nonhazardous. When hazardous locations, turn power before replacing wiring modules.
Note:
This equipment suitable Class Division groups non-hazardous locations only.
Refer your system's Installation Operation Manual more information.
Publication 1746-6.22
Appendix
Module Specifications
This appendix lists specifications 1746-NT8 Thermocouple/millivolt Input Module.
Electrical Specifications
Backplane Current Consumption Backplane Power Consumption Number Channels Chassis Location Conversion Method Input Filtering 24Vdc 2.28W maximum (0.6W 1.68W (backplane channel-to-channel isolated) module slot except Sigma-Delta Modulation pass digital filter with programmable notch (filter) frequencies
Normal Mode Rejection (between input Greater than 50/60 input) Common Mode Rejection (between input ground) Input Filter Cut-Off Frequencies filter frequency 13.1 filter frequency 15.72 filter frequency 65.5 filter frequency Calibration Input Over-voltage Protection Isolation Greater than 50/60
Greater than 50/60
Module autocalibrates power-up approximately every minutes afterward ±30V continuous 600W pulsed msec. 500V continuous between inputs chassis ground between inputs backplane. 12.5V continuous between channels.
Physical Specifications
Indicators Module Code Recommended Cable: thermocouple inputs. inputs. Maximum Wire Size green status indicators, each channels module status 3533 Appropriate shielded twisted pair thermocouple extension wire1 Belden8761 equivalent wire wires terminal
Refer thermocouple manufacturer correct extention wire.
Publication 1746-6.22
Module Specifications
Environmental Specifications
Operating Temperature Storage Temperature Relative Humidity Certification Hazardous Environment Classification +60°C (+32°F +140°F) -40°C +85°C (-40°F +185°F) (without condensation) approved Class Division Hazardous Environment Groups compliant
Input Specifications
Thermocouple Type Thermocouple Type Thermocouple Type Thermocouple Type Type Input (Selectable Thermocouple Type Thermocouple Type Thermocouple Type Thermocouple Type -210°C +760 -270°C +1370°C -270°C +400°C -270°C +1000°C +1768°C +1768°C +300°C +1820°C +1300°C (-346°F +1400°F) (-454°F +2498°F) (-454°F +752°F) (-454°F +1832°F) (+32°F +3214°F) (+32°F +3214°F) (+572°F +3308°F) (+32°F +2372°F)
Millivolt (-50mV +50mV Millivolt (-100mV +100mV Thermocouple Linearization Cold Junction Compensation Input Impedence NIST ITS-90 standard Accuracy ±1.72°C, -25°C +105°C Greater than 10M:
Temperature Scale (Selectable) 0.1°C 0.1°F Millivolt Scale (Selectable) 0.01 Open Circuit Detection (Selectable) Time Detect Open Circuit Input Step Response Display Resolution Overall Module Accuracy 25°C (77°F) Overall Module Accuracy Overall Module Drift Module Update Time Channel Turn-Off Time Upscale, Downscale, Zero, Disabled channel cycle time msec Channel Data Word Resolution table page Module Accuracy Tables, page Module Accuracy Tables, page Module Accuracy Tables, page Dependent upon enabled channels (see Update Time, page module update time
Overall Accuracy
accuracy module determined many aspects hardware software functionality module. following discussion explains what user expect terms accuracy based thermocouple millivolt inputs 1746-NT8 module.
Publication 1746-6.22
Module Specifications
accuracies specified follows include errors cold junction compensation thermocouples hardware software errors associated with system. hardware software errors include calibration system non-linearity ADC. sake calculations, resolution assumed least bits (use filter frequencies). Note: frequency should applied thermocouple inputs (See table page 3-4).
Millivolt
millivolt inputs, error typical 25°C, ±120 maximum over temperature filter frequencies. filter frequency accuracy highly dependent upon operating environment worse noisy environments. with high precision analog input device, system grounding does affect accuracy readings. Care should taken ensure that proper filter frequency been selected based environmental conditions which module used. compensation does affect millivolt inputs terms accuracy. following diagrams provided give measure "system" accuracy using test data from single test module. tests recorded deviation between measured expected values. This data taken over entire range thermocouple millivolt range, applicable) over module's temperature range 60°C). maximum deviation each thermocouple temperature millivolt range) plotted.
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Publication 1746-6.22
Deviation
10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00
Deviation
10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 0.00 5.00
Module Specifications
0.00
5.00
Err, ±100mV Span, Prop Cts,
Err, ±100mV Span, Prop Cts, 25°C
Input Input
Error
Error
Module Specifications
Err, ±100mV Span, Prop Cts, 60°C
90.00
80.00
70.00
60.00
50.00
Deviation
Error
40.00
30.00
20.00
10.00
0.00
Thermocouple
following table provides total error expected thermocouple based thermocouple type, given reference point, 25°C. calculations assumed typical hardware/ software error typical accuracy 25°C.
Thermocouple Type Thermocouple Reference Point +275°C (+527°F) +550°C (+1022°F) +65°C (+149°F) +365°C (+689°F) +885°C (+1625°F) +885°C (+1625°F) +1060°C (+1940°F) +500°C (+932°F) Error ±1.4°C (±2.52°F) ±1.5°C (±2.7°F) ±1.3°C (±2.34°F) ±1.0°C (±1.8°F) ±3.6°C (±6.48°F) ±3.4°C (±6.12°F) ±2.7°C (±4.86°F) ±1.3°C (±2.34°F)
Input
Publication 1746-6.22
Module Specifications
following table provides total error expected over temperature range module 60°C) each thermocouple based upon type, given reference point, extremes temperature range 60°C). calculations based maximum hardware/software error maximum inaccuracy over temperature.
Thermocouple Type Thermocouple Reference Point +275°C (+527°F) +550°C (+1022°F) +65°C (+149°F) +365°C (+689°F) +885°C (+1625°F) +885°C (+1625°F) +1060°C (+1940°F) +500°C (+932°F) Error ±3.0°C (±5.4°F) ±3.0°C (±5.4°F) ±3.4°C (±6.12°F) ±2.5°C (±4.5°F) ±6.5°C (±11.7°F) ±7.2°C (±12.96°F) ±8.4°C (±15.12°F) ±3.0°C (±5.4°F)
diagrams that follow each thermocouple type give data sample module over input range thermocouple over temperature. Thermocouples usually parabolic their curves. Normally, ends given thermocouple range, ratio change temperature increases result change voltage. other words, ends, smaller change voltage results larger change data that follows gives idea sample module's error over thermocouple range, versus single reference point provided with tables above. Note: data recorded Values would comparable.
Publication 1746-6.22
Module Specifications
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Input
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Input
Publication 1746-6.22
Module Specifications
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Input
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Input
Publication 1746-6.22
Module Specifications
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Input
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Data
Degrees Input
Publication 1746-6.22
A-10
Module Specifications
Thermocouple Deviations Over Temp
Degrees Deviation
Channel Delta
Degrees Deviation
Degrees Input
Thermocouple Deviations Over Temp
Channel Delta
Degrees Input
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Appendix
Using Grounded Junction, Ungrounded Junction, Exposed Junction Thermocouples
This appendix describes types thermocouples available explains trade-offs using them with 1746-NT8 module.
Thermocouple Types
There three types thermocouple junctions: Grounded Junction measuring junction physically connected protective sheath forming completely sealed integral junction. sheath metal electrically conductive), then there electrical continuity between junction sheath. junction protected from corrosive erosive conditions. response time approaches that exposed junction type. Ungrounded Junction measuring junction electrically isolated from protective metal sheath. This also referred insulated junction. This type often used where noise would affect reading frequent rapid temperature cycling. response time longer than grounded junction. Exposed Junction measuring junction does have protective metal sheath, exposed. This junction style provides fastest response time leaves thermocouple wires unprotected against corrosive mechanical damage.
Publication 1746-6.22
Using Grounded Junction, Ungrounded Junction, Exposed Junction Thermocouples
following illustrations show each three thermocouple types. Grounded Junction
Metal Sheath Extension Wire
Measuring Junction connected sheath
Ungrounded (Insulated) Junction
Measuring Junction isolated from sheath
Exposed Junction
Measuring Junction sheath
Isolation
1746-NT8 module provides following electrical isolation: 12.5V electrical isolation channel-to-channel 500V electrical isolation channel-to-chassis ground 500V electrical isolation channel-to-backplane Care must taken when choosing thermocouple type connecting 1746-NT8 module from environment being measured. adequate precautions taken given thermocouple type, electrical isolation 1746-NT8 module compromised.
Publication 1746-6.22
Using Grounded Junction, Ungrounded Junction, Exposed Junction Thermocouples
Grounded Junction Thermocouples
shown following illustration page B-3, shield input terminals internally connected together, which then connected chassis ground. Using grounded junction thermocouples with electrically conductive sheaths removes thermocouple signal chassis ground isolation module. This inherent thermocouple construction. addition, multiple grounded junction thermocouples used, module's channel-to-channel isolation removed since there isolation between signal sheath sheaths tied together. should noted that isolation removed even sheaths connected chassis ground location other than module, since module connected chassis ground.
1746-NT8 MUXES Grounded junction with nonconductive protective sheath.
Metal sheath with electrical continuity thermocouple signal wires. (floating ground connection)
grounded junction thermocouples, recommended that they have protective sheaths made electrically insulated material (e.g. ceramic), metal protective sheaths floated. metal sheaths would need floated with respect path chassis ground another thermocouple metal sheath. This means metal sheath must insulated from electrically conductive process material have connections chassis ground broken. should noted that floated sheath result less noise immune thermocouple signal.
Publication 1746-6.22
Using Grounded Junction, Ungrounded Junction, Exposed Junction Thermocouples
Exposed Junction Thermocouples
Recommended wiring exposed junction thermocouples shown following illustration. Using exposed junction thermocouples result removal channel-to-channel isolation. This occur multiple exposed thermocouples direct contact with electrically conductive process material. prevent violation channel-to-channel isolation: multiple exposed thermocouples, allow measuring junction thermocouple make direct contact with electrically conductive process material. ungrounded junction thermocouple instead exposed junction type.
1746-NT8 Conductive Material
MUXES
Exposed junction with shielded cable
Nonconductive Material
Exposed junction with shielded cable
Publication 1746-6.22
Glossary
should understand following terms abbreviations before using this guide. Refers analog-to-digital conversion. conversion produces digital value whose magnitude proportional instantaneous magnitude analog input signal. Attenuation reduction magnitude signal passes through system. opposite gain. Channel Refers eight, small-signal analog input interfaces modules's terminal block. Each channel configured connection thermocouple millivolt (mV) input device, configuration status words. Chassis hardware assembly that houses devices such modules, adapter modules, processor modules, power supplies. (Cold-Junction Compensation) means which module compensates offset voltage error introduced temperature junction between thermocouple lead wire input terminal block (the cold junction). Common mode rejection ratio (CMRR) ratio device's differential voltage gain common mode voltage gain. Expressed CMRR comparative measure device's ability reject interference caused voltage common terminal relative ground. Common mode voltage voltage difference between negative terminal analog common during normal differential operation. Configuration word Contains channel configuration information needed module configure operate each channel. Information written configuration word through logic supplied your ladder program. Cut-off frequency frequency which input signal attenuated digital filter. Frequency components input signal that below cut-off frequency passed with under attenuation low-pass filters. (decibel) logarithmic measure ratio signal levels. Data word 16-bit integer that represents value analog input channel. channel data word valid only when channel enabled there channel errors.
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Glossary
Digital filter low-pass filter converter. digital filter provides high-frequency noise rejection. Effective resolution number bits channel data word that vary noise. Full-scale error (gain error) difference slope between actual ideal analog transfer functions. Full-scale range (FSR) difference between maximum minimum specified analog values. Gain drift change full-scale transition voltage measured over operating temperature range module. Input data scaling Depends data format that select channel data word. select from scaled-for-PID Engineering Units millivolt, thermocouple, inputs, which must compute your application's temperature voltage resolution. Local system control system with chassis within several feet processor, using 1746-C7 1746-C9 ribbon cable communication. (least significant bit) that represents smallest value within string bits. "weight" this value defined full-scale range divided resolution. Multiplexer switching system that allows several input signals share common converter. Normal mode rejection (differential mode rejection) logarithmic measure, device's ability reject noise signals between among circuit signal conductors, between equipment grounding conductor signal reference structure signal conductors. Remote system control system where chassis located several thousand feet from processor chassis. Chassis communication 1747-SN Scanner 1747-ASB Remote Adapter. Resolution smallest detectable change measurement, typically expressed engineering units (e.g. 0.15°C) number bits. example, 12-bit value 4,096 possible counts. therefore used measure part 4096. Sampling time time required converter sample input channel.
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Glossary
Status word Contains status information about channel's current configuration operational state. this information your ladder program determine whether channel data word valid. Step response time time required signal reach expected, final value, given full-scale step change input signal. Update time time module sample convert channel input signal make resulting value available processor.
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Index
Addressing 3-2, 3-4, 3-6, 3-7, 3-9, 4-5, 4-6, 4-9, 4-10, 4-14, 4-15 Allen-Bradley contacting assistance Analog-to-digital conversion Attenuation Avoiding electrostatic damage
Detection open-circuit determining determining power requirements Diagnostic information LEDs Drift
channel status 4-14 field channel filter frequency 4-14 data format 4-5, 4-14 input type 4-5, 4-14 open-circuit 4-9, 4-14
Effective resolution Electrical noise Engineering units 4-5, proportional counts scaled-for-PID Error channel 4-15 full-scale open-circuit 4-14 over-range 4-10, 4-15 under-range 4-15 Error codes Exposed junction B-1,
Calibration Channel configuration configuration word 4-2, data word 4-2, 4-8, 4-9, 4-10 diagnostics enable error 4-15, filter frequency 4-10 filter frequency field 4-14 status 4-14 update time Channel-status LEDs Cold junction compensation, 2-10 Common mode rejection Condition open-circuit 4-9, 4-10 out-of-range 4-15 over-range
Filter frequency 4-2, 4-10, 4-15 Full-scale error range
Gain drift Gain error Grounded junction B-1,
Hardware features
under-range
Configuration words contacting Allen-Bradley assistance Cut-off frequency
Hot-swapping
error codes 6-1, Indicator lights Input field 4-5, 4-14 channel data image type 4-11
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Data format field 4-5, 4-14 Data resolution Data word 4-2, G-1,
I-ii
Index
Installing module
Range full-scale millivolt analog input signal temperature Resolution G-2,
Junction exposed B-1, grounded B-1, ungrounded
indicators scale value 4-10
Safety circuits considerations Sampling time Scaled-for-PID 4-5, 4-6, Scaled-for-PID engineering units Shipping 2-6, 2-8, 2-10 Signal attenuation Static shielded container 2-6, 2-8, 2-10, 3-2, 3-3, 3-4, 3-6, 3-7, 3-9, 4-6, 4-9, 4-10, 4-14, 4-15 Status Step response time
Maintenance Millivolt analog input signal ranges Module Addressing 1-4, diagnostics code level operation status
Normal mode rejection
Temperature ranges units 4-10 units field 4-14 Terminal block removal Troubleshooting 6-1, 6-2, contacting Allen-Bradley
Open-circuit field 4-9, 4-14 condition 4-9, 4-10 detection 1-4, error 4-14 error bits Out-of-range condition 4-15 Over-range condition error 4-10, 4-15
Under-range condition error 4-15 Ungrounded junction Update time Useful resolution
Preventive maintenance Programming 3-2, 3-3, 3-4, 3-6, 3-9, 4-5, 4-6, 4-9, 4-10, 4-14, Proportional counts 4-5, Proportional counts engineering units
Wiring signal cables
Publication 1746-6.22
Back Cover
Publication 1746-6.22 July 1999
xxxxxxx-xx
1999 Rockwell International Corporation. rights reserved. Printed U.S.A.
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