Allen-Bradley 1746-NT8 User Manual
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Allen-Bradley 1746-NT8 User Manual

Thermocouple/mv analog input module
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SLC 500
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Summary of Contents for Allen-Bradley 1746-NT8

  • Page 1 SLC 500 Thermocouple/mV Analog Input Module 1746-NT8 User Manual...
  • Page 2 Important User Information Solid state equipment has operational characteristics differing from those of electromechanical equipment. Safety Guidelines for the Application, Installation and Maintenance of Solid State Controls (Publication SGI-1.1 available from your local Rockwell Automation sales office or online at http://www.ab.com/manuals/gi) describes some important differences between solid state equipment and hard-wired electromechanical devices.

  • Page 3: Table Of Contents

    Table of Contents Preface Who Should Use This Manual ..... . P-1 What This Manual Covers ......P-1 Related Documentation .
  • Page 4 Table of Contents Chapter 4 Channel Configuration, Data, and Channel Configuration ......4-1 Channel Configuration Procedure ....4-2 Status Select Channel Enable (Bit 0) .
  • Page 5 Grounded Junction ......B-3 Exposed Junction Thermocouples....B-4 Appendix C Configuring the 1746-NT8 Module with RSLogix 500 Glossary...
  • Page 6 Table of Contents Publication 1746-UM022B-EN-P - January 2005...
  • Page 7 Summary of Changes The information below summarizes the changes to this manual since the last printing. Updates to the manual include using RSLogix 500 instead of APS software. To help you find new and updated information in this release of the manual, we have included change bars as shown to the right of this paragraph.
  • Page 8 Summary of Changes Publication 1746-UM022B-EN-P - January 2005...

  • Page 9: Who Should Use This Manual

    Automation representative for the proper training before using these products. What This Manual Covers This manual covers the 1746-NT8 thermocouple/millivolt analog input module. It contains the information you need to install, wire, use, and maintain these modules. It also provides diagnostic and troubleshooting help should the need arise.

  • Page 10: Related Documentation

    If you would like to: • view and download the publication, go to Literature Library at http://www.rockwellautomation.com/literature • order printed copies, contact your Allen-Bradley Distributor or Rockwell Automation Sales Office. Common Techniques Used The following conventions are used throughout this manual: in this Manual •...

  • Page 11: General Description

    Chapter Module Overview This chapter describes the thermocouple/mV input module and explains how the SLC 500 processor reads thermocouple or millivolt analog input data from the module. Read this chapter to familiarize yourself further with your thermocouple/mV analog input module. This chapter covers: •...

  • Page 12: Hardware Features

    Module Overview Type °C Temperature Range °F Temperature Range 0°C to +1768°C +32°F to +3214°F 0°C to +1300°C +32°F to +2372°F CJC Sensor -25°C to +105°C -13°F to +221 °F Millivolt Input Ranges -50 to +50 mV -100 to +100 mV Each input channel is individually configured for a specific input device, and provides open-circuit, over-range, and under-range detection and indication.

  • Page 13: Diagnostic Leds

    Module Overview Side Label Channel Status LEDs (green) INPUT Door Label CHANNEL STATUS Module Status MODULE LEDs (green) THERMOCOUPLE/mV 1746-NT8 Removable CJC A+ CJC A- CHL 0+ Terminal Block CHL 0- SHIELD CHL 1+ CHL 1- CHL 2+ CHL 2-...

  • Page 14: System Operation

    Module Overview Each module channel can receive input signals from a thermocouple or a mV analog input device. You configure each channel to accept either one. When configured for thermocouple input types, the module converts analog input voltages into cold-junction compensated and linearized, digital temperature readings.

  • Page 15: Module Operation

    Module Overview Module Operation The module’s input circuitry consists of eight differential analog inputs, multiplexed into an A/D convertor. The A/D convertor reads the analog input signals and converts them to a digital value. The input circuitry also continuously samples the CJC sensors and compensates for temperature changes at the cold junction (terminal block).

  • Page 16: Block Diagram

    Module Overview Block Diagram Terminal Block Module Circuitry C JC A Sensor ungrounded thermocouple Shield multiplexer User Selected Filter F requency Wit hin 12.5V Shield Analog to Digital Digital Digital Filter grounded Value C onverter thermocouple Analog Shield Ground Shield C JC B Sensor When using multiple thermocouples, the potential IMPORTANT...

  • Page 17: Linear Millivolt Device Compatibility

    Module Overview Linear Millivolt Device Compatibility A large number of millivolt devices may be used with the 1746-NT8 module. For this reason we do not specify compatibility with any particular device. However, millivolt applications often use strain gage bridges. A resistive voltage divider using fixed resistors is recommended for this application.
  • Page 18 Module Overview Publication 1746-UM022B-EN-P - January 2005...

  • Page 19: Electrostatic Damage

    Chapter Installing And Wiring Your Module Read this chapter to install and wire your module. This chapter covers: • avoiding electrostatic damage • determining power requirements • installing the module • wiring signal cables to the module’s terminal block Electrostatic Damage Electrostatic discharge can damage semiconductor devices inside this module if you touch backplane connector pins.

  • Page 20: Power Requirements

    Installing And Wiring Your Module Power Requirements The module receives its power through the SLC 500 chassis backplane from the fixed or modular +5 V dc/+24 V dc chassis power supply. The maximum current drawn by the module is shown in the table below.

  • Page 21: Fixed I/O Chassis - I/O Module Compatibility

    Installing And Wiring Your Module Fixed I/O Chassis - I/O Module Compatibility The following chart depicts the range of current combinations supported by the fixed I/O expansion chassis. To use it, find the backplane current draw and operating voltage for both modules being used in the chassis.

  • Page 22: General Considerations

    Installing And Wiring Your Module When using the BAS or KE module to supply power to a 1747-AIC Link Coupler, the link coupler draws its power through the module. The higher current drawn by the AIC at 24V dc is shown in the table as BASn (BAS networked) and KEn (KE networked).

  • Page 23: Module Installation And Removal

    Installing And Wiring Your Module Module Installation and Removal Possible Equipment Operation ATTENTION Before installing or removing your module, always disconnect power from the SLC 500 system and from any other source to the module (in other words, do not ’hot swap’ your module), and disconnect any devices wired to the module.

  • Page 24: Terminal Block Removal

    Installing And Wiring Your Module 4. Cover all unused slots with the Card Slot Filler, Allen-Bradley part number 1746-N2. Terminal Block Removal To remove the terminal block: 1. Loosen the two terminal block release screws. To avoid cracking the terminal block, alternate between screws as you remove them.
  • Page 25 Installing And Wiring Your Module Terminal block diagram with CJC sensors Terminal Block Release Screws CJC Sensors R ecommended Torque: wiring screws: 0.25 Nm (2.2 in-lb) release screws: 0.25 Nm (2.2 in-lb) CJC Sensors Terminal Block Release Screws Possible Equipment Operation ATTENTION Before wiring your module, always disconnect power from the SLC 500 system and from any other...

  • Page 26: Wiring Your Module

    Installing And Wiring Your Module Wiring Your Module Follow these guidelines to wire your input signal cables: • Power, input, and output (I/O) wiring must be in accordance with Class 1, Division 2 wiring methods [Article 501-4(b) of the National Electrical Code, NFPA 70] and in accordance with the authority having jurisdiction.

  • Page 27: Preparing And Wiring The Cables

    Installing And Wiring Your Module Preparing and Wiring the Cables To prepare and connect cable leads and drain wires, follow these steps: Cable (Remove foil shield and drain wire Signal Wires from sensor end of the cable.) Drain Wire Signal Wires 1.
  • Page 28 2-10 Installing And Wiring Your Module 6. Connect the signal wires of each channel to the terminal block. Only after verifying that your connections are IMPORTANT correct for each channel, trim the lengths to keep them short. Avoid cutting leads too short. 7.

  • Page 29: Cold-Junction Compensation (Cjc)

    Installing And Wiring Your Module 2-11 Terminal Block Diagram with Input Cable CJC A+ CJC A- Ch annel 0+ Thermocouple or mV Ca ble Ch annel 0- Shield for CH 0 and CH 1 Ch annel 1+ Ch annel 1- Ch annel 2+ Ch annel 2- Shield for CH 2 and CH 3...
  • Page 30 2-12 Installing And Wiring Your Module Publication 1746-UM022B-EN-P - January 2005...

  • Page 31: Chapter 3 Module Id Code

    The ID code defines the type of I/O module and the number of words used in the processor’s I/O image table. The module ID code for the 1746-NT8 module is 3533. No special I/O configuration is required. The module ID automatically assigns the correct number of input and output words.

  • Page 32: Module Addressing

    Considerations Before Using Your Module Module Addressing The following memory map shows you how the SLC processor’s output and input tables are defined for the module. Image Table Bit 15 Bit 0 Address Word 0 Channel 0 Configuration Word O:e .0 Word 1 O:e .1 Channel 1 Configuration Word...

  • Page 33: Input Image - Data Words And Status Words

    Considerations Before Using Your Module Chapter 4 provides detailed bit information about the data content of the configuration word. Input Image - Data Words and Status Words Eight words of the SLC processor’s input image table are reserved for the module. Input image words are multiplexed since each channel has one data word and one status word.

  • Page 34: Channel Cut-Off Frequencyc

    Considerations Before Using Your Module The following table shows the available filter frequencies, cut-off frequency, step response, and a DC effective resolution for each filter frequency. Cut-off frequency, Step Response Time, and Effective Resolution (Based on Filter Frequency) Filter Frequency Cut-Off Frequency Step Response ADC Effective...
  • Page 35 Considerations Before Using Your Module Signal Attenuation with 10 Hz Input Filter -3 dB -100 Amplitude (in dB) -120 -140 -160 -180 -200 60 Hz 2.62 Hz Signal Frequency Signal Attenuation with 50 Hz Input Filter -3 dB -100 Amplitude (in dB) -120 -140 -160...

  • Page 36: Channel Step Response

    Considerations Before Using Your Module Signal Attenuation with 60 Hz Input Filter -3 dB -100 Amplitude (in dB) -120 -140 -160 -180 -200 360 Hz 15.7 Hz Signal Frequency Signal Attenuation with 250 Hz Input Filter -3 dB -100 Amplitude (in dB) -120 -140 -160...

  • Page 37: Update Time

    Considerations Before Using Your Module Update Time The thermocouple module update time is defined as the time required for the module to sample and convert the input signals of all enabled input channels and make the resulting data values available to the SLC processor.

  • Page 38: Update Time Calculation Example

    Considerations Before Using Your Module Update Time Calculation Example The following example shows how to calculate the module update time for the given configuration: Channel 0 configured for 250 Hz filter frequency, enabled Channel 1 configured for 250 Hz filter frequency, enabled Channel 2 configured for 50 Hz filter frequency, enabled Channel 3 through 7 disabled Using the values from the table on page 3-7, add the sum of all...

  • Page 39: Response To Slot Disabling

    Considerations Before Using Your Module CJC sensors are acquired at 60 Hz to maximize the trade-off between resolution and update rate. For example, if some channels are acquired at 250 Hz and some are acquired at 50 Hz, then the total auto-calibration time would be: Frequency Auto-Calibration...
  • Page 40 3-10 Considerations Before Using Your Module Publication 1746-UM022B-EN-P - January 2005...

  • Page 41: Channel Configuration

    Chapter Channel Configuration, Data, and Status Read this chapter to: • configure each input channel • check each input channel’s configuration and status Channel Configuration Channel configuration words appear in the SLC processor’s output image table as shown below. Words 0 to 7 correspond to module channels 0 to 7.

  • Page 42: Channel Configuration Procedure

    Channel Configuration, Data, and Status The configuration word default settings are all zero. Next, we describe how you set configuration bits of a channel configuration word to set up the following channel parameters: • data format such as engineering units, counts, or scaled-for-PID •...
  • Page 43 Channel Configuration, Data, and Status 5. If the channel is configured for thermocouple inputs, determine if the channel data word should read in degrees Fahrenheit or degrees Celsius and enter a one or a zero in bit 9 of the configuration word.
  • Page 44 Channel Configuration, Data, and Status A detailed explanation appears in the following table: Channel Configuration Word (0:e.0 through 0:e.7) - Bit Definitions To Select Make these bit settings Channel Channel Disable Enable Channel Enable Thermocouple J Thermocouple K Thermocouple T Thermocouple E Thermocouple R Thermocouple S...

  • Page 45: Select Channel Enable (Bit 0)

    Channel Configuration, Data, and Status Select Channel Enable (Bit 0) Use the channel enable bit to enable a channel. The thermocouple module only scans enabled channels. To optimize module operation and minimize throughput times, unused channels should be disabled by setting the channel enable bit to zero (default value). When set (1) the channel enable bit is used by the module to read the configuration word information selected.

  • Page 46: Using Scaled-For-Pid And Proportional Counts

    These are 0.1°F, 0.1°C, 1°F, 1°C, 0.01 mV, 0.1 mV, Scaled-for-PID, and Proportional Counts. The first six options represent real Engineering Units displayed by the 1746-NT8 and do not require explanation. The Scaled-for-PID and Proportional Counts selections provide the highest NT8 display resolution, but also require you to manually convert the channel data to real Engineering Units.

  • Page 47: Scaling Examples

    Channel Configuration, Data, and Status Scaling Examples Scaled-for-PID to Engineering Units Equation: Engineering Units Equivalent = S + [(S ) x (Scaled-for-PID value displayed/16384)] HIGH Data: Assume type J input type, scaled-for-PID display type, channel data = 3421. Want to calculate °C equivalent. From Channel Data Word Format table, S = -210°C and S = 760°C.
  • Page 48 (1) When millivolts are selected, the temperature setting is ignored. Analog input data is the same for either °C or °F selection. (2) Type B thermocouple cannot be represented in engineering units x1 (°F) above 3276.7°F. Software treats it as an over range error. 1746-NT8 Thermocouple Module - Channel Data Word Resolution Data Format...

  • Page 49: Select Open-Circuit State (Bits 7 And 8)

    Type B thermocouple temperature range of 0 to 1820°C provides a voltage input range of 0 to 13.82mV to the 1746-NT8. This is a very small input range and, when it is scaled to PID or proportional counts ranges, a small input change results in many counts being changed.

  • Page 50: Select Temperature Units (Bit 9)

    4-10 Channel Configuration, Data, and Status For example, if channel one is configured as a thermocouple type when the CJC breaks in an open-circuit condition, if open-circuit detection is disabled, the data word remains unchanged. If the circuit selection is set at minimum, the data word is set to the low scale value for the range and format.

  • Page 51: Unused Bits (Bits 12 Through 14)

    Channel Configuration, Data, and Status 4-11 Guidelines for filter frequency are listed below. • 250 Hz setting provides minimal noise filtering. • 60 Hz setting provides 60 Hz AC line noise filtering. • 50 Hz setting provides 50 Hz AC line noise filtering. •...

  • Page 52: Channel Status Checking

    4-12 Channel Configuration, Data, and Status Channel Status Checking You can use the information provided in the status word to determine if the input configuration data for any channel is valid per your configuration in O:e.0 through O:e.7. The channel status can be analyzed bit by bit. In addition to providing information about an enabled or disabled channel, each bit’s status (0 or 1) tells you how the input data from the thermocouple or millivolt analog sensor connected to a specific channel will be translated for...

  • Page 53: Channel Status (Bit 0)

    Channel Configuration, Data, and Status 4-13 Channel 0 to 7 Status Word (I:e.0 through I:e.7) - Bit Definitions To Select Make these bit settings 10 Hz input filter 50 Hz input filter Channel filter frequency 60 HZ input filter 250 Hz input filter Open-circuit No error error...

  • Page 54: Data Format Type Status (Bits 5 And 6)

    4-14 Channel Configuration, Data, and Status Data Format Type Status (Bits 5 and 6) The data format bit field indicates the data format you have defined for the channel. This field reflects the data type selected in bits 5 and 6 of the channel configuration word.

  • Page 55: Over-Range Error (Bit 14)

    Channel Configuration, Data, and Status 4-15 Over-Range Error (Bit 14) This bit is set (1) whenever a configured channel detects an over range condition for the channel data. An over-range condition exists when the input value is equal to or above the specified upper limit of the particular sensor connected to that channel.
  • Page 56 4-16 Channel Configuration, Data, and Status Publication 1746-UM022B-EN-P - January 2005...
  • Page 57 Chapter Programming Examples Earlier chapters explained how the configuration word defines the way a channel operates. This chapter shows the programming required to configure the module. It also provides you with segments of ladder logic specific to unique situations that might apply to your programming requirements.

  • Page 58: Procedure

    Length 0001 On power up, bit S:1/15 is set for the first program scan. During the first program scan, the configuration data in N10:0 through N10:7 will be sent to the 1746-NT8 channel configuration words. Publication 1746-UM022B-EN-P - January 2005...

  • Page 59: Automatic Monitoring Thermocouples And Cjc Sensors

    Changes the time the 1746-NT8 supplies a data word using that new configuration information. Also, the ladder program should use the thermocouple temperature data location N10:20 for thermocouple temperature readings and data location N10:12 for CJC temperature readings.
  • Page 60 Programming Examples During the first pass, send the channel configuration data to the thermocouple module. #NT8_CONFIGURATION F irst Pa ss 0000 Copy File Source #N10:0 Dest #O:1.0 Length CHECKING_CJC B3:6 If not Checking CJC, copy Channel 0 temperature data into data location for use. Temperature control logic should use N10:20 rather than the TC image (I:1.0) to eliminate problems during CJC checking.
  • Page 61 Programming Examples Wait 7 seconds for Channel 0 to accept CJC configuration and provide a data value (time depends on module configuration). CHECKING_CJC CJC_CFG_TMR B3:6 0005 Timer On Delay Timer T11:1 Time Base Preset 7< Accum 0< Copy CJC Temperature (I:1.0) into CJC register (N10:12) CJC_CFG_TMR/DN CJC_TEMP T11:1...
  • Page 62 Programming Examples Data Table for Configuration Changes address data address data N10:0 0000 0010 0010 0011 N10:8 0000 0010 0011 1111 N10:1 0000 0010 0010 0011 N10:2 0000 0010 0010 0011 N10:3 0000 0010 0010 0011 N10:4 0000 0010 0010 0011 N10:5 0000 0010 0010 0011 N10:6...

  • Page 63: Interfacing To The Pid Instruction

    SLC 5/02 or later processor PID instruction without the need for an Instruction intermediate scale operation. Example - Use 1746-NT8 channel data as the process variable in the PID instruction. 1. Select scaled-for-PID as the data type in the channel configuration word.

  • Page 64: Monitoring Channel Status Bits

    Programming Examples Monitoring Channel Status The following example shows how to monitor the open-circuit error bits of each channel and set an alarm in the processor if one of the Bits thermocouples opens. An open-circuit error can occur if the thermocouple breaks, one of the thermocouple wires gets cut or disconnected from the terminal block, or if the CJC sensors are not installed or are damaged.

  • Page 65: Monitoring Channel Status Bits Example

    Programming Examples Monitoring Channel Status Bits Example During 1st program scan, copy thermocouple channel configuration words (N10:0 - N10:7) to NT8. In addition, initialize channel error registers (N10:20 - N10:27) and Error Flags (B3/119). #NT8_CH_CNF 0000 Copy File Source #N10:0 Dest #O:1.0 Length...
  • Page 66 5-10 Programming Examples AFter waiting for the NT8 to update its I/O image, check each channel’s status error bits by masking off the appropriate bits and checking if these bits are set (non-zero). If an error is detected, set the appropriate channel status error bits (B3:112 - B3/119).
  • Page 67 Programming Examples 5-11 NT8_CH2_STS_FLAGS NT8_CH2_ERROR B3:7 Not Equal Source A N10:22 0< Source B 0< NT8_CH3_STS_FLAGS Masked Move Source I:1.3 0< Mask 0F000h -4096< Dest N10:23 0< NT8_CH3_STS_FLAGS NT8_CH3_ERROR B3:7 Not Equal Source A N10:23 0< Source B 0< After waiting for the NT8 to update its I/O image, check each channel’s status error bits by masking off the appropriate bits and checking if these bits are set (non-zero).
  • Page 68 5-12 Programming Examples NT8_CH5_STS_FLAGS NT8_CH5_ERROR B3:7 Not Equal Source A N10:25 0< Source B 0< NT8_CH6_STS_FLAGS Masked Move Source I:1.6 0< Mask 0F000h -4096< Dest N10:26 0< NT8_CH6_STS_FLAGS NT8_CH6_ERROR B3:7 Not Equal Source A N10:26 0< Source B 0< NT8_CH7_STS_FLAGS Masked Move Source I:1.7...

  • Page 69: Plc 5 Example With Nt8 In Remote I/O Rack

    Remote I/O Rack Remote I/O network. The PLC/5 must use Block transfer reads and writes to communicate with the 1746-NT8 module in a remote rack. Note, the example provides code which will reconfigure the module if the PLC/5 senses are remote rack fault. Also, the PLC/5 processor uses the exact same configuration words as the SLC 500 processors.
  • Page 70 5-14 Programming Examples During the first scan, clear the NT8 Configurated bit (B3/4) to initiate the NT8 configuration process. First scan or SFC step NT8_CONFIGURED B3:0 If the NT8 is configured and a rack fault occurs, clear the NT8 Configured bit (B3/4) to initiate the NT8 configuration process. NT8_CONFIGURED RIO_RACK1_FLT B3:0...

  • Page 71: Slc 500 Example With Nt8 In Remote I/O Rack

    Remote I/O Rack network. The SLC must use Block transfer reads and writes to communicate with the 1746-NT8 module in a remote rack. RIO example with SLC processor SLC processors with a 1747-SN series B RIO Scanner can use the block transfer instructions similarly to the PLC/5.
  • Page 72 5-16 Programming Examples Publication 1746-UM022B-EN-P - January 2005...

  • Page 73: Module And Channel Diagnostics

    Chapter Troubleshooting Your Module This chapter describes troubleshooting with channel-status and module-status LEDs. It explains the types of conditions that might cause the module to flag an error and suggests what corrective action you could take. Topics include: • module and channel diagnostics •...
  • Page 74 Troubleshooting Your Module channel fault bit (bits 12-15 of the channel status word). Channel fault bits and LEDs are self-clearing when fault conditions are corrected. If you clear the channel enable bit, the channel IMPORTANT status bits are reset. The module has nine LEDs; as shown below. •...

  • Page 75: Led Troubleshooting Tables

    The module is No action required. operating properly. The module is Cycle power. If the condition persists, call turned off, or it your local Allen-Bradley distributor for detected a module assistance. fault. Flashing Jumper may be in Check jumper 1 position.

  • Page 76: Channel-Status Leds (Green)

    Troubleshooting Your Module Channel-status LEDs (Green) The channel-status LED operates with status bits in the channel status word to indicate the following faults detected by the module: • invalid channel configuration • an open-circuit input • out-of-range errors • selected filter frequency data acquisition or auto-calibration errors When the module detects any of the following fault conditions, it causes the channel-status LED to flash and sets the corresponding...

  • Page 77: Channel Error (Bit 15)

    • disables all channels • clears all data and status words A module failure is non-recoverable and requires the assistance of your local Allen-Bradley distributor. Interpreting I/O Error Codes I/O error codes appear in word S:6 of the SLC processor status file.
  • Page 78 CJC set (1) connections. Correct and retry. An open-circuit condition Contact your local Contact your local Contact your local is present. Check channel Allen-Bradley Bit 12 Allen-Bradley Allen-Bradley and CJC wiring for open or set (1) distributor. distributor. distributor.

  • Page 79: Preventive Maintenance

    Chapter Maintaining Your Module And Safety Considerations Read this chapter to familiarize yourself with: • preventive maintenance • safety considerations The National Fire Protection Association (NFPA) recommends maintenance procedures for electrical equipment. Refer to article 70B of the NFPA for general safety-related work practices. Preventive Maintenance The printed circuit boards of your module must be protected from dirt, oil, moisture, and other airborne contaminants.
  • Page 80 Maintaining Your Module And Safety Considerations Stand Clear Of Machinery – When troubleshooting a problem with any SLC 500 system, have all personnel remain clear of machinery. The problem may be intermittent, and the machine may move unexpectedly. Have someone ready to operate an emergency stop switch.

  • Page 81: Electrical Specifications

    Appendix Module Specifications This appendix lists the specifications for the 1746-NT8 Thermocouple/millivolt Input Module. Electrical Specifications Backplane Current Consumption 120 mA at 5V dc 70 mA at 24Vdc Backplane Power Consumption 2.28W maximum (0.6W at 5V dc, 1.68W at 24V dc)

  • Page 82: Physical Specifications

    Module Specifications Physical Specifications LED Indicators 9 green status indicators, one for each of 8 channels and one for module status Module ID Code 3533 Recommended Cable: for thermocouple inputs… Appropriate shielded twisted pair thermocouple extension wire for mV inputs… Belden™...

  • Page 83: Input Specifications

    Module Specifications Input Specifications Thermocouple Type J -210°C to +760°C (-346°F to +1400°F) Thermocouple Type K -270°C to +1370°C (-454°F to +2498°F) Thermocouple Type T -270°C to +400°C (-454°F to +752°F) Thermocouple Type E -270°C to +1000°C (-454°F to +1832°F) Thermocouple Type R 0°C to +1768°C (+32°F to +3214°F) Type of Input (Selectable)

  • Page 84: Overall Accuracy

    The following discussion explains what the user can expect in terms of accuracy based on the thermocouple and millivolt inputs for the 1746-NT8 module. The accuracies specified as follows include errors due to the cold junction compensation for thermocouples and hardware and software errors associated with the system.
  • Page 85 Module Specifications uV Err, ±100mV Span, Prop Cts, 60 Hz, 0°C 50.00 45.00 40.00 35.00 30.00 25.00 uV Error 20.00 15.00 10.00 5.00 0.00 mV Input uV Err, ±100mV Span, Prop Cts, 60 Hz, 25°C 50.00 45.00 40.00 35.00 30.00 25.00 uV Error 20.00...

  • Page 86: Thermocouple

    Module Specifications uV Err, ±100mV Span, Prop Cts, 60 Hz, 60°C 90.00 80.00 70.00 60.00 50.00 uV Error 40.00 30.00 20.00 10.00 0.00 mV Input Thermocouple The following table provides the total error expected of the thermocouple based on the thermocouple type, and the given reference point, at 25°C.
  • Page 87 Module Specifications Thermocouple Type Thermocouple Reference Point Error +275°C (+527°F) ±3.0°C (±5.4°F) +550°C (+1022°F) ±3.0°C (±5.4°F) +65°C (+149°F) ±3.4°C (±6.12°F) +365°C (+689°F) ±2.5°C (±4.5°F) +885°C (+1625°F) ±6.5°C (±11.7°F) +885°C (+1625°F) ±7.2°C (±12.96°F) +1060°C (+1940°F) ±8.4°C (±15.12°F) +500°C (+932°F) ±3.0°C (±5.4°F) The diagrams that follow for each thermocouple type give data for a sample module over the input range of the thermocouple over temperature.
  • Page 88 Module Specifications uV Err, ±100mV Span, Prop Cts, 60 Hz, 0°C, 25°C, 60°C 100 mV Deviation Over Temp 0.06 0.04 0.02 Delta 60˚C Delta 25˚C -0.02 Delta 0˚C -0.04 -0.06 -0.08 -40000 -20000 20000 40000 -0.1 Input Voltage (counts) uV Err, ±50mV Span, Prop Cts, 60 Hz, 25°C 50 mV Deviation Over Temp 0.03 0.02...
  • Page 89 Module Specifications Thermocouple J Deviations Over Temperature Delta 60˚C Delta 25˚C Delta 0˚C -400 -200 1000 Degrees C TC Input Thermocouple K Deviations Over Temperature Delta 60˚C Delta 25˚C Delta 0˚C -500 1000 1500 Degrees C TC Input Publication 1746-UM022B-EN-P - January 2005...
  • Page 90 A-10 Module Specifications Thermocouple T Deviations Over Temperature -400 -200 Delta 60˚C Delta 25˚C Delta 0˚C Degrees C TC Input Thermocouple E Deviations Over Temperature -400 -200 1000 1200 Delta 60˚C Delta 25˚C Delta 0˚C Degrees C TC Input Publication 1746-UM022B-EN-P - January 2005...
  • Page 91 Module Specifications A-11 Thermocouple B Deviations Over Temperature 1300 1800 Delta 60˚C Delta 25˚C Delta 0˚C Degrees C TC Input Thermocouple N Deviations Over Temperature Delta 60˚C Delta 25˚C Delta 0˚C 1000 1200 1400 -0.5 -1.5 Degrees C TC Input Publication 1746-UM022B-EN-P - January 2005...
  • Page 92 A-12 Module Specifications Publication 1746-UM022B-EN-P - January 2005...

  • Page 93: Appendix B Thermocouple Types

    Junction, and Exposed Junction Thermocouples This appendix describes the types of thermocouples available and explains the trade-offs in using them with the 1746-NT8 module. Thermocouple Types There are three (3) types of thermocouple junctions: • Grounded Junction - The measuring junction is physically connected to the protective sheath forming a completely sealed integral junction.

  • Page 94: Grounded Junction

    • 500V dc electrical isolation channel-to-backplane Care must be taken when choosing a thermocouple type and connecting it to the 1746-NT8 module from the environment being measured. If adequate precautions are not taken for a given thermocouple type, the electrical isolation of the 1746-NT8 module may be compromised.

  • Page 95: Grounded Junction

    It should be noted that the isolation is removed even if the sheaths are connected to chassis ground at a location other than the module, since the module is connected to chassis ground. 1746-NT8 Grounded junction with MUXES nonconductive protective sheath Metal sheath with electrical continuity to thermocouple signal wires.

  • Page 96: Exposed Junction Thermocouples

    • For multiple exposed thermocouples, do not allow the measuring junction of the thermocouple to make direct contact with electrically conductive process material. • Use all ungrounded junction thermocouple instead of the exposed junction type. 1746-NT8 Grounded junction with MUXES nonconductive protective sheath Metal sheath with electrical continuity to thermocouple signal wires.
  • Page 97 Appendix Configuring the 1746-NT8 Module with RSLogix 500 This appendix describes how to configure the NT8 module with RSLogix 500 v6.10 or higher. To configure your module: 1. Access the I/O Configuration menu. 2. Determine the chassis number and slot location of where the NT8 module is located.
  • Page 98 Configuring the 1746-NT8 Module with RSLogix 500 Adv. Configuration menu 4. Press the Configure button. The following dialog box appears. This allows you to configure options for each channel. Publication 1746-UM022B-EN-P - January 2005...
  • Page 99 Configuring the 1746-NT8 Module with RSLogix 500 Module configuration Options The dialog box allows you to access the parameters for all channels. Each tab has an identical menu with the parameters shown. Publication 1746-UM022B-EN-P - January 2005...
  • Page 100 Configuring the 1746-NT8 Module with RSLogix 500 Menu Options Opening the drop down menus of the various parameters shows the available choices. The following summarizes the different options for each parameter. Parameter Description Channel Controls bit 0 of the configuration file and sets whether Enabled the channel is being used.
  • Page 101 Configuring the 1746-NT8 Module with RSLogix 500 Each tab edits the word of configuration data for that channel for a total of 8 words of configuration data. 5. Press OK to set the parameters. The following dialog box appears. Added Rung Parameters 6.
  • Page 102 Configuring the 1746-NT8 Module with RSLogix 500 Publication 1746-UM022B-EN-P - January 2005...
  • Page 103 Glossary You should understand the following terms and abbreviations before using this guide. Refers to analog-to-digital conversion. The conversion produces a digital value whose magnitude is proportional to the instantaneous magnitude of an analog input signal. Attenuation The reduction in magnitude of a signal as it passes through a system. The opposite of gain.
  • Page 104 Glossary Configuration word Contains the channel configuration information needed by the module to configure and operate each channel. Information is written to the configuration word through the logic supplied in your ladder program. Cut-off frequency The frequency at which the input signal is attenuated 3 dB by the digital filter.
  • Page 105 Glossary Input data scaling Depends on the data format that you select for the channel data word. You can select from scaled-for-PID or Engineering Units for millivolt, thermocouple, or CJC inputs, which you must compute to fit your application’s temperature or voltage resolution. Local system A control system with I/O chassis within several feet of the processor, and using 1746-C7 or 1746-C9 ribbon cable for communication.
  • Page 106 Glossary Status word Contains status information about the channel’s current configuration and operational state. You can use this information in your ladder program to determine whether the channel data word is valid. Step response time The time required for the A/D signal to reach 95% of its expected, final value, given a full-scale step change in the input signal.
  • Page 107 Index diagnostics at powerup diagnostics channel addressing auto calibration automatic monitoring thermocouples and CJC sensors electrical specifications electrostatic damage environmental specifications before using module block diagram fixed I/O chassis module compatibility fixed I/O current draw cables channel configuration channel configuration procedure data format select general considerations effective resolutions...
  • Page 108 Index electrical environmental millivolt input ranges input modular system physical 1-5, 3-2 module addressing status words input image data words and status words system operation system overview output image config words block diagram module and channel diagnostics linear millivolt device compatibility module general description module addressing module ID code...
  • Page 110 Rockwell Automation Rockwell Automation provides technical information on the web to assist you in using our products. At http://support.rockwellautomation.com, you can Support find technical manuals, a knowledge base of FAQs, technical and application notes, sample code and links to software service packs, and a MySupport feature that you can customize to make the best use of these tools.

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