Allen-Bradley CompactBlock LDX 1790D-T4T0 User Manual
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Allen-Bradley CompactBlock LDX 1790D-T4T0 User Manual

Allen-Bradley CompactBlock LDX 1790D-T4T0 User Manual

I/o thermocouple modules
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CompactBlock LDX
I/O Thermocouple
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1790D-T4T0, 1790D-4T0, 1790P-T4T0
User Manual
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Summary of Contents for Allen-Bradley CompactBlock LDX 1790D-T4T0

  • Page 1 CompactBlock LDX I/O Thermocouple Modules 1790D-T4T0, 1790D-4T0, 1790P-T4T0 User Manual AB Drives...
  • Page 3 Allen-Bradley publication SGI-1.1, Safety Guidelines for the Application, Installation and Maintenance of Solid-State Control (available from your local Allen-Bradley office), describes some important differences between solid-state equipment and electromechanical devices that should be taken into consideration when applying products such as those described in this publication.

  • Page 4: Your Questions Or Comments On This Manual

    Rockwell Automation Before you contact Rockwell Automation for technical assistance, we suggest you please review the troubleshooting information contained Support in this publication first. If the problem persists, call your local Rockwell Automation representative or contact Rockwell Automation in one of the following ways: Phone United...

  • Page 5: Table Of Contents

    Table of Contents Important User Information ......iii Rockwell Automation Support ..... . . iv Your Questions or Comments on this Manual .
  • Page 6 Chapter 3 Module Data, Status, and Channel Module Memory Map ......3-1 Input Image....... . . 3-1 Configuration for DeviceNet Accessing Input Image File Data .
  • Page 7 Appendix B Two’s Complement Binary Positive Decimal Values ......B-1 Negative Decimal Values ......B-2 Numbers Appendix C Thermocouple Descriptions...
  • Page 8 viii Publication 1790-UM003A-EN-P - May 2002...

  • Page 9: Overview

    Chapter Overview This chapter describes the 1790D-4TO/T4TO (1790P-T4TO) Thermocouple/mV Input module and explains how the module reads thermocouple or millivolt analog input data. Included is: • the module’s hardware and diagnostic features • an overview of system and module operation •...

  • Page 10: Thermocouple/Mv Inputs And Ranges

    Overview Thermocouple/mV Inputs and Ranges The table below defines thermocouple types and their associated full-scale temperature ranges. The second table lists the millivolt analog input signal ranges that each channel will support. Table 1.1 Thermocouple Analog Input Signal Types Thermocouple Temperature Scaling (Counts) Resolution Accuracy...

  • Page 11: Hardware Features

    Overview Hardware Features The thermocouple/mV module contains either a fixed terminal block or a removable D-sub connector, which provides connections for four inputs for any combination of thermocouple and mV input devices. Channels are wired as differential inputs. The illustration below shows the hardware features of the module.

  • Page 12: General Diagnostic Features

    Overview Internal to the module, Cold Junction Compensation (CJC) sensors are attached to the terminal block to enable accurate readings from each channel. These sensors compensate for offset voltages introduced into the input signal as a result of the cold-junction where the thermocouple wires are connected to the module.

  • Page 13: Module Operation - Devicenet Example

    Overview Module Operation - DeviceNet Example When the module recieves a differential input from an analog device, the module’s circuitry multiplexes the input into an A/D converter. The converter reads the signal and converts it as required for the type of input. The module also continuously samples the CJC sensors and compensates for temperature changes at the terminal block cold junction, between the thermocouple wire and the input channel.

  • Page 14: Chapter Summary

    Overview From the readings taken by the converter, the module sends thermocouple or mV data through the microcontroller to the DeviceNet network. The PROFIBUS block diagram is similar. Chapter Summary In this chapter, you learned about the 1790D-4T0/T4T0 (1790P-T4T0) thermocouple/mV module. See Chapter 2 to learn how to install and wire the module.

  • Page 15: Installation And Wiring

    Chapter Installation and Wiring Before You Begin This chapter tells you how to: • determine the power requirements for the modules • avoid electrostatic damage • install the module • wire the module’s terminal block Power Requirements 1790D-4T0/T4T0 The module receives system power from the DeviceNet network. An auxiliary field supply provides power for the thermocouple/mV channels.

  • Page 16: General Considerations

    Installation and Wiring General Considerations The modules are suitable for use in a commercial or light industrial environment when installed in accordance with these instructions. Specifically, this equipment is intended for use in clean, dry environments (Pollution degree 2 ) and to circuits not exceeding Over Voltage Category II (IEC 60664-1) Hazardous Location Considerations...
  • Page 17 Installation and Wiring The following information applies when operating this Informations sur l’utilisation de cet équipement en equipment in hazardous locations: environnements dangereux : Products marked “CL I, DIV 2, GP A, B, C, D” are suitable for use in Les produits marqués "CL I, DIV 2, GP A, B, C, D"...
  • Page 18 60529, as applicable, for explanations of the degrees of protection provided by different types of enclosure. Also, see the appropriate sections in this publication, as well as the Allen-Bradley publication 1770-4.1 ("Industrial Automation Wiring and Grounding Guidelines"), for additional installation requirements pertaining to this equipment.

  • Page 19: Selecting A Location

    Installation and Wiring Preventing Electrostatic Discharge ATTENTION This equipment is sensitive to electrostatic discharge, which can cause internal damage and affect normal operation. Follow these guidelines when you handle this equipment: • Touch a grounded object to discharge potential static. •...

  • Page 20: Protecting The Circuit Board From Contamination

    Installation and Wiring Protecting the Circuit Board from Contamination The printed circuit boards of analog modules must be protected from dirt, oil, moisture, and other airborne contaminants. To protect these boards, the system must be installed in an enclosure suitable for the environment.

  • Page 21: Set The Station Address On The 1790P-T4T0 Profibus Dp Base Block

    Installation and Wiring Set the Station Address on the 1790P-T4T0 PROFIBUS DP Base Block To set the station address, adjust the switches on the front of the base block. The two switches are most significant digit (MSD) and least significant digit (LSD). The switches can be set between 00 and 99. The rotary switches are read at base block power up only Example: Node Address is set at 26...

  • Page 22: Din Rail Mounting

    Installation and Wiring 5. Replace the block on the panel and place a screw through each of the two mounting holes. Tighten the screws until the block is firmly in place 95 mm 3.74 in Expansion 41 mm Cover 1.6 in 43242 DIN Rail Mounting 1.

  • Page 23: Connect The Devicenet Cable To The 1790D-4T0/T4T0 Base Block

    Installation and Wiring Connect the DeviceNet Cable to the 1790D-4T0/T4T0 Base Block Follow these procedures when connecting the DeviceNet cable to the base block. The required DeviceNet connector is not supplied with the block - you must purchase it separately. There are three types of connectors that you can order directly from Rockwell Automation or your local distributor: •...

  • Page 24: Connect The Profibus Dp Terminal Connector To The 1790P-T4T0 Base Block

    2-10 Installation and Wiring Connect the PROFIBUS DP Terminal Connector to the 1790P-T4T0 Base Block Follow these procedures to connect the PROFIBUS DP terminal connector to the base block. If you connect or disconnect the PROFIBUS cable WARNING with power applied to this module or any device on the network, an electrical arc can occur.

  • Page 25: Connect Power To The 1790P-T4T0 Block

    Installation and Wiring 2-11 Once you have properly wired the connector, attach it to the base block as shown below. Use the locking screws on the connector to fasten it to the base block. Module Power Connector (underneath module) PROFIBUS Connector Green - GND Black - COM Red - +24V dc...

  • Page 26: Field Wiring Connections

    2-12 Installation and Wiring Field Wiring Connections System Wiring Guidelines Consider the following when wiring your system: General • Route field wiring away from any other wiring and as far as possible from sources of electrical noise, such as motors, transformers, contactors, and ac devices.
  • Page 27 DIN rail mounting screw. • Refer to Industrial Automation Wiring and Grounding Guidelines, Allen-Bradley publication 1770-4.1, for additional information. Noise Prevention • To limit the pickup of electrical noise, keep thermocouple and millivolt signal wires as far as possible from power and load lines.

  • Page 28: Wiring The Module

    2-14 Installation and Wiring Wiring the Module ATTENTION To prevent shock hazard, care should be taken when wiring the module to analog signal sources. Before wiring any module, disconnect power from the system power supply and from any other source to the module.

  • Page 29: Wiring The Terminal Blocks

    Installation and Wiring 2-15 4. At the other end of the cable, cut the drain wire and foil shield back to the cable and apply shrink wrap. 5. Connect the signal wires to the terminal block. Connect the other end of the cable to the analog input device. 6.

  • Page 30: Cold Junction Compensation

    2-16 Installation and Wiring Cold Junction To obtain accurate readings from each of the channels, the cold junction temperature (temperature at the module’s terminal junction Compensation between the thermocouple wire and the input channel) must be compensated for. Cold junction compensating thermistors have been integrated in the module.

  • Page 31: Chapter 3 Module Memory Map

    Chapter Module Data, Status, and Channel Configuration for DeviceNet After installation of the thermocouple/mV input module, you must configure it for operation, usually using the programming software compatible with the controller (for example, RSLogix 500™ or RSLogix 5000™) or scanner (RSNetWorx for DeviceNet). Once configuration is complete and reflected in ladder logic, you will need to get the module up and running and then verify its operation.

  • Page 32: Input Data File

    Module Data, Status, and Channel Configuration for DeviceNet Input Data File The input data table lets you access thermocouple/mV input module read data for use in the control program, via word and bit access. The data table structure is shown in the tables below. Table 3.1 Input Data Table Word/ 7 6 5 4 3...

  • Page 33: Over-Range Flag Bits (S8 To S11)

    Module Data, Status, and Channel Configuration for DeviceNet Over-Range Flag Bits (S8 to S11) Over-range bits for channels 0 through 3 are contained in word 4, bits 8-11. When set (1), the over-range flag bit indicates a thermocouple temperature that is greater than the maximum allowed temperature, a resistance input that is greater than the maximum allowed resistance for the module or an open channel is detected.

  • Page 34: Filter Frequency

    Module Data, Status, and Channel Configuration for DeviceNet Filter Frequency The module supports filter selections corresponding to filter frequencies of 10 Hz, 25Hz, 50 Hz, 60 Hz, 100 Hz, 250 Hz, and 500 Hz. Your filter frequency selection is determined by the desired range for the input type, and the required effective resolution, which indicates the number of bits in the input data that do not vary due to noise.

  • Page 35: Channel Step Response

    Module Data, Status, and Channel Configuration for DeviceNet Channel Step Response Another module characteristic determined by filter frequency is channel step response, as shown in the following table. The step response is the time required for the analog input signal to reach 100 percent of its expected final value, given a full-scale step change in the input signal.
  • Page 36 Module Data, Status, and Channel Configuration for DeviceNet Figure 3.2 Frequency Response Graphs 10 Hz Input Filter Frequency 50 Hz Input Filter Frequency –3 dB –3 dB –20 –20 –40 –40 –60 –60 –80 –80 -100 -100 -120 -120 -140 -140 -160 -160...

  • Page 37: Effective Resolution

    Module Data, Status, and Channel Configuration for DeviceNet Effective Resolution The effective resolution for an input channel depends upon the filter frequency selected for that channel. The table below identifies the number of significant bits used to represent the data for the mV input range for each available filter frequency.
  • Page 38 Module Data, Status, and Channel Configuration for DeviceNet Figure 3.4 Type E Thermocouple Figure 3.5 Type J Thermocouple Publication 1790-UM003A-EN-P...
  • Page 39 Module Data, Status, and Channel Configuration for DeviceNet Figure 3.6 Type K Thermocouple Figure 3.7 Type R Thermocouple AB Drives Publication 1790-UM003A-EN-P...
  • Page 40 3-10 Module Data, Status, and Channel Configuration for DeviceNet Figure 3.8 Type S Thermocouple Figure 3.9 Type T Thermocouple Publication 1790-UM003A-EN-P...

  • Page 41: Cold Junction Compensation

    Module Data, Status, and Channel Configuration for DeviceNet 3-11 Figure 3.10 Type N Thermocouple Cold Junction When using thermocouples, cold junction compensation (CJC) is required at the termination of the thermocouple wire. A cold junction can be Compensation accomplished different ways: •...

  • Page 42: Determining Module Update Time

    3-12 Module Data, Status, and Channel Configuration for DeviceNet Determining Module The module update time is defined as the time required for the module to sample and convert the input signals. Module update time is dependent Update Time on the number of input channels and the input filter selection. The fastest update time occurs with the 500Hz filter enabled.
  • Page 43 Module Data, Status, and Channel Configuration for DeviceNet 3-13 Thermocouple Error The table below summarizes thermocouple error (for more Thermocouple Type information see Appendix C). Table 3.10 Thermocouple Error Thermocouple Useable Range °C Standard Tolerance Special Tolerance Type Error Error 870 to 1700 ±0.5% ±0.25%...

  • Page 44: Configuring Devicenet Thermocouple/Mv Module

    3-14 Module Data, Status, and Channel Configuration for DeviceNet Total Error As an example, a B Type thermocouple operating at 100°C with 1000 ohms of lead wire, internal CJC and 10Hz filter enabled, in an ambient temperature of 30 to 50°C, is accurate to within: Table 3.12 Example Error Calculation Error Factor From...

  • Page 45: Configure Devicenet Thermocouple/Mv Modules Using

    Module Data, Status, and Channel Configuration for DeviceNet 3-15 Configure DeviceNet Following the steps below to configure 1790D-4T0/T4T0 thermocouple/ mV modules. Thermocouple/mV 1. Open RSNetWorx for DeviceNet. Modules Using 2. Using the selections on the left of the window below, construct you RSNetWorx system.
  • Page 46 3-16 Module Data, Status, and Channel Configuration for DeviceNet 3. After setting up your system, double-click on the module you want to configure. (If you are online, upload the configuration and existing parameters from the module display.) A window similar to the following appears.
  • Page 47 Module Data, Status, and Channel Configuration for DeviceNet 3-17 Module configuration parameters include Temperature Units/Notch Filter frequency, Thermocouple/mV Input type, Cold Junction Compensation Enable/Manual Offset Value and Autobaud. Select the desired temperature units (in degrees C or F) and notch filter frequency.
  • Page 48 3-18 Module Data, Status, and Channel Configuration for DeviceNet Select to Enable or Disable built-in cold junction compensation. If built-in CJC is disabled, you can enter a constant cold junction offset value. 70°C is entered as 700 The value is always (158°F as 700 also).

  • Page 49: Chapter Summary

    Module Data, Status, and Channel Configuration for DeviceNet 3-19 Thermocouple/mV module parameters may be monitored real time. The most convenient way to monitor module parameters is to: a. Click the Groups checkbox. b. Close the No Group Specified folder c. Open the I/O Input Values and I/O Input Status folders. d.
  • Page 50 3-20 Module Data, Status, and Channel Configuration for DeviceNet Publication 1790-UM003A-EN-P...

  • Page 51: Safety Considerations

    Chapter Diagnostics and Troubleshooting This chapter describes module troubleshooting, containing information • safety considerations when troubleshooting • module vs. channel operation • the module’s diagnostic features • critical vs. non-critical errors • module condition data • contacting Rockwell Automation for assistance Safety Considerations Safety considerations are an important element of proper troubleshooting procedures.

  • Page 52: Stand Clear Of The Equipment

    Diagnostics and Troubleshooting Stand Clear of the Equipment When troubleshooting any system problem, have all personnel remain clear of the equipment. The problem could be intermittent, and sudden unexpected machine motion could occur. Have someone ready to operate an emergency stop switch in case it becomes necessary to shut off power. Program Alteration There are several possible causes of alteration to the user program, including extreme environmental conditions, Electromagnetic Interference...

  • Page 53: Power-Up Diagnostics

    Diagnostics and Troubleshooting Power-up Diagnostics Power-up diagnostics includes module status and network status. Module Status At module power-up, a series of internal diagnostic tests are performed. These diagnostic tests must be successfully completed. The following table shows module status LED indictor operation. Table 4.1 1790D-4T0/T4T0, 1790P-4T0 LED Indicator:...

  • Page 54: Channel Diagnostics

    Diagnostics and Troubleshooting Channel Diagnostics When an input channel is enabled, the module performs a diagnostic check to see that the channel has been properly configured. In addition, the channel is tested on every scan for configuration errors, over-range and under-range, and open-circuit conditions. Over- or Under-Range Detection Whenever the data received at the channel word is out of the defined operating range, an over-range or under-range error is indicated in input...

  • Page 55: Module Error Definition Table

    Diagnostics and Troubleshooting Module Error Definition Table Thermocouple/mV module errors are expressed on a channel basis in input read word 4. The structure of the status data is shown in the following table. Table 4.4 Word Bit Position Word Bit Description 15 14 13 12 11 Not Used S11 S10 S9 S8...
  • Page 56 Diagnostics and Troubleshooting Publication 1790-UM003A-EN-P...

  • Page 57: Environmental Specifications

    Appendix Specifications Environmental Environmental Specifications Specifications Operating Temperature 0 to 55°C (32 to 131°F) IEC 60068-2-1 (Test Ad, Operating Cold), IEC 60068-2-2 (Test Bd, Operating Dry Heat), IEC 60068-2-14 (Test Nb, Operating Thermal Shock) Storage Temperature -40 to 85°C (-40 to 185°F) IEC 60068-2-1 (Test Ab, Un-packaged Non-operating Cold), IEC 60068-2-2 (Test Bb, Un-packaged Non-operating Dry Heat), IEC 60068-2-14 (Test Na, Un-packaged Non-operating Thermal Shock)

  • Page 58: Devicenet Specifications

    Specifications DeviceNet Specification Value Specifications Network protocol I/O Slave messaging: - Poll command - Bit Strobe command - Cyclic command - COS command Network length 500 meters maximum @ 125Kbps 100 meters maximum @ 500Kbps Indicators 1 red/green module status 1 red/green network status Number of nodes 64 maximum - rotary switch type node address setting...

  • Page 59: General Specifications

    Specifications General Specifications General Specifications Wiring Category Product Certifications c-UL-us UL Listed for Class I, Division 2 Group A,B,C,D Hazardous (when product is marked) Locations, certified for U.S. and Canada UL Recognized Component Industrial Control Equipment European Union 89/336/EEC EMC Directive, compliant with: EN 61000-6-4;...

  • Page 60: Thermocouple/Mv Specifications

    Specifications Thermocouple/mV Thermocouple/mV Specifications Inputs per module 4 channel, Thermocouple/mV Input Specifications Input Range ±76.50 mV Sensors Supported Sensor Type Degree Counts µ -76.5 to +76.5 -7650 to +7650 Voltage 10 300 to 1800°C 3000 to 18000 -270 to +1000°C -2700 to +10000 -210 to +1200°C -2100 to +12000...

  • Page 61: Positive Decimal Values

    Appendix Two’s Complement Binary Numbers The processor memory stores 16-bit binary numbers. Two’s complement binary is used when performing mathematical calculations internal to the processor. Analog input values from the Thermocouple/mV module are returned to the processor in 16-bit two’s complement binary format. For positive numbers, the binary notation and two’s complement binary notation are identical.

  • Page 62: Negative Decimal Values

    Two’s Complement Binary Numbers Negative Decimal In two’s complement notation, the far left position is always 1 for negative values. The equivalent decimal value of the binary number is obtained by Values subtracting the value of the far left position, 32768, from the sum of the values of the other positions.

  • Page 63: International Temperature Scale Of 1990

    Appendix Thermocouple Descriptions The information in this appendix was extracted from the NIST Monograph 175 issued in January 1990, which supersedes the IPTS-68 Monograph 125 issued in March 1974. NIST Monograph 175 is provided by the United States Department of Commerce, National Institute of Standards and Technology.
  • Page 64 Thermocouple Descriptions Studies by Ehringer [39], Walker et al. [25,26], and Glawe and Szaniszlo [24] have demonstrated that thermocouples, in which both legs are platinum-rhodium alloys, are suitable for reliable temperature measurements at high temperatures. Such thermocouples have been shown to offer the following distinct advantages over types R and S thermocouples at high temperatures: (1) improved stability, (2) increased mechanical strength, and (3) higher operating temperatures.

  • Page 65: Type E Thermocouples

    Thermocouple Descriptions The suggested upper temperature limit of 1700°C given in the ASTM standard [7] for protected type B thermocouples applies to AWG 24 (0.51 mm) wire. This temperature limit applies to thermocouples used in conventional closed-end protecting tubes and it is intended only as a rough guide to the user.
  • Page 66 Thermocouple Descriptions Type E thermocouples should not be used at high temperatures in sulfurous, reducing, or alternately reducing and oxidizing atmospheres unless suitably protected with protecting tubes. They also should not be used in vacuum (at high temperatures) for extended times because the chromium in the positive thermoelement, a nickel-chromium alloy, vaporizes out of solution and alters the calibration.

  • Page 67: Type J Thermocouples

    Thermocouple Descriptions The suggested upper temperature limit, 870°C, given in the ASTM standard [7] for protected type E thermocouples applies to AWG 8 (3.25 mm) wire. It decreases to 650°C for AWG 14 (1.63 mm), 540°C for AWG 20 (0.81 mm), 430°C for AWG 24 or 28 (0.51 mm or 0.33 mm), and 370°C for AWG 30 (0.25 mm).
  • Page 68 Thermocouple Descriptions Type J thermocouples are recommended by the ASTM [5] for use in the temperature range from 0°C to 760°C in vacuum, oxidizing, reducing, or inert atmospheres. If used for extended times in air above 500°C, heavy gauge wires are recommended because the oxidation rate is rapid at elevated temperatures.

  • Page 69: Type K Thermocouples

    Thermocouple Descriptions Type K Thermocouples This section describes Nickel-Chromium Alloy Versus Nickel-Aluminum Alloy thermocouples, called type K thermocouples. This type is more resistant to oxidation at elevated temperatures than types E, J, or T thermocouples and, consequently, it finds wide application at temperatures above 500°C.
  • Page 70 Thermocouple Descriptions The ASTM Manual [5] indicates that type K thermocouples should not be used at high temperatures in sulfurous, reducing, or alternately oxidizing and reducing atmospheres unless suitably protected with protecting tubes. They also should not be used in vacuum (at high temperatures) for extended times because the chromium in the positive thermoelement, a nickel-chromium alloy, vaporizes out of solution and alters the calibration.

  • Page 71: Type N Thermocouples

    Thermocouple Descriptions Type N Thermocouples This section describes Nickel-Chromium-Silicon Alloy Versus Nickel-Silicon-Magnesium Alloy thermocouples, commonly referred to as type N thermocouples. This type is the newest of the letter-designated thermocouples. It offers higher thermoelectric stability in air above 1000°C and better air-oxidation resistance than types E, J, and K thermocouples. The positive thermoelement, NP, is an alloy that typically contains about 84 percent nickel, 14 to 14.4 percent chromium, 1.3 to 1.6 percent silicon, plus small amounts (usually not exceeding about 0.1 percent) of other...
  • Page 72 C-10 Thermocouple Descriptions Type N thermocouples, in general, are subject to the same environmental restrictions as types E and K. They are not recommended for use at high temperatures in sulfurous, reducing, or alternately oxidizing and reducing atmospheres unless suitably protected with protecting tubes. They also should not be used in vacuum (at high temperatures) for extended times because the chromium and silicon in the positive thermoelement, a nickel-chromium-silicon alloy, vaporize out of solution and alter the...

  • Page 73: Type R Thermocouples

    Thermocouple Descriptions C-11 ASTM Standard E230-87 in the 1992 Annual Book of ASTM Standards [7] specifies that the initial calibration tolerances for type N commercial thermocouples be ±2.2°C or ±0.75 percent (whichever is greater) between 0°C and 1250°C. Type N thermocouples can also be supplied to meet special tolerances that are equal to approximately one-half the standard tolerances given above.

  • Page 74: Type S Thermocouples

    C-12 Thermocouple Descriptions Type R thermocouples have about a 12 percent larger Seebeck coefficient than do Type S thermocouples over much of the range. Type R thermocouples were not standard interpolating instruments on the IPTS-68 for the 630.74°C to gold freezing-point range. Other than these two points, and remarks regarding history and composition, all of the precautions and restrictions on usage given in the section on type S thermocouples also apply to type R thermocouples.
  • Page 75 Thermocouple Descriptions C-13 A reference function for the type S thermocouple, based on the ITS-90 and the SI volt, was determined recently from new data obtained in an international collaborative effort involving eight national laboratories. The results of this international collaboration were reported by Burns et al. [28].

  • Page 76: Type T Thermocouples

    C-14 Thermocouple Descriptions McLaren and Murdock [30-33] and Bentley and Jones [34] thoroughly studied the performance of type S thermocouples in the range 0°C to 1100°C. They described how thermally reversible effects, such as quenched-in point defects, mechanical stresses, and preferential oxidation of rhodium in the type SP thermoelement, cause chemical and physical inhomogeneities in the thermocouple and thereby limit its accuracy in this range.
  • Page 77 Thermocouple Descriptions C-15 The negative thermoelement, TN or EN, is a copper-nickel alloy known ambiguously as constantan. The word constantan refers to a family of copper-nickel alloys containing anywhere from 45 to 60 percent copper. These alloys also typically contain small percentages of cobalt, manganese and iron, as well as trace impurities of other elements such as carbon, magnesium, silicon, etc.
  • Page 78 C-16 Thermocouple Descriptions Type T thermocouples are recommended by the ASTM [5] for use in the temperature range from -200°C to 370°C in vacuum or in oxidizing, reducing or inert atmospheres. The suggested upper temperature limit for continuous service of protected type T thermocouples is set at 370°C for AWG 14 (1.63 mm) thermoelements since type TP thermoelements oxidize rapidly above this temperature.

  • Page 79: References

    Thermocouple Descriptions C-17 References [1] Preston-Thomas, H. The International Temperature Scale of 1990 (ITS-90). Metrologia 27, 3-10; 1990. ibid. p. 107. [2] The International Practical Temperature Scale of 1968, Amended Edition of 1975. Metrologia 12, 7-17, 1976. [3] Mangum, B. W.; Furukawa, G. T. Guidelines for realizing the International Temperature Scale of 1990 (ITS-90).
  • Page 80 C-18 Thermocouple Descriptions [14] Potts, J. F. Jr.; McElroy, D. L. The effects of cold working, heat treatment, and oxidation on the thermal emf of nickel-base thermoelements. Herzfeld, C. M.; Brickwedde, F. G.; Dahl, A. I.; Hardy, J. D., ed. Temperature: Its Measurement and Control in Science and Industry;...
  • Page 81 Thermocouple Descriptions C-19 [24] Glawe, G. E.; Szaniszlo, A. J. Long-term drift of some noble- and refractory-metal thermocouples at 1600K in air, argon, and vacuum. Temperature: Its Measurement and Control in Science and Industry; Vol. 4; Plumb, H. H., ed.; Pittsburgh: Instrument Society of America; 1972. 1645-1662.
  • Page 82 C-20 Thermocouple Descriptions [33] McLaren, E. H.; Murdock, E. G. Properties of some noble and base metal thermocouples at fixed points in the range 0-1100°C. Temperature: Its Measurement and Control in Science and Industry; Vol. 5; Schooley, J. F., ed.; New York: American Institute of Physics; 1982. 953-975. [34] Bentley, R.
  • Page 83 Thermocouple Descriptions C-21 [46] Burley, N. A.; Hess, R. M.; Howie, C. F. Nicrosil and nisil: new nickel-based thermocouple alloys of ultra-high thermoelectric stability. High Temperatures- High Pressures 12, 403-410; 1980. [47] Burley, N. A.; Cocking, J. L.; Burns, G. W.; Scroger, M. G. The nicrosil versus nisil thermocouple: the influence of magnesium on the thermoelectric stability and oxidation resistance of the alloys.
  • Page 84 C-22 Thermocouple Descriptions 6; Schooley, J. F., ed.; New York: American Institute of Physics; 1992. 579-584. [57] Bentley, R. E. The new nicrosil-sheathed type N MIMS thermocouple: an assessment of the first production batch. Mater. Australas. 18(6), 16-18; 1986. [58] Bentley, R. E.; Russell, Nicrosil sheathed mineral-insulated type N thermocouple probes for short-term variable-immersion applications to 1100°C.

  • Page 85: Using A Grounded Junction Thermocouple

    Appendix Using Thermocouple Junctions This appendix describes the types of thermocouple junctions available, and explains the trade-offs in using them with the thermocouple/mV analog input module. ATTENTION Take care when choosing a thermocouple junction, and connecting it from the environment to the module. If you do not take adequate precautions for a given thermocouple type, the electrical isolation of the module might be compromised.

  • Page 86: Using An Ungrounded (Isolated) Junction Thermocouple

    Using Thermocouple Junctions The shield input terminals for a grounded junction thermocouple are connected together and then connected to chassis ground. Use of this thermocouple with an electrically conductive sheath removes the thermocouple signal to chassis ground isolation of the module. In addition, if multiple grounded junction thermocouples are used, the module channel-to-channel isolation is removed, since there is no isolation between signal and sheath (sheaths are tied together).

  • Page 87: Using An Exposed Junction Thermocouple

    Using Thermocouple Junctions Measuring Junction Isolated from Sheath Using an Exposed An exposed junction thermocouple uses a measuring junction that does not have a protective metal sheath. A thermocouple with this junction Junction Thermocouple type provides the fastest response time but leaves thermocouple wires unprotected against corrosive or mechanical damage.
  • Page 88 Using Thermocouple Junctions To prevent violation of channel-to-channel isolation: • For multiple exposed junction thermocouples, do not allow the measuring junctions to make direct contact with electrically conductive process material. • Preferably use a single exposed junction thermocouple with multiple ungrounded junction thermocouples.

  • Page 89: Configure Profibus Thermocouple/Mv Modules (1790P-T4R0

    Appendix Module Configuration for PROFIBUS After installation of the thermocouple/mV module, you must configure it for operation, usually by using the programming software compatible with the controller or scanner. This appendix includes PROFIBUS configuration information. Chapter 3 contains detailed information on module parameters and performance.
  • Page 90 Module Configuration for PROFIBUS If it’s not already installed, add the thermocouple/mV module GSD file from the dropdown menu. Access: 1. Library>Add GSD. 2. Click File>New. If the PROFIBUS devices pane is closed, choose: 3. View>Library to open the pane. If the on-line Browse pane is closed, choose: 4.
  • Page 91 Module Configuration for PROFIBUS Choose the Master communication parameters You can add modules to the network by: 1. Selecting slaves from the PROFIBUS Device pane 2. Dragging and dropping them to the network pane Or, if online, by performing a search for slaves See the following screens for an outline of this procedure.
  • Page 92 Module Configuration for PROFIBUS Highlight the slave, right click the mouse and select GSD Files>1790P-T4T0.gsd 7. Highlight the slave from the Online Browse pane and drag and drop it to the Network pane. The slave station number should be set. (If you dragged and dropped from the PROFIBUS Device pane, you must set the station number.) Station number should be set...
  • Page 93 Module Configuration for PROFIBUS The produced 5 The 1790P-T4T0 words will appear in module produces 5 the processor input words of data. data table. 9. Click the Ext. Prms tab. This is where the parameters that can be set for the slave thermocouple/mV module are configured.
  • Page 94 Module Configuration for PROFIBUS Select the temperature units (°C or °F). All four channels will be configured identically. Select the filter cutoff frequency desired. All four channels will be configured identically. Select to enable (auto) or disable (manual) built-in cold junction compensation.

  • Page 95: Save The Configuration

    Module Configuration for PROFIBUS Select the thermocouple/mV input type for each channel from the dropdown list. 10. When configuration is complete, click the OK button to close the module properties screen. Save the Configuration To close the configuration: 1. Choose File>Save As. 2.
  • Page 96 Module Configuration for PROFIBUS 4. Right click to select Connect from the menu. (Or, choose Edit>Connect). Highlight the Master and then right click to select Connect. You may be prompted with a message indicating a configuration mismatch between what is in the scanner and your current PROFIBUS project.
  • Page 97 Module Configuration for PROFIBUS 5. Load the configuration to the Master through one of the following methods. • Right click on the Master and select Load Configuration from the menu. • Select the Load configuration icon in the toolbar. If the scanner is online, the following message displays: Card is online.

  • Page 98: Summary

    E-10 Module Configuration for PROFIBUS The Net LED on the thermocouple/mV module should turn solid green as should the Comm LED on the scanner. The connection should report OK. The master should now display: Summary This appendix illustrated how to configure your PROFIBUS thermocouple/mV module with the SST PROFIBUS Configuration tool.

  • Page 99: Glossary

    Glossary The following terms and abbreviations are used throughout this manual. For definitions of terms not listed here refer to Allen-Bradley’s Industrial Automation Glossary, Publication AG-7.1. A/D Converter– Refers to the analog to digital converter inherent to the module. The converter produces a digital value whose magnitude is proportional to the magnitude of an analog input signal.
  • Page 100 effective resolution – The number of bits in a channel configuration word that do not vary due to noise. filter – A device that passes a signal or range of signals and eliminates all others. filter frequency – The user-selectable frequency for a digital filter. full-scale –...
  • Page 101 normal mode rejection – (differential mode rejection) A logarithmic measure, in dB, of a device’s ability to reject noise signals between or among circuit signal conductors. The measurement does not apply to noise signals between the equipment grounding conductor or signal reference structure and the signal conductors.
  • Page 102 Publication 1790-UM003A-EN-P...

  • Page 103: Index

    Index Numerics channel LED indicator operation channel status LED 1790D-4T0 3-4, 3-5 channel step response general description channel update time hardware features definition power requirements circuit board 1790D-T4T0 protecting general description CJC. See Cold Junction Compensation. hardware features CMRR. See common mode rejection ratio power requirements 1-4, 2-16, Cold Junction Compensation...
  • Page 104 frequency response graphs frequency. See filter frequency. data configuration for DeviceNet full-scale data format definition data word full-scale range definition definition definition decibel. See dB. definition of terms general diagnostic features 3-12 determining module update time general specifications 2-13 DeviceNet cable grounding connecting DeviceNet specifications...
  • Page 105 set station address (PROFIBUS) mounting negative decimal values base block network status connecting DeviceNet cable noise connecting power to PROFIBUS block noise rejection 2-11 normal mode rejection connecting PROFIBUS DP connector definition 2-10 number of significant bits DIN rail mounting definition panel mounting power requirements...
  • Page 106 2-16 thermistors thermocouple register analog input signal types configuration compatibility resolution descriptions definition 3-13 error exposed junction grounded junction safety circuits junction types safety considerations 3-13 lead wire error activating devices when troubleshooting Type B description indicator lights effective resolution graph program alteration Type E safety circuits...
  • Page 107 2-14 wire type wiring 2-12 guidelines 2-14 modules routing considerations 2-15 terminal blocks AB Drives Publication 1790-UM003A-EN-P - May 2002...
  • Page 108 Publication 1790-UM003A-EN-P - May 2002...
  • Page 109 ___Yes, please call me ___Yes, please email me at __________________________ ___Yes, please contact me via ________________________ Return this form to: Allen-Bradley Marketing Communications, 1 Allen-Bradley Dr., Mayfield Hts., OH 44124-9705 AB Drives Phone: 440-646-3176 Fax: 440-646-3525 Email: RADocumentComments@ra.rockwell.com Publication ICCG-5.21- January 2001...
  • Page 110 PLEASE FASTEN HERE (DO NOT STAPLE) Other Comments PLEASE FOLD HERE NO POSTAGE NECESSARY IF MAILED IN THE UNITED STATES BUSINESS REPLY MAIL FIRST-CLASS MAIL PERMIT NO. 18235 CLEVELAND OH POSTAGE WILL BE PAID BY THE ADDRESSEE 1 ALLEN-BRADLEY DR MAYFIELD HEIGHTS OH 44124-9705...
  • Page 111 AB Drives...
  • Page 112 Publication 1790-UM003A-EN-P - May 2002 PN 957657-67 Copyright © 2002 Rockwell Automation. All rights reserved. Printed in the U.S.A.

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