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Important User Information Because of the variety of uses for the products described in this publication, those responsible for the application and use of this control equipment must satisfy themselves that all necessary steps have been taken to assure that each application and use meets all performance and safety requirements, including any applicable laws, regulations, codes and standards.
Purpose of Manual This manual shows you how to use your Thermocouple/Millivolt input module with an Allen–Bradley programmable controller. It helps you install, program, calibrate, and troubleshoot your module. Audience You must be able to program and operate an Allen–Bradley programmable controller (PLC) to make efficient use of your input module. In particular, you must know how to program block transfer instructions. We assume that you know how to do this in this manual.
P–2 Using This Manual Chapter Title Topics Covered Appendix D Block Transfer with Mini-PLC-2 and Mini-PLC-2/20 How to use GET-GET instructions for block transfer with Mini-PLC-2 and Mini-PLC-2/20 processors Appendix E Differences between Series A, B, C and D versions Lists differences from Series A 1771-IXE module Appendix F Thermocouple Characteristics Extractions from NBS Monograph 125 (IPTS-68) Warnings and Cautions This manual contains warnings and cautions.
Using This Manual P–3 Table P.A Compatibility and Use of Data Table Catalog Number +-10 * %$ '0/ Use of Data Table 10-10 $ # * %$ ),"( '0/ ,.#/ .'0$ ),"( ,.#/ Compatibility /),0 $/ ##.$//'+% & //'/ /),0 /),0 $.'$/ $/ $/ +# ,*- 0'!)$ 2'0& "& //'/ ,*- 0'!)$ 2'0& "& //'/ $/ ,*- 0'!)$ 2'0&,10 .$/0.'"0',+ , $/0.'"0$# 0, ",*-)$*$+0 .
P–4 Using This Manual
Table of Contents Overview of the Thermocouple/Millivolt Input Module Chapter 1 Installing the Thermocouple/Millivolt Input Module Chapter 2 Module Programming Chapter 3 *#26'4 $,'%6+8'5 1&7.' '5%4+26+10 '#674'5 1( 6*' 0276 1&7.' 19 0#.1) 1&7.'5 1//70+%#6' 9+6* 41)4#//#$.' 10641..
toc-ii Table of Contents Module Configuration Chapter 4 +$37(5 %-(&7,9(6 21),*85,1* 7+( +(502&283/( ,//,92/7 1387 2'8/( " 1387 ;3( (03(5$785( &$/( $7$ 250$7 ($/ ,0( $03/,1*
Table of Contents Programming Examples Appendix B Sample Programs for the Input Module . . . . . . . . . . . . . . . . . . . . . PLC-2 Family Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLC-3 Family Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLC-5 Family Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Table Formats toc-iii B-1 B-1 B-2 B-3 Appendix C 4-Digit Binary Coded Decimal (BCD) . . . . . . . . . . . . . . . . . .
Table of Contents
1 Chapter Overview of the Thermocouple/Millivolt Input Module Chapter Objectives This chapter gives you information on: • features of the input module • how an input module communicates with programmable controllers Module Description The Thermocouple/Millivolt input module is an intelligent block transfer module that interfaces analog input signals with any Allen–Bradley programmable controllers that have block transfer capability.
1–2 Overview of the Thermocouple/Millivolt Input Module • • • • • How Analog Modules Communicate with Programmable Controllers all features selectable through programming self–diagnostics and status reporting at power–up detection of open circuit if thermocouple fails automatic offset and gain calibration for each channel software calibration of all channels, eliminating potentiometers The processor transfers data to and from the module using BTW (block transfer write) and BTR (block transfer read) ins
Overview of the Thermocouple/Millivolt Input Module 1–3 3. The module converts analog signals into binary or BCD format, and stores theses values until the processor requests their transfer. 4. When instructed by your ladder program, the processor performs a read block transfer of the values and stores them in a data table. 5. The processor and module determine that the transfer was made without error, and that input values are within specified range. 6.
1–4 Overview of the Thermocouple/Millivolt Input Module
Chapter 2 Installing the Thermocouple/Millivolt Input Module Chapter Objectives This chapter gives you information on: • • • • • Before You Install Your Input Module calculating the chassis power requirement choosing the module’s location in the I/O chassis keying a chassis slot for your module wiring the input module’s field wiring arm installing the input module Before installing your input module in the I/O chassis you must: Action required: Refer to: ) ( ( $#* & & %) & ! "(' # !# ) '
2–2 Installing the Thermocouple/Millivolt Input Module Understand Compliance to European Union Directives If this product has the CE mark it is approved for installation within the European Union and EEA regions. It has been designed and tested to meet the following directives.
Installing the Thermocouple/Millivolt Input Module Calculate Power Requirements 2–3 The module receives its power through the 1771 I/O power supply and requires 850mA from the backplane. Add this current to the requirements of all other modules in the I/O chassis to prevent overloading the chassis backplane and/or backplane power supply. ! Determine Module Placement in the I/O Chassis ATTENTION: Do not insert or remove modules from the I/O chassis while system power is ON.
2–4 Installing the Thermocouple/Millivolt Input Module Install the Module and Field Wiring Arm ! ATTENTION: Remove power from the 1771 I/O chassis backplane and field wiring arm before removing or installing an I/O module. • Failure to remove power from the backplane or wiring arm could cause module damage, degradation of performance, or injury. • Failure to remove power from the backplane could cause injury or equipment damage due to possible unexpected operation.
Installing the Thermocouple/Millivolt Input Module Connect Wiring to the Field Wiring Arm 2–5 Connect your I/O devices to the cat. no. 1771-WI wiring arm shipped with the module. ! ATTENTION: Remove power from the 1771 I/O chassis backplane and field wiring arm before removing or installing an I/O module. • Failure to remove power from the backplane or wiring arm could cause module damage, degradation of performance, or injury.
2–6 Installing the Thermocouple/Millivolt Input Module Cable Lengths Recommended maximum cable length for voltage-mode input devices is 50 feet, due to possible signal degradation and electrical noise immunity in typical industrial environments. Grounding 1 When using shielded cable wire, ground the foil shield and drain wire only at one end of the cable.
Installing the Thermocouple/Millivolt Input Module Interpret Status Indicators ! Chapter Summary ! 2–7 The front panel of the thermocouple/mV input module contains a green RUN indicator and a red FAULT indicator.
2–8 Installing the Thermocouple/Millivolt Input Module
Chapter Chapter Objectives 3 In this chapter, we describe • Block Transfer programming • Sample programs in the PLC–2, PLC–3 and PLC–5 processors • Module scan time issues Block Transfer Programming Your module communicates with the processor through bidirectional block transfers. This is the sequential operation of both read and write block transfer instructions.
3–2 Module Programming PLCĆ2 Programming Example Note that PLC–2 processors that do not have the block transfer instruction must use the GET–GET block transfer format which is outlined in Appendix D. Figure 3.1 PLC-2 Family Sample Program Structure 2&'0* " ! $$$ $$$ $$$ 32* %%%% $$$$ $$$ $$$ $$$ 735&,* .7 03(/ 5&26+*5 *&) 32* .7 86-'87732 03(/ 5&26+*5 #5.7* 32* .7 735&,* .
Module Programming 3–3 Program Action Rung 1 – Block transfer read buffer: the file–to–file move instruction holds the block transfer read (BTR) data (file A) until the processor checks the data integrity. 1. If the data was successfully transferred, the processor energizes the BTR done bit, initiating a data transfer to the buffer (file R) for use in the program. 2. If the data is corrupted during the BTR operation, the BTR done bit is not energized and data is not transferred to the buffer file.
3–4 Module Programming PLCĆ3 Programming Example Block transfer instructions with the PLC–3 processor use one binary file in a data table section for module location and other related data. This is the block transfer control file. The block transfer data file stores data that you want transferred to the module (when programming a block transfer write) or from the module (when programming a block transfer read). The address of the block transfer data files are stored in the block transfer control file.
Module Programming 3–5 Rungs 1 and 2 – Rungs 1 and 2 are the block transfer read and write instructions. The BTR enable bit in rung 1, being false, initiates the first read block transfer. After the first read block transfer, the module performs a block transfer write and then does continuous block transfer reads until the pushbutton is used to request another block transfer write. After this single block transfer write is performed, the module returns to continuous block transfer reads automatically.
3–6 Module Programming Module Scan Time Scan time is defined as the amount of time it takes for the input module to read the input channels and place new data into the data buffer. Scan time for your module is shown in Figure 3.4. The following description references the sequence numbers in Figure Figure 3.4.
Chapter 4 Module Configuration Chapter Objectives Configuring the Thermocouple/Millivolt Input Module (1771-IXE/D) In this chapter you will read how to configure your module’s hardware, condition your inputs and enter your data. Because of the many analog devices available and the wide variety of possible configurations, you must configure your module to conform to the analog device and specific application that you have chosen.
4–2 Module Configuration Input Type The thermocouple/millivolt input module accepts the following types of inputs: Table 4.
Module Configuration Data Format 4–3 You must indicate what format will be used to read data from your module. Typically, BCD is selected with PLC–2 processors, and binary (also referred to as integer or decimal) is selected with PLC–3 and PLC–5 processors. See Table 4.B and Appendix C for details on Data Format. Table 4.
4–4 Module Configuration Table 4.
Module Configuration Configuration Block for a Block Transfer Write 4–5 The complete configuration block for the block transfer write to the module is defined in Table 4.D below. Table 4.D Configuration Block for Thermocouple/Millivolt Input Module Block Transfer Write Word 17 16 15 14 13 12 ),(# ')# 11 10 07 +.) 0 +0 /#" '%& ( .)/ +( .'03 +*# '0 ,#. '*,10 !& **#( 06 05 04 03 02 3,# +2 ( .)/ +( .'03 +*# '0 ,#. '*,10 !& **#( & **#( '%& ( .
4–6 Module Configuration Bit/Word Descriptions Bit/word descriptions of BTW file words 1 thru 3 (configuration), 4 thru 19 (channel alarm values), and 20 thru 27 (calibration values) are presented in Table 4.E. Enter data into the BTW instruction after entering the instruction into your ladder diagram program. Table 4.E Bit/Word Definitions for Thermocouple/Millivolt Input Module Bits Word ,.# !(0/ Description +-10 04-$ ",#$/ %,. (+-10/ 0'.1 ,. 0'.
Module Configuration Word Bits Word 1 (cont.) bits 11-12 4–7 Description Format bits tell the module which format to use for reporting input values to the processor. Format 12 11 4-digit BCD 0 0 2's complement binary 0 1 Signed magnitude binary 1 0 1 1 Select the format used by your processor. bits 13-17 Real time sample interval bits determine the sample time for updating module inputs. You select sample time in 0.1 second intervals using binary code. (All values between 0.1 and 3.
4–8 Module Configuration Word Chapter Summary - $# ,#'& 1 1 0 Bits Description '* + ,"*- $# * ,#'& /'* + * '%('+#, ' ,/' #& ( & &, 0, + '* " " && $ &, * $# * ,#'& , #& +#!& % !&#,- #& *0 '&$0 " %'+, +#!&# # &, #, #& " 0, #+ ," +#!& #, + , '* & ! ,#. * + , '* ('+#,#.
Chapter 5 Module Status and Input Data Chapter Objectives In this chapter you will read about: • reading data from your module • input module read block format Reading Data from the Module Block transfer read programming moves status and data from the input module to the processor’s data table in one I/O scan (Table 5.A). The processor user program initiates the request to transfer data from the input module to the processor.
5–2 Module Status and Input Data Bit/Word Descriptions The complete bit/word description for the block transfer read from the module is defined in Table 5.B. Table 5.
Module Status and Input Data Word #$ #"& "' Chapter Summary Bit 5–3 Definition & ( &# & &% #& '% & '!& & & ! $ & #" '!& & &% " ! $ & "" ! &% In this chapter you learned the meaning of the status information that the input module sends to the processor.
5–4 Module Status and Input Data
Chapter 6 Chapter Objective Tools and Equipment Tool or Equipment In this chapter we tell you how to calibrate your module. In order to calibrate your input module you will need the following tools and equipment: Description Model/Type + $,$(' (%- " (.+ & µ + ,(%.-$(' ' %("$ - + $,$(' (+ *.$/ % '- ' .
6–2 Module Calibration Performing AutoĆCalibration Calibration of the module consists of applying 0.000mV across each input channel for offset calibration, and +100.000mV across each input channel for gain correction. Offset Calibration Normally all inputs are calibrated together. To calibrate the offset of an input, proceed as follows: 1. Apply power to the module. 2. Connect shorting links, or apply 0.000mV across each input channel on the 1771–WI field wiring arm as shown in Figure 6.1. Figure 6.
Module Calibration 6–3 Table 6.A Write Block Transfer Word 28 Word Bit 17 16 15 14 13 12 11 10 07 06 05 04 03 '#$ $- %$ + -$(' (+ 02 01 00 !*.!,-! .-( %$ + -$(' !- -#!,! $-, -( !*.!,-! /! %.!, !*.!,-! $' % !*.!,-! "",!- % NOTE: Normally, all channels are calibrated simultaneously (bits 10–17 of word 28 are octal 0). To disable calibration on any channel, set the corresponding bit 10 through 17 of word 28. 4.
6–4 Module Calibration Figure 6.2 Applying 100.00mV for Gain Calibration !*&$' % !',$"$ ,$(' 1 ( '(, -+! -' ,$(' ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! (, +! (, -+! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! ')-, %! !*&$' % + $*$'# *& , ( ))%.
Module Calibration 6–5 The module can be run with the new calibration values, but will lose them on power down. To save these values, proceed as follows: 1. Request a ”save to EEPROM” by setting bit 02 in BTW word 28 and sending the BTW to the module. Refer to Table 6.A. 2. Queue BTRs to monitor for ”save complete”, ”EEPROM fault” and ”calibration fault.
6–6 Module Calibration Figure 6.4 Shorting Inputs for Offset Calibration $/+(, * #$,1(%(" 1(-, # # # # # # # # # # # # # # # # 2,"1(-, ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ -1 0$# -1 20$# ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ ,.21 *$ '-/1(,& *(,) $.$ 1 %-/ $ "' "' ,,$* 1 $/+(, * - ,-1 20$ '-/1 $ "' (,.21 -/ ..
Module Calibration 6–7 For example, if the observed value was 17, enter –53 [(0 – 17) x 3.0933 = –53] in signed magnitude binary into the upper byte of the calibration word for that channel. Enter 10110101 in bits 17–10 of word 20. The lower byte will remain zero at this time. 6. Repeat steps 3 through 5 for each of the remaining input channels. 7. Initiate a write block transfer to send the corrections to the module. The input value read by the processor should now be 0000 for all channels.
6–8 Module Calibration 2. Record the input value read by the processor in the BTR file (word 4 for channel 1). Determine the percentage difference from 10000 and the sign of the correction. You can adjust the correction up to +0.19379%. A negative correction means that the reading was too high and you want to subtract a corrective amount from that reading. A positive correction means that the reading was too low and you want to add a corrective amount to that reading.
Module Calibration 6–9 4. Repeat the above steps 2 and 3 for channels 2 through 8. 5. Initiate a write block transfer to send the corrections to the module. The input value read by the processor should now be 10000 (A000 for BCD) for all channels. 6. If the correction changes the result in the wrong direction, change the sign and reenter it. Important: Chapter Summary If the % correction required is larger than +0.19379, check your reference voltage.
6–10 Module Calibration
Chapter Chapter Objective Diagnostics Reported by the Module 7 We describe how to troubleshoot your module by observing LED indicators and by monitoring status bits reported to the processor.
7–2 Troubleshooting Troubleshooting with the Indicators Table 7.A shows LED indications and probable causes and recommended actions to correct common faults. Table 7.A Troubleshooting Chart for Thermocouple/Millivolt Input Module (1771-IXE/D) Probable Cause Indication Recommended Action Both LEDs are OFF No power to module Possible short on the module LED driver failure Check power to I/O chassis. Recycle as necessary. Replace module.
Troubleshooting Word Bit 7–3 Explanation +/ 0."! (& - /&+* +*./ */. +0(! *+/ " -" ! %" )+!0(" 2&(( +*/&*0" /+ +,"- /" 0/ -" !&*$. ) 4 " &* 0- /" &$* &/. #+- " % % **"( Status Reported in Words 2 and 3 Design your program to monitor over/under range bits, and to take appropriate action depending on your application requirements. You may also want to monitor these bits while troubleshooting with your industrial terminal.
7–4 Troubleshooting Status Reported in Word 13 Design your program to monitor status bits in word 13 during auto–calibration, and to take appropriate action depending on your requirements. You may also want to monitor these bits while troubleshooting with your industrial terminal. The module sets a bit (1) to indicate it has detected one or more of the following conditions as shown in Table 7.D. Table 7.
Appendix A Number of Inputs 8, all of the same type or 4 each of 2 different types I/O Chassis Location Any single I/O module slot Type of Input (Selectable) Type E, chromel/constantan Type J, iron/constantan Type K, chromel/alumel Type R, Pt/Pt-13% Rh Type T, copper/constantan Type S, Pt/Pt-10% Rh Millivolt Thermocouple Linearization IPTS-68 standard, NBS MN-125 Cold Junction Compensation Range: 0 to 60oC Accuracy: +0.
A–2 Specifications Thermocouple/Millivolt Input Module Accuracy The accuracy of your thermocouple readings depends on: • module accuracy • lead resistance effect • accuracy of the thermocouple The accuracy of the module is shown in NO TAG and NO TAG at ambient temperature (25oC) and over the temperature range (0–60oC). Use the calibration procedure in Chapter 6 to adjust your module to compensate for your specific environment. Table A.
Specifications Lead Resistance Compensation A–3 Allowable Distances The open thermocouple detection circuit injects a current of approximately 7.3 nanoamps into the thermocouple cable. A total lead resistance of 1370 ohms (685 ohms one–way) cable resistance will produce +1 count (10uV) of error. Source Impedance Compensation for Millivolt Inputs Source resistance causes similar errors to occur with millivolt inputs.
A–4 Specifications
Appendix Sample Programs for the Input Module PLC-2 Family Processors B The following are sample programs for entering data in the configuration words of the write block transfer instruction when using the PLC–2, PLC–3 or PLC–5 family processors. To enter data in the configuration words, follow these steps. NOTE: For complete programming sample, refer to Figure 4.1.
B–2 Programming Examples Use the above procedure to enter the required words of the write block transfer instruction. Be aware that the block length will depend on the number of channels selected and whether alarming or user calibration are implemented. For example, the block may contain only 1 word if no alarming or user calibration are implemented, but may contain 27 words if using 8 inputs with alarming and user calibration. The PLC–2 family write block transfer data file should look like Figure B.1.
Programming Examples B–3 1. Press [SHIFT][MODE] to display your ladder diagram on the industrial terminal. 2. Press DD,03:0[ENTER] to display the block transfer write file. The industrial terminal screen should look like Figure B.2. Notice the highlighted block of zeroes. This highlighted block is the cursor. It should be in the same place as it appears in Figure B.2. If it is not, you can move it to the desired position with the cursor control keys.
B–4 Programming Examples 1. Enter the following rung: " # " ! ! ! ! .4(0 !/ +2 +1 2*( $''0(11 .) 2*( " 20$-1)(0 )+,( 2. Press [F8],[F5] and enter N7:60 to display the configuration block. The industrial terminal screen should like Figure B.3. Figure B.
Appendix 4-Digit Binary Coded Decimal (BCD) C The 4–digit BCD format uses an arrangement of 16 binary digits to represent a 4–digit decimal number from 0000 to 9999 (NO TAG). The BCD format is used when the input values are to be displayed for operator viewing. Each group of four binary digits is used to represent a number from 0 to 9. The place values for each group of digits are 20, 21, 22 and 23 (NO TAG).
C–2 Data Table Formats Table C.A BCD Representation 23 (8) Signed-magnitude Binary Place Value 22 (4) 21 (2) Decimal Equivalent 20 (1) Signed–magnitude binary is a means of communicating numbers to your processsor. It should be used with the PLC–2 family when performing computations in the processor.
Data Table Formats C–3 First, the two’s complement method places an extra bit (sign bit) in the left–most position, and lets this bit determine whether the number is positive or negative. The number is positive if the sign bit is 0 and negative if the sign bit is 1. Using the complement method: 0 10110 = 22 To get the negative using the two’s complement method, you must invert each bit from right to left after the first ”1” is detected.
C–4 Data Table Formats
Appendix D Block Transfer (Mini-PLC-2 and PLC-2/20 Processors) Multiple GET Instructions - Mini-PLC-2 and PLC-2/20 Processors Programming multiple GET instructions is similar to block format instructions programmed for other PLC–2 family processors. The data table maps are identical, and the way information is addressed and stored in processor memory is the same. The only difference is in how you set up block transfer read instructions in your program.
D–2 Block Transfer (Mini–PLC–2 and PLC–2/20 Processors) Rung Summary: Once the block transfer read operation is complete, the processor automatically sets bit 07 in the input image table status byte and stores the block length of the data transferred. Figure D.
Block Transfer (Mini–PLC–2 and PLC–2/20 Processors) D–3 The bits in the output image table control byte (bits 00 – 05) must be programmed to specify a binary value equal to the number of words to be transferred. For example, NO TAG shows if your input module is set up to transfer 6 words, you would set bits 01 and 02 of the lower image table control byte. The binary equivalent of 6 words is 000110. You would also set bit 07 when programming the module for block transfer read operations.
D–4 Block Transfer (Mini–PLC–2 and PLC–2/20 Processors)
Appendix E Differences Between Series A, Series B, Series C and Series D Thermocouple/Millivolt Input Modules Major Differences between Series The following is a list of major differences between Series A, Series B, Series C and Series D Thermocouple/Millivolt Input module (cat. no. 1771–IXE). Definition Series A Series B Series C and Series D Calibration Uses potentiometers for calibration settings with calibration done at -99 and +99mV.
E–2 Differences Between Series A, Series B, Series C and Series D Thermocouple/Millivolt Explanation of Differences • Calibration is now done automatically using auto–calibration • • • • • • • • • • • feature, or manually through programming. calibration is now done at 0.000mV and +100.000mV . If EEPROM read of the auto cal values fails, BTR WORD 1 bit 7 is asserted. Series A used potentiometers for calibration settings with calibration done at –99 and +99mV.
Differences Between Series A, Series B, Series C and Series D Thermocouple/Millivolt E–3 • Accuracy specifications over typical RANGES and TEMPERATURES are: Input Type Range IS ! Range WAS "! Accuracy IS ! ! "! "! ! "! ! ! "! ! "! ! ! "! ! "! ! ! "! ! "! ! ! "! ! "! ! !
E–4 Differences Between Series A, Series B, Series C and Series D Thermocouple/Millivolt • The Series B module requires approximately 2 seconds to • • • • • • execute initialization after power is applied. The red LED will be turned on and the green LED extinguished when the watchdog timer times out. A type code of 1112 will yield S type thermocouple. Data format of 112 yields signed magnitude instead of 2’s complement.
Appendix F Thermocouple Restrictions (Extracted from NBS Monograph 125 (IPTS-68)) General Following are some restrictions extracted from NBS Monograph 125 (IPTS–68) issued March 1974 on thermocouples J, K, T, E, R and S: J (Iron vs Copper-Nickel ) Type Thermocouple The J thermocouple “is the least suitable for accurate thermometry because there are significant nonlinear deviations in the thermoelectric output from different manufacturers. ...
F–2 Thermocouple Restrictions “ASTM Standard E230–72 in the Annual Book of ASTM Standards [1972] specifies that the standard limits of error for Type J commercial thermocouples be +/–2.2C between 0 and 277C and +/–3/4 percent between 277 and 760C. Limits of error are not specified for Type J thermocouples below 0C or above 760C. Type J thermocouples can also be supplied to meet special limits of error, which are equal to one half the limits given above.
Thermocouple Restrictions F–3 “ASTM Standard E230–72 in the Annual Book of ASTM Standards [1972] specifies that the standard limits of error for Type K commercial thermocouples be +/–2.2C between 0 and 277C and +/–3/4 percent between 277 and 1260C. Limits of error are not specified for the Type K thermocouples below 0C. Type K thermocouples can also be supplied to meet special limits of error, which are equal to one half the standard limits of error given above.
F–4 Thermocouple Restrictions “Because of the high thermal conductivity of Type TP thermoelements, special care should be exercised in the use of the thermocouples to insure that both the measuring and reference junctions assume the desired temperatures.” ASTM Standard E230–72 in the Annual Book of ASTM Standards [1972] specifies that the standard limits of error for Type T commercial thermocouples be +/–2 percent between –101 and –59C, +/–.8C between –59 and 93C and +/–3/4 percent between 93 and 371C.
Thermocouple Restrictions F–5 “ASTM Standard E230–72 in the Annual Book of ASTM Standards [1972] specifies that the standard limits of error for the Type E commercial thermocouples be +/–1.7C between 0 and 316C and +/–1/2 percent between 316 and 871C. Limits of error are not specified for Type E thermocouples below 0C. Type E thermocouples can also be supplied to meet special limits of error, which are less than the standard limits of error given above: +/–1.
F–6 Thermocouple Restrictions
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