HART® Transmitter Calibration
Contents
1. CST S98 O300 51 pm Loop 24 J SOURCE MEASURE ERROR 0 000 psi 4 407 mA 2 002 psi 12 502 ma 5 000 psi 20 268 mA Prev Next Abort Page Page Done Figure 7 7 Fluke Corporation 5 If the As Found test failed i e there were highlighted errors in the error summary table adjustment is neces sary Press the Adjust softkey Select Sensor Trim and press f Do not select Pressure Zero Trim It is the same as trimming the lower sensor point at zero which is useful for pressure transmit ters that do not offer Sensor Trim The 744 screen should look like Figure 8 O21 5499 03 24 74 pr Loop 24 im WAN sakes Measure 4 076 mA PF13579 3 Source 0 014 psi Select sensor trim operation Perform user trim both Perform user trim lower Perform user trim Upper select factory data Abort Figure 8 6 Select Perform user trim both and press f Zero the pressure module vented to atmosphere by pressing 5 Press the Continue softkey and you are prompted for the Lower Trim value For best results apply the LRV pres sure and press Fetch to load the value being measured by the pressure module Press Trim Then press Continue to move to the Upper Trim As before apply the URV pressure press Fetch and press Trim If the 3051 is used with the digital PV output skip to step 8 and perform the As Left test If the 4 20 mA analog output is used in the process con tinue o2. HART Connection ra Black 3144 Transmitter Figure 10 Hart Transmitter Calibration OsM03 199 12011 prm Loop 24t TE HART hea sure 3 992 MA Source O 0 C TTOOZ3 elect calibrator mode of operation Abort Figure 12 3 Press the As Found softkey and then press to select Instrument for a linear transmitter calibration Notice that the calibration template is automatically completed with the exception of the Tolerance Fill in the appro priate test tolerance and press the Done softkey 4 Press the Auto Test softkey to begin calibration Once the test is complete an error summary table is displayed Figure 13 Test errors ex ceeding the tolerance are highlighted When done viewing the table press the Done softkey Press Done again to accept or to change the tag serial num ber or ID fields Canes 042756 pm Loop 24 C SOURCE MEASURE ERROR 6 o 0 C 3 940 m4 150 0 C 11 972m4 0 17 300 0 C 20 000 mA 0 00 Prev Next Abort Page Page Done Figure 13 9 Fluke Corporation 5 If the As Found test failed i e there were highlighted errors in the error summary table adjustment is neces sary Press the Adjust softkey Select Sensor Trim and press Select Perform user trim both and press The 744 screen should look like Figure 14 Dari SS 04 45 25 pri Loop 244 im HART SERVICE Py 0 0 C Last Trim 20 0 C 744 Sourc
3. jagga 115925 am Loop 244 n SOURCE MEASURE ERROR o 0 C 3 950 m4 50 0 11 952 m 100 0 C 15 962 ma 0 24 Prev Mest Abort Page Page Done Figure 22 If errors are highlighted adjustment is necessary by performing an Output Trim Press Done to leave the re sults screen edit the tag serial number or ID fields as necessary and press Done again 5 Press the Adjust softkey select Output Trim and press The value of the primary variable PVAO is in the upper right corner of the display Figure 23 This is normally a 4 mA signal The real time mA value as mea sured by the Fluke 744 is in the center of the display Press the Fetch softkey to load the measured mA value Press the Send softkey to send the value to the trans mitter to trim the output section for the 4 mA value Press Continue for the 20 mA adjustment and repeat this step gan A99 044974 pri Loop 244 onl HART SERVICE Ea 4 0000 mA 744 Measure 3 961 mA Fetch or ENTER value Trim Current Abort Fetch Send ai Figure 23 6 Now perform an As Left test Press As Left press Done and then press Auto Test On completion the error sum mary table is displayed If errors are highlighted the test has failed and further adjustment is required Note If the failure error is large sensor trim adjustment with a communicator may be nec essary Often however adjustment can be ac complished with a 744 by m
4. FEKE 744 DOCUMENTING process CALIBRATOR 10 793 mA Em Feos ZERO 23 059 psi HART Connection Hand Pump Pressure Module 3 FA Red mA Measure 24V Loop Pressure Input Pa Black Figure 4 Hart Transmitter Calibration 3 Vent the pressure line and press to zero the pressure module Press the As Found softkey and then press to select Instrument for a linear transmitter calibration If the 3051 is configured for square root output select v Instrument Notice that the calibration template is automatically completed with the exception of Tolerance Fill in the appropriate test tolerance and press Done Press the Manual Test softkey to begin calibration Apply the input pressures as instructed in the SOURCE screen Press the Accept Point softkey when the cor rect pressure is applied for each point When the test is complete the error summary table is displayed Figure 7 Test errors exceeding the tolerance are highlighted When done viewing the table press the Done softkey Press Done again to accept or to change the tag serial number or ID fields
5. duce The output value is ob tained using a calibrator to measure the resulting current This test also implies a linear relationship between the input and output and both are re corded in the same engineering units milliamps The desired accuracy for this test should also reflect the manufacturer s accu racy specification If the test does not pass then follow the manufacturer s rec ommended procedure for trim ming the output section This may be called a 4 20 mA trim a current loop trim or a D A trim The trim procedure should re quire two trim points close to or just outside of 4 and 20 mA Do not confuse this with any form of re ranging or any procedure that involves using zero and span buttons FLUKE Testing overall performance After calibrating both the Input and Output sections a HART transmitter should operate correctly The middle block in Figure A2 only involves compu tations That is why you can change the range units and transfer function without neces sarily affecting the calibration Notice also that even if the in strument has an unusual trans fer function it only operates in the conversion of the input value to a milliamp output value and therefore is not involved in the testing or calibration of ei ther the input or output sections If there is a desire to validate the overall performance of a HART transmitter run a Zero and Span test just like a con ventional instrument As you
6. Section Section Section PV may be mA may be set read digitally and read digitally Figure A2 HART Transmitter Block Diagram Hart Transmitter Calibration FLUKE o 14 Fluke Corporation HART calibration requirements Based on this analysis you can see why a proper calibration procedure for a HART instru ment is significantly different than for a conventional instru ment The specific calibration requirements depend upon the application If the application uses the digital representation of the process variable for monitoring or control then the sensor input section must be explicitly tested and adjusted Note that this reading is completely indepen dent of the milliamp output and has nothing to do with the zero or span settings The PV as read via HART communication con tinues to be accurate even when it is outside the assigned output range For example a range 2 Rosemount 3051c has sensor limits of 250 to 250 inches of water If you set the range to O 100 inches of water and then apply a pres sure of 150 inches of water the analog output will saturate at just above 20 milliamps How ever a communicator can still read the correct pressure If the current loop output is not used that is the transmitter is used as a digital only device then the input section calibra tion is all that is required If the application uses the milliamp output then the output section must be explicitly tested and calib
7. and it read 101 0 with 100 inches of water applied Using the com municator the technician per forms a current loop trim so that the display reads correctly at O and 100 essentially correcting the output to be 4 and 20 mA respectively While this also appears to be successful there is a fundamen tal problem with this procedure To begin with the communica tor will show that the PV still reads 1 and 101 inches of water at the test points and the digi tal reading of the mA output still reads 4 16 and 20 16 mA even though the actual output is 4 and 20 mA The calibration problem in the input section has been hidden by introducing a compensating error in the out put section so that neither of the digital readings agrees with the calibration standards As published in Intech May 1996 and also in HART Book 8 July 1998 Reprinted with the permission of the author 16 Fluke Corporation Documentation of results The scheduling of calibrations creation of proce dures and documentation of your calibration results are facilitated by a number of instrumen tation management software packages Honeywell DocuMint Plant Resource Manager PRM Plant Resource Manager from Yokogawa Electric Corporation OnTime Support Fluke DPC TRACK Meridium ProCALvV Intools Ordering Information FLUKE 744 Documenting Process Calibrator HART Includes TL224 Industrial Test Leads two sets AC220 Test Clip
8. will see in a moment however passing this test does not nec essarily indicate that the trans mitter is operating correctly Effect of damping on test performance Many HART instruments support a parameter called damping If this is not set to zero it can have an adverse effect on tests and adjustments Damping in duces a delay between a change in the instrument input and the detection of that change in the digital value for the instrument input reading and the corresponding instru ment output value This damp ing induced delay may exceed the settling time used in the test or calibration The settling time is the amount of time the test or calibration waits between set ting the input and reading the resulting output It is advisable to adjust the instrument s damping value to zero prior to performing tests or adjustments After calibration be sure to return the damping constant to its required value Operations that are NOT proper calibrations Digital range change There is a common misconcep tion that changing the range of a HART instrument by using a communicator somehow cali brates the instrument Remem ber that a true calibration requires a reference standard usually in the form of one or more pieces of calibration equipment to provide an input and measure the resulting out put Therefore since a range change does not reference any external calibration standards it is really a configuration change
9. not a calibration Notice that in the HART transmitter block dia gram Figure 2 changing the range only affects the second block It has no effect on the digital process variable as read by a communicator Zero and span adjustment Using only the zero and span adjustments to calibrate a HART transmitter the standard prac tice associated with conven tional transmitters often corrupts the internal digital readings You may not have noticed this if you never use a communicator to read the range or digital process data As shown in Figure 2 there is more than one output to con sider The digital PV and milliamp values read by a com municator are also outputs just like the analog current loop Consider what happens when using the external zero and span buttons to adjust a HART instrument Suppose that an instrument technician in stalls and tests a differential pressure transmitter that was set at the factory for a range of O to 100 inches of water Test ing the transmitter reveals that it now has a 1 inch of water 15 Fluke Corporation zero shift Thus with both ports vented zero its output is 4 16 mA instead of 4 00 mA and when applying 100 inches of water the output is 20 16 mA instead of 20 00 mA To fix this he vents both ports and presses the zero button on the trans mitter The output goes to 4 00 mA so it appears that the ad justment was successful However if he now checks the transmitter with a
10. or trim sensor section with a communicator Note If you encounter any difficulty with any of these examples you may call 1 800 44 FLUKE for assistance 1 800 443 5853 Appendix A Calibrating HART Transmitters By Kenneth L Holladay P E Calibrating a conventional instrument For a conventional 4 20 mA instrument a multiple point test that stimulates the input and measures the output is sufficient to characterize the overall accu racy of the transmitter The normal calibration adjustment involves setting only the zero value and the span value since there is effectively only one adjustable operation between the input and output as illus trated below Zero and Span Adjustments Sensing i 4 20 mA Element Analog Output Electronics Figure A1 Conventional Transmitter Block Diagram This procedure is often re ferred to as a Zero and Span Calibration If the relationship between the input and output range of the instrument is not linear then you must know the transfer function before you can calculate expected outputs for each input value Without knowing the expected output values you cannot calculate the performance errors Calibrating a HART instrument For a HART instrument a mul tiple point test between input and output does not provide an accurate representation of the transmitter s operation Just like a conventional transmitter the measurement process begins with a technology
11. that converts 13 Fluke Corporation a physical quantity into an elec trical signal However the simi larity ends there Instead of a purely mechanical or electrical path between the input and the resulting 4 20 mA output signal a HART transmitter has a micro processor that manipulates the input data As shown in Figure A2 there are typically three calculation sections involved and each of these sections may be individually tested and adjusted Just prior to the first box the instrument s microprocessor measures some electrical prop erty that is affected by the pro cess variable of interest The measured value may be milli volts capacitance reluctance inductance frequency or some other property However before it can be used by the micropro cessor it must be transformed to a digital count by an analog to digital A D converter In the first box the micropro cessor must rely upon some form of equation or table to relate the raw count value of the electrical measurement to the actual prop erty PV of interest such as tem perature pressure or flow The principle form of this table is usually established by the manufacturer but most HART instruments include commands to perform field adjustments This is often referred to as a sensor trim The output of the first box is a digital representa tion of the process variable When you read the process variable using a communicator this is the value tha
12. the accuracy and stability of HART instruments eliminate the need for calibration Another misconception is that calibration can be accomplished by re ranging field instruments using only a HART communica tor Still another misconception is that the control system can remotely calibrate smart instru ments These are not true All instruments drift Re ranging with just a communicator is not calibration A precision calibra tor or standard is required Regular performance verifica tion with a calibrator traceable to national standards is neces sary due to 1 Shifts in performance of electronic instruments over time due to exposure of the electronics and the primary sensing element to tempera ture humidity pollutants vibration and other field environmental factors 2 Regulations governing occu pational safety consumer safety and environmental protection 3 Quality programs such as ISO 9000 standards for all instruments that impact product quality 4 Commercial requirements such as weights measures and custody transfer Regular calibration is also pru dent since performance checks will often uncover problems not directly caused by the instru mentation such as solidified or congealed pressure lines in stallation of an incorrect ther mocouple type or other errors and faults A calibration procedure con sists of a verification As Found test adjustment to within ac ceptable tolerance if nece
13. FLUKE HART Transmitter Calibration Application Note Introduction In today s process plants most new field instruments are smart digital instruments Smart im plies a microprocessor based instrument with extra functional ity and digital compensation supporting multiple sensor types or multiple variables These in struments generally offer better accuracy long term stability and reliability than conventional analog instruments The most common class of smart instruments incorporates the HART protocol with more than five million HART instru ments in use in 100 000 plants worldwide HART an acronym for Highway Addressable Remote Transducer is an industry stan dard that defines the communi cations protocol between smart field devices and a control sys tem that employs traditional 4 20 mA wiring Two capabilities are required to properly service HART instru ments precision analog source and measure capability and digi tal communication capability Until recently this required two separate tools a calibrator and a communicator Today the capa bilities of those two tools are available in a single HART Docu menting Process Calibrator that can help you quickly and effec tively service HART instruments VON FIELD COMMUNICATIONS PR AVA OY From the Fluke Digital Library www fluke com library 2 Fluke Corporation HART calibration is required A common misconception is that
14. commu nicator he will find that the range is 1 to 101 inches of wa ter and the PV is 1 inch of water instead of 0 The zero and span buttons changed the range the second block This is the only action that the in strument can take under these conditions since it does not know the actual value of the reference input Only by using a digital command which con veys the reference value can the instrument make the appro priate internal adjustments The proper way to correct a zero shift condition is to use a zero trim This adjusts the in strument input block so that the digital PV agrees with the cali bration standard If you intend to use the digital process values for trending statistical calcula tions or maintenance tracking then you should disable the external zero and span buttons and avoid using them entirely Loop current adjustment Another observed practice among instrument technicians is to use a hand held commu nicator to adjust the current loop so that an accurate input to the instrument agrees with some display device on the loop If you are using a Rosemount model 268 commu nicator this is a current loop trim using other scale Refer again to the zero drift example just before pressing the zero Hart Transmitter Calibration FLUKE button Suppose there is also a digital indicator in the loop that displays 0 0 at 4 mA and 100 0 at 20 mA During testing it read 1 0 with both ports vented
15. e 0 0 C ENTER value in the range 180 0 to 1372 0 C Lower Trim QE c Abort LAY Trim Figure 14 6 For best results press LRV to apply the LRV for the Lower Trim value Press Trim and then Continue to move to the Upper Trim Press URV press Trim and then press Done If the 3144 is used with the digital PV output skip to step 8 and perform the As Left test If the analog 4 20 mA output is used in the process continue on to step 7 7 Select Output Trim and press The value of the primary variable PVAO is in the upper right corner of the display Figure 18 This is normally a 4 mA signal The mA value as constantly measured by the Fluke 744 is in the center of the dis play Press the Fetch softkey to load the measured mA value Press Send to send the value to the 3144 to trim the output section for the 4 mA value Press Continue for the 20 mA trim and repeat this step Hart Transmitter Calibration FLUKE Can Se 04451 4 pm Loop 24 Cm PAC 4 0000 mA 744 Measure 3 961 mA Fetch or ENTER alue Trim Current Abort Fetch Send Figure 15 8 After completing Output Trim press the Done softkey and proceed with the As Left verification test Press the As Left softkey Press Done and then press Auto Test On completion an error summary table is displayed If errors are highlighted the test has failed and further adjustment is required Return to step 5 fo
16. e the new LRV and URV as follows LRV LRV a Span x Error 0 LRV 0 4 C 100 0 C x 0 84 LRV 0 4 C 100 0 C x 0 0084 LRV 0 4 C 0 8 C LRV 1 2 C URV ew URV a Span x Error 100 URV 102 0 C 100 0 C x 2 41 URV 102 0 C 100 0 C x 0 0241 URV 102 0 C 2 4 C URV 99 6 C new 10 Press and then press the Setup softkey Select Basic from the menu and press to display the basic setup parameters shown in Figure 24 To ENTER the new LRV move the cursor to Lower Range Value and press e Type the new LRV and press fe Also type in the new URV and press Press the Send softkey FLUKE C2699 12 26 09 pm HART J SETUP Measure Press ENTER Loop 24 Cm 4001 mA o change iter Taq MATESE PY Unit ge Walue PE 0 4 C 102 0 C 0 0000 Linear Lower Ra Upper Range Walue Damping Function Transtel Reset Page Recall Page store Page Done Figure 24 11 Now press Done and then press Abort 3 times Per form a new As Found test by pressing As Found Re member to make sure that the original nominal zero and span values are shown as the 0 Value and 100 Value Press Done and then press Auto Test On completion the error sum mary table is displayed If errors are highlighted the test has failed repeat the adjustment
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18. fers capabili ties far beyond those generally required for daily HART instru ment maintenance HART calibration applications The following examples demon strate how the 744 makes HART calibration an efficient opera tion The 744 enables easy hookup using its HART cable fast access to the most impor tant HART data automatic branching to appropriate adjust ment choices automatic completion of test templates and automatic fetching and sending of analog readings during trim Manufacturer Pressure Instruments Temperature Instruments Coriolis Instruments ABB Kent Taylor 600T 658T ABB Contrans P Hartmann amp Braun AS 800 Series Endress amp Hauser CERABAR S TMT 122 TMT 182 CERABAR M TMT 162 DELTABAR S Foxboro Eckardt TI RTT20 Foxboro Invensys I A Pressure Fuji FCX FRC FCXAZ Honeywell ST3000 STT25T STT25H Micro Motion 2000 2000 IS 9701 9712 9739 Moore Products 344 Rosemount 1151 3044C 2088 644 3001C 3144 3051 3051S 3244 3144P Siemens SITRANS P DS SITRANS P ES SMAR LD301 TT301 Viatran I A Pressure Wika UNITRANS T32H Yokogawa EJA YTA 110 310 and 320 Table 1 Sensor Trim not supported 5 Fluke Corporation Hart Transmitter Calibration FLUKE 6 Fluke Corporation Calibration of a Rosemount 3051 HART Pressure Transmitter Basic connections This example assumes that the transmitter is isolated from the process and i
19. ion gether to complete field calibra tions However the desire to carry less equipment and to perform maintenance in the field has created a need for a new class of calibration tool The new 744 Documenting Process Calibrator from Fluke is the first powerful yet easy to use tool for field calibration of HART instrumentation Pressing Hart Transmitter Calibration a single key enters the HART mode and displays the essential HART information in the Active Device Screen shown in Figure 2 Additional HART functionality is accessed with only a few more keystrokes per the menu tree in Figure 3 FLUKE View process Tag Keypad input variables PV units Adjust URV LRV to Process View variable Basic L LRYV URV applied values map Damping Re map process Transfer function variables Sensor 1 Dual sensor e Sensor serial number temperature z e Sensor lower and devices Detailed e Config upper limits coriolis Config Output a e Sensor minimum span Temperature Sensor devices only Change Sensor Type Change Sensor Connections e Software Version Final assembly number Setu Device LRV URV Sra p Identification a Change Sensor Type Damping i e Change Sensor Transfer function Connections Dual sensor temperature devices cae Dual Sensor Config utput Dual sensor tempera
20. n to step 7 Hart Transmitter Calibration 7 Select Output Trim and press f The value of the primary variable PVAO is in the upper right corner of the display This is normally a 4 mA signal The mA value as constantly measured by the Fluke 744 is in the cen ter of the display Press the Fetch softkey to load the measured mA value Press Send to send the value to the 3051 to trim the output section for the 4 mA value Press Continue for the 20 mA trim and repeat this step 8 After completing Output Trim press the Done softkey and proceed with the As Left verification test Press the As Left softkey Press Done and then press Manual Test Apply the requested pres sures and press Accept Point when the readings are stable On completion an error summary table is dis played If none of the errors are highlighted Figure 9 the 3051 passes the calibra tion test If errors are high lighted the test has failed and further adjustment is required Return to step 5 for adjustment of the 3051 Ce SSS Os 5e40 pr Loop 24 Cm SOURCE MEASURE ERROR 0 001 psi 3 999 m4 0 03 2 500 psi 11 997 m 0 02 5 000 psi 19 998 m 0 01 Abort Prev Next Done Fage Page Figure 9 FLUKE o 8 Fluke Corporation Calibration of a Rosemount 3144 HART Temperature Transmitter Basic connections This example assumes that the transmitter is isolated from the process and is not electrically connected to a l
21. nctions that are common to many but not all field devices for example read multiple vari ables set damping time or perform loop test Device specific commands provide functions that are unique to a particular field device for example sensor trim The 744 Version 2 5 supports these devices HART operating modes supported e For Point to Point operation the most commonly used mode connects the 744 toa single HART device in a 4 20 mA loop In Multi Drop mode several HART instruments can be bussed together The 744 searches for each identifies addresses in use and allows you to select the instrument for calibration and related operations In Burst Mode the HART instrument transmits bursts of data without waiting to be interrogated by a master unit The 744 can take transmitters out of burst mode during test or calibration then later restore them to burst mode Is there still a role for the communicator Commissioning a HART instru ment or modifying HART vari ables not supported by the 744 requires the use of a communi cator The 744 is designed to perform the vast majority of day to day operations you nor mally perform with a separate communicator The HART capa bility of the 744 is comparable to that of the model 275 HART communicator with the excep tion of the DD interpreter While the DD interpreter enables the 275 communicator to read com mand set libraries from any HART supplier it of
22. odifying the LRV Lower Range Value and URV Upper Range Value to compensate for Input Section error 7 In the case of a pressure transmitter that has on board Zero and Span adjust ment buttons calibration is easy Simply apply a cali brated source at the LRV and URV values and press the respective Zero and Span buttons on the transmitter Then verify the condition of the transmitter by complet ing an As Left test as in step 6 Many HART transmitters do not have physical adjust ments and need either a communicator or a Fluke 744 to adjust the LRV and URV values For those cases pro ceed to step 8 8 The error summary table displayed from step 6 pro vides the data necessary to make LRV and URV changes Write down the ERROR values for the failed 0 and 100 test points If the error summary table is no longer displayed you can use the Review Memory softkey to recall the As Left data Return the 744 to the normal Measure Source screen dis playing the As Left softkey by pressing the Done softkey 3 times 12 Fluke Corporation Hart Transmitter Calibration 9 Calculate the new LRV or URV by multiplying the span by the error in percent and adding that to the old value If our example has the fol lowing nominal Source val ues errors and old LRV and URV values Error Old LRV URV 0 Value 0 0 C 0 84 0 4 C 100 Value 100 0 C 2 41 102 0 C Table 2 Calculat
23. oop power supply Make basic connections to the 3144 per the diagram in Figure 10 Polarity of the HART communication connection is not important A separate 250 ohm resistor is not neces sary because the 744 incorpo rates a resistor in series with the 24V loop supply through its mA jacks The 3144 in this ex ample is configured for a type K thermocouple sensor with a span of 0 300 C Procedure 1 Power on the Fluke 744 Calibrator Press the red key followed by the Loop Power softkey Press to bypass the warning screens and the 744 will display the basic HART information for the 3144 Figure 11 Osf03 99 1200 45 pm Loop 24 HART Measure 3 990 mA source o 0 C 3144 Temp TTO023 PY 0 2 C PYAC 3 9900 mA PY LR O 0 C PY URY 300 0 C select operation for this device Abort Process Service Setup Figure 11 FLUKE 2 Press the key again and you are prompted to select the 744 configuration Fig ure 12 Selecting MEAS mA SOURCE T C typ K config ures the calibrator to mea sure the analog mA output of the transmitter and source the correct temperature stimulus at the 3144 input Selecting MEAS PV SOURCE T C typ K will configure the 744 to evalu ate the digital PV output from the transmitter Press to select TC Type K 100 0 C Int Ref 248 C _ ITS 90 _3 105mv As Step Save More 7 Found
24. or both sensor trim and output trim Adjusting range values LRV and URV without a calibrator is not calibration Performing an output trim while ignoring the input section is not proper calibration Adjusting range values with a calibrator may be a practical calibration alternative for instru ments operated in 4 20 mA analog mode provided that the PV and PVAO are not used for process control 4 20 mA Analog Input Conversion Output Analog Input Section digital Section digital Section mA Output input 4 20 mA JN JN J D4 DI v Sensor Trim LRV URV Adjust Output Trim Figure 1 Hart Transmitter Calibration FLUKE Model Number PV Primary Variable PVAO Digital representation of the Primary Variable Analog Output a FLUKE F7 eaten ele ster o Source 644 Temp TT 644 1 Analog Measure Value Analog Source Value PY 28 4 C 15 4440 MA PY LRV 0 0 C Tag ID PV LRV PV URV 40 0 C Select operation for this device Primary Variable Lower Range Value PV URV Primary Variable Upper Range Value Figure 2 New tool speeds calibration Today instrument maintenance is moving out of the shop and into the field This reduces pro cess interruptions and avoids the time and expense of return ing instruments to the shop Portable communicators and calibrators are often used to 3 Fluke Corporat
25. r adjustment of the 3144 Cass 0454 25 pr Loop 24 C SOURCE MEASURE ERROR O 0 C 3 900 m4 0 08 150 0 C 11 995 m4 0 04 300 0 C 20 006 m4 0 04 Prev Next Abort Page Page Dore Figure 16 10 Fluke Corporation Calibration of HART instruments using universal commands The 744 supports a majority of the installed workload of HART transmitters see Table 1 by supporting sensor trim which employs device specific com mands that are unique to a par ticular instrument So how can you calibrate instruments that are not supported by the 744 The short answer is that the 744 supports a substantial set of the universal HART commands and the common practice HART commands The 744 can com municate with virtually any HART instrument and in most cases can complete a calibration procedure except for sensor trim for unsupported instruments This example applies to instruments used in analog mode 4 20 mA If the instru ment is operated in digital mode i e its PV is the output variable that is used for control a calibration of the Input Section is all that is needed Adjustment will require a Sensor Trim see Figure 17 which means that for instruments not supported by the 744 you will need to use both a 744 to perform the As Found and As Left tests and record the results and a communicator to perform sensor trim For instruments used in ana log mode i e where the 4 20 mA analog output i
26. rated Note that this cali bration is independent of the input section and again has nothing to do with the zero and span settings Calibrating the input section The same basic multiple point test and adjust technique is employed but with a new defi nition for output To run a test use a Calibrator to measure the applied input but read the associated output PV with a communicator Error calculations are simpler since there is Hart Transmitter Calibration always a linear relationship between the input and output and both are recorded in the same engineering units In gen eral the desired accuracy for this test will be the manufacturer s accuracy specification If the test does not pass then follow the manufacturer s rec ommended procedure for trim ming the input section This may be called a sensor trim and typically involves one or two trim points Pressure transmit ters also often have a zero trim where the input calculation is adjusted to read exactly zero not low range Do not confuse a trim with any form of re rang ing or any procedure that in volves using zero and span buttons Calibrating the output section Again the same basic multiple point test and adjust technique is employed but with a new definition for input To run a test use a communicator to put the transmitter into a fixed current output mode The input value for the test is the mA value that you instruct the transmitter to pro
27. riate test tolerance 0 25 in this ex ample Verify that the 0 Value and 100 Value are the proper nominal operat ing values for the transmitter 0 0 C and 100 0 C in this example Figure 21 If the Lower 0 and Upper 100 Range Values LRV and URV have been previ ously modified for calibration purposes you will need to ENTER the nominal values For example if a previous calibration modified the URV to 100 2 C you need to manually ENTER the nomi nal value of 100 0 C for the 100 Value Entering nomi nal zero and span values ensures that errors are calcu lated correctly Dar ergg 05 00 09 pr Loop a4 Pa MEASURE 0 Value 4 000 mA 100 Value 20 000 ma Tolerance O25 Delay 105 SOURCE TC Type K 0 Value o 0 C 100 Value EE Test Strategy aft sd 04 29 49 pri Loop 244 imm Measure 20 002 mA TT Bad K Source 300 0 C Select calibrator mode of operation Cort change calibrator rode MEAS m SOURCE T C typ K MEAS PY SOURCE T C typ K Abort Figure 20 User Custom Abort Value Units Dore Figure 21 4 Press Done and then press Auto Test Once the test is complete an error summary table is displayed Figure 22 Test errors exceeding the tolerance are highlighted If the test passed i e if no errors are highlighted ad justment is not required 11 Fluke Corporation Hart Transmitter Calibration FLUKE
28. s 2 sets TP220 Test Probes 1 set BP7235 NiMH Battery Pack BC7217 Battery Charger serial port cable HART communications cable DPC TRACK Sample with free PC communication utility software Instruction Manual HART User s Manual NIST traceable calibration certificate and data three year warranty Optional Accessories Fluke 700 Pxx Pressure Modules Included with each Fluke Pressure Module BSP ISO to NPT Adapter s except with P29 P31 Instruction Sheet NIST traceable calibration report and data one year warranty Fluke 7JOOBCW Bar Code Wand Fluke 700PTP Pneumatic Test Pump 360 psi 25 bar Fluke 700TC1 TC Mini Plug Kit 9 types Fluke 700TC2 TC Mini Plug Kit JKTERS BE9005 Battery Eliminator BC7217 Battery Charger BP7217 NiCd Battery Pack BP7235 NiMH Battery Pack C700 Hard Carrying Case C781 Soft Carrying Case C789 Soft Carrying Case Hart Transmitter Calibration FLUKE o Fluke Keeping your world up and running Fluke Corporation PO Box 9090 Everett WA USA 98206 Fluke Europe B V ae PO Box 1186 5602 BD Eindhoven The Netherlands For more information call U S A 800 443 5853 or Fax 425 446 5116 Europe M East Africa 1 31 40 2 675 200 or Fax 1 31 40 2 675 222 Canada 1 800 36 FLUKE or Fax 905 890 6866 Other countries 1 425 446 5500 or Fax 1 425 446 5116 Web access http www fluke com 2004 Fluke Corporation All rights reserved Printed in U S A 12 2004 1262439 A US N R
29. s not electrically connected to a loop power sup ply Make basic connections to the 3051 per the diagram in Figure 4 Polarity of the HART communication connection is not important A separate 250 ohm resistor is not neces sary because the 744 incorpo rates a resistor in series with the 24V loop supply through its mA jacks The 3051 in this ex ample is configured for psi units Procedure 1 Power on the Fluke 744 Calibrator Press the red key followed by the Loop Power softkey and the 744 will display the basic HART information for the 3051 Figure 5 Tasos 023154 pm Loop 24 a Measure 4 484mA4 Source oft 3051 PF13579 3 PY 0 1530 psi PMAO 4 4670 mA PY LRY 0 0000 psi PY URY 5 0001 psi select operation for this device Abort Service Process Setup Figure 5 FLUKE 2 Press the key again and you are prompted to select the 744 configuration Figure 6 Selecting MEAS mA SOURCE psi will configure the calibrator to measure the analog mA output and the pressure being applied si multaneously to the trans mitter input and the pressure module Selecting MEAS PV SOURCE psi will configure the 744 to evaluate the digi tal PV output from the trans mitter Press to select 0an 5499 0236 05 pm Loop 24 id Measure 4 485 m P13579 3 Source ott select calibrator mode of operation Dort change calibrator mode MESS PY SOURCE psi Abort Figure 6 gt
30. s used for control the 744 can be used for calibration After performing an adjustment is required this example first performs an Output Trim to bring the instrument within tolerance Failing that the example performs an adjust ment to the Lower and Upper Range Values LRV and URV to compensate for input section error Note Appendix A explains that these adjust ments do not constitute a proper HART cali bration While this is true these adjustments are a practical calibration alternative for instruments operated in 4 20 mA analog mode if error corrections are not large How to determine digital or analog The transmitter is in digital mode if its HART Poll Address is set between 1 to 15 An address of O zero sets it to 4 20 mA analog output mode The 744 will automatically connect to a device at address 0 if a device FLUKE o is not found at O the 744 will begin polling addresses 1 to 15 The 744 also displays a non zero address with the basic HART information Basic connections This example assumes that the transmitter is isolated from the process and is not electrically connected to a loop power sup ply Make basic connections to the transmitter per the diagram in Figure 18 Polarity of the HART communication connec tion is not important A sepa rate 250 ohm resistor is not necessary because the 744 incorporates a resistor in series with the 24V loop supply through its mA jacks This ex ample ass
31. ssary and a final verification As Left test if an adjustment has been made Data from the calibration are collected and used to com plete a report of calibration documenting instrument per formance over time All instruments even HART instruments must be calibrated on a regular preventive main tenance schedule The calibra tion interval should be set short enough to insure that an in strument never drifts out of tolerance yet long enough to avoid unnecessary calibrations Alternatively the interval may be determined by critical pro cess requirements e g calibra tion before each batch FLUKE How are HART instruments properly calibrated To calibrate a HART instrument consistent with its application it is very helpful to understand the functional structure of a typical HART transmitter The article in Appendix A by Kenneth L Holladay of Southwest Research Institute describes a typical HART instrument and defines both proper and improper cali bration practices Originally published in Intech May 1996 it is reprinted with permission of the author Note If you are unfamiliar with HART calibration or need a review this is an excellent point to stop and read the article in Appendix A It covers the basics of HART instrumentation and addresses issues critical to instrument maintenance HART instruments consist of three distinct sections see Figure 1 Proper HART calibra tion may involve either
32. t you see The second box is strictly a mathematical conversion from the process variable to the equivalent milliamp representa tion The range values of the instrument related to the zero and span values are used in conjunction with the transfer function to calculate this value Although a linear transfer func tion is the most common pres sure transmitters often have a square root option Other special instruments may implement common mathematical transfor mations or user defined break point tables The output of the second block is a digital repre sentation of the desired instru ment output When you read the loop current using a communi cator this is the value that you see Many HART instruments support a command which puts the instrument into a fixed out put test mode This overrides the normal output of the second block and substitutes a specified output value The third box is the output section where the calculated output value is converted to a count value that can be loaded into a digital to analog con verter This produces the actual analog electrical signal Once again the microprocessor must rely on some internal calibration factors to get the output correct Adjusting these factors is often referred to as a current loop trim or 4 20 mA trim High and Low Range and High and Low Sensor Trim Transfer Function Output Trim A D D A Counts gt Counts As Counts Input Conversion Output
33. ture devices Loop test Manufacturer Service r Pressure Mote e Write protect zero trim HART Device HART ID Alarm state upu ih Information Software revision HART poll address e Hardware revision HART burst mode Sensor trim Number of preambles e HART burst command Abort Figure 3 No communicator is required The 744 requires no external box or communicator for every day HART calibration and main tenance It supports many popular models of HART trans mitters with more device specific command support than any other HART field calibrator 4 Fluke Corporation Hart Transmitter Calibration Interrogate HART devices to determine type manufacturer model tag ID PV and PVAO Perform automated HART sensor trim and output trim for selected devices Adjust ranging damping and other basic process configu ration settings data e Read and write HART tag and message fields to re label smart transmitters e Clone additional transmitters with basic HART configuration Versatile HART protocol support The 744 supports the commands contained in HART protocol ver sion 5 7 With 2 MB of memory the 744 supports a substantial set of HART instructions e Universal commands provide functions that are implemented in all field devices for example read manufacturer and device type read primary variable PV or read current output and percent of span Common practice com mands provide fu
34. umes a type K ther mocouple transmitter with an input range of 0 100 C 4 20 mA output and a 0 25 test tolerance As Found and determining that Foe 18 Analog Sensor Input PV Conversion PVAO Output 4 20 mA Analog Input Section digital Section digital Section mA Output input 4 20 mA J v yY v Sensor Trim LRV URV Adjust Output Trim Figure 17 Hart Transmitter Calibration Procedure 1 Power on the Fluke 744 Calibrator Press the key and the Loop Power softkey if loop power is not already supplied Press until any device warnings are cleared and the basic HART informa tion is displayed Figure 19 0arggr99 11 45 23 am Loop 24 im Measure 27 503 m Source Off 644 Temp TT 644 K PY 1465 1 C PYAC 21 5000 m PY LARW 0 0 C PY URY 100 0 C Select operation for this device Abort Service Setup Process Figure 19 2 Press the key again and you are prompted to select the 744 configuration Figure 20 Move the cursor to MEAS mA SOURCE T C typ K and press f If you were verifying the digital PV instead of the mA output i e the transmitter has a non zero HART poll address you would select MEAS PV SOURCE T C typ K instead Press the As Found softkey and press fe to select Instrument calibration Move the cursor to Tolerance and ENTER the approp
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