sysrsn [iii-`P51
Contents
1. 340 825 07 bo Hung pes 4 749 993 A 6 1988 Szabo et al 340 870 31 C Tee ei ego 25009 An SS s S s us 6 574 515 6 2003 Kirkpatrick et al 700 19 4 860 232 A 8 1989 Leeetal 364 57 1 04 2075 OS pa s Ael 6 593 857 Bl 7 2003 Roper et al 340 870 3 d os As SSO pr 6 609 427 8 2003 Westfield et al 73 153 A CEA PD Ph e 200 6 662 662 Bl 12 2003 Nord et al 73 715 oS A 6 680 690 Bl 1 2004 Nilsson et al 342 124 4 977 480 X 12 1990 Nishihara 73 724 6 711 446 B2 3 2004 Kirkpatrick et al 700 19 dodge UO Con s DNE ae 6 747 573 6 2004 Gerlach et al 340 870 21 poA SIAO 6 765 968 Bl 7 2004 Nelson et al 44 375 257 5 045 963 A 9 1991 Hansen et al 361 87 d o Ton A 5 060 295 A 10 1991 Borras et al 455 186 CS NND ROC a DO 3107870 07 5 094 109 A 3 1992 Dean et al 73 718 9 CMP DS aac 6 792 259 B1 9 2004 Parise 455 343 1 5 168 419 A 12 1992 Delatorre 361 283 reer Hedtke Ed n 5 194 819 A 3 1993 Briefer 73 718 9465 E es 5230250 A 7 1993 Delatorre 73 733 6 898 230 B21 3 2005 Behri et al z 06 5 233 875 A 8 1993 Obermeier et al 73 718 Sod BS 5 222425 345 107 S 3 1994 Williams D10 46 Falo eor 60508 5 329 818 A 7 1994 Frick et al lt 73 708 6661 553 B3 Sid 5 492 016 A 2 1996 Pinto et al 73 7242. BACKGROUND OF THE INVENTION The present invention relates to industrial process control or monitoring systems More specifically the present inven tion relates to field devices in such systems which are capable of Radio Frequency RF communication In industrial settings control systems are used to monitor and control inventories of industrial and chemical processes and the like Typically the control system performs these functions using field devices distributed at key locations in the industrial process and coupled to the control circuitry in the control room by a process control loop The term field device refers to any device that performs a function in a distributed control or process monitoring system including all devices currently known or yet to be known used in the measurement control and monitoring of industrial processes Some field devices include a transducer A transducer is understood to mean either a device that generates an output signal based on a physical input or that generates a physical output based on an input signal Typically a transducer trans forms an input into an output having a different form Types of transducers include various analytical equipment pressure sensors thermistors thermocouples strain gauges flow transmitters positioners actuators solenoids indicator lights and others Typically each field device also includes communication circuitry that is used for communicating with
3. 4 The apparatus of claim 1 wherein the wireless commu nication circuitry includes a resistor coupled in series with the two wire process control loop 5 The apparatus of claim 1 including a battery configured to power the wireless communication circuitry 6 The apparatus of claim 1 wherein the wireless commu nication circuitry includes two wire loop communication cir cuitry configured to communicate on the two wire communi cations loop 7 The apparatus of claim 1 wherein the wireless commu nication circuitry includes HART communication circuitry 20 25 30 35 40 45 50 55 65 12 8 The apparatus of claim 1 wherein the wireless commu nication circuitry includes intrinsic safety protection cir cuitry 9 The apparatus of claim 1 wherein the wireless commu nication circuitry includes an analog to digital converter con figured to provide a digital representation of current flowing through the two wire process control loop 10 The apparatus of claim 8 wherein the RF signal is based upon the sensed current 11 The apparatus of claim 1 wherein the wireless commu nication circuitry includes a microprocessor 12 The apparatus of claim 1 wherein the wireless commu nication circuitry includes a memory containing addressing information 13 The apparatus of claim 1 wherein the wireless commu nication circuitry includes an antenna 14 The apparatus of claim 1 wherein the wireless commu nication circu
4. 52 from microprocessor 224 Both the circuit 230 and the RF circuit 232 are configured to communicate with the microprocessor 224 on an SCI bus depending on which chip select is active Microprocessor 224 is also configured to provide a shut down signal to operational amplifier 222 Microprocessor 224 includes a memory 236 which is used for storing programming instructions temporary and permanent variables and other information and may include both volatile and non volatile memory The memory can include for example an EEPROM and can contain addressing informa tion which uniquely identifies circuitry 170 RF circuit 232 couples to an antenna 240 which can be configured as an internal antenna external antenna or combination as desired Circuitry 170 is configured to couple across the two wire process control loop 156 such that the loop 156 can terminate at another field device such as a process transmitter or process controller The circuitry 170 illustrated in FIG 7 can be implemented on a single printed circuit board such that RF antenna 240 is formed integral with the board This configuration allows the circuitry 170 to be easily implemented in existing field devices and does not require the use of an external antenna This reduces installation complexity The optional HART transmit receive circuit 230 be used to monitor digital signals such as a process variable carried on the process control loop 156 Based
5. 11 nique The power supply circuitry is configured as desired and is not limited to the configurations set forth herein In some embodiments the field device includes an address which can be included in any RF transmissions such that the device can be identified Similarly such an address can be used to deter mine if a received signal is intended for that particular device However in other embodiments no address is utilized and data is simply transmitted from the wireless communication circuitry without any addressing information In such a con figuration if receipt of data is desired any received data may not include addressing information In some embodiments this may be acceptable In others other addressing techniques or identification techniques can be used such as assigning a particular frequency or communication protocol to a particu lar device assigning a particular time slot or period to a particular device or other techniques Any appropriate com munication protocol and or networking technique can be employed including token based techniques in which a token is handed off between devices to thereby allow transmission or reception for the particular device Although the present invention has been described with referenceto preferred embodiments workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention As used herein Radio Frequency
6. 7 2003 9 2003 5 2008 9 1978 5 1985 6 1990 5 1996 10 1998 7 2001 10 2001 3 2002 5 2002 11 2005 2 1991 1 1993 Wireless R amp D Aims to Boos Traffic by M Moore InTech with Industrial Computing Feb 2002 pp 40 41 System Checks Farawy Machines Health by J Strothman In Tech with Industrial Computing Feb 2002 pp 42 43 Notification of Transmittal of the International Search Report or the Declaration PCT US03 10403 Wireless Management Toolkit XYR 5000 by Honeywell Interna tional Inc Phoenix Arizona 3 pgs Oct 2003 Wireless Analog Input Transmitters XYR 5000 by Honeywell International Inc Phoenix Arizona 4 pgs Oct 2003 Quad Analog Output Module Installation and User s Manual by Honeywell International Inc Phoenix Arizona pp Ii iii iv and 1 12 Dec 2003 International Search Report and Written Opinion of Application No PCT US2005 015848 file May 5 2005 Wireless Dual Analog Input Interface Transmitter Installation and User s Manual by Honeywell International Inc Phoenix Arizona pp Ii vi and 7 43 Dec 2003 5000 Wireless Dual Analog Input Interface Model Selection Guide by Honeywell International Inc Phoenix Arizona Dec 2003 Wireless Measure Monitor amp Control by Accutech 4 pgs May 2003 Wireless Instrumentation Multi Input Field Unit by Accutech 2 pgs Dec 2003 Quad Analog Output Module by Accutech 1 pg D
7. requires power which is within the power constraints avail able in the field device For example one display currently used within field devices uses 3 6 volts at 0 5 mA If a trans mitter which is capable of operating an LCD meter is employed the wireless communication circuitry can replace the LCD meter and use the same power source that is used to drive the LCD meter In another example the wireless com munication circuitry is powered directly from the process control loop for example using the voltage developed across a diode drop connected in series with the process control loop Inembodiments in which no battery is used with the commu nication circuitry the circuitry can more easily meet intrinsic safety or other safety approval requirements and provide an indefinite field life without battery replacement or mainte nance In configurations in which the wireless configuration is only for sending information power requirements can be reduced In another example ifa greater transmission range is desired a stationary device such as display 32 as illustrated in FIG 1 can include an RF repeater for re transmission of data received from or sent to a field device The RF repeater can be loop powered or can derive its power from other sources Further once the RF data is received it can be reformatted for transmission over other medium for example an Ethernet connection into existing data transmission structures used within process
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10. OTHER PUBLICATIONS US 2007 0285224 A1 Dec 13 2007 Office Action from Russian Patent Office in Russian Serial No 2006145434 Related U S Application Data Continued 63 Continuation of application No 10 878 235 filed on Jun 28 2004 now Pat No 7 262 693 Primary Examiner Donnie L Crosland 51 Int Cl 74 Attorney Agent or Firm Westman Champlin amp 040 11 04 2006 01 Kelly P A G08B 29 00 2006 01 G08B 1 08 2006 01 57 ABSTRACT 52 0 8 340 538 340 508 340 506 340 539 1 67 700 9 A field device for use in an industrial process control or 58 Field of Classification Search 340 538 monitoring system includes terminals configured to connect _ 340 508 toatwo wire process control loop The loop carries data and See application file for complete search history provides power to the field device RF circuitry in the field device is provided for radio frequency communication A 56 References Cited power supply powers the RF circuitry using power received from the two wire process control loop U S PATENT DOCUMENTS 2 533 339 A 12 1950 Willenborg 177 311 2 883 489 A 4 1959 Eadie Jr et al 335 148 97 Claims 6 Drawing Sheets US 7 956 738 B2 Page2 U S PATENT DOCUMENTS D439 181 S 3 2001 Fandrey et al D10 46 4 177 496
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13. current level carried on the two wire process control loop 88 The method of claim 78 wherein the RF signal carries information related to a digital signal carried on the two wire process control loop 89 The method of claim 78 including completely power ing RF circuitry with power from the two wire process control loop 90 The method of claim 78 including storing addressing information in a memory 91 The method of claim 78 including placing RF circuitry in a sleep mode during idle periods 92 The method of claim 78 including providing a bi directional HART to RF gateway 93 The method of claim 78 including transmitting an RF signal related to a process variable 94 The apparatus of claim 78 wherein the RF signal includes error correction information 95 The apparatus of claim 78 wherein the RF signal is in accordance with a topology selected from the group of topologies consisting of point to point spoke and hub and mesh topologies 96 The apparatus of claim 78 including providing a shunt element configured to shunt electrical current from the two wire process control loop 97 The apparatus of claim 78 including regulating power with a switch mode voltage regulator
14. generally in the position shown for wireless com munication circuit 22 in FIG 3 In such a configuration the wireless communication circuit 22 can be used in place ofthe local display In such a configuration the communication wireless circuitry 22 simply transmits an RF signal which couples directly to the process control loop 16 and transmits an RF signal which corresponds to any analog and or digital signals carried on the loop 16 In general the process control loop discussed herein can comprise any type of process control loop for use in industrial process control and monitoring systems Such loops include 4 20 mA current loops in which a analog current level is varied between 4 and 20 mA to transmit information The same control loop can be used to provide power to the field device Another type of process control loop is in accordance with the HART communication protocol in which digital transmissions are superimposed on the 4 20 mA signal for transmission of additional information Another example two wire process control loop uses a protocol set forth by the Instrument Society of America ISA which is called the Field Bus SP50 protocol However end signaling protocol can be used Some process control loops are configured to connect to multiple field devices such that the field devices can commu nication one another or monitor transmissions from another field device In general any type of information transmitted on such process c
15. power received from the two wire process control loop and power supply circuitry configured to use power from the electrical charge stored on the energy storage capacitor to power the RF circuit 59 The apparatus of claim 32 wherein the RF circuit is carried on a modular circuit board configured to mount to the field device the process variable transmitter 60 The apparatus of claim 32 including an explosion proof housing configured to enclose the RF circuit 61 The apparatus of claim 60 wherein the explosion proof housing includes anintegral RF transparent region in the housing configured to allow RF transmission therethrough 62 The apparatus of claim 61 wherein the RF transparent region comprises glass 63 The apparatus of claim 61 wherein the RF transparent region comprises plastic 64 The apparatus of claim 32 including a circuit board configured to carry the RF circuit and an RF antenna coupled to the RF circuit and carried on the circuit board 65 The apparatus of claim 32 including a HART module coupled to the RF circuit configured to operate as a bi direc tional HART to RF gateway unit 66 The apparatus of claim 32 wherein the RF circuit is configured to transmit an RF signal related to a process vari able 67 The apparatus of claim 32 including a directional antenna coupled to the RF circuit 68 The apparatus of claim 32 wherein the RF signal includes error correction information 69 The app
16. 07 McLaughlin 370 389 2007 0275755 Al 11 2007 Chaeetal 455 557 OTHER PUBLICATIONS 20070280178 Al 12007 Hodson etal 330338 Oficial Communication in Application 2006 145434 filed 2007 0280286 Al 12 2007 Hodson etal 370 466 5 2005 2007 0280287 Al 2007 0282463 1 2007 0285224 1 2007 0288204 1 2008 0010600 1 2008 0280568 1 2008 0310195 1 2009 0015216 1 2009 0081957 1 2009 0146502 1 2009 0253388 1 2009 0309558 1 2009 0311975 1 2009 0311976 1 2009 1311971 2010 0000316 1 CN CN CN DE DE DE DE DE DE DE DE DE DE EP EP 12 2007 12 2007 12 2007 12 2007 1 2008 11 2008 12 2008 1 2009 3 2009 6 2009 10 2009 12 2009 12 2009 12 2009 12 2009 1 2010 370 466 700 20 Samundrala et al Hodson et al Karschnia et al 340 538 Gienke et al 702 188 Katano 715 748 Kielb et al 455 74 1 Seberger et al 363 26 Seberger et al 323 234 Sinreich 2 455 68 Sinreich 307 104 Kielb et al 455 117 Kielb essen 323 234 Vanderaa et al 455 90 3 3 455 74 1 RS 73 295 Vanderaa et al Kielb et al Fehrenbach et al FOREIGN PATENT DOCUMENTS 1429 354 1442822 100386602 2710211 3340834 38 42 379 196 22 295 37 11 754 201 07 112 10104 582 100 41 160 102 21 931 10 2004 020393 0 518916 0 524 550 A A C Al Al Al Ul Al Al Bl Al
17. 8 First Office Action from Chinese Patent Application No 2005800142124 dated Mar 14 2008 Notification of Transmittal of the International Search Report and Written Opinion PCT US2009 0036616 dated Jan 13 2010 Notification of Transmittal of the International Search Report and the Written Opinion of the International Searching Authority for PCT US2008 011451 filed Oct 3 2008 date mailed Mar 30 2009 16 pages The International Search Report and Written Opinion in Application No PCT US2009 003636 dated Oct 6 2009 The International Search Report and Written Opinion in Application No PCT US2009 003611 dated Nov 4 2009 The International Search Report and Written Opinion in Application No PCT US2009 003621 dated Sep 30 2009 Third Office Action for Chinese Application No 200680015575 4 dated May 11 2010 Communication for European Application No 06774208 0 dated Apr 16 2010 Second Office Action for Chinese Application No 2006800155754 dated Sep 25 2009 Official Action for Russian Application No 2008103014 First Office Action for Chinese Application No 200680015575 4 dated 2008 Communication for European Application No 06774208 0 dated Feb 29 2008 First Office Action for Japanese Application No 20008 518521 dated Aug 24 2010 Notification of Transmittal of the International Search Report and the Written Opinion for the international patent application no PCT US2010 047463 da
18. A 12 1979 Bell et al s 361 283 UE gt stalo De 236 getal 2 257 419 ao 2 po UA 6236334 Bl 5 2001 Tapperson et al 340 825 37 4 322 775 A 3 1982 Delatorre 361 283 M gzon Ar 133007 d os Pd 6 338 283 BI 1 2002 Blazquez Navarro 73 865 8 4320890 cis ud EIS 6 360 277 3 2002 Ruckley et al 709 250 370 v 6 366 436 BL 4 2002 Maier et al 361 03 2 d 2580 E 22 6 385 972 Bl 5 2002 Fellows 2 60 517 4 422 125 12 1983 Antonazzi et al 361 283 624 B 2225 PE OU al c unns dues 429 ansemir et al 340 870 27 4 422 335 A 12 1983 Ohnesorge et al 73 724 6 441 747 Bl 8 2002 Khair et al o 340 870 16 4 434 451 A 2 1984 Delatorre 361 283 6 457 367 10 2002 Behm et al 73 753 4 455 874 A 6 1984 Paros 73 704 6 484 107 Bl 11 2002 Roper et al 702 50 pars A TSS Bel by al e 6487912 12 2002 Behm et al 222222222222 73 753 4 476 853 10 1984 Arbogast 126 578 PM B AME HRAS 4 490 773 A 12 1984 Moffatt 361 283 f THUS 4 542436 A 9 1985 Carusillo 361 283 BiU ions 502350 4 562 742 A 1 1986 Bell 73 718 D471 829 S 3 2003 Dennis al D10 85 4 590 466 A 5 1986 Wiklund et al 340 870 28 D472 831 lt 4 2003 Dennis et al D10 85 PE K Pell E 6 546 805 B2 4 2008 Fandrey et al 73 753 4 704 607 A 11 1987 Teather et al
19. RF can comprise electro magnetic transmissions of any frequency and is not limited to a particular group of frequencies range of frequencies or any other limitation Any communication protocol can be used as desired including IEEE 802 1 1b 802 154 or other protocols including proprietary communication protocols What is claimed is 1 A process control transmitter for monitoring a process variable in an industrial process comprising a process variable sensor configured to sense the process variable I O circuitry configured to couple to a two wire process control loop and communicate on the process control loop wireless communication circuitry coupled to the two wire process control loop configured to transmit an RF signal and power supply circuitry coupled to the two wire process control loop including a voltage regulator the power supply circuitry electronically connected in series with the process control loop the voltage regulator config ured to receive a voltage drop and responsively provide a regulated voltage output to power the wireless com munication circuitry 2 The apparatus of claim 1 including a terminal block configured to electronically connect to the two wire process control loop and wherein the wireless communication cir cuitry couples to the terminal block 3 The apparatus of claim 1 wherein the wireless commu nication circuitry is completely powered with power from the two wire process control loop
20. United States Patent US007956738B2 12 10 Patent No US 7 956 738 B2 Karschnia et al 45 Date of Patent Jun 7 2011 54 PROCESS FIELD DEVICE WITH RADIO 3 012 432 A 12 1961 Moore etal 73 40 FREQUENCY COMMUNICATION 3 218 863 A 11 1965 Calvert 73 398 3 232 712 2 1966 Stearns 23 255 3 249 833 5 1966 Vosteen 317 246 75 Inventors Robert J Karschnia Chaska MN 3374112 A 3 1968 Danon 7 117 226 US Charles R Willcox Eden Prairie 3 557 621 V 1971 Ferran m 73 398 MN US David A Broden Andover 3 612 851 A 10 1971 Fowler 362 30 MN US Brian L Westfield Victoria 3 697 835 A 10 1972 Satori 317 246 D225 743 S 1 1973 Seltzer D10 102 MN US Kelly M Orth Apple Valley 3 742 450 A 6 1973 Weller 375 257 05 3 808480 4 1974 Johnston 2 317 256 3 924 219 A 12 1975 Braun 338 34 73 Assignee Rosemount Inc Eden Prairie MN US 4 008 619 A 2 1977 Alcaide et al 73 398 4 158217 6 1979 Bell 361 283 Notice Subject to any disclaimer the term of this 4 168 518 A 9 1979 Lee sse 361 283 patent is extended or adjusted under 35 Continued U S C 154 b by 806 days FOREIGN PATENT DOCUMENTS 21 Appl 11 842 356 CH 672368 AS 11 1989 22 Filed Aug 21 2007 Continued 65 Prior Publication Data
21. a process con trol room or other circuitry over a process control loop In some installations the process control loop is also used to deliver a regulated current and or voltage to the field device for powering the field device The process control loop also carries data either in an analog or digital format Traditionally analog field devices have been connected to the control room by two wire process control current loops with each device connected to the control room by a single two wire control loop Typically a voltage differential is maintained between the two wires within a range of voltages from 12 45 volts for analog mode and 9 50 volts for digital mode Some analog field devices transmit a signal to the control room by modulating the current running through the current loop to a current proportional to the sensed process variable Other analog field device can perform an action under the control of the control room by controlling the mag nitude ofthe current through the loop In addition to or in the alternative the process control loop can carry digital signals used for communication with field devices In some installations wireless technologies have begun to be used to communicate with field devices For example completely wireless installations are used in which the field device uses a battery solar cell or other technique to obtain power without any sort of wired connection However the majority of field devices are ha
22. amount of voltage that can enter this circuit in an intrinsic safety protected system Similarly the sense resistor 180 can beused to limitthe maximum current that can enter the circuit 170 and snub any discharge of stored energy from the circuit through its external terminals This provides an equivalent capacitance of substantially zero The loop measurement cir cuitry is further protected by two intrinsic safety rated high value resistors 194 connected between the two ends of the sense resistor 180 and the filter 220 Other circuit components can be protected from any outside energy sources by the use of potting material or the like which also prevents hazardous gases and vapors from reaching any internal storage elements and nodes in the circuitry 170 For other non hazardous loca tions intrinsic safety components may not be required The term field device as used herein can be any device which is used in a process controller monitoring system and does not necessarily require placement in the field The device can be located anywhere in the process control system including in a control room or control circuitry The terminals used to connect to the process control loop refer to any elec trical connection and may not comprise physical or discrete terminals Any appropriate radio frequency communication circuitry can be used as desired as can any appropriate com munication protocol frequency or communication tech US 7 956 738 B2
23. aratus of claim 32 wherein the RF signal is in accordance with a topology selected from the group of topologies consisting of point to point spoke and hub and mesh topologies US 7 956 738 B2 15 70 The apparatus of claim 32 including a digital chip responsive to a chip select signal 71 The apparatus of claim 32 including a shunt element configured to shunt electrical current from the two wire pro cess control loop 72 apparatus of claim 32 including loop communica tion circuitry coupled to the third electrical connection 73 The apparatus of claim 72 including a microprocessor coupled to the loop communication circuitry 74 The apparatus of claim 73 wherein the microprocessor is coupled to the RF circuit 75 The apparatus of claim 32 including power supply circuitry connected in series with the first and second electri cal connections 76 The apparatus of claim 75 wherein the power supply circuitry includes a linear voltage regulator 77 apparatus of claim 75 wherein the power supply circuitry includes a switch mode voltage regulator 78 method for RF communicating with a two wire pro cess control loop comprising connecting first and second electrical connections in series to the two wire process control loop and a field device connecting a third electrical connection to the field device allowing electrical current from the two wire process con trol loop to flow from the first connection throu
24. at field device An optional user input 48 can be used to for example select the format of the display the process variable dis played or used to interrogate a field device 14 FIG 3is a simplified cutaway partially exploded view ofa pressure transmitter 60 which is one example ofa field device Pressure transmitter 60 couples to two wire process control loop 16 and includes a transmitter housing 62 Process control loop 16 couples to terminals 56 carried on terminal board 58 pressure sensor 64 provides one example of a transducer and is configured to couple to a process fitting to measure a differential pressure occurring in a process fluid The output from the sensor 64 is provided to measurement circuitry 66 which couples to field device circuit 68 The field device circuit 68 implements aspects of the I O power supply 18 shown in FIG 1 The wireless communication circuitry 22 couples to field device circuit 68 and may in some embodi ments couple to process control loop 16 The housing 62 includes end caps 70 and 72 which can be screwed into the housing 62 End cap 72 includes an RF transparent window 74 configured to align generally with an antenna 26 carried on wireless communication circuit 22 When attached the end caps provide a intrinsically safe enclosure for circuitry within transmitter 60 The materials typically used in end caps for example metal are not trans parent to RF signals However RF transparent window 74 al
25. con figured to mount to a main housing and wherein the end cap includes the RF transparent region 23 The apparatus of claim 1 including a circuit board configured to carry the wireless communi cation circuitry and an RF antenna coupled to the wireless communication circuitry and carried on the wireless communication circuit board 24 The apparatus of claim 19 wherein the wireless com munication circuitry is integral with a terminal block which carries the terminals 25 The apparatus of claim 1 wherein the wireless commu nication circuitry is configured to transmit an RF signal related to an analog current level carried through the process loop 26 The apparatus of claim 1 wherein the wireless commu nication circuitry is configured to transmit an RF signal related to a digital signal carried by the process control loop US 7 956 738 B2 13 27 The apparatus of claim 1 including a HART module coupled to the wireless communication circuitry configured to operate as a bi directional HART to RF gateway unit 28 The apparatus of claim 1 wherein the wireless commu nication circuitry is configured for periodic communication 29 The apparatus of claim 1 wherein the wireless commu nication circuitry is configured to transmit an RF signal related to a process variable 30 The apparatus of claim 1 wherein the voltage regulator comprises a linear regulator 31 The apparatus of claim 1 wherein the voltage regulator compr
26. control systems over an extended range communication link such as a cell phone or relaying using another technique FIG 4 is a simplified diagram of a process controller or monitoring system 100 which illustrates another aspect ofthe present invention In system 100 a field device 14 connects to a control system 12 through process control loop 16 through junction box 102 In the embodiment of FIG 4 a field device 104 couples to the process control loop 16 and includes wire less communication circuitry 122 The wireless communica tion circuitry 122 is configured to send an RF signal 106 and to becompletely powered by power received from the process control loop 16 Process device 104 includes a power regulator 110 a shunt or bypass 112 and a super capacitor 114 During operation the super capacitor 114 is slowly charged trickle charged using a power regulator 110 by using excess voltage tapped 20 25 30 35 40 45 50 55 60 65 6 from the process control loop 16 The bypass 112 allows loop 16 to operate normally and is connected in series with loop 16 Communication circuit 122 includes circuitry for receiv ing information analog and or digital information carried on process control loop 16 The circuit 122 can responsively transmit an RF signal 106 based upon the received informa tion If operated as a receiver circuitry 122 is capable of modulating data onto the electrical current carried in the l
27. cted at opposed ends of sense resistance 180 Diode 182 is part ofa power supply 196 which includes capacitor 198 input filter 200 regulator 202 capacitor 204 and secondary filter 206 Secondary filter 206 includes capacitor 208 and resistor 210 The power supply circuitry 196 generates a power supply voltage V pp relative to a circuit ground for use by circuitry in measuring the loop current and wirelessly transmitting a resultant signal Although a specific power supply implementation is shown any appropriate power supply configuration or embodiment may be used as desired In this embodiment input circuitry 218 includes sense resistance 180 and is configured to measure the current I flowing through loop 156 Input circuitry 218 also includes a filter 220 which provides a differential connection to an OP amp 222 The OP amp provides an amplified input signal to an analog to digital converter 226 which is illustrated as part of a microprocessor 224 A clock circuit 228 is provided and used to provide a clock signal to for example microprocessor 222 Optional HART transmit and receive circuit 230 nects to microprocessor 224 loop 156 clock circuit 228 and an RF transmit receive circuit 232 The optional HART circuit 230 is configured to receive a digital chip select signal CS1 from microprocessor 224 The RF circuit 232 is con 0 20 40 45 60 65 8 figured to receive a separate digital chip select signal
28. diagram of circuitry for pro viding wireless communications ina process controller moni toring system DETAILED DESCRIPTION The present invention provides a field device configured to couple to a process control loop which further includes a wireless communication module for one way or bi direc tional wireless communication The wireless communication module can transmit and or receive an RF signal from a remote device or location The module can be directly pow ered with power received from the two wire process control loop orcan be powered with power received from the process control loop and stored for subsequent use The module can bea removable module in which the module need only couple to those field devices in which wireless communication 18 desired FIG 1 is a simplified block diagram of a process control or monitoring system 10 in which a control room or control system 12 couples to a field device 14 over a two wire process control loop 16 The field device 14 includes I O power cir cuitry 18 actuator transducer 20 and wireless communica tion circuitry 22 The wireless communication circuitry 22 is configured to send and or receive an RF signal 24 using an antenna 26 Currently industrial instrumentation often includes a local display or meter which can be used for local monitoring of process information The meter can be quite useful in many installations however such alocal display configuration does have several lim
29. e formed integral with the circuitry 170 for example in the form of traces routed around an outside edge of a circuit board The RF circuitry 232 can in some embodi ments include a wireless receiver such that the circuitry 232 can be configured as a transceiver The same antenna 240 can be used for both transmission and reception if desired A typical low powered transceiver may have a communication 20 25 30 35 40 45 50 55 60 65 10 range ofabout 200 feet however other ranges can be achieved using different power requirements circuit sensitivity antenna configuration and the like If the circuitry 170 is mounted in a metal enclosure such as a field housing com partment of a transmitter an RF transparent portion of the housing should be used to allow transmission and reception of signals from antenna 240 For example as discussed above a glass window can be used Other example materials include any material which is sufficiently transmissive to RF signals including plastic or other materials The addition of the optional HART circuitry 230 allows the circuitry 170 to selectively listen to a HART message on the 4 20 mA signal carried on the current loop 156 Informa tion such as measured process variables diagnostic informa tion or other information can be transmitted to a wireless receiver Further ifthe HART circuitry 230 is configured to modulate a digital signal onto the process control loop
30. e microprocessor can enable the measurement of the loop current by the A D converter The measurement circuitry is allowed to settle before the A D conversion occurs After the A D conversion is completed both the loop measurement circuitry and the A D converter are turned off to conserve power The microprocessor passes the measured value to the RF circuitry 232 for transmission Uponcompletion ofthe transmission the microprocessor and RF circuitry return to the low power mode until the next cycle The microprocessor may even put itself to sleep temporarily to save power Using these power management techniques the microprocessor is able to manage overall current require ments of the circuit by staggering the load demands on the regulator stage Loop current measurement is achieved using the 10 ohm sense resistor 180 coupled in series with the 4 20 mA current loop 156 to measure the analog current level The voltage developed across the sense resistor 180 is filtered to remove fluctuations due to HART digital communications as well as any loop noise operational amplifier stage 222 pro vides further signal conditioning and the signal is passed to the A D converter 226 of microprocessor 224 The RF circuitry 232 can be any appropriate circuitry or configuration as desired In one simple form the RF circuitry 232 simply transmits a measured variable to a wireless receiver The antenna 240 can be used to broadcast the RF signal and can b
31. e process control loop This can be particu larly beneficial in hazardous locations where explosive gases or vapors may be present digital or analog process variable can be sensed by the wireless communication circuitry and transmitted to a wireless meter or hand held device as dis cussed above During operation circuit 170 15 placed in series with the process control loop 156 where it utilizes the 4 20 mA current flowing through the loop to power itself For field devices that employ a common electrical ground circuitry 170 can be inserted on the high voltage side ofthe loop connection This configuration allows access to other bus circuitry within the field device such as a CAN interface The configuration includes a test connection 186 for use in measuring loop current during testing The sense resistance 180 is preferably configured to provide an equivalent of capacitance of zero as US 7 956 738 B2 9 measured at terminals 181 which connect to loop 156 in accordance with intrinsic safety standards Circuitry 170 is configured for nominal operation at between 3 and 4 volts and the zener diode 182 along with sense resistance 180 sets this operating voltage The excess voltage available on typical 4 20 mA current loop is sufficient to operate circuitry 170 Further power management techniques can be employed to limit the current drawn from the loop to about 3 mA This allows any field device connected to the process control loop to s
32. ec 2003 3 Pages from Website www chemicalprocessing com Apr 2004 Notification of Transmittal ofthe International Search Report and the Written Opinion PCT US2005 021757 International Search Report for International Application No PCT US 03 27561 filed Mar 9 2003 dated Jun 15 2004 US 7 956 738 B2 Page4 2002 Microchip Technology Inc Stand Alone CAN Controller with SPI Interface pp 1 75 Mar 1 2002 Rosemount Reference Manual 00809 0100 4022 Rev AA Jul 2002 Model 4600 Oil amp Gas Panel Transmitter 65 pages Transmitter Schematic Sold Jul 2002 5 pages Notification of Transmittal of the International Search Report and the Written Opinion of the International Searching Authority for Inter national Application No PCT US2005 007328 filed Mar 7 2005 Date of Mailing Jan 12 2006 4 Pages from Website http content honeywell com imc eznews eznews0403 news htm 2004 Notification of Transmittal of the International Search Report and the Written Opinion of the International Searching Authority for Inter national Application No PCT US2006 025206 filed Jun 27 2006 Mechatronic Drives in Mobile Hydraulics Internet Article Soncebox News No 4 Oct 2004 International Search Report and Written Opinion in No US2005 021757 filed Jun 21 2005 International Search Report and Written Opinion in Application No PCT US2006 035728 filed Sep 13 2006 Examination
33. endan alarm level signal of 3 6 mA without collapsing the circuit by drawing more than the available current level Zener diode 182 acts as a shunt element which is placed in series with the loop 156 to develop a preregulated voltage on the input filter stage Any portion ofthe loop current which is not used by circuitry 170 is shunted through zener diode 182 The input filter 200 can comprise capacitive inductive and resistive elements and is used to isolate the loop from any noise or load fluctuation generated by circuitry 170 This also suppresses noise in the HART extended frequency band in order to conform with HART standards The voltage regulator 202 can be any appropriate voltage regulator such as but not limited to linear or switch mode regulators and is used to supply the voltage V pp to the cir cuitry Filter 206 is used to store energy and further decouples circuit loads from the regulator 202 The output voltage ofthe secondary filter 206 is allowed to sag by several hundred millivolts during circuit load changes This allows peak cur rent draws by the circuitry 172 to be averaged from the 4 20 mA current loop Inthis embodiment the microprocessor 224 including A D converter along with the RF circuitry 232 and input circuitry 218 can be placed into a sleep mode or low power mode during periods of idle operation in order to reduce power drain For example at a selected interval such as every 10 seconds an internal timer in th
34. g super capacitor 114 in greater detail In this example super capacitor 114 comprises two 10 Farad capacitors con figured to each carry a 2 5 volt potential This yields an equivalent capacitance of 5 farads witha 5 volt potential drop Assuming that the wireless communication circuit 122 is capable of operating at a voltage of between 4 and 5 volts the available energy from each of the 5 Farad capacitors is Y2 C V V 2 which is 2 5 57 47 22 5 FIG 6 is a graph of voltage versus time measured across super capacitor 114 In this example 600 mW wireless trans mitter which transmits a burst signal for a period of t of 1 second will require 0 6J S 1s 0 6J of energy Thus there is ample energy available for operation of such a communica tion circuit 122 A typical power supply used to provide power to a process control loop provides 24 volts DC However in a 4 20 mA system a transmitter may only require 12 volts to operate Wiring losses in the process control loop may cause 2 to 4 volts of voltage drop Assuming only 5 volts is available for charging the super capacitor 114 and that the process control loop is operating at a low current level 1 e 4 mA there is still 20 mW available to charge the super capacitor 114 Because only 0 6 J was consumed during the transmit cycle the available 20 mW will charge the super capacitor to full capacity ina time t 0 6J 0 02 W 30s Therefore such a con figuration will be capable of transm
35. gh the second connection and through the electrical third con nection to the field device transmitting RF signal which contains information related to data carried on the two wire process control loop 79 method of claim 78 wherein the transmitting an RF signal comprises transmitting RF data as a function of infor mation received from the two wire process control loop in accordance with the HART protocol 80 The method of claim 78 wherein the transmitting com prises digital communicating 81 The method of claim 78 wherein the transmitting com prises analog communicating 82 The method of claim 78 including receiving an RF signal which contains incoming data and responsively trans mit the incoming data on the two wire process control loop 20 25 30 35 40 16 83 The method of claim 78 wherein the first and third electrical connections are electrically coupled together 84 The method of claim 78 including using an electrical element coupled between the first and second electrical con nections for use in communication on the two wire process control loop 85 The method of claim 78 including using an electrical element coupled between the first and second electrical con nections for use in providing power to the RF circuit 86 The method of claim 78 including coupling an RF circuit to an existing field device 87 The method of claim 78 wherein the RF signal carries information related to an analog
36. ises a switch mode regulator 32 Radio frequency RF communication apparatus con figured to couple to a field device in a two wire process control loop comprising first second electrical connections configured to couple in series with the two wire process control loop a third electrical connection configured to couple to the two wire process control loop wherein the second and third electrical connections are configured to couple in parallel with the field device and an RF circuit configured to receive power from the two wire process control loop through the first and second electrical connections and transmit an RF signal which contains information related to data carried on the two wire process control loop 33 The apparatus of claim 32 wherein the RF circuit is configured to receive an RF signal which contains incoming data and further including circuitry configured to respon sively transmit the incoming data on the two wire process control loop 34 The apparatus of claim 32 including a forth electrical connection and wherein the third and forth electrical connec tions are electrically coupled together 35 apparatus of claim 32 including an electrical ele ment coupled between the first and second electrical connec tions for use in communication on the two wire process con trol loop 36 The apparatus of claim 32 including an electrical ele ment coupled between the first and second electrical connec tion
37. it can be used to remotely command or interrogate a field device coupled to the loop 156 For example the HART circuitry 230 can be configured to act as a secondary master on the 4 20 current loop This in conjunction with RF circuitry 232 configured as a full transceiver enables bi directional com munication and configuration of field device from a wireless master unit for example a hand held device 80 shown in FIG 3 Microprocessor 224 can also preferably be used to imple ment diagnostics functionality Microprocessor 224 is con figured to monitor the voltage and current characteristics of the process control loop 156 improper or problematic varia tions in current and voltage can be identified using diagnostic techniques and can be transmitted to a remote location either wirelessly or using the HART transmission capabilities provided by circuitry 230 or by setting the current level carried on loop 156 to an alarm value or other pre determined value Circuitry 170 is preferably configured to allow operation in hazardous locations and to meet the appropriate approval and specifications such as intrinsic safety standards For example the intrinsic safety protection 190 along with intrinsically safety rated resistor 180 is used on the input to the circuitry 170 Using appropriate components and circuit layout the addition of a redundant zener diode 192 in parallel with zener 182 provides a level of redundancy and limits the
38. itations local display requires direct visual access to the field device Further typically an operator can only view a single meter at a time The instruments which contain the meter are often not at a convenient location or viewing angle One technique which has been used to address such a configuration is the use of a meter which is wired to a process transmitter This allows the meter to be mounted at a more convenient location Another technique is shown and described in U S patent application Ser No 10 128 769 filed Apr 22 2002 entitled PROCESS TRANSMITTER WITH WIRELESS COMMUNICATION LINK With the present invention an RF communication module is included in a field device which can be used in addition to US 7 956 738 B2 3 the connection to a process control loop such as loop 16 The wireless communication module 22 can be configured to be compact and lower power such that it can be easily included in existing field device confieurations The module can be used for wireless transmission of information for use in moni toring control and or display of data Such a radio transmitter can make the field device information available in a local area For example a single local display such as display 32 can be provided and used to display information from the field device 14 The display 32 can be configured to display infor mation from several devices either simultaneously sequen tially or through commands provided to the di
39. itry is configured to receive an RF signal and responsively transmit a signal on the two wire process control loop 15 The apparatus of claim 1 wherein the power supply circuitry includes an electrical element comprises a zener diode configured to couple in series with the two wire process control loop 16 The apparatus of claim 1 wherein the power supply circuitry includes a wireless communication circuitry is con figured to enter a sleep mode during idle periods 17 The apparatus of claim 1 including anenergy storage capacitor configured to store an electrical charge using power received from the two wire process control loop and wherein the power supply circuitry is configured to use power from the electrical charge stored on the energy storage capacitor 18 The apparatus of claim 1 wherein the wireless circuitry is carried on a modular circuit board configured to mount in a housing of the process variable transmitter 19 The apparatus of claim 1 wherein the wireless commu nication circuitry includes terminals configured to couple in series with the two wire process control loop 20 The apparatus of claim 1 including an explosion proof housing configured to enclose the wire less circuitry anintegral RF transparent region in the housing configured to allow RF transmission therethrough 21 The apparatus of claim 20 wherein the RF transparent region comprises glass 22 The apparatus of claim 20 including an end cap
40. itting a signal having a 1 second duration every 30 seconds Assuming that the band width ofthe communications signal is 200 Kb s and a packet size of 200 b the burst time is reduced to one millisecond and the resulting transmit time is 0 03 seconds In such a configu ration diagnostic data can easily be transmitted because it is not of a time critical nature However if sufficiently fast US 7 956 738 B2 7 charge times are available control and process variable sig nals can also be transmitted wirelessly Although a super capacitor is described any energy stor age device can be employed including a battery or other The energy that is used to charge the storage device can be elec trical or magnetic and can be derived or collected from any source FIG 7 is a simplified diagram of process controller moni toring system 150 which includes a control room 152 coupled to a field device 154 through two wire process control loop 156 Process control loop 156 extends across an intrinsic safety barrier 158 The control room 152 is modeled as including a power supply 160 and a load resistance 162 The field device 154 can be of any configuration and is not limited to the specific schematic shown in FIG 7 RF com munication circuitry 170 is shown coupled in series with loop 156 Circuitry 170 can be implemented in a terminal block of a field device For example circuitry 170 can be configured as an add on module such that the two wire pr
41. lows RF signals to be sent from or received by antenna 26 One example RF transparent material for use with window 74 is glass or the like However any appropriate material can be used The window and housing configuration can help to meet intrinsic safety requirements and provide flame proof explo sion proof capability Further the cavity within housing 62 0 5 25 40 45 55 4 can be configured to provide a desired radiation pattern of RF signals generated by antenna 26 For example it may be desirable to have the RF transmission be directional in some implementations or omnidirectional in others In other implementations the cover 62 can be lengthened to provide an additional interior cavity for placement of wireless com munication circuit 22 The wireless communication circuitry 22 can be selected as desired One example circuit is the 1 transmitter device available from Millennial Net However other cir cuitry can be used Analog or digital signals carried on pro cess control loop 16 can be read and transmitted using the wireless communication circuit 22 without disrupting opera tion ofthe process control loop 16 or field device circuitry 68 circuitry used for wireless transmission should be suffi ciently small and low powered to fit within the physical and power constraints of process field devices Some prior art transmitters are configured to receive an optional display arranged
42. ocess control loop 156 can connect to existing transmitter circuitry In the configuration illustrated in FIG 7 the communica tion circuitry 170 enables wireless communication abilities to be added to a new or existing process control loop or field device The circuitry is configured to be powered by the process controlloop and can be installed anywhere in the loop ranging from the control room anywhere along the loop itself in the intrinsic safety IS barrier or junction box 158 as a stand alone field device or included in another field device The circuitry can be configured for any type of communica tion However in one simple configuration the circuit 170 is configured to measure the current carried in process control loop 156 and transmit an output related to the measured current to a wireless receiver Turning now to one specific embodiment of circuitry 170 shown in FIG 7 a sense resistance 180 and a power supply diode 182 couple in series with process control loop 156 The sense resistance 180 can be for example 10 ohms and is used in sensing the current level I carried in the process control loop 156 A test diode 184 is also coupled in series with the loop 156 and provides a test point 186 This can be used to calibrate or characteristize a field device coupled to circuitry 170 An intrinsic safety protection circuit 190 is provided which includes diode 192 connected as shown across diode 182 and isolation resistors 194 conne
43. ontrol loops or available or generated inter nally or received by a field device or otherwise used to control a field device or other type of information can be transmitted using the wireless communication techniques of the present invention In another example a hand held unit or device used to configure field devices can be carried into the field by an operator The operator uses the hand held device to send or receive information to a field device when the hand held deviceis within proximity ofthe field device This allows the operator to gather information or program a field device without having to physically couple to the device or the physi cal process control loop In some embodiments it is also desirable for communica tions from a field device or to a field device to carry address ing information The addressing information can be indica tive of the source of the transmission or the intended recipient of the transmission The wireless communication circuitry can transmit continuously or on a periodic or intermittent basis as desired In another example the wireless communi cation circuitry only transmits when activated or polled The activation can be from a source internal to the field device received through the process control loop received from a wireless source or received or generated by another source In environments in which multiple field devices may US 7 956 738 B2 5 transmit simultaneously the tran
44. oop 16 This can be either analog or digital information This configuration allows data to be relayed over a wireless com munication network The network can be configured in accor dance with any type of topology including point to point spoke and hub and mesh topologies Process device 104 can be positioned at any location along the loop including con figured as an individual device such as that illustrated in FIG 4 In some installations the field device 104 should be field hardened and configured for intrinsically safe operation The device 104 can also be positioned within another field device 14 as part of a junction box 102 or even located within the control room which houses control system 12 The field device 104 can connect to more than one RF circuit 122 and or more than one process control loop 16 either simul taneously or through the use of multiplexers or other tech niques The use of a super capacitor allows the device to operate without internal batteries or other techniques The use of a capacitor allows quick charging and the storage of suffi ciently large energy potentials When used in a hazardous environment large energy storage may not be acceptable in order to meet intrinsic safety standards However the process device 104 can be moved away from the hazardous environ ment such as at the junction box 102 where intrinsic safety is not required FIG 5isa simplified schematic diagram of field device 104 showin
45. pperson et al 340 825 37 870 2003 0079553 Al 5 2003 Cain etal 73 861 27 VERA 522 e et al SN 2003 0083038 Al 5 2003 Poon etal 455 344 SOIL Dans 2003 0143958 Al 7 2003 Elias etal 455 73 PS aig eod tn 2003 0171827 Al 9 2003 Keyes IV et al 700 19 PRO AC 2003 0204371 Al 10 2003 Sciamanna 14222222 702 183 Bano 2004 0086021 Al 5 2004 Litwin 002222222 374 120 6 038 927 3 2000 Karas ccce 73 706 2004 0124854 Al 7 2004 Slezak 324 644 6 062 095 A 5 2000 et al 73 866 5 2004 0142733 Al 7 2004 Parise 455 572 6 079 276 A 6 2000 Frick et al 22222222222 73 18 2004 0183550 A1 9 2004 Fehrenbach et al vs 27 26 6 127 739 10 2000 Appa 290 55 2004 0184517 1 9 2004 Westfield et al 375 219 D439 177 S 3 2001 Fandrey et al D10 46 2004 0199681 Al 10 2004 Hedtke 710 37 D439 178 S 3 2001 Fandrey et al D10 46 2004 0203434 Al 10 2004 Karschnia et al 455 67 11 D439 179 S 3 2001 Fandrey et al D10 46 2004 0211456 Al 10 2004 Keyes et al 136 243 D439 180 S 3 2001 Fandrey et al D10 85 2004 0214543 Al 10 2004 Osone et al 455 197 2 US 7 956 738 B2 Page3 2004 0218326 Al 11 2004 Duren et al 361031 EP 0895209 Al 2 1999 2004 0242169 Al 12 2004 Albsmeier et
46. rdwired to a process control room and do not use wireless communication techniques SUMMARY field device for use in an industrial process control or monitoring system includes terminals configured to connect to a two wire process control loop configured to carry data 20 25 30 35 40 45 50 55 60 65 2 and to provide power RF circuitry in the field device is configured for radio frequency communication one embodiment power supply circuitry powers the RF circuitry using power received completely from the two wire process control loop method 15 also provided BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a simplified block diagram of a process control monitoring system including a field device configured for wireless communication FIG 2 is a block diagram of a process controller monitor ing system in which multiple field devices transmit informa tion to a remote meter FIG 3 is an exploded cut away view of a field device including wireless communication circuitry for communicat ing with a remote device such as a hand held unit FIG 4 is a diagram of a process controller monitoring system which includes a field device for wireless communi cation which scavenges power from the process control loop FIG 5 is a more detailed schematic diagram of circuitry shown in FIG 4 FIG 6is a graph of voltage versus time as measured across a capacitor shown in FIG 5 FIG 7 is an electrical block
47. s for use in providing power to the RF circuit 37 The apparatus of claim 36 including a voltage regulator coupled to the electrical element which provides a regulated voltage output to the RF 38 The apparatus of claim 32 including HART commu nication circuitry configured to receive information from the two wire process control loop in accordance with the HART communication protocol 39 The apparatus of claim 38 wherein the information contained in the RF signal comprises information received by the HART communication circuitry 40 The apparatus of claim 32 including a microprocessor coupled to the RF circuit configured to control the RF signal 41 The apparatus of claim 32 wherein the RF circuit is configured to be added to an existing field device 42 The apparatus of claim 32 wherein the RF signal carries information related to an analog current level carried on the two wire process control loop 43 The apparatus ofclaim 32 wherein the RF signal carries information related to a digital signal carried on the two wire process control loop 44 The apparatus of claim 32 including a filter configured to couple the RF circuit to the two wire process control loop 45 The apparatus of claim 32 including a terminal block configured to electronically connect to the two wire process control loop and wherein the RF circuit couples to the termi nal block 20 25 30 35 40 45 50 55 60 65 14 46 The appara
48. smission protocol should be selected to avoid or address any type of collisions which might interfere with the transmissions For example different frequencies or frequency skipping techniques can be used random or semi random transmission windows can be used repeated transmissions or token based techniques can be implemented or other collision avoidance techniques as desired If the transmission includes error detection or cor rection information this information can be used to detect an error in the transmission and or correct any errors in the transmissions If an error is not correctable the receiving unit can request a re transmission of the corrupt data or can indi cate an error or can wait for a subsequent transmission ofthe data or take other steps as desired FIG 3 also shows an example hand held device 80 for communication with circuitry 22 over RF connection 82 Hand held device 80 includes a display 84 and user input 86 Other types of inputs and outputs can be included in hand held device 80 Preferably the hand held device 80 is battery operated and can be carried into the field by an operator for communication with field device 60 Information from the field device 60 or from other sources is displayed on display 84 and the hand held device is controlled using input 86 Commands or other information can be transmitted by the hand held device 80 to field device 60 Inone configuration the wireless communication circuitry
49. splay for example using a manual input such as buttons available to an operator The display 32 can be placed at a fixed location or can be a portable device such that it can carry throughout the process control system to monitor and observe operation of various field devices Depending on the strength of the RF signal 24 and the sensitivity of the transmit and receive cir cuitry the area covered by the RF transmission can be con trolled as desired For example FIG 2 is a simplified diagram of a process control system 50 in which a number of field devices 14 are coupled to the control room 12 through indi vidual process control loops 16 Each field device 14 trans mits an RF signal 24 for receipt by display 32 In this example display 32 is capable of displaying four process variables PV1 PV2 PV3 and PV4 which are received from the field devices 14 using antenna 52 As mentioned above the display 32 can be a fixed display or can be a portable display such as a hand held unit In this particular configuration the display 32 is illustrated as showing two process variables which relate to process pressure and two process variables which relate to process temperature This allows the field devices 14 to pro vide information over the RF connection within a desired range for example within a local area For example if the display 32 is within 40 meters of a field device 14 it will be capable of receiving an displaying information from th
50. ted Dec 1 2010 U S Patent Jun 7 2011 Sheet 1 of 6 US 7 956 738 B2 DISPLAY 26 MA WIRELESS COMMUNICA TIONS ACTUATOR TRANSDUCER Fig 1 U S Patent Jun 7 2011 Sheet 2 of 6 US 7 956 738 B2 273 PST 7 63 PST U S Patent Jun 7 2011 Sheet 3 of 6 US 7 956 738 B2 MEASUREMENT SENSOR il E Missa s U S Patent Jun 7 2011 Sheet 4 of 6 US 7 956 738 B2 104 100 SUPER CAPACITOR U S Patent Jun 7 2011 Sheet 5 of 6 US 7 956 738 B2 114 107 225 y LOf 25V VOLTAGE lt wj US 7 956 738 B2 Sheet 6 of 6 Jun 7 2011 U S Patent AlddfiS er3MOd 3 297 bi 4 057 HOISISTY WOON 700100 997 OST E dd RENS LP M I81 9 SIZ 962 A 222 e ee ET m aW NMOGINHS 2012 A aV emm 922 Amd 0200 Lavy 002 YUT 33 iNet SOW INDI idi din LINII POZ T J 1 ERE EG OES 0 a A amp UGOSID ED 53208 01 US 7 956 738 B2 1 PROCESS FIELD DEVICE WITH RADIO FREQUENCY COMMUNICATION The present application is a Continuation of and claims priority of U S patent application Ser No 10 878 235 filed Jun 28 2004 now U S Pat No 7 262 693 the content of which is hereby incorporated by reference in its entirety
51. tus of claim 32 wherein the RF circuit is completely powered with power from the two wire process control loop 47 The apparatus of claim 32 including a resistor coupled in series with the two wire process control loop 48 The apparatus of claim 32 including a battery config ured to power the RF circuit 49 The apparatus of claim 32 including two wire loop communication circuitry configured to communicate on the two wire communications loop 50 The apparatus of claim 32 including intrinsic safety protection circuitry 51 The apparatus of claim 32 including an analog to digital converter configured to provide a digital representation of current flowing through the two wire process control loop 52 The apparatus of claim 32 including a microprocessor 53 The apparatus of claim 32 including a memory con taining addressing information 54 The apparatus of claim 32 including an antenna 55 apparatus of claim 32 wherein the RF circuit is configured to receive an RF signal and responsively transmit a signal on the two wire process control loop 56 The apparatus of claim 36 wherein the electrical ele ment comprises a zener diode configured to couple in series with the two wire process control loop 57 apparatus of claim 32 wherein the RF circuit is configured to enter a sleep mode during idle periods 58 The apparatus of claim 32 including anenergy storage capacitor configured to store an electrical charge using
52. upon the sensed digital signal the circuitry 230 can control operation of the RF transmit receive circuit 232 for transmis sion of information related to the sensed process variable or other information If the HART circuitry is implemented accordance with the complete HART protocol and priate RF protocol stacks the circuitry can implement gate way level functionality which will allow a HART master to communication in a bi directional manner through the RF HART gateway device with a HART capable field device on the process control loop 156 This allows wireless com munication with a field device for monitoring configuration diagnostics or exchange of other information or data Frequently in process control or monitoring installations an operator is required to physically access a field device or the process control loop in order to exchange information with the field device This allows the operator to repair equip ment and do preventive maintenance on the equipment The wireless communication configuration set forth herein allows the operator to interrogate field devices which may be in locations which are difficult to access Further even in con figurations in which the field devices are easily accessible the wireless communication circuitry does not require an opera tor to remove covers on equipment such as transmitters or junction boxes in order to expose loop wiring for physical connection to th
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