WO1996011390A1 - Detecteur transmetteur - Google Patents

Detecteur transmetteur Download PDF

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Publication number
WO1996011390A1
WO1996011390A1 PCT/IB1995/000896 IB9500896W WO9611390A1 WO 1996011390 A1 WO1996011390 A1 WO 1996011390A1 IB 9500896 W IB9500896 W IB 9500896W WO 9611390 A1 WO9611390 A1 WO 9611390A1
Authority
WO
WIPO (PCT)
Prior art keywords
thermocouple
thermocouple sensor
sensor
sensor means
malfunction
Prior art date
Application number
PCT/IB1995/000896
Other languages
English (en)
Inventor
Mark Kroll
Original Assignee
Honeywell S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB9420319A external-priority patent/GB9420319D0/en
Priority claimed from GB9420321A external-priority patent/GB9420321D0/en
Application filed by Honeywell S.A. filed Critical Honeywell S.A.
Priority to AU36179/95A priority Critical patent/AU3617995A/en
Publication of WO1996011390A1 publication Critical patent/WO1996011390A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
    • G01K7/026—Arrangements for signalling failure or disconnection of thermocouples

Definitions

  • the present invention relates to a transmitter sensor.
  • a transmitter sensor for use in manufacturing processes has a sensing probe in the medium to be measured and linked to the main unit of the transmitter for initial processing and/or analysis of the sensed data.
  • the unit and probe are often placed a number of meters apart due to the hazardous or unpleasant nature of the medium or inaccessibility of the location in which the sensing has to be done.
  • the sensing probe has a thermowell to contain and protect a thermocouple to measure characteristics of the medium. Frequently a thermocouple breaks, causes the manufacturing operation to be halted.
  • the present invention provides a transmitter sensor comprising thermocouple sensor means for the sensing of a parameter for measurement in the locality of the sensor, characterised in that the sensor comprises means to monitor the thermocouple sensor means to predict failure or deterioration of the thermocouple sensor means.
  • the invention can ensure that normal transmitter sensor operation is maintained regardless of any deterioration or failure of an individual thermocouple.
  • the present invention may also provide any one or more of the following features: means to estimate failure of thermocouple sensor means comprising means to determine whether the rate of change of one or more ch racteristics of the thermocouple sensor means has exceeded a threshold value; means to estimate failure of thermocouple sensor means based on measured values of resistance with respect to time of thermocouple sensor means; the means to monitor and/or the estimation means comprises means to measure the change in resistance of thermocouple sensor means with respect to time; the means to monitor and/or the estimation means comprises means to note a combination and/or sequence of values of resistance, and of change in resistance with respect to time, of thermocouple sensor means; the means to monitor and/or the estimation means includes means to apply a current signal to thermocouple sensor means; means to generate a warning signal in response to an output of the monitor means and/or the estimation means.
  • the present invention can provide a simple and low cost arrangement to predict and/or estimate thermocouple failure and/or deterioration and so can reduce or eliminate the inconvenience and expense of unplanned stoppages.
  • the present invention is applicable to all types of transmitter sensors including flow transmitter sensors, temperature transmitter sensors and pressure transmitter sensors.
  • Figure 2 is a block diagram of operation of the sensor of Figure 1;
  • Figure 3 is a flow chart showing operation of the sensor of Figure 1.
  • a temperature transmitter sensor for use in an oil refinery has a thermowell located in a pipe within the petroleum processing section such that the thermowell is in the stream of petroleum as it passes along the pipe.
  • the thermowell is linked to a main unit of the transmitter situated on the exterior of the pipe.
  • the thermowell contains two high temperature thermocouples 1 and 2 each of which has a platinum/6% rhodium alloy wire and a platinum/30% rhodium alloy wire.
  • the main unit has an electronic controller 3 whose port A is linked to one side of both thermocouples while port B is linked to the other side of thermocouple 1 and port C is linked to the other side of thermocouple 2. Ports D and E are used as outputs.
  • thermocouple 1 In normal operation, ports A and B (see Figure 1) are enabled so that thermocouple 1 is used for sensing and measurement of the petroleum flow by measurement of the e.m.f. from the thermocouple with processing including amplification with configurable gain at amplifier 4, digital conversion at A D converter 5 and treatment by the microprocessor 6. Every 0.5 seconds, constant current generator 7 in microprocessor unit 3 injects via multiplexer 8 a current signal ij of 170 micro Amperes and duration 80 milli seconds out through port A and into thermocouple 1.
  • thermocouple 1 The resultant voltage drop Vi across ports A and B, which is dependent on the resistance B. ⁇ of thermocouple 1, is measured and if it exceeds a threshold voltage of 20 millivolts (the actual size of voltage can vary according to application) microprocessor 6 disables port B and enables port C while outputting a non- critical alarm to the operator of the oil refinery.
  • Current generator 7 injects a current signal, ij, in similar manner as for thermocouple 1 through port A and the voltage drop V2 between ports A and C is measured; provided that V2 is less than the same threshold voltage, the microprocessor unit 6 utilizes the e.m.f. of thermocouple 2 in all subsequent measurements of the parameter of the petroleum flow. Failed thermocouple 1 is replaced by an engineer at the next convenient opportunity for interrupting the processing in the relevant part of the oil refinery.
  • controller 3 uses stored information about measured resistance and calculated change of resistance in order to monitor the change of resistance with time, such that once a threshold limit is exceeded, the switching of use from one thermocouple to another is done in the same way as described above. With both monitoring methods utilised, the switching between thermocouples can be done when one or both (or any specified sequence of) threshold(s) is or are exceeded.
  • the controller unit If the voltage V2 exceeds an appropriate threshold, the controller unit outputs a critical alarm to the operator of the oil refinery so that a decision can be made as to whether the petroleum operation is to be stopped for the failed thermocouples to be replaced.
  • the controller can operate such that, when the failed thermocouple has not yet been replaced so the thermocouple 2 is operating with no back-up, then the appropriate thresholds (e.g. for producing a warning signal) are different, typically lower than when a thermocouple is operating with a back ⁇ up.
  • the normal voltage drop across the thermocouples 1 or 2 for the injected current would be for example 2 millivolts representing a thermocouple resistance of 10 Ohms, and the threshold value of 20 millivolts (i.e. thermocouple resistance of 118 Ohms) represents the point at which performance of such a thermocouple has significantly deteriorated and a warning signal is to be generated, whereas the further threshold value of 35 millivolts, (i.e.
  • the controller unit is able to measure resistances in the range 0 to 2000 Ohms, and resistance changes in the range 50 Ohms/second to 1 Ohm/day.
  • controller 3 can activate a warning signal indicating failure or deterioration, and/or cause other appropriate action.
  • the controller estimates failure or deterioration of a thermocouple based on the measurement of change of resistance with respect to time (optionally also linked to resistance), and displays or otherwise outputs the results together with the warning signal, or produce a suitably modified warning.
  • the controller 3 can also determine the relationship between the estimated failure time and the next service or maintenance due, and give an appropriate signal. Thus there may be provided means to correlated estimated time of malfunction with expected next service and means to issue an appropriate warning if estimated malfunction is before or just after the next service.
  • the controller 3 provides temperature compensation of the resistance, and/or change of resistance, measurements.
  • a thermocouple such as to obtain a temperature reading at the thermocouple
  • the e.m.f. voltage of the hot junction is measured and compensated with the e.m.f. voltage of the cold junction.
  • the measured voltage after injection of the current is compensated with the previously measured thermocouple e.m.f. to obtain the corrected resistance of the hot junction.
  • vhot-junction ( * measured - Ve.m.f./ / Icont nt.
  • the lead wire resistance can be significant in relation to the hot junction resistance (albeit constant in time), such that:
  • the microprocessor 6 may effect intermittent checks of thermocouple 2 even when thermocouple 1 is in circuit and being used for measurement of the petroleum, such checks being less frequent than those of thermocouple 1.
  • thermowell may have a third (or more) thermocouple ⁇ ) to be switched into operation in case thermocouple 2 fails before thermocouple 1 is replaced.
  • the invention ensures that, at minimal complexity and cost, the processing operation of the oil refinery is not interrupted by failure of a thermocouple.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Or Calibration Of Command Recording Devices (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

Un transmetteur de température d'une raffinerie possède un puits thermométrique situé dans une conduite à l'intérieur d'une section de traitement de pétrole. Le puits thermométrique contient deux thermocouples (1 et 2) servant à détecter et mesurer l'écoulement de pétrole. Le taux de variation de la résistance des thermocouples est vérifié régulièrement afin de déterminer tout fonctionnement défectueux, tel que panne ou détérioration.
PCT/IB1995/000896 1994-10-08 1995-10-09 Detecteur transmetteur WO1996011390A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU36179/95A AU3617995A (en) 1994-10-08 1995-10-09 Transmitter sensor

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9420319.7 1994-10-08
GB9420319A GB9420319D0 (en) 1994-10-08 1994-10-08 Transmitter sensor
GB9420321.3 1994-10-08
GB9420321A GB9420321D0 (en) 1994-10-08 1994-10-08 Transmitter sensor

Publications (1)

Publication Number Publication Date
WO1996011390A1 true WO1996011390A1 (fr) 1996-04-18

Family

ID=26305762

Family Applications (2)

Application Number Title Priority Date Filing Date
PCT/IB1995/000890 WO1996011389A1 (fr) 1994-10-08 1995-10-09 Detecteur transmetteur
PCT/IB1995/000896 WO1996011390A1 (fr) 1994-10-08 1995-10-09 Detecteur transmetteur

Family Applications Before (1)

Application Number Title Priority Date Filing Date
PCT/IB1995/000890 WO1996011389A1 (fr) 1994-10-08 1995-10-09 Detecteur transmetteur

Country Status (3)

Country Link
EP (1) EP0784786A1 (fr)
AU (2) AU3617695A (fr)
WO (2) WO1996011389A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105021299A (zh) * 2014-03-27 2015-11-04 洛克威尔自动控制技术股份有限公司 具有导线电阻补偿的热电偶模块

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6556145B1 (en) * 1999-09-24 2003-04-29 Rosemount Inc. Two-wire fluid temperature transmitter with thermocouple diagnostics
US6859755B2 (en) 2001-05-14 2005-02-22 Rosemount Inc. Diagnostics for industrial process control and measurement systems
US8898036B2 (en) 2007-08-06 2014-11-25 Rosemount Inc. Process variable transmitter with acceleration sensor
US9207670B2 (en) 2011-03-21 2015-12-08 Rosemount Inc. Degrading sensor detection implemented within a transmitter
US9052240B2 (en) 2012-06-29 2015-06-09 Rosemount Inc. Industrial process temperature transmitter with sensor stress diagnostics
US9207129B2 (en) 2012-09-27 2015-12-08 Rosemount Inc. Process variable transmitter with EMF detection and correction
US9602122B2 (en) 2012-09-28 2017-03-21 Rosemount Inc. Process variable measurement noise diagnostic

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2302514A1 (fr) * 1975-02-28 1976-09-24 Solartron Electronic Group Procede et dispositif pour l'essai de thermocouples
DE3006669A1 (de) * 1980-02-22 1981-08-27 Brown, Boveri & Cie Ag, 6800 Mannheim Messanordnung mit einem thermoelement
US4841286A (en) * 1988-02-08 1989-06-20 Honeywell Inc. Apparatus and method for detection of an open thermocouple in a process control network
FR2673288A1 (fr) * 1991-02-26 1992-08-28 Nec Corp Detecteur d'anomalie de temperature pour appareil electronique.

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2457791A (en) * 1946-06-21 1948-12-28 Brown Instr Co Safe failure measuring and controlling apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2302514A1 (fr) * 1975-02-28 1976-09-24 Solartron Electronic Group Procede et dispositif pour l'essai de thermocouples
DE3006669A1 (de) * 1980-02-22 1981-08-27 Brown, Boveri & Cie Ag, 6800 Mannheim Messanordnung mit einem thermoelement
US4841286A (en) * 1988-02-08 1989-06-20 Honeywell Inc. Apparatus and method for detection of an open thermocouple in a process control network
FR2673288A1 (fr) * 1991-02-26 1992-08-28 Nec Corp Detecteur d'anomalie de temperature pour appareil electronique.

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105021299A (zh) * 2014-03-27 2015-11-04 洛克威尔自动控制技术股份有限公司 具有导线电阻补偿的热电偶模块

Also Published As

Publication number Publication date
EP0784786A1 (fr) 1997-07-23
WO1996011389A1 (fr) 1996-04-18
AU3617995A (en) 1996-05-02
AU3617695A (en) 1996-05-02

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