EP0784786A1 - Detecteur transmetteur - Google Patents
Detecteur transmetteurInfo
- Publication number
- EP0784786A1 EP0784786A1 EP95933566A EP95933566A EP0784786A1 EP 0784786 A1 EP0784786 A1 EP 0784786A1 EP 95933566 A EP95933566 A EP 95933566A EP 95933566 A EP95933566 A EP 95933566A EP 0784786 A1 EP0784786 A1 EP 0784786A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- thermocouple
- sensor
- thermocouple sensor
- sensor means
- resistance
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
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, requiring the manufacturing operation to be halted while the thermocouple is replaced.
- the thermowell in addition to the thermocouple connected in circuit and being used, the thermowell contains one or more additional unconnected thermocouples so that, when the thermocouple in use breaks, the operator can wire another thermocouple to the transmitter.
- thermowell there are provided a number of thermocouples grouped to give a composite reading so that if one thermocouple malfunctions, an adjustment in the reading is made to compensate for the loss.
- the present invention provides a transmitter sensor comprising a transmitter sensor head remote from a station for the processing of information derived by the sensing head, the sensor head characterised by means to switch operation from one thermocouple sensor means, for the sensing of a parameter for measurement in the locality of the sensor head, to another such thermocouple sensor means which had not been in use, upon malfunction of the said one thermocouple sensor means.
- thermocouple sensor means In use, and hence when fitted with thermocouple sensor means, the present invention provides a transmitter sensor comprising a sensor head remote from a station for the processing of information derived by the sensing head, the sensor head characterised by: at least two thermocouple sensor means for the sensing of a parameter for measurement in the locality of the sensor head; and means to switch operation from one thermocouple sensor means upon malfunction to another which had not been in use.
- the invention enables the continued effective operation of the transmitter sensor even in the event of a thermcouple sensor means malfunction, while providing a low-cost reliable arrangement.
- the present invention may also provide any one or more of the following features: means to monitor the thermocouple sensor means for failure or deterioration; the means to monitor comprises means to test the state of the thermocouple sensor means which is not in use; the means to monitor is operable to test the thermocouple sensor means which is not in use less frequently than the thermocouple sensor means which is in use; the means to monitor comprises means to determine whether a characteristic of the thermocouple sensor means has exceeded a threshold value; the means to monitor comprises means to measure the resistance of thermocouple sensor means, and/or means to measure the change in resistance of thermocouple sensor means with respect to time; the means to monitor includes means to apply a current signal to thermocouple sensor means.
- the present invention also provides a method of operating a transmitter sensor comprising a sensor head remote from a station for the processing of information derived by the sensing head, the method characterised by switching operation from one thermocouple sensor means for the sensing of a parameter for measurement in the locality of the sensor head to another thermocouple sensor means which had not been in use, upon malfunction of the said one thermocouple sensor means.
- the present invention can provide a simple and low cost arrangement which eliminates the need for stopping the manufacturing process when failure of a thermocouple occurs. Replacement of the broken thermocouple can be delayed until a convenient intermission in the manufacturing process arises.
- thermocouples including in particular to all types of transmitter sensors including flow transmitter sensors, temperature transmitter sensors and pressure transmitter sensors, to controllers and to recorders.
- FIG. 1 is a schematic diagram of a transmitter sensor embodying the present invention
- Figure 2 is a block diagram of operation of the sensor of Figure 1; and 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, i 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 Rj 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, i , 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.
- the switching between thermocouples can be done when one or both (or any specified sequence of) threshold(s) is or are exceeded.
- a given rate of change of resistance with time might not be considered of concern when the resistance is at one, comparatively low value, but the same rate of change of resistance might be considered of great concern if it occurs when the resistance is at a higher value, closer to the threshold resistance.
- 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 1 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 appropriate thresholds e.g. for producing a warning signal
- 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. 200 Ohms) represents the point at which there is danger of the thermocouple imminently failing. Either threshold can be used as that which causes change of the thermocouples.
- a resistance change of 10 Ohms/minute is an indication of a problem with the thermocouple, the values when monitoring of resistance change being very application specific.
- 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 can estimate failure of a thermocouple based on the measurement of resistance or change of resistance with respect to time, and display or otherwise output 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.
- 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. Assuming that the resistance of the lead wires and the connection resistance is zero, then
- the lead wire resistance can be significant in relation to the hot junction resistance (albeit constant in time), such that:
- Jtvhot-junc ion (.V measured - Ve.m.f. / lconstant - iVto
- 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 typically 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 status of all thermocouples not in use at any time may be checked, and the frequency of such checks may be the same for all thermcouples not in use, or they may vary in relation to the condition of the thermocouple (for example the frequency can increase as the checks as the values approach a threshold) and/or the sequence in which they will take over operation.
- 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. On vérifie le thermocouple (1) régulièrement pour détecter tout fonctionnement défectueux, et, si sa résistance dépasse une tension de seuil, il est alors replacé par l'activation du thermocouple (2) qui n'était pas en utilisation.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9420321A GB9420321D0 (en) | 1994-10-08 | 1994-10-08 | Transmitter sensor |
GB9420321 | 1994-10-08 | ||
GB9420319A GB9420319D0 (en) | 1994-10-08 | 1994-10-08 | Transmitter sensor |
GB9420319 | 1994-10-08 | ||
PCT/IB1995/000890 WO1996011389A1 (fr) | 1994-10-08 | 1995-10-09 | Detecteur transmetteur |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0784786A1 true EP0784786A1 (fr) | 1997-07-23 |
Family
ID=26305762
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP95933566A Withdrawn EP0784786A1 (fr) | 1994-10-08 | 1995-10-09 | Detecteur transmetteur |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0784786A1 (fr) |
AU (2) | AU3617995A (fr) |
WO (2) | WO1996011390A1 (fr) |
Families Citing this family (8)
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 |
US20150276498A1 (en) * | 2014-03-27 | 2015-10-01 | Rockwell Automation Technologies, Inc. | Thermocouple module with wire resistance compensation |
Family Cites Families (5)
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 |
GB1534280A (en) * | 1975-02-28 | 1978-11-29 | Solartron Electronic Group | Method and apparatus for testing 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 |
JP2826387B2 (ja) * | 1991-02-26 | 1998-11-18 | 甲府日本電気株式会社 | 温度異常検出方式 |
-
1995
- 1995-10-09 WO PCT/IB1995/000896 patent/WO1996011390A1/fr active Application Filing
- 1995-10-09 WO PCT/IB1995/000890 patent/WO1996011389A1/fr not_active Application Discontinuation
- 1995-10-09 EP EP95933566A patent/EP0784786A1/fr not_active Withdrawn
- 1995-10-09 AU AU36179/95A patent/AU3617995A/en not_active Abandoned
- 1995-10-09 AU AU36176/95A patent/AU3617695A/en not_active Abandoned
Non-Patent Citations (1)
Title |
---|
See references of WO9611389A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO1996011389A1 (fr) | 1996-04-18 |
WO1996011390A1 (fr) | 1996-04-18 |
AU3617695A (en) | 1996-05-02 |
AU3617995A (en) | 1996-05-02 |
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Legal Events
Date | Code | Title | Description |
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PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
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17P | Request for examination filed |
Effective date: 19970421 |
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AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): BE DE DK ES FR GB IT NL SE |
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17Q | First examination report despatched |
Effective date: 19980305 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 19990521 |