WO2010015569A1 - Transducteur de mesure de pression et procédé pour le faire fonctionner - Google Patents

Transducteur de mesure de pression et procédé pour le faire fonctionner Download PDF

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Publication number
WO2010015569A1
WO2010015569A1 PCT/EP2009/059911 EP2009059911W WO2010015569A1 WO 2010015569 A1 WO2010015569 A1 WO 2010015569A1 EP 2009059911 W EP2009059911 W EP 2009059911W WO 2010015569 A1 WO2010015569 A1 WO 2010015569A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
calibration
measured
evaluation device
pressure sensor
Prior art date
Application number
PCT/EP2009/059911
Other languages
German (de)
English (en)
Inventor
Wolfgang Ens
Original Assignee
Siemens Aktiengesellschaft
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 DE102008036747A external-priority patent/DE102008036747A1/de
Priority claimed from DE102009019055A external-priority patent/DE102009019055A1/de
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2010015569A1 publication Critical patent/WO2010015569A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/06—Means for preventing overload or deleterious influence of the measured medium on the measuring device or vice versa
    • G01L19/0627—Protection against aggressive medium in general
    • G01L19/0645—Protection against aggressive medium in general using isolation membranes, specially adapted for protection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/08—Means for indicating or recording, e.g. for remote indication
    • G01L19/12—Alarms or signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
    • G01L27/002—Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
    • G01L27/005—Apparatus for calibrating pressure sensors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/24—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow
    • H01H35/26—Details
    • H01H35/2657—Details with different switches operated at substantially different pressures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/24—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow
    • H01H35/34—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow actuated by diaphragm
    • H01H35/346—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow actuated by diaphragm in which the movable contact is formed or directly supported by the diaphragm

Definitions

  • the invention relates to a pressure transducer according to the preamble of claim 1 and to a method for operating a pressure transducer according to the preamble of claim 9.
  • Transmitters are used to record process variables, such as temperature, pressure, flow rate, level, density or gas concentration of a medium.
  • process variables such as temperature, pressure, flow rate, level, density or gas concentration of a medium.
  • actuators By means of actuators, the process flow can be influenced as a function of detected process variables in accordance with a strategy predetermined, for example, by a control station.
  • actuators may be mentioned a control valve, a heater or a pump.
  • pressure transmitters are essential sensory components in the context of automated production processes. With regard to an optimal plant behavior and a permanently high product quality, high-quality transducers are necessary, which provide long-term stable and low error measured values even under extreme conditions.
  • a transmitter with a defective pressure sensor does not provide any or a faulty measured value in an automation system. This can lead to inferior quality of a product manufactured in the plant or to a plant standstill, especially if the measured value is relevant for the operational safety of the plant. If the pressure transmitter is used in a control loop, a faulty measured value has a negative effect on the control accuracy and thus reduces the product quality.
  • a pressure transmitter for process instrumentation in which the pressure to be measured (system pressure) of the process medium via a separation membrane and a measuring chamber filled with silicone oil is transferred to a pressure sensor, which is designed as a piezoresistive silicon sensor.
  • a second pressure sensor with a larger overload range is provided in addition to this first pressure sensor.
  • An evaluation device for determining and outputting a measured value as a function of the measuring signal of the first pressure sensor is designed such that in normal operation a calibration of the second pressure sensor takes place cyclically on the basis of the first measuring signal of the first pressure sensor.
  • the second pressure sensor with lower sensitivity and generally lower measurement accuracy serves to generate the measurement signal, on the basis of which the measured value is determined and output in the evaluation device in the event of a fault of the first pressure sensor becomes.
  • a calibration of the first pressure sensor, however, is not described.
  • Pressure sensors often have a silicon membrane, which bends due to the applied pressure. This bending leads to material stresses on the surfaces of the membrane, which are converted into a measurement signal, for example with the aid of piezoresistive resistors embedded in the silicon membrane and connected in a Wheatstone bridge.
  • a disadvantage is that the measurement signal over a longer period of operation due to aging effects of the resistors, mechanical tension of the membrane or other reasons experience a drift can, so that the measurement results no longer meet the accuracy requirements.
  • manual recalibrations are therefore required from time to time.
  • Such measures are relatively expensive, since usually the pressure transmitter must be removed from the automation system and recalibrated in the factory or in a special calibration.
  • the invention has for its object to provide a pressure transducer of the type mentioned above and a method for its operation, with which the calibration of the pressure transducer is simplified.
  • the new pressure transmitter has the features specified in claim 1.
  • Advantageous developments are described in the dependent claims, in claim 9 a method for operating a pressure transducer is described.
  • the invention is based on the idea that in a pressure transducer a pressure sensor must be recalibrated from time to time due to moderate long-term stability in order to supplement a reference with comparatively good long-term stability.
  • at least one pressure switch is used as reference, since such components are characterized by a comparatively long-term stable construction.
  • the pressure sensor itself then no longer needs to be of particularly long-term stability, since a calibration or recalibration of the pressure sensor can be accomplished automatically cyclically or at predeterminable times. Therefore, lower-priced pressure sensors can be used without having to accept significant disadvantages with regard to the measurement accuracy and the long-term stability of the pressure transducer.
  • the pressure switch has a diaphragm, which is acted upon by the pressure to be measured and whose deflection is limited by a stop. It is thus designed for an operating point and only in this have long-term stability. Since the pressure switch is moved less frequently than the diaphragm of the pressure sensor and since the movement path is comparatively small, the pressure switch undergoes a lower mechanical stress. If possible use of the same materials in pressure switch and pressure sensor high accuracy of the predetermined threshold and good long-term stability is already achieved for this reason.
  • the pressure sensor and the at least one pressure switch are arranged on the same silicon substrate. This has the advantage that pressure sensor and pressure switch can be manufactured in the same process steps and that the manufacturing costs are significantly reduced compared to the use of several separate components.
  • the stop of the pressure switch is dimensioned such that the predetermined threshold is located in the middle half of the working range of the pressure sensor, that is between 25% and 75% of the span.
  • the calibration points are thus not near the extremes of the pressure sensor but in an area that is often used during operation. As a result, too infrequent recalibration of the pressure sensor is avoided.
  • a comparatively accurate detection of reaching the stop is made possible in a particularly simple manner when the stop an electrical contact for generating a switching signal is provided, which is performed as a digital signal to an input of the evaluation.
  • suitable contact surfaces must be provided in the pressure switch and these are led out via lines from the pressure switch.
  • a capacitive or optical detection would be conceivable, a resistive detection by detecting the closing of a contact, however, can be realized with comparatively simple circuit means.
  • An alternative possibility for generating the switching signal is to form the pressure switch in the same way as the continuously measuring pressure sensor, which generates an analog measurement signal.
  • the detection of the switching point that is, the detection of whether the stop was reached by the membrane of the pressure switch, then takes place via a comparison of the waveforms of the signals supplied by the pressure sensor and the pressure switch. Occurs, for example, in the time course of the output signal of the pressure switch on a kink, while the measurement signal of the pressure sensor continues to change with a constant slope, it can be concluded upon reaching the stop at the time of occurrence of Knicks.
  • Advantage in this variant is that the pressure sensor and the pressure switch in the same technology and with the same manufacturing process or
  • an electronics which receives the output signals of the pressure sensor and the pressure switch and preprocessed, also be the same structure. It is even a multiplex operation possible in which the same electronics successively processed the output of the pressure sensor and the output of the pressure switch.
  • a non-linear calibration curve of a pressure sensor can easily be adapted to changes in the calibration data by tilting and / or shifting when two pressure switches with two different switching thresholds are used as a reference.
  • an adaptation of the shape of the calibration curve is also or adaptation by section approximation of the calibration curve to the switching thresholds possible.
  • the position of the switching threshold of the pressure switch of a pressure transmitter is determined in a particularly advantageous embodiment in a factory calibration and stored in a memory of the evaluation.
  • the dependence of the switching threshold on the respective temperature of the pressure transducer can be determined and stored in a factory calibration.
  • cheaper pressure switch can be used because their switching threshold does not have to have a predetermined value and no absolute accuracy of the switching threshold is required.
  • Their exact position and temperature dependency is rather determined speci fi cally in the factory calibration and only needs to meet certain requirements with regard to the long-term stability.
  • the term "exceeding" of a switching threshold used in this application naturally includes both directions, that is to say an overflow from bottom to top as well as from top to bottom
  • two different switching thresholds can be realized with the same pressure switch. because effective for the calibration threshold is to be selected according to the direction of exceeding the switching threshold.
  • FIG. 1 shows a sectional view of a transducer of a pressure transducer
  • FIG. 2 is a block diagram of the pressure transmitter
  • Figure 3 is a characteristic diagram for explaining the calibration
  • Figure 4 is a sectional view of pressure switches based on silicon.
  • a transducer 1 of a pressure transducer has, according to FIG. 1, a process connection 3 with which it can be connected to a pipeline or a container in an automation system.
  • a process medium having a pressure P is supplied to the sensor 1 through an opening in the process connection 3.
  • the process medium reaches a separating membrane 4, by means of which the process medium is separated from a filling oil which is located in a measuring chamber 5.
  • the process pressure P is hydrostatically transmitted to a pressure sensor 6 and a pressure switch 7.
  • the pressure sensor 6 generates a measuring signal and the pressure switch 7 a switching signal, which are transmitted by in the figure for clarity not shown electrical lines to an evaluation device for further processing.
  • the pressure switch 7 serves as a long-term stable reference for the calibration of the pressure sensor 6 and thus for the compensation of drift phenomena, which can occur, for example due to aging effects in the pressure sensor 6.
  • transducer 1 of a measuring transducer for absolute pressure is shown.
  • transducers with variable reference pressure for relative pressure transmitter or transducer for differential pressure transmitter with one or more pressure switches as Reference to calibrate the transmitter are shown.
  • the transducer 1 supplies a measuring signal 9 of the pressure sensor 6 and a switching signal 10 of the pressure switch 7 to an evaluation device 11.
  • the two signals 9 and 10 in a Signalverrbei- processing unit 12 for determining a measured value 13 further processed.
  • the signal processing unit 12 status messages relating to the state of the transmitter are additionally generated.
  • Status messages and measured value 13 are forwarded by an interface 14 via a bus system 15 to a control system 16 in which they are further processed for use in an automation system, for example as an actual value in a control loop.
  • the evaluation device 11 is displayed as to whether the pressure P to be measured is above or below a predetermined threshold.
  • the value of the threshold was determined in a factory calibration and stored in a memory 17. If the pressure P exceeds the predetermined threshold, the value of the measuring signal 9 transmitted thereby is compared with a calibration date already stored in the memory 17 of the evaluation device 11 and associated with the respective threshold. If deviations occur compared to previously stored calibration data, a recalibration of the pressure transducer is carried out with the aid of the signal processing unit 12. The recalibration based on the calibration date determined in this way, which was obtained as a reference with the aid of the long-term stable pressure switch 7, therefore compensates for influences of aging effects of the pressure sensor 6 on the measurement result and restores the measurement accuracy of the pressure transmitter.
  • FIG. the procedure for recalibrating a pressure transmitter with two pressure switches is shown in FIG. explained.
  • a measurement signal U plotted on the ordinate a measured pressure P.
  • the value range of the pressure transmitter ranges from an initial value PO to a final value Pl.
  • a first pressure switch has a switching threshold PS1
  • a second pressure switch has a switching threshold PS2.
  • the diagram shows three characteristic curves K, K 'and K''whose distance and slope deviation are greatly oversubscribed for better illustration.
  • the characteristic curve K 'in the evaluation device is used to determine a pressure measurement value P on the basis of the measurement signal U.
  • the value US1 of the measuring signal U output by the pressure sensor is stored as a new calibration date and the characteristic K 'is shifted in parallel such that the point (US1, PS1) lies on the new characteristic curve comes. In this way, the characteristic K "is obtained. If only one pressure switch was used in the pressure transmitter, the recalibration would have been completed. If, in normal operation, the switching threshold PS2 of the second pressure switch is also exceeded, the value US2 of the measuring signal recorded in this case is present as a further calibration date, which enables a further improvement of the calibration accuracy. Now, in the recalibration, the characteristic curve K "is rotated by the point (US1, PS1) and in this way transferred to the characteristic curve K, which includes both the point (US1, PS1) and the point (US2, PS2) ,
  • linear characteristic curves K, K 'and K are shown by way of example.
  • the type of recalibration described can of course also be applied to slightly non-linear characteristics.
  • pressure switches 18, 19 and 20 based on silicon is illustrated.
  • the three pressure switches 18, 19 and 20 are constructed identically to the dimensions of their membrane, so that an exemplary description of the pressure switch 20 is sufficient.
  • a carrier material 21 of silicon for example, a square diaphragm 22 is held, on the upper side of which to be measured
  • Pressure P acts.
  • the underside 24 of the membrane 22 is acted upon by the reference pressure of a reference pressure chamber 25.
  • the membrane 22 carries a dome-shaped elevation 26, which projects into the reference pressure chamber 25.
  • the underside of the elevation 26 is provided with an electrical contact surface 27, which faces an electrical contact surface 28 on a base plate 29. If the pressure P exceeds the pressure of the reference pressure chamber 25 by a threshold value which may be predetermined, for example, during a factory calibration, the electrical contact between the two contact surfaces 27 and 28 is closed and a reaching of the stop is detected.
  • the elevation 26 and the base plate 29 thus form with the respective contact surface 27 or 28 a stop which limits the deflection of the membrane 22.
  • the closing of the contact at the meeting of the two contact surfaces 27 and 28 can be determined by a simple resistance measurement and the evaluation device (11 in Figure 1) are displayed by means of a binary signal.
  • the evaluation device 11 in Figure 1
  • capacitive or optical detection is possible.
  • the upper side 23 of the membrane 22 may be provided with doped, resistive elements which correspond to those of the pressure sensor. The detection of the switching point then takes place via a comparison of the signal curves which are obtained with the pressure switch 20 and the pressure sensor, not shown in FIG. Occurs in the signal obtained with the help of the pressure switch 20, a discontinuity of the slope, while the Signal curve, which was obtained with the help of the pressure sensor, no such discontinuity shows, it can be concluded that the stop in the pressure switch 20.
  • the switching threshold of the pressure switch 20 is determined substantially by the thickness of the membrane 22, its width dl, the material properties of the material used for the membrane 22 and the distance between the electrical contact surfaces 27 and 28. It can thus be varied by changing one or more of the mentioned parameters.
  • the pressure switches 18, 19 and 20 differ only with regard to the diaphragm width d3, d2 or d1, the width d3 being the smallest and the width d1 the largest.
  • the switching threshold of the pressure switch 20 the lowest and the switching threshold of the pressure switch 18 is the highest.
  • the switching thresholds are preferably located in the middle section of the working range of the pressure sensor, so that during operation of the transmitter frequent switching of the pressure switch and recalibration of the pressure sensor is achieved.
  • the pressure switches 18, 19 and 20 are designed for an operating point and need only be long-term stable in this. Because they are less frequently moved and restricted in their travel relative to the pressure sensor, their membrane is subjected to less mechanical stress than the membrane of the pressure sensor. This also has an advantageous effect on the long-term stability of the switching points.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

La présente invention concerne un transducteur de mesure de pression et un procédé pour faire fonctionner un transducteur de mesure de pression comprenant un capteur de pression (6) destiné à produire un signal de mesure (9) qui correspond à la pression à mesurer (P) d'une substance gazeuse ou liquide; et un dispositif d'évaluation (11) destiné à déterminer et fournir une valeur de mesure (13) en fonction du signal de mesure. Pour simplifier le calibrage du transducteur de mesure de pression, au moins un manostat (18...20) destiné à produire un signal de commutation et comprenant une membrane (22) soumise à la pression à mesurer (P), est utilisé, la flexion de la membrane étant limitée par une butée (26...29). Le signal de commutation permet d'indiquer au dispositif d'évaluation (11) que la butée (26...29) est atteinte ou non, et ainsi que la pression à mesurer est supérieure ou inférieure à une valeur seuil (PS1, PS2) prédéterminée. En cas de dépassement de la valeur seuil, des données de calibrage ((US1, PS1), (US2, PS2)) sont déterminées et enregistrées. Ces données de calibrage permettent un nouveau calibrage du transducteur de mesure de pression. Le manostat (7) qui se trouve dans le transducteur de mesure de pression, représente une référence à long terme au calibrage automatique du transducteur de mesure de pression. Avantageusement, un calibrage manuel ne s'avère plus nécessaire.
PCT/EP2009/059911 2008-08-07 2009-07-30 Transducteur de mesure de pression et procédé pour le faire fonctionner WO2010015569A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE102008036747.8 2008-08-07
DE102008036747A DE102008036747A1 (de) 2008-08-07 2008-08-07 Druckmessumformer sowie Verfahren zu dessen Betrieb
DE102009019055.4 2009-04-27
DE102009019055A DE102009019055A1 (de) 2009-04-27 2009-04-27 Druckmessumformer sowie Verfahren zu dessen Betrieb

Publications (1)

Publication Number Publication Date
WO2010015569A1 true WO2010015569A1 (fr) 2010-02-11

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114864124A (zh) * 2022-03-24 2022-08-05 中国核动力研究设计院 核安全级压力变送器鉴定试验的测量系统、方法、介质

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06103866A (ja) * 1992-09-18 1994-04-15 Seiko Instr Inc 圧力スイッチ
WO2000008432A2 (fr) * 1998-08-05 2000-02-17 Cardio Technologies, Inc. Dispositif de mesure de la pression
DE19860500A1 (de) * 1998-12-28 2000-07-27 Heinz Ploechinger Vorrichtung und Verfahren zur Druckmessung
DE102005044410A1 (de) * 2005-09-16 2007-03-29 Siemens Ag Druckmessumformer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06103866A (ja) * 1992-09-18 1994-04-15 Seiko Instr Inc 圧力スイッチ
WO2000008432A2 (fr) * 1998-08-05 2000-02-17 Cardio Technologies, Inc. Dispositif de mesure de la pression
DE19860500A1 (de) * 1998-12-28 2000-07-27 Heinz Ploechinger Vorrichtung und Verfahren zur Druckmessung
DE102005044410A1 (de) * 2005-09-16 2007-03-29 Siemens Ag Druckmessumformer

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114864124A (zh) * 2022-03-24 2022-08-05 中国核动力研究设计院 核安全级压力变送器鉴定试验的测量系统、方法、介质

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