WO2000008432A2 - Dispositif de mesure de la pression - Google Patents

Dispositif de mesure de la pression Download PDF

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Publication number
WO2000008432A2
WO2000008432A2 PCT/US1999/017667 US9917667W WO0008432A2 WO 2000008432 A2 WO2000008432 A2 WO 2000008432A2 US 9917667 W US9917667 W US 9917667W WO 0008432 A2 WO0008432 A2 WO 0008432A2
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
transducer
switch
triggered
switches
Prior art date
Application number
PCT/US1999/017667
Other languages
English (en)
Other versions
WO2000008432A3 (fr
WO2000008432A9 (fr
Inventor
Paul C. Michelman
Original Assignee
Cardio Technologies, Inc.
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
Application filed by Cardio Technologies, Inc. filed Critical Cardio Technologies, Inc.
Priority to AU57718/99A priority Critical patent/AU5771899A/en
Publication of WO2000008432A2 publication Critical patent/WO2000008432A2/fr
Publication of WO2000008432A9 publication Critical patent/WO2000008432A9/fr
Publication of WO2000008432A3 publication Critical patent/WO2000008432A3/fr

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Classifications

    • 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

Definitions

  • the present invention generally relates to the field of pressure measuring devices. More specifically, the invention is directed to a pressure measuring system that provides relatively accurate readings while incorporating relatively inexpensive sensing components.
  • a number of mechanical and electro-mechanical systems incorporate pressure transducers or sensors to measure or detect a desired pressure in a vessel, conduit, or other fluid-containing member. Sensing the pressure in such a member is a good indication of the status of the system, and can be used to detect dangerous pressure levels so that remedial measures can be taken to prevent the components of the system from being damaged by high pressure levels.
  • the sensed pressure is used for comparison with a preselected set point and, if the sensed pressure varies from the set point, some correcting device is actuated to eliminate the difference between the desired and actual values. Because a very accurate pressure measurement is typically desired, such systems normally incorporate one or more relatively expensive high-precision pressure transducers. Many such systems require several pressure transducers in order to sense pressures at different locations within the system. Thus, the cost of such systems rises considerably, because a large number of the high-precision transducers are needed.
  • strain gauge devices for determining pressure levels in fluid-containing members.
  • strain gauge pressure measuring devices are quite inexpensive and for that reason they are desirable; however, strain gauges are relatively limited in terms of both the range and accuracy they provide. Thus, strain gauges do not address the need for a relatively inexpensive and relatively precise pressure measuring device.
  • One object of the present invention is to use a relatively imprecise and inexpensive pressure transducer in connection with a pressure switch in order to achieve relatively accurate pressure readings.
  • a relatively inexpensive pressure transducer or sensor is incorporated in a pressure-measuring system, the system also includes a pressure switch with a preselected pressure set point.
  • the pressure transducer or sensor repeatedly senses the pressure in a fluid-containing vessel or other member, and the pressure sensed by the transducer is preferably displayed to a user or output for other use.
  • the pressure switch is triggered.
  • the reading from the pressure transducer at the time the switch is triggered is determined and, if that reading from the transducer does not match the pressure set point, an error correction is calculated and future readings from the transducer are adjusted based upon the error correction.
  • the pressure measuring system in one illustrative embodiment comprises: a pressure transducer in communication with a fluid-containing member to sense the pressure in the member and generate a pressure signal corresponding to the pressure sensed by the transducer; a pressure switch in communication with the member, the pressure switch having a preselected set pressure point and being operative to trigger when the pressure in the member crosses the set point; and circuitry electrically connected to the pressure sensor and to the pressure switch, the circuitry being responsive to triggering of the pressure switch to determine the pressure sensed by the pressure transducer and to calibrate signals from the pressure transducer.
  • FIG. 1 is a block diagram of a pressure measuring system comprising one illustrative embodiment of the present invention
  • FIG. 2 is a schematic diagram showing another embodiment of a pressure measuring system connected to a fluid-containing member for measuring the pressure in the member;
  • FIG. 3 is a flow chart depicting the operational flow of the system of FIG. 1;
  • FIG. 4 is a block diagram of another illustrative embodiment of the pressure measuring system of the present invention.
  • FIG. 1 there is shown a pressure measuring system 10 depicting one illustrative embodiment of the present invention.
  • the pressure measuring system comprises a pressure sensor or transducer 12, a pressure switch 14, and a controller 16 electrically connected to the pressure transducer and to the pressure switch.
  • the pressure measuring system is operative to sense the pressure within a fluid-containing member 18 and, if appropriate, to automatically correct the sensed values to obtain a more precise value than that sensed by the pressure transducer.
  • the system is operative to sense pressures in members containing either gases or liquids.
  • the pressure measuring system 10 in one illustrative embodiment comprises the pressure transducer 12.
  • the pressure transducer is connected to a fluid-containing member 18 fox fluid communication with the member, for example, through a conduit 20 (FIG. 2).
  • the pressure transducer includes an inlet, for example in the form of a threaded nipple (not shown), to threadedly engage a complementarily formed, internally threaded outlet port of the conduit (not shown).
  • the pressure transducer is operative to sense the pressure in the conduit, and thus the pressure in the fluid-containing member.
  • the pressure transducer can take many different forms which are well known to those of ordinary skill in the art, such as a piezoresistive or a metallic strain gauge that incorporates a sensing diaphragm, a quartz pressure transducer, a capacitive pressure sensor, an inductive pressure sensor, or the like.
  • the strain gauge-type transducers incorporate a strain gauge, which is a resistive element whose resistance changes with the amount of strain (or pressure) placed on it.
  • the pressure transducer 12 incorporated in the system 10 of the present invention is further operative to generate an electrical output signal that is proportional to the sensed pressure.
  • the output may be either a voltage or a current, with the voltage or current level output by the transducer being proportional to the sensed pressure. It will be apparent that the signal from the pressure transducer can be either a digital or analog signal.
  • the pressure measuring system 10 may incorporate either a pressure sensor or a pressure transducer, so long as the device includes an electronic output for generating an electronic signal, in the form of either a voltage or a current, having a value corresponding to the pressure sensed in the member.
  • the two terms, sensor and transducer are used herein interchangeably.
  • the pressure measuring system 10 further includes the pressure switch 14, which can also take many different forms which are well known to those of ordinary skill in the art, such as a membrane-type or diaphragm-operated pressure switch, one that incorporates sliding or pivoting actuating members, and the like.
  • the pressure switch is preferably adjustable and set at the factory with a preselected pressure set point at which it will be actuated.
  • the pressure switch 14 includes an inlet, such as a threaded port, to engage a complementary outlet in the conduit 20 to establish fluid communication between the pressure switch and fluid-containing member 18.
  • the pressure transducer 12 and pressure switch 14 are each connected to the same conduit 20 and sense the same pressure in that conduit.
  • the switch In the case of the diaphragm-type pressure switch, the switch is normally open, with the pressure, when it exceeds the preselected set point for that pressure switch, operating across the deflectable diaphragm to establish electrical communication across plural electrical contacts to close the switch and generate an electrical output signal. Conversely, if the pressure in conduit 20 subsequently drops below the set point for the switch, the diaphragm will return to its normal position and the electrical contacts will no longer be in contact with each other, and the switch will return to its normal, untriggered state, such that its output goes low.
  • the electrical signal generated by the pressure switch can be either a digital or analog signal.
  • the actuating member of the pressure switch 14 is typically spring biased toward the open position, with the pressure in the conduit 20 serving to overcome the force from the spring to drive the actuating member to the closed position to trigger the switch.
  • the biasing force applied by the spring is preferably adjustable, such as with an adjustment screw, so that the pressure set point may be changed for the pressure switch.
  • the pressure measuring system 10 further includes the controller 16.
  • the controller comprises circuitry, for example a microprocessor, that is electrically connected to the pressure switch 14 and to the pressure transducer 12.
  • the controller is connected to the switch and transducer through respective amplifiers 22 (FIG. 2) for receipt of electrical signals from the switch and transducer.
  • Some transducers output signals having a value on the order of millivolts, and thus the amplifier is incorporated in certain embodiments and is operative to amplify the low level output from the transducer to a high level output, on the order of several volts. Some other transducers output signals that do not require amplification.
  • the switch 14 is shown in Fig.
  • the particular switch used may require the use of an amplifier (FIG. 2).
  • FOG. 2 an amplifier
  • the amplifiers are optional and depend upon the particular types of switches and transducers used by the system 10.
  • the controller 16 is programmed to process the electrical signals from the switch 14 and transducer 12 and output a value corresponding to the pressure within the member 18, as described in greater detail below in connection with Fig. 3.
  • the controller 16 is also programmed to take readings from the transducer at a selected sampling rate, which is dependent on the frequency characteristics of the pressure waveform being monitored. For example, if the pressure waveform is varying rapidly (corresponding to a high frequency), the sampling rate is preferably also high. In addition, the accuracy of the system is dependent on the ability to read the pressure transducer 12 quickly. Thus, the sampling rate is preferably made relatively high to ensure better accuracy of the system.
  • the controller may include an analog-to-digital converter (not shown) to convert analog signals from the pressure transducer and pressure switch into digital signals.
  • the controller 16 is also electrically connected to a memory 24 that stores characteristic information for the transducer 12 and switch 14, and which is accessed by the controller.
  • the memory may be in the form of a look-up table or the like.
  • the memory may store corresponding pressure values for particular electrical signal values received from the transducer, as described in greater detail below.
  • the system may perform two-point interpolations to interpolate between the two closest points stored in the look-up table in cases where the electrical signal value received by the controller falls between two entries in the look-up table.
  • the system 10 is actuated at step 30, for example by delivering a suitable supply of power to the pressure transducer 12, pressure switch 14, and controller 16.
  • the controller receives an amplified electrical signal from the pressure transducer, and processes the signal to determine the pressure within the member 18.
  • the controller preferably receives the signal, determines the value of the signal (in volts or amps), and accesses the memory 24 to determine the corresponding pressure value.
  • an amplified signal from the transducer with a voltage of 3 volts may correspond to a pressure of 5 psi in the member, whereas a voltage of 5 volts may correspond to a pressure of 8 psi, and so on, and those values may be associated in the look-up table of memory 24.
  • the controller determines whether the pressure switch 14 has been triggered, for example by checking whether the signal line from the pressure switch 14 has gone from low (or off) to high (or on). If not, operation flows to step 36, and the controller outputs an uncorrected pressure reading, for example to a display 26, or to another device for further processing. Operation then flows back to step 32, and the process is repeated.
  • the process described above will continue, with the output generated by the controller 16 corresponding to the uncorrected reading from the transducer, until the switch 14 is triggered. Once the switch is triggered, the controller sets a trigger flag in memory to true, and operation flows to step 38 rather than to step 36. The controller then adjusts the reading from the pressure transducer based on an error correction.
  • the error correction is calculated as follows:
  • Poutput P 2 " Perror
  • the controller corrects the value and outputs a pressure value of 12 psi (13 psi - 1 psi).
  • the controller corrects for values that are either too high or too low.
  • the controller 16 is signaled due to the line from the pressure switch going low, and the controller preferably determines a new correction factor using the above-mentioned error correction equation.
  • the pressure measuring system 10 of the present invention may include virtually any type of pressure transducer or sensor 12. Where cost is a concern, for example where a large number of pressure transducers are required to monitor an extensive network of fluid conduits or members, relatively inexpensive pressure transducers, such as strain gauge transducers, may be employed.
  • Each transducer may have an associated pressure switch, with the look-up table in the memory 24 serving to associate the transducer and switch pairs, such that when a particular pressure switch is triggered, an error correction for the associated pressure transducer is calculated, and future readings from that transducer are corrected based upon the error correction.
  • the controller is programmed to calculate individual error corrections for each transducer, and to store each error correction in the memory for future access.
  • the system includes a pressure transducer 102, multiple pressure switches 104, and a controller 106.
  • the pressure switches preferably each have a different pressure set point, and each is electrically connected to the controller via a separate line 108, 110, and 112.
  • this system provides a multi-point calibration, and produces accurate pressure readings throughout a range of pressures.
  • the controller is signaled via one of the lines 108, 110, or 112, and thus the controller knows which of the pressure switches was triggered.
  • the controller accesses the memory, for example the look-up table, and determines the set point for that particular pressure switch.
  • the controller then performs the necessary error correction using the above-described equation to determine p error , and stores the value of p error in memory 24.
  • the subsequent readings from the pressure transducer are then corrected by subtracting (or adding) p error to the reading. If another one of the pressure switches is subsequently triggered, the controller determines the set point for that switch, calculates a new p error based upon the new set point, and corrects subsequent readings from the pressure transducer based upon the new value of p error and stores the new value of p error in memory along with the first value of p error .
  • the system After calculating the new value of p error , if the pressure changes and is closer to the set point of the first switch than that of the second switch, the system preferably uses the correction factor for the first switch switch, i.e. the first value of p error .
  • the correction factor for the first switch switch i.e. the first value of p error .
  • the controller is programmed to use the correction factor for the first switch to correct the readings from the pressure transducer.
  • the controller uses the correction factor for the second switch to correct the readings from the pressure transducer.
  • the system 100 provides a more accurate output through a range of pressures, especially in cases when the error is non-linear.
  • Such a system provides a technique for "zeroing" the pressure transducer at multiple non-zero values.
  • the pressure measuring system 100 may also include more than one pressure transducer, with each having a particular range in which it is relatively accurate, and that the system may include multiple pressure switches that are used to adjust the readings from the respective transducers.
  • the controller is preferably programmed to select readings from only one of the transducers, based upon the approximate pressure value within the member 18. For example, if a first one of the transducers has a range from 0 to 10 psi, and a second transducer has a range from 0 to 20 psi, the controller will select the readings from the first transducer when each transducer provides a reading of about 5 psi.
  • the multiple transducers and switches are preferably connected to the single controller 16, with the controller selecting between the various transducers and monitoring each of the pressure switches.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

On décrit un système de mesure de la pression plus précis que le capteur ou transducteur de pression incorporé dans le système. Le système inclut un manostat et un capteur ou transducteur de pression, chacun desdits éléments pouvant être mis en oeuvre pour détecter la pression dans un récipient, une ligne fluidique, ou analogue. Le manostat comprend un point de réglage présélectionné, si bien que le passage de la pression en cours de détection au point de réglage déclenche le manostat. Un circuit surveille le capteur et le manostat de sorte que le déclenchement de ce dernier permet au circuit de déterminer une erreur éventuelle de lecture depuis le capteur, et corrige les lectures ultérieures depuis le capteur, sur la base de la valeur de l'erreur calculée.
PCT/US1999/017667 1998-08-05 1999-08-05 Dispositif de mesure de la pression WO2000008432A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU57718/99A AU5771899A (en) 1998-08-05 1999-08-05 Pressure measuring device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US9541998P 1998-08-05 1998-08-05
US60/095,419 1998-08-05

Publications (3)

Publication Number Publication Date
WO2000008432A2 true WO2000008432A2 (fr) 2000-02-17
WO2000008432A9 WO2000008432A9 (fr) 2000-08-03
WO2000008432A3 WO2000008432A3 (fr) 2007-12-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1999/017667 WO2000008432A2 (fr) 1998-08-05 1999-08-05 Dispositif de mesure de la pression

Country Status (2)

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AU (1) AU5771899A (fr)
WO (1) WO2000008432A2 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010015569A1 (fr) * 2008-08-07 2010-02-11 Siemens Aktiengesellschaft Transducteur de mesure de pression et procédé pour le faire fonctionner
DE102008036747A1 (de) * 2008-08-07 2010-03-25 Siemens Aktiengesellschaft Druckmessumformer sowie Verfahren zu dessen Betrieb
DE102009019055A1 (de) * 2009-04-27 2010-11-04 Siemens Aktiengesellschaft Druckmessumformer sowie Verfahren zu dessen Betrieb

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5274664A (en) * 1990-07-23 1993-12-28 Danieli & C. Officine Meccaniche Spa Method and device to control the force applied to the electrode-bearing arms of an electric arc furnace

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5274664A (en) * 1990-07-23 1993-12-28 Danieli & C. Officine Meccaniche Spa Method and device to control the force applied to the electrode-bearing arms of an electric arc furnace

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010015569A1 (fr) * 2008-08-07 2010-02-11 Siemens Aktiengesellschaft Transducteur de mesure de pression et procédé pour le faire fonctionner
DE102008036747A1 (de) * 2008-08-07 2010-03-25 Siemens Aktiengesellschaft Druckmessumformer sowie Verfahren zu dessen Betrieb
DE102009019055A1 (de) * 2009-04-27 2010-11-04 Siemens Aktiengesellschaft Druckmessumformer sowie Verfahren zu dessen Betrieb

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Publication number Publication date
WO2000008432A3 (fr) 2007-12-06
AU5771899A (en) 2000-02-28
WO2000008432A9 (fr) 2000-08-03

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