PIEZOELECTRIC SENSOR FOR MEASURING PRESSURE FLUCTUATIONS

• US 20110166459A1
• Filed: 07/17/2009
• Published: 07/07/2011
• Est. Priority Date: 05/20/2008
• Status: Active Grant

• Current Assignee: Mohammad Nasseri, Roland Kopetsch, Stephan Bergmann
• Original Assignee: SectorCon Ingenieurgesellschaft fur System- und Softwaretechnik mbH
• Inventors: Nasseri, Mohammad, Bergmann, Stephan, Kopetsch, Roland
• Granted Patent: US 9,642,539 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/02035 Determining blood viscosity
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025

Abstract

The invention relates to a piezoelectric sensor for the improved measurement of mechanical variables such as force, pressure or measurement variables which are derived there from, particularly a PVDF film sensor having an improved sensitivity and temperature stability of the measurement signal for pressure measurements that vary in time and/or space, and for the one- and two-dimensional determination of the position and propagation velocity of pressure fluctuations and pressure waves with a single measurement sensor at a measurement location. A preferred field of application of the invention is the non-invasive, low strain and continuous measurement of the pulse rate and the systolic and diastolic blood pressure of humans and animals by determining the velocity and the signal form of the pulse waves. The object of the invention is to allow the measurements of the blood pressure and the pulse rate, for example even in the case of emergency patients having only a very low blood pressure and patients having circulatory disorders in the extremities, for example patients which have developed diabetes or the “smoker'"'"'s leg”, by using only one sensor at a measurement location due to the improved measurement sensitivity of the piezoelectric sensor, with the result that the continuous application of a pressurized jacket for continuously measuring and monitoring the blood pressure is not necessary. The present invention solves this problem in that a plurality of parallel strips of a piezoelectric material (1) are associated as a measurement membrane in the pressure sensor according to the invention with a sensor base body (4) in such a manner that the parallel strips are tension preloaded in a one-dimensional and elastic manner in the direction of the piezo dipole orientation and that an empty cavity (5) is provided between the tension preloaded piezoelectric sensor material (1) in the measurement portion and the sensor base body (4), formed by a recess/cutout.

Claims

1. A piezo electric sensor for improved measurement of mechanical parameters like force, pressure and measurement values derived there from, in particular a piezo electric sensor with improved measurement signal sensitivity and -temperature stability for measuring pressures that vary with respect to space and time and for determining a position and propagation velocity of a pressure fluctuation and of pressure waves, the piezo electric sensor comprising:

at least two parallel strips made from a piezo electric material;

at least one sensor base element;

at least one cavity between the piezo electric material and the sensor base element; and

at least one piece of amplifier electronics,

wherein the parallel strips are made from a piezo electric material with a protective foil and a flexible circuit board configured as a measurement membrane laminate are glued onto the sensor base element, so that they are elastically preloaded in one dimension in a direction of a piezo-dipole orientation and a free cavity is provided between the piezo electric sensor material mounted under tension in the measurement portion and the sensor base element through a recess/milled recess.

2. The piezo electric sensor according to claim 1, wherein a piezo electric foil is used for the piezo electric material for the sensor.

3. The piezo electric sensor according to claim 2, wherein a metal coated polyvinylidenfluoride foil is used for the piezo electric material for the sensor.

4. The piezo electric sensor according to claim 3, wherein the piezo electric material for the sensor is coated with a protective foil.

5. The piezo electric sensor according to claim 4, wherein the protective foil of the piezo electric material is configured as a polyimide foil.

6. The piezo electric sensor according to claim 5, wherein the metal coating is disposed between the piezo electric material of the sensor and the protective foil.

7. The piezo electric sensor according claim 6, wherein the sensor base element is configured as a rigid carrier circuit board.

8. The piezo electric sensor according to claim 7, wherein the amplifier electronics of the piezo electric sensor are attached directly to the rigid carrier circuit board.

9. The piezo electric sensor according to claim 8, wherein the piezo electric material of the sensor is glued onto a flexible circuit board.

10. The piezo electric sensor according to claim 9, wherein the flexible circuit board is configured as a polyimide circuit board.

11. The piezo electric sensor according to claim 10, wherein the piezo electric sensor is capable of being used for non invasive low impact continuous detection and processing of a pulse frequency for humans and animals,

wherein a measurement of the systolic and the diastolic blood pressure is performed by determining a pulse wave velocity in an artery of a human being and the measurement of the pulse wave signal form is performed through a piezo electric sensor according to the invention,

wherein a measurement of the pulse frequency of a living being is performed from time based pulse wave signals through a piezo electric sensor according to the invention,

wherein a calibration of the measurement device for determining the diastolic and systolic blood pressure is performed at a beginning of the measurement and monitoring cycle in that for at least two calibration measurements with different blood pressure the jacket pressure of a pressure loadable jacket is increased to a value above the systolic blood pressure at the beginning of the measurement or monitoring cycle and thus an association of the blood pressure values derived according to a Riva-Rocci-Method is performed with the values of the pulse wave velocity and the signal wave signal form,

wherein the detection and processing of the systolic and the diastolic blood pressure and of the pulse frequency is performed in an automated manner through a control and processing unit.

14. The piezo electric sensor according to claim 1, wherein a metal coated polyvinylidenfluoride foil is used for the piezo electric material for the sensor.

15. The piezo electric sensor according to claim 14, wherein the piezo electric material for the sensor is coated with a protective foil.

16. The piezo electric sensor according to claim 15, wherein two measurement membrane laminate layers disposed on top of one another whose sensor material strips are preferably aligned perpendicular to one another are being used to facilitate a two dimensional determination of the position and the propagation velocity of pressure fluctuations and pressure waves and measurement values that are derivable there from for a random angular placement of the sensor at the measurement location.

17. The piezo electric sensor according to claim 16, wherein portions of measurement membrane laminates disposed adjacent to one another whose sensor material strips are preferably aligned perpendicular to one another are being used for facilitating a two dimensional determination of the position and propagation velocity of pressure fluctuations and pressure waves and measurement values derivable there from, for a random angular arrangement of the sensor at the measurement location.

18. The piezo electric sensor according to claim 1, wherein two measurement membrane laminate layers disposed on top of one another whose sensor material strips are preferably aligned perpendicular to one another are being used to facilitate a two dimensional determination of the position and the propagation velocity of pressure fluctuations and pressure waves and measurement values that are derivable there from for a random angular placement of the sensor at the measurement location.

19. The piezo electric sensor according to claim 18, wherein portions of measurement membrane laminates disposed adjacent to one another whose sensor material strips are preferably aligned perpendicular to one another are being used for facilitating a two dimensional determination of the position and propagation velocity of pressure fluctuations and pressure waves and measurement values derivable there from, for a random angular arrangement of the sensor at the measurement location.

20. A method for non invasive low impact continuous detection and processing of a pulse frequency for humans and animals, the method comprising:

measurement of a systolic and a diastolic blood pressure by determining a pulse wave velocity in an artery of a human being or animal, wherein the measurement of the pulse wave signal form is performed through a piezo electric sensor according to claim 1,

wherein a measurement of the pulse frequency of a living being is performed from time based pulse wave signals through the piezo electric sensor,

wherein a calibration of the measurement device for determining the diastolic and systolic blood pressure is performed at a beginning of the measurement and monitoring cycle such that for at least two calibration measurements with different blood pressure the jacket pressure of a pressure loadable jacket is increased to a value above the systolic blood pressure at the beginning of the measurement or monitoring cycle and an association of the blood pressure values derived according to a Riva-Rocci-Method is performed with the values of the pulse wave velocity and the signal wave signal form,

wherein the detection and processing of the systolic and the diastolic blood pressure and of the pulse frequency is performed in an automated manner through a control and processing unit.

12. The piezo electric sensor according to claim, wherein two measurement membrane laminate layers disposed on top of one another whose sensor material strips are preferably aligned perpendicular to one another are being used to facilitate a two dimensional determination of the position and the propagation velocity of pressure fluctuations and pressure waves and measurement values that are derivable there from for a random angular placement of the sensor at the measurement location.

13. The piezo electric sensor according to claim 12, wherein portions of measurement membrane laminates disposed adjacent to one another whose sensor material strips are preferably aligned perpendicular to one another are being used for facilitating a two dimensional determination of the position and propagation velocity of pressure fluctuations and pressure waves and measurement values derivable there from, for a random angular arrangement of the sensor at the measurement location.