Device for measuring pressure

• US 20060275907A1
• Filed: 04/30/2004
• Published: 12/07/2006
• Est. Priority Date: 05/09/2003
• Status: Active Grant

• Current Assignee: MHM Harzbecher Medizintechnik GmbH
• Original Assignee: CGS Sensortechnik GmbH
• Inventors: Glocker, Raymond
• Granted Patent: US 7,803,628 B2
• Time in Patent Office: Days
• US Class Current: 436/70
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3641 Pressure isolators
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3324 PH measuring means
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2230/207 hematocrit
• CPC Class Codes: A61M 5/1413 Modular systems comprising interconnecting elements
• CPC Class Codes: A61M 5/16854 by monitoring line pressure
• CPC Class Codes: G01L 19/0023 for flowthrough systems having a flexible pressure transmitting element
• CPC Class Codes: G01L 9/0044 Constructional details of non-semiconductive diaphragms
• CPC Class Codes: G01L 9/0051 using variations in ohmic resistance

Abstract

In a device (1) for measuring the pressure of a medium (28), in particular a liquid medium, said device comprising a measuring chamber (10) through which the medium can flow and which has at least one elastically deformable wall (12), at least one wall (14) that is more rigid by comparison to said first wall, and an inlet (20) and outlet (22) for the medium, at least one excitation electrode (30) is provided in or on the at least one more rigid wall (14) of the measuring chamber (10), and at least one signal electrode (32) is provided on the elastically deformable wall (12), for impedance measurement.

Claims

1. Device for measuring the pressure of a medium, in particular a liquid medium, said device comprising a measuring chamber through which the medium can flow and which has at least one elastically deformable wall, at least one wall that is more rigid by comparison to said first wall, and an inlet and outlet for the medium, characterized in that at least one excitation electrode is provided in or on the at least one more rigid wall of the measuring chamber, and at least one signal electrode is provided on the elastically deformable wall, for impedance measurement.

2. Device according to claim 1, characterized in that an excitation system is provided for supplying the at least one excitation electrode.

3. Device according to claim 2, characterized in that the excitation system delivers a high-frequency alternating current of low current intensity, and, in particular, the alternating current is adjustable.

4. Device according to claim 1, characterized in that the at least one excitation electrode is made of a material providing good conduction of high-frequency alternating currents, and, in particular, is hard silver-plated.

5. Device according to claim 1, characterized in that the elastic wall is made of a reversibly deformable material, in particular an elastomer.

6. Device according to claim 1, characterized in that the at least one signal electrode is designed substantially flat, being applied in particular as a film material, conductive coating, conductive imprint and/or lacquer, in particular onto the elastic wall of the measuring chamber by a vacuum deposition method or being sprayed on, adhesively bonded on or otherwise applied.

7. Device according to claim 1, characterized in that the at least one elastic wall is or can be connected to the other walls of the measuring chamber by a tongue-and-groove joint, the elastic wall having in particular an annular bead element on its edge facing toward the other walls, and the walls which are or can be connected to the elastic wall having at least one groove for insertion of the bead element.

8. Device according to claim 1, characterized in that an arrangement is provided for ensuring free mobility of the elastic wall.

9. Device according to claim 8, characterized in that the arrangement is a protective cap, or a recess which permits free mobility of the elastic wall and which is situated in a retaining means for securing the device in the area of the measuring chamber.

10. Device according to claim 9, characterized in that the protective cap and/or the recess in the retaining means has such a shape and such dimensions, and is arranged in the area of the elastic wall such that it forms an abutment surface for the latter for pressure limitation.

11. Device according to claim 8, characterized in that an arrangement is provided for adjusting the device and for holding it at an adjustable height, this arrangement in particular being provided on the retaining means.

12. Device according to claim 1, characterized in that the measuring chamber has in at least some areas a means for coupling out capacitive fields and/or is surrounded by a means acting as a Faraday cage, and in particular the measuring chamber and/or the retaining means is/are provided with a metallic coating.

13. Device according to claim 1, characterized in that, in order to determine the conductivity of the medium located in the measuring chamber, an excitation electrode and a second electrode are provided outside the elastic wall.

14. Device according to claim 1, characterized in that an evaluation unit is provided for determining the hematocrit value from the determined conductivity value and/or the internal pressure of the measuring chamber and in particular for correction of zero line and sensitivity.

15. Device according to claim 1, characterized in that at least one contact pin is provided for attaching the measuring chamber onto the retaining means.

16. Device according to claim 15, characterized in that the retaining means has a retaining plate which is provided with contact surfaces or contact pads and which is used to generate concealed contacting between retaining means and measuring chamber.

17. Device according to claim 16, characterized in that the contact surfaces and/or contact pads and the contact pins are distributed in such a way that false contacting and false polarity are substantially avoided.

18. Device according to claim 15, characterized in that at least some of the contact pins and electrodes are formed integrally.

19. Device according to claim 18, characterized in that the contact pins and electrodes are molded onto the measuring chamber, in particular in an insert injection-molding operation.

20. Device according to claim 15, characterized in that the protective cap has a base part for protecting the elastic wall of the measuring chamber, and a collar part which at least partially surrounds the area of the electrodes and/or contact pins so as to protect the contact pins.

21. Method for determining the hematocrit value of blood contained in a measuring chamber, in particular using a device as claimed in claim 1, in which method blood flows through the measuring chamber in an extracorporeal circuit, and the hematocrit value is determined by determining the conductivity value between two fixed electrodes projecting into the measuring chamber.

22. Method according to claim 21, characterized in that, in order to draw up a liquid balance, the hematocrit value is determined by conductivity value calculation at the start of a measurement path and at the end of the measurement path and is compared.