FLUID SENSOR AND METHODS OF MAKING COMPONENTS THEREOF

• US 20090120169A1
• Filed: 11/12/2007
• Published: 05/14/2009
• Est. Priority Date: 11/12/2007
• Status: Abandoned Application

• Current Assignee: Meas France
• Original Assignee: Visyx Technologies, Inc. (TE Connectivity Limited)
• Inventors: Goslin, Gregory Ray, Chandler,, William H. JR., McNeil, Douglas B.
• Application Number:
  US11/938,621
• Publication Number:
  US 20090120169A1
• Time in Patent Office: Days
• US Class Current: 73/54.410
• CPC Class Codes: G01N 11/16 by measuring damping effect upon oscillatory body
• CPC Class Codes: G01N 2291/02818 Density, viscosity
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/028 by measuring mechanical or acoustic impedance
• CPC Class Codes: G01N 9/002 using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis G01N9/34 takes precedence
• CPC Class Codes: H05K 1/148 Arrangements of two or more hingeably connected rigid printed circuit boards, i.e. connected by flexible means
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A fluid sensor has an electrically grounded header and a plurality of feedthrough conductors extending through the header between opposite ends of the header. The feedthrough conductors are connected to a piezoelectric tuning fork resonator. A temperature sensor is adjacent the tuning fork resonator. A shroud partially encloses the tuning fork resonator and temperature sensor. A printed circuit board is in conductive electrical contact with the feedthrough conductors. The printed circuit board includes an ASIC chip operable to transmit a variable frequency signal to the tuning fork resonator through the feedthrough conductors to oscillate the tuning fork resonator and to monitor impedance of the tuning fork resonator as a function of frequency. The ASIC chip is spaced from the feedthrough conductors a distance of no more than about 2 mm. The printed circuit board is spaced from the tuning fork a distance of no more than about 20 mm.

Claims

1. A fluid sensor for determining properties of a fluid, the sensor comprising:

a header assembly comprising an electrically grounded header and a plurality of feedthrough conductors extending through the header between opposite ends of the header, each of the feedthrough conductors being surrounded by an electrically insulating sheath, the feedthrough conductors being fused to the sheaths and the sheaths being fused to the header;

a tuning fork resonator having a base portion and a pair of tines extending from the base portion, each of the tines including a piezoelectric substrate and electrodes on the substrate for applying an electric field to the substrate, some of the feedthrough conductors being in conductive electrical contact with the electrodes;

a temperature sensor in conductive electrical contact with some of the feedthrough conductors, the temperature sensor being spaced from the tuning fork resonator a distance that is no more than about 2 mm;

an electrically grounded shroud partially enclosing the tuning fork resonator and temperature sensor, the shroud comprising a substantially cylindrical wall extending circumferentially around the tuning fork resonator and temperature sensor, the shroud including a plurality of openings in the wall for allowing said fluid to enter the shroud and contact the tuning fork resonator and temperature sensor, the shroud being secured to the header assembly;

a fitting adapted to be installed in an opening of a support structure, the fitting having a central opening, the header assembly being received in the central opening and secured to the fitting;

a printed circuit board in conductive electrical contact with the feedthrough conductors, the printed circuit board including an ASIC chip operable to transmit a variable frequency signal to the electrodes on the tuning fork resonator through the feedthrough conductors to energize the electrodes so the tines oscillate in opposite phase and to monitor impedance of the tuning fork resonator as a function of frequency, the ASIC chip being spaced from the feedthrough conductors a distance of no more than about 2 mm, the printed circuit board being spaced from the electrodes on the tuning fork a distance of no more than about 20 mm.

2. A fluid sensor as set forth in claim 1 wherein the piezoelectric substrate comprises quartz.

3. A fluid sensor as set forth in claim 1 wherein the piezoelectric substrate comprises lithium niobate.

4. A fluid sensor as set forth in claim 1 wherein the temperature sensor is an RTD sensor.

5. A fluid sensor as set forth in claim 1 wherein the fitting comprises a threaded ring having external threads for installing the fluid sensor in threaded opening of the support structure.

9. A fluid sensor as set forth in claim 1 wherein the temperature sensor is adjacent the base portion of the tuning fork resonator.

6. A fluid sensor as set forth in claim 6 wherein the fitting further comprises a housing secured to the threaded ring, the printed circuit board being at least partially received in the housing.

7. A fluid sensor as set forth in claim 6 wherein the housing comprises a nut configured for being engaged by a tool to facilitate installation of the fluid sensor in the opening.

8. A fluid sensor as set forth in claim 6 wherein the printed circuit board is hermetically sealed within the housing.

10. A method of making a printed circuit board assembly for a fluid sensor comprising a piezoelectric tuning fork resonator and a temperature sensor, the method comprising:

attaching a first set of electrical components to a first printed circuit board and attaching a second set of electrical components to a second printed circuit board connected to the first printed circuit board by a flex cable, the first and second printed circuit boards being in a first configuration while the electrical components are being attached, the first set of electrical components including an ASIC chip adapted to;

(a) oscillate the tuning fork resonator using a variable frequency signal swept over a predetermined range of frequencies; and

(b) monitor the response of the mechanical resonator to the fluid at various different frequencies, at least one of the first and second set of electrical components including circuitry for operating the temperature sensor;

testing at least some of the electrical components on at least one of the first and second printed circuit boards while they are in said first configuration;

calibrating one or more electrical components on at least one of the first and second printed circuit boards while they are in said first configuration; and

reconfiguring the first and second printed circuit boards to a second configuration for installation in the fluid sensor, the second configuration being a more compact configuration than the first configuration.

11. A method as set forth in claim 10 wherein the first and second printed circuit boards are substantially co-planar and in side-by-side relation to one another in said first configuration.