Sensor arrangement for detecting the physical properties of liquids

• US 6,407,479 B1
• Filed: 05/04/2001
• Issued: 06/18/2002
• Est. Priority Date: 11/04/1998
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Eisenschmid, Heinz, Herrmann, Falk, Moellendorf, Manfred
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/831,055
• Time in Patent Office: 410 Days
• Field of Search: 310/313.R, 310/313.A
• US Class Current: 310/313.00A
• CPC Class Codes: G01N 2291/0226 Oils, e.g. engine oils
• CPC Class Codes: G01N 2291/02416 Solids in liquids
• CPC Class Codes: G01N 2291/0251 Solidification, icing, curing composites, polymerisation
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• 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 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: G01N 29/326 compensating for temperature variations
• CPC Class Codes: H03H 9/02551 of quartz substrates

Abstract

A sensor arrangement for ascertaining physical properties of a liquid is proposed, having electro-acoustical converters (6) on a substrate (5) which are wettable with the liquid and are suitable for generating and detecting acoustical surface waves with predetermined wave modes. A Y-rotated quartz slice is used as the substrate (5), and above the substrate (5) is a waveguide layer (16); the standard of the Y rotation of the quartz slice and the material of the waveguide layer (16) are selected such that an extensive temperature compensation within the range of temperature of the liquid to be investigated is obtained.

Claims

1. A sensor arrangement for ascertaining physical properties of a liquid, comprising a substrate;

electro-acoustical convertors applied to said substrate and operatively connected to a liquid, said convertors being formed for generating and detecting acoustical surface waves embodied as Love-waves, so that a propagation behavior of the Love-waves along a measurement path can be ascertained as a standard for physical properties, said substrate being formed as Y-rotated quartz slice; and

a wave guide layer exposed above said substrate, a standard of the Y rotation of said quartz slice and a material of said wave guide layer being selected so that an extensive temperature compensation of the Love-waves employed is obtained within a range of a temperature of the liquid to be investigated.

2. A sensor arrangement as defined in claim 1, wherein said Y-rotated quartz slice has an angle of rotation between 25°

and 36°

, said waveguide layer being composed of SiO₂.

3. A sensor arrangement as defined in claim 1, wherein said Y-rotated quartz slice has an angle of rotation between 40°

and 60°

, said waveguide layer being formed as a layer with a negative temperature coefficient.

4. A sensor arrangement as defined in claim 1, wherein said Y-rotated quartz slice has an angle of rotation of approximately 48°

, said waveguide layer being formed as a layer with a virtually linear negative temperature coefficient.

5. A sensor arrangement as defined in claim 1, wherein said waveguide layer is a polymer layer.

6. A sensor arrangement as defined in claim 1, wherein said sensor arrangement is usable in a motor vehicle to determine a quality of a motor oil or operating liquids, said substrate being dipped directly into an oil to be measured.