Apparatus and method for detecting small changes in attached mass of piezoelectric devices used as sensors
Patent 4905701 Issued on March 6, 1990. Estimated Expiration Date: 
June 15, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
June 15, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesSandwich immunoassay using piezoelectric oscillator Method and apparatus for sensing fluids using surface acoustic waves Temperature probe using a plate of quartz Rheological testing apparatus and method Sensor having piezoelectric crystal for microgravimetric immunoassays Patent #: 4735906 InventorAssigneeApplicationNo. 206768 filed on 06/15/1988US Classes:600/437, Ultrasonic73/64.53, By vibration422/68.1, Means for analyzing liquid or solid sample436/806ELECTRICAL PROPERTY OR MAGNETIC PROPERTYExaminersPrimary: Jaworski, Francis J.Attorney, Agent or FirmInternational ClassA61B 008/00AbstractIn analysis, particularly for medical diagnostics, material can be selectively bound to the surface of a piezoelectric crystal by a reagent. The amount of material so bound affects the speed of propagation of an acoustic wave launched and received on the crystal surface by respective electrode pairs. Previously the crystal was used as a resonant element in an oscillator controlling the frequency of oscillation and so indicating the amount of bound material. However, the oscillator was either unstable or the range of bound masses too small to be of practical use. In the present invention delay between launch and reception of the acoustic wave provides a control signal for a voltage controlled oscillator. A much more stable system can therefore be constructed with a wide working range and high stability since the crystal is no longer the resonant element. Much greater sensitivity is also possible since the oscillator frequency may be greatly increased. A control signal representative of delay may be produced by a phase comparator comparing the phase of two input signals: one direct from the oscillator, and one from the reception of an acoustic wave on the crystal surface launched using a signal from the oscillator. The signal to the crystal may be modulated using a low frequency oscillator before it reaches the crystal to aid the oscillator in following frequency changes due to changing crystal surface conditions and the resulting signal may be summed with the output of a resonance oscillator before application to the crystal to aid the oscillator in initially settling to a stable frequency.Other References
Field of SearchInvolving vibration of substance or the measuring apparatusBy a vibratory effect (e.g., resonant frequency, acoustical) Surface acoustic wave devices Interdigitated electrodes Delay lines including elastic surface wave propagation means Spurious signal or mode cancellation means Variable delay DETERMINING NONELECTRIC PROPERTIES BY MEASURING ELECTRIC PROPERTIES ELECTRICAL PROPERTY OR MAGNETIC PROPERTY |
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