Passive sensor system using ultrasonic energy
First Claim
1. A passive compensated sensor system utlizing ultrasonic energy, the system comprising:
- at least one compensated pair of ultrasonically vibratable sensors, each of said sensors of said at least one compensated pair of passive sensors having at least one vibration frequency which is a function of at least a physical variable to be sensed; and
an ultrasonic activation and detection system for exciting said at least one compensated pair of sensors and for detecting said at least one vibration frequency of each of said sensors thereby to determine a value of said physical variable, said value being compensated for the effects of other physical variables on said at least one vibration frequency.
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Abstract
A passive sensor system utilizing ultrasonic energy is disclosed. The passive sensor system includes at least one ultrasonically vibratable sensor and an ultrasonic activation and detection system. The sensor has at least one vibration frequency which is a function of a physical variable to be sensed. The ultrasonic activation and detection system excites the sensor and detects the vibration frequency from which it determines a value of the physical variable. The sensor includes a substrate having at least one cavity therein, and a vibratable membrane overlying the cavity. Another preferred embodiment of the sensor is a compensated sensor pair including a first sensor whose vibration frequency is responsive to the physical variable to be sensed, and a second sensor whose vibration frequency is non-responsive to the physical variable to be sensed. The second sensor provides a reference vibration frequency for compensating for the effect of other physical variables on the vibration frequency of the first sensor. Another preferred embodiment of the compensated sensor pair includes a second sensor which has a different response characteristic than that of the first sensor to the physical variable to be sensed. In still another preferred embodiment of the compensated sensor of the present invention each of the pair of sensors has multiple vibratable membranes overlying multiple cavities.
27 Citations
28 Claims
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1. A passive compensated sensor system utlizing ultrasonic energy, the system comprising:
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at least one compensated pair of ultrasonically vibratable sensors, each of said sensors of said at least one compensated pair of passive sensors having at least one vibration frequency which is a function of at least a physical variable to be sensed; and an ultrasonic activation and detection system for exciting said at least one compensated pair of sensors and for detecting said at least one vibration frequency of each of said sensors thereby to determine a value of said physical variable, said value being compensated for the effects of other physical variables on said at least one vibration frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of measuring a physical variable of a body, the method comprising the steps of:
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activating, via an ultrasonic wave, at least one compensated pair of passive sensors located within the body and having two output vibration frequencies, at least one of said output vibration frequencies being a function of said physical variable; detecting said two output vibration frequencies; and determining a compensated value of said physical variable from said detected two output vibration frequencies. - View Dependent Claims (15, 16, 17, 18)
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19. A method of measuring a physical variable of a body, the method comprising the steps of:
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activating, via an ultrasonic wave, at least one compensated pair of passive sensors located within the body and having two output vibration frequencies which are substantially close to each other, at least one of said output vibration frequencies being a function of said physical variable; detecting the beat frequency created by said two output vibration frequencies; and determining a compensated value of said physical variable from said detected beat frequency. - View Dependent Claims (20, 21)
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22. A method of measuring a physical variable of a body, the method comprising the steps of:
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transmitting an ultrasonic wave having a first range of vibration frequencies through said body thereby to activate at least one compensated pair of passive sensors located within said body, said at least one compensated pair of passive sensors having at least one input vibration frequency within said first range and at least two output vibration frequencies, wherein at least one of said output vibration frequencies is a function of said physical variable; detecting said two output vibration frequencies; and determining a compensated value of said physical variable from said detected two output vibration frequencies. - View Dependent Claims (23, 24, 25, 26)
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27. A method of measuring a physical variable of a body, the method comprising the steps of:
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transmitting an ultrasonic wave having a first range of vibration frequencies through said body thereby to activate at least one passive compensated pair of sensors located within said body, said at least one passive compensated pair of sensors having at least one input vibration frequency within said first range, and two output frequencies, at least one of said output frequencies is a function of said physical variable, said two output vibration frequencies being substantially close to each other; detecting the beat frequency created by said two output vibration frequencies; and determining a compensated value of said physical variable from said detected beat frequency. - View Dependent Claims (28)
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Specification