High output differential pyroelectric sensor
First Claim
1. A differential thermal sensor having compensation for variations in ambient temperature and for mechanical vibration comprising:
- a first elongate thermal detector having a polarized pyroelectric crystal disposed between two conductive electrodes;
a second elongate thermal detector identical to said first thermal detector and having a polarized pyroelectric crystal disposed between two conductive electrodes;
a mounting base, said first detector mounted on said base and extending therefrom in a cantilevered manner, and said second detector mounted on said base adjacent said first detector and extending from said base in a cantilevered manner; and
a pair of conductors conductively attached to said electrodes of said first and second detectors so as to form a parallel opposing connection of said detectors, said pair of conductors also forming output connections for said sensor.
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Accused Products
Abstract
A dual pyroelectric crystal sensor suitable for infrared intruder alarms and the like having two separate closely spaced identical pyroelectric crystal detectors connected in parallel opposition. The sensor includes a single ended field effect transistor amplifier with the entire sensor encapsulated in a TO-5 can. The two crystals each have one end cemented to a ceramic substrate in a cantilevered fashion, permitting shock or vibration to affect each crystal equally. Therefore, voltages due to the piezoelectric responses of the crystals are equal and cancel. If both crystals are irradiated by a common heat source, the pyroelectric generated voltages will cancel. If either crystal is irradiated separately, an output voltage will be produced.
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Citations
22 Claims
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1. A differential thermal sensor having compensation for variations in ambient temperature and for mechanical vibration comprising:
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a first elongate thermal detector having a polarized pyroelectric crystal disposed between two conductive electrodes; a second elongate thermal detector identical to said first thermal detector and having a polarized pyroelectric crystal disposed between two conductive electrodes; a mounting base, said first detector mounted on said base and extending therefrom in a cantilevered manner, and said second detector mounted on said base adjacent said first detector and extending from said base in a cantilevered manner; and a pair of conductors conductively attached to said electrodes of said first and second detectors so as to form a parallel opposing connection of said detectors, said pair of conductors also forming output connections for said sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A differential thermal sensor having an extended low frequency response and compensation for ambient temperature variation and for vibration comprising:
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a ceramic substrate having first and second electrodes on one surface thereof; a first pyroelectric crystal detector having a positive electrode and a negative electrode, said first detector having a small portion of one of said positive and negative electrodes conductively attached to said first substrate electrode so as to cantilever said first detector from said substrate; a second pyroelectric crystal detector having a positive electrode and a negative electrode, said second detector having a small portion of one of said positive and negative electrodes conductively attached to said second substrate electrode adjacent to and essentially parallel to said first detector so as to cantilever said second detector from said substrate; and electrical connections between said first and second detectors for connecting the positive electrode of said first detector to the negative electrode of said second detector, and the negative electrode of said first detector to the positive electrode of said second detector. - View Dependent Claims (12)
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13. An intrusion detection device having ambient temperature compensation and vibration compensation comprising:
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a header having a ground lead and a pair of output leads; a pyroelectric differential sensor having a rectangular ceramic substrate, a pair of rectangular pyroelectric crystal detectors attached to and cantilevered from said substrate, electrical connections connecting said pair of detectors in a parallel opposing connection, and first and second output leads from said sensor; a load resistor connected in parallel with said output leads, said second output lead also connected to said header ground lead; and amplifier means having an input and a pair of output terminals, said input connected to said first sensor output lead and said pair of output terminals connected to said pair of header output leads. - View Dependent Claims (14, 15, 16)
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17. A differential thermal sensor having extended low frequency response and compensation for ambient temperature variations and for vibration comprising:
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a mounting base; a first pyroelectric detector having front and rear electrodes, said first detector having a small portion of said rear electrode attached to said base so as to cantilever said first detector from said base; a second pyroelectric detector having front and rear electrodes; a spacer attached to said front electrode of said first detector adjacent to the small attachment portion of said first detector, a small portion of said rear electrode of said second detector attached to said spacer so that said rear electrode of said second detector is in parallel opposition to said front electrode of said first detector, said second detector thereby serving to prevent radiation incident on said front electrode of said second detector from falling on said first detector; and electrical connections between said first and second detectors for connecting said first detector and said second detector in a parallel opposing electrical connection. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification