Low cost pressure transducer particularly for medical applications
First Claim
1. In a pressure transducer having a strain gauge including at least one thick film pressure measuring resistor formed on a diaphragm and having a resistance value varying in response to pressure forces flexing the diaphragm, and further including conductors coupled to the pressure measuring resistor by which the pressure forces may be determined by monitoring at the conductors for an electrical signal which varies in relation to changes in the resistance of the pressure measuring resistor, the improvement comprising:
- at least one thick film patch-in resistor formed on the diaphragm such that its resistance also varies with flexing of the diaphragm; and
structure associated with the pressure transducer to selectively electrically connect the patch-in resistor to the measuring resistor such that the electrical signal being monitored at the conductors is affected without altering resistance values of the measuring and patch-in resistors.
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Accused Products
Abstract
A pressure transducer (10) for measuring fluid pressure in a fluid path comprising a strain gauge circuit (37) of thick film piezoresistors formed on an alumina diaphragm (36) in a Wheatstone bridge configuration. Each resistance leg of the bridge typically includes a thick film measuring piezoresistor (R1A) to which selected thick film patch-in piezoresistors (R1B, R1C, R1D, R1E) are selectively connected to create a measuring resistance network (PN1). The measuring resistance network is adjusted to a predetermined resistance value to balance and optimize the electrical symmetry of the bridge. The pressure transducer (10) includes a mechanical stop member (46) located adjacent the alumina diaphragm (36) such that the fully deflected diaphragm contacts the stop thereby physically preventing the diaphragm from deflecting an amount that would cause the diaphragm to rupture.
71 Citations
31 Claims
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1. In a pressure transducer having a strain gauge including at least one thick film pressure measuring resistor formed on a diaphragm and having a resistance value varying in response to pressure forces flexing the diaphragm, and further including conductors coupled to the pressure measuring resistor by which the pressure forces may be determined by monitoring at the conductors for an electrical signal which varies in relation to changes in the resistance of the pressure measuring resistor, the improvement comprising:
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at least one thick film patch-in resistor formed on the diaphragm such that its resistance also varies with flexing of the diaphragm; and structure associated with the pressure transducer to selectively electrically connect the patch-in resistor to the measuring resistor such that the electrical signal being monitored at the conductors is affected without altering resistance values of the measuring and patch-in resistors. - View Dependent Claims (2, 3, 4)
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5. A pressure transducer comprising:
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a diaphragm flexing in response to pressure forces; and a strain gauge formed on the diaphragm and including; a thick film pressure measuring resistor formed on the diaphragm arid having a measuring resistance value changing in response to changes in the pressure forces; a plurality of thick film patch-in resistors formed on the diaphragm adjacent the pressure measuring resistor and having a plurality of patch-in resistance values changing in response to changes in the pressure forces; and structure for selectively electrically connecting the plurality of patch-in resistors with the measuring resistor to form a thick film measuring resistance network having a network resistance value, whereby selectively connecting the plurality of patch-in resistors with the measuring resistor changes the network resistance value without altering the measuring and patch-in resistance values. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A pressure transducer for measuring a pressure of a bodily fluid comprising:
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a substrate having a generally yieldable diaphragm and a generally rigid support member supporting the diaphragm, the diaphragm flexing in response to the pressure of the bodily fluid exerted on one side of the substrate; a strain gauge located on an opposite side of the substrate and having; a thick film measuring resistor formed on the diaphragm; and a group of thick film patch-in resistors formed on the diaphragm, the measuring resistor and the group of patch-in resistors having first resistance values changing in response to the diaphragm flexing from the pressure; means for electrically connecting selected ones of the group of patch-in resistors with the measuring resistor to form a measuring resistance network having a network resistance value, whereby connecting selected ones of the group of patch-in resistors in the measuring resistance network changes the network resistance value without changing the first resistance values of the measuring resistor and the patch-in resistors; input terminals connected to the strain gauge for providing a source of power; and output terminals connected to the strain gauge for providing an output signal changing as a function of changes in the pressure of the bodily fluid. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification