Capacitance variometer

Claim 2

A variometer comprising: a. a differential pressure transducer having a sensing element that deflects in response to changes in ambient pressure and effects relative movement of a pair of capacitive elements, the capacitance of each element varying oppositely in response to deflection of said sensing element, said capacitive elements having one plate electrically connected in common with each other at a fixed potential; b. an oscillator circuit connected to said capacitive elements, said oscillator circuit being adapted to generate a pair of output signals whose frequencies are modified in accordance with the capacitance of said capacitive elements; c. a pair of filter circuits coupled to said oscillator circuit to receive said output signals, said filter circuit having a pass band so as to exclude the frequency of said oscillator circuit; d. combining means, said filter circuits being coupled to the inputs of said combining means, said combining means being adapted to combine the outputs of said filter circuits; and e. an indicator coupled to said combining means and being responsive to the output of said combining means for displaying an indication of the actual deflection of said sensing element.

Claim 3

A variometer as defined in claim 1 wherein said oscillator circuit comprises: an astable multivibrator circuit, said astable multivibrator circuit having a pair of gate control inputs; a bistable multivibrator circuit having a set and reset input, the two outputs of said bistable multivibrator being connected respectively to said gate control inputs of said astable multivibrator, the two outputs of said bistable multivibrator also being coupled respectively to said filter circuits; said pair of capacitive elements being coupled together at a common juncture, each of said capacitive elements being coupled respectively to an output of said astable multivibrator, the outputs of said astable multivibrator circuit being connected respectively to the set and reset inputs of said bistable multivibrator, whereby said bistable multivibrator circuit is triggered by said astable multivibrator circuit.

Claim 4

A rate of climb indicator, comprising: a. a housing having a back chamber and an atmospheric chamber, said atmospheric chamber being adapted to be exposed to the atmosphere; b. at least one diaphragm in said housing, said diaphragm separating said atmospheric chamber from said back chamber; c. a conduit extending between said atmospheric chamber and said back chamber to provide a response time constant; d. a pair of stator plates respectively disposed in said atmospheric chamber and said back chamber adjacent to said diaphragm, each stator plate forming a separate capacitive element with said diaphragm; e. an oscillator circuit connected to said capacitive elements, said oscillator circuit being adapted to generate a pair of output signals whose frequencies are modulated in accordance with the capacitance of said capacitive elements; f. a pair of filter circuits coupled to said oscillator circuit to receive said output signals, said filter circuits having a pass band so as to exclude the frequency of said oscillator circuit; g. a differential amplifier, said filter circuits being coupled to the input of said differential amplifier; and h. an indicator coupled to said differential amplifier for displaying an indication of the deflection of said sensing element.

Claim 5

A rate of climb indicator, comprising: a. a housing having a back chamber and an atmospheric chamber, said atmospheric chamber being adapted to be exposed to the atmosphere; b. at least one diaphragm in said housing, said diaphragm separating said atmospheric chamber from said back chamber; c. a conduit extending between said atmospheric chamber and said back chamber to provide a response time constant; d. a pair of stator plates respectively disposed in said atmospheric chamber and said back chamber adjacent to said diaphragm, each stator plate forming a separate capacitive element with said diaphragm; e. an oscillator circuit connected to said capacitive elements, said oscillator circuit being adapted to generate a pair of output signals whose frequencies are modulated in accordance with the capacitance of said capacitive elements; f. a pair of filter circuits coupled to said oscillator circuit to receive said output signals, said filter circuits having a pass band so as to exclude the frequency of said oscillator circuit; g. a differential amplifier, said filter circuits being coupled to the input of said differential amplifier; and h. an indicator coupled to said differential amplifier for displaying an indication of the deflection of said sensing element.

Claim 6

A rate of climb indicator as defined in claim 3 wherein said electronic oscillator circuit comprises: an astable multivibrator circuit having a first and second gate control input and first and second outputs; a first of said capacitive elements being coupled between said first output of said multivibrator circuit and a point of fixed potential; a second of said capacitive elemEnts being coupled between said second input of said multivibrator circuit and said point of fixed potential; a first NAND gate having a first and second input and an output, said first input of said first NAND being d-c coupled to said output of said multivibrator circuit, said second input of said first NAND gate being connected to said first gate control input of said multivibrator circuit; a second NAND gate having a first and second input and output, said output of said second NAND gate being coupled to said second input of said first NAND gate, said first input of said second NAND gate being coupled to said output of said first NAND gate and also to said second gate control input of said multivibrator circuit, said second input being d-c coupled to said second output of said multivibrator circuit; said outputs of said first and second NAND gates being coupled to said pair of filter circuits.

Claim 7

A variometer comprising: a differential pressure transducer having a sensing element that deflects in response to changes in ambient pressure and a pair of capacitive elements, the capacitive of each capacitive element varying oppositely in response to deflection of said sensing element, said capacitive elements having one plate electrically connected in common with each other at a fixed potential; means coupled to said capacitive elements for generating a pair of signals whose frequencies are modulated in accordance with the capacitance of said capacitive elements; means coupled to said means for generating a pair of signals for producing a pair of average value signals having an amplitude proportional to the change in capacitance of said capacitive element; and means for indicating said pair of average value signals, whereby there will be produced an output indication proportional to the actual deflection of said sensing element.

Claim 8

A variometer comprising: a differential pressure transducer having a sensing element that deflects in response to changes in ambient pressure and a pair of capacitive elements, the capacitive of each capacitive element varying oppositely in response to deflection of said sensing element, said capacitive elements having one plate electrically connected in common with each other at a fixed potential; means coupled to said capacitive elements for generating a pair of signals whose frequencies are modulated in accordance with the capacitance of said capacitive elements; means coupled to said means for generating a pair of signals for producing a pair of average value signals having an amplitude proportional to the change in capacitance of said capacitive element; and means for indicating said pair of average value signals, whereby there will be produced an output indication proportional to the actual deflection of said sensing element.