Capacitive Sensor

Abstract

A capacitive sensor for measuring pressure comprises a fixed charge plate integral to a printed circuit board, a flexible charge plate that is grounded, a conductive donut-shaped adhesive spacer between the charge plates, a lid, a non-conductive donut-shaped adhesive spacer between the second charge plate and the lid, means of providing a pressure, fixed or variable, to both sides of the flexible charge plate, wherein a microcontroller controls a power supply and provides a voltage to the first charge plate wherein the accumulative voltage may be measured as a means of determining differential pressure.

What is claimed is: 
     
         1 . An oxygen conserving delivery system and operative to regulate a flow of oxygen during an inspiration event of a respiratory cycle based on a calculated differential air pressure, and comprising:
 an oxygen source;   a valve assembly including a valve for receiving oxygen from the oxygen source, and having an output port coupled to a respiration tube;   an inspiration sensor resides on a printed circuit board with an aperture, wherein the inspiration sensor includes:   a first fixed charge plate with an aperture affixed to the printed circuit board wherein the first fixed charge plate aperture and the printed circuit   board aperture define a port coupled to the respiration tube; a flexible charge plate;   means for securely separating the first fixed charge plate and the flexible charge plate wherein the charge plates are an initial distance apart;   means for electrically grounding the flexible charge plate; a lid with an aperture, thereby defining a second inspiration sensor port which is coupled to ambient pressure;   means for securely separating the flexible charge plate and the lid;   means for providing a voltage to the first fixed charge plate;   means for measuring an accumulated voltage across the first fixed charge plate and the flexible charge plate for a given amount of time wherein the accumulated voltage is a function of a variable distance between the first fixed charge plate and the flexible charge plate; and   means for calculating the differential air pressure based on the change in the accumulated voltage at the initial distance and the variable distance;   a microcontroller for regulating operation of the oxygen conserving delivery system, wherein the microcontroller repeatedly receives a variable signal from the inspiration sensor and therefrom detects an inspiration event; and   a means for regulating a bolus of oxygen supplied to the respiration tube.   
     
     
         2 . An oxygen conserving delivery system according to  claim 1 , wherein the first fixed charge plate is integral the printed circuit board. 
     
     
         3 . An oxygen conserving delivery system according to  claim 2 , further comprising a microcontroller which resides on the printed circuit board and wherein the microcontroller includes the means for measuring the accumulated voltage. 
     
     
         4 . An oxygen conserving delivery system according to  claim 3 , further comprising a power source wherein the microcontroller controls the power source to provide a voltage to the first fixed charge plate. 
     
     
         5 . An oxygen conserving delivery system according to  claim 4 , further comprising a resistor through which the microcontroller applies a pulse of voltage. 
     
     
         6 . An oxygen conserving delivery system according to  claim 1 , wherein the printed circuit board further comprises a means for electro-magnetic shielding the first fixed charge plate. 
     
     
         7 . An oxygen conserving delivery system according to  claim 1 , wherein the means for grounding is for the first fixed charge plate and wherein the means for providing a voltage is to the flexible charge plate and wherein the lid further comprises a means for shielding the flexible charge plate. 
     
     
         8 . An oxygen conserving delivery system according to  claim 1 , wherein the flexible charge plate is comprised of metalized Mylar. 
     
     
         9 . An oxygen conserving delivery system according to  claim 1 , wherein means for securely separating the first fixed charge plate and the flexible charge plate is comprised of a first adhesive spacer. 
     
     
         10 . An oxygen conserving delivery system according to  claim 9 , wherein the first adhesive spacer is in electrical contact with the printed circuit board and which further comprises the means for grounding the flexible charge plate. 
     
     
         11 . An oxygen conserving delivery system according to  claim 1 , further comprising means for non-conductively masking the first fixed charge plate from the flexible charge plate. 
     
     
         12 . An oxygen conserving delivery system according to  claim 1 , wherein the means for measuring the accumulated voltage resides in the microcontroller. 
     
     
         13 . An oxygen conserving delivery system according to  claim 12 , wherein the microcontroller is measuring an accumulation of voltage more than once for each of the pulses of voltage applied. 
     
     
         14 . An oxygen conserving delivery system according to  claim 13 , wherein the microcontroller measures more than one accumulation of voltage before an air pressure is calculated by the microcontroller. 
     
     
         15 . An oxygen conserving delivery system according to  claim 12 , further comprising a means of tracking the accumulated voltage in the microcontroller. 
     
     
         16 . An oxygen conserving delivery system according to  claim 1 , wherein the first inspiration sensor port is coupled to ambient pressure, and wherein the second inspiration sensor port is coupled to the valve assembly output port and with the respiration tube. 
     
     
         17 . An oxygen conserving delivery system according to  claim 1 , wherein the system further comprises a barometer for detecting changes in altitude, wherein the barometer provides a signal to the microcontroller and the microcontroller determines when a sufficient change in altitude warrants a modification in oxygen delivery. 
     
     
         18 . An oxygen conserving delivery system according to  claim 1 , wherein the lid is a second fixed charge plate and the means for providing a voltage to the first fixed charge plate further comprises means to provide the voltage to the second charge plates. 
     
     
         19 . A method for monitoring respiration, said method comprising the steps of
 (1) providing a respiration monitor which includes a capacitive pressure sensor assembly;   (2) providing mean of controlling the respiration monitor;   (3) providing means of applying a voltage to the capacitive sensor assembly;   (4) providing a means of measuring an accumulated voltage on the capacitive sensor assembly; and   (5) providing a means of determining respiration based on the measuring of the accumulated voltage.   
     
     
         20 . The method as defined in  claim 19  wherein the means of applying the voltage results in an asymptotic accumulation of voltage on the capacitive sensor assembly. 
     
     
         21 . The method as defined in  claim 19  wherein the method further comprises more than one measuring of the accumulated voltage. 
     
     
         22 . The method as defined in  claim 19  wherein the method further comprises applying a pulse of voltage to the capacitive sensor assembly. 
     
     
         23 . The method as defined in  claim 19  wherein the method further comprises a capacitive sensor assembly with a metalized Mylar charge plate. 
     
     
         24 . A method for supplying oxygen to a user's respiratory system during a respiration cycle, said method comprising the steps of:
 (1) providing an oxygen conserving delivery system which includes a valve assembly, a capacitive inspiration sensor assembly, a microcontroller for positively controlling operation of the valve assembly and the inspiration sensor assembly, and a power source;   (2) providing a pulse of voltage to the capacitive inspiration sensor assembly wherein the accumulation of voltage on the capacitive inspiration assembly is asymptotic;   (3) providing a means of measuring the accumulation of voltage on the capacitive inspiration sensor assembly;   (4) providing a means of determining an inspiration event based on the measuring of the accumulated voltage; and   (5) providing sufficient energy to open a valve of the valve assembly for supplying oxygen to the user.   
     
     
         25 . The method as defined in  claim 24  wherein the method further comprises more than one measuring of the accumulation of voltage for each of the pulses of voltage provided to the inspiration sensor assembly. 
     
     
         26 . The method as defined in  claim 24  further comprising the steps of providing a capacitive inspiration sensor assembly comprising:
 (1) producing a fixed charge plate and a flexible charge plate; 
 (2) securing and separating the fixed charge plate and the flexible charge plate a first distance apart: 
 (3) providing means to ground the flexible charge plate; 
 (4) producing a lid; 
 (5) securing and separating the flexible charge plate and the lid; 
 (6) providing means to apply a first pressure to one side of the flexible charge plate and means to apply a second pressure to the other side of the flexible charge plate; 
 (7) providing means to apply a voltage to the fixed plate; 
 (8) providing means to calculate a differential between the first pressure and the second pressure. 
 
     
     
         27 . The method as defined in  claim 26  wherein the flexible charge plate is a metalized Mylar. 
     
     
         28 . The method as defined in  claim 27  further comprising the step of heating the metalized Mylar flexible charge plate.