Capacitive Sensor
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.
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This application is a divisional of U.S. patent application Ser. No. 11/655,762, entitled “Capacitive Sensor,” filed Jan. 19, 2007, the disclosure of which is incorporated herein in its entirety by this reference.
CROSS REFERENCE TO RELATED APPLICATIONU.S. Pat. No. 6,220,244, “Conserving device for use in oxygen delivery and therapy”, McLaughlin, is herein incorporated in its entirety by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIXNot applicable.
BACKGROUND OF THE INVENTIONRefer to U.S. Pat. No. 6,220,224, “Conserving device for use in oxygen delivery and therapy”, McLaughlin.
BRIEF SUMMARY OF THE INVENTIONNone included.
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only illustrated embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The single capacitor sensor 210 in
Regarding the assembly of the single capacitor depicted in
Alternatively the lid may be comprised of a second PCB 266. PCB 266 (or PCB 206) may originally include a copper laminate, or copper laminates, which may be etched to form copper sensing plates 268 and 258 (or copper sensing plate 208), and provide copper shielding plates 257 and 267 (or 207).
A second copper sensing plate 268 as illustrated in
Shielding plates 207, 257 and 267 provide electromagnetic shielding so metalized membranes 203 and 252 and copper sensing plates 208 and 258 and 268 respectively are electromagnetically isolated so as to improve the performance of the capacitive sensors.
Any of a number of alternative insulating, spacing, and securing means well known in the arts could be employed to achieve the function of spacer 202. Alternative means of defining a chamber 219a are may include a concave cavity (chamber) on the underside of lid 201 and alternative means for non-conductively securing the lid 201 to the membrane 203 including any of a number of adhesives well known in the art. Alternatively various manufacturing processes could be employed wherein these components and their functions could be combined into different, fewer or even a single part such as a plastic molded top that included the functions of lid 201 and means to affix to, and insulate from, membrane 203.
Preferably, the metalized membrane 203 is comprised of a flexible aluminized Mylar and is approximately 0.010 inches from the surface of the lid and 0.006 inches from non-conductive mask 209). This distance permits the lid 201 to act as a stop when the membrane experiences a significant pressure (negative pressure from the first pressure source in chamber 219a or positive pressure from a second pressure source in chamber 219b—see below). The stop prevents the membrane from experiencing excessive excursion which can be damaging, such as plastic deformation or premature fatigue from repeated excessive pressures/loads.
Conductive adhesive spacer 204 provides a means of grounding the membrane 203 and securing membrane 203 to the printed circuit board 206 and thereby defining chamber 219b.
As was the case with adhesive spacer 202 preferably adhesive spacer 204 is square with a round aperture therein, but any adequate aperture in the spacers could be equally functional and while it is preferred the spacers have the same dimensions it is not necessary. Alternative means of grounding the membrane 203 include a separate electrical contact between the membrane 203 and ground which is independent of the other components in
The metalized membrane 203 is a first charge plate and the copper sensing plate 208 is a second charge plate of a capacitor. As described herein, printed circuit board 206 and sensing plate 208 preferably have apertures which share an axis such that they are coupled to a second pressure source which is introduced to chamber 219b.
Preferably a non-conductive mask 209 may be disposed between the copper sensing plate 208 and the membrane 203 which will keep the metalized membrane 203 from shorting in the event it is deflected so as to come in contact with copper sensing plate 208.
An alternative embodiment, which does not conceptually depart from the single capacitor sensor depicted in
Alternatively, lid 201 may simply be replaced with printed circuit board 266 if the device needs another board—the PCB 266 could easily provide all the functions as lid 201. The non-conductive mask 269 and copper shielding 267 are preferred if this alternative is a dual capacitor sensor which requires a second sensing plate to enable the second capacitor—in this case copper sensing plate 268. The second sensing plate will provide for two capacitors which is preferred if the application is for a symmetrical differential pressure sensor. Obviously, and consistent with the embodiments described herein apertures in the conductive mask 269, copper sensing plate 268, copper shielding plate 267 and printed circuit board 266 would be necessary to maintain a port so as to introduce a pressure to chamber 279a. Introduction of a pressure to chamber 279b would be akin to the chambers 219a and 219b depicted in
Capacitive sensors depicted in
As depicted in
To illustrate a function of the RC circuit 101, refer to
To elaborate, in
The bolus delivered to the inspiration tube 606 may be delivered to a delivery device such as a cannula or face mask. The bolus will vary depending upon the physical characteristics of the delivery device used by the patient or pilot. It should be appreciated that while the subject invention has been described for use in an oxygen delivery system there are many other applications, non-medical and medical for which it could be utilized. In particular the subject invention could be utilized in a respiratory monitoring system to detect, measure, and report respiratory characteristics based on calculated differential air pressures put upon sensor 210 or alternatively 250.
Regarding microcontroller 112 (or 102) any of a number of adequate off the shelf controllers are well known in the art would suffice including Microchip PIC12C672 or PIC16F676. While the circuits depicted in
For an oxygen delivery system, or a respiratory monitoring system, preferably the first pressure source introduced to chamber 219a is ambient air and the second pressure source introduced to chamber 219b by the user via a respiratory tube 606.
The metalized membrane 203 or 252 is preferably a metalized Mylar. Due its properties it may be heated to predictably or controllably shrink, which increases the tension in the membrane, which controls the calibration point and may provide a robust and reliable sensor that is easy to make and easy to calibrate and which provides precise measurements in the capacitor 210.
An earlier version of the oxygen delivery system 601 is described in detail in the referenced U.S. Pat. No. 6,220,244 issued to the applicant. Many of the embodiments therein can be implemented into the subject oxygen delivery system including: a plurality of status indicators both visual and audio; power conservation methods and devices; means of measuring altitude to improve sensor performance and oxygen delivery performance—including changing the bolus; compilation of sensor data to more accurately detect the optimal time to deliver the bolus and duration of the bolus; and means of rejecting spurious data.
In regards to the means of detecting barometric pressure to detect changes in altitude, the barometric sensing device 107 or 117 may provide an input signal to the microcontroller when a sufficient change is altitude warrants a modification in oxygen delivery to the pilot or patient or indicates that supplemental oxygen must be used per laws and/or regulations.
While the '244 patent had a start drive line and sustain drive line in recognition that the solenoid valve in the valve assembly needed less power to be held open than to initially open, the subject invention saves power by going into pulse width modulation to not only use the least power possible to sustain an open valve but to change the duty cycle depending upon the power available—for example the battery voltage. This provides improved energy conservations.
The disclosed invention has been set forth in the forms of its preferred and alternative embodiments, and described for use in specific applications, but numerous modifications, which do not require independent invention, may be made to the disclosed devices, systems and methods without departing from inventive concepts embodied in the single capacitor sensor 210 which is disclosed and/or claimed herein.
Specifically, while an application of the subject invention discloses use in an oxygen conserving delivery system and certain embodiments have been directed to a system for pilots it should be assumed aspects of the subject invention and the embodiments thereof are equally applicable to general medicine wherein patients are in need of supplemental oxygen or medical treatment requires careful, accurate and timely respiratory monitoring. Moreover, the improved capacitive sensor may have myriad applications outside of general aviation or medicine.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims
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.
Type: Application
Filed: Jan 28, 2014
Publication Date: May 22, 2014
Applicant: IPG, LLC (Redmond, OR)
Inventors: Patrick L. McLaughlin (Redmond, OR), Thomas D. Decker (Redmond, OR)
Application Number: 14/166,505
International Classification: A61M 16/00 (20060101); A61M 16/12 (20060101); A61M 16/08 (20060101); A61M 16/20 (20060101);