US4856317A — Vacuum calibration system and method for fiberopt…

Claim 1

Independent Claim 240 words

In a fiber optic pressure measurement system having one or more optical fibers extending from a proximal end to a distal end within an enclosed sensor tip, means for directing light of known intensity through the fiber(s) from the proximal to and through the distal end, reflecting means within the sensor tip for directing at least a portion of the light back through the fiber(s) to the proximal end, and means for attenuating the intensity of the reflected light as a function of the pressure differential across the outside and inside of the sensor tip, means for calibrating the measurement system to establish a known relationship between the intensity of reflected light and pressure differential the calibrating means comprising: (a) means for applying a pressure differential across the outside and inside of said sensor tip; (b) means for varying said pressure differential continuously from a first to a second value over a time period; (c) means for measuring the value of said pressure differential at a plurality of discrete times during said time period; (d) means for measuring the value of the intensity of reflected light at said plurality of discrete times; and (e) means for storing said measured values of pressure differential and intensity of reflected light, whereby a known pressure value may be determined after calibration of the pressure measurement system by matching a measured value of reflected light intensity with the corresponding stored value of pressure differential.

Claim 2

Dependent Claim 240 words

In a fiber optic pressure measurement system having one or more optical fibers extending from a proximal end to a distal end within an enclosed sensor tip, means for directing light of known intensity through the fiber(s) from the proximal to and through the distal end, reflecting means within the sensor tip for directing at least a portion of the light back through the fiber(s) to the proximal end, and means for attenuating the intensity of the reflected light as a function of the pressure differential across the outside and inside of the sensor tip, means for calibrating the measurement system to establish a known relationship between the intensity of reflected light and pressure differential the calibrating means comprising: (a) means for applying a pressure differential across the outside and inside of said sensor tip; (b) means for varying said pressure differential continuously from a first to a second value over a time period; (c) means for measuring the value of said pressure differential at a plurality of discrete times during said time period; (d) means for measuring the value of the intensity of reflected light at said plurality of discrete times; and (e) means for storing said measured values of pressure differential and intensity of reflected light, whereby a known pressure value may be determined after calibration of the pressure measurement system by matching a measured value of reflected light intensity with the corresponding stored value of pressure differential.

Claim 3

Dependent Claim 39 words

The invention according to claim 1 wherein said means for applying a pressure differential comprise means for reducing the air pressure within said sensor tip, whereby the inside of said sensing tip is at a pressure less than atmospheric.

Claim 4

Dependent Claim 30 words

The invention according to claim 2 wherein said means for reducing air pressure comprise a cylinder having one end in essentially air-tight communication with the inside of said sensor tip.

Claim 5

Dependent Claim 49 words

The invention according to claim 3 wherein said means for reducing air pressure further comprise a piston movable toward said one end and means biasing said piston for movement away from said one end with a force at least great enough to produce said first value of pressure differential.

Claim 6

Dependent Claim 18 words

The invention according to claim 2 wherein said first pressure differential is larger than said second pressure differential.

Claim 7

Dependent Claim 28 words

The invention according to claim 5 wherein said first pressure differential is at least as great as the maximum pressure differential to be measured by said transducer system.

Claim 8

Dependent Claim 18 words

The invention according to claim 6 wherein said first pressure differential is at least about 300 mm Hg.

Claim 9

Dependent Claim 41 words

The invention according to claim 6 wherein said means for varying said pressure differential comprises a metering orifice in communication with the inside of said sensor tip to permit controlled entry of air into said sensor tip over said time period.

Claim 10

Dependent Claim 26 words

The invention according to claim 8 wherein said first pressure differential is at least about 300 mm Hg and said second pressure differential is substantially zero.

Claim 11

Dependent Claim 31 words

The invention according to claim 6 wherein said means for measuring the value of said pressure differential comprises a high accuracy pressure transducer communicating with the inside of said sensor tip.

Claim 12

Dependent Claim 66 words

The invention according to claim 10 wherein said means for reducing air pressure comprise a cylinder having one end in essentially air-tight communication with both the inside of said sensor tip and said pressure transducer, and a piston movable away from said one end to reduce the air pressure in said one end and thus in the inside of said sensor tip and said pressure transducer.

Claim 13

Independent Claim 230 words

The method of calibrating a pressure measurement system of the type having one or more optical fibers for conducting light from a proximal to a distal end within an enclosed sensor tip reflecting means within the sensor tip for directing at least a portion of the light back through the fiber(s) to the proximal end, and means for attenuating the intensity of the reflected light as a function of the pressure differential across the outside and inside of the sensor tip, said method comprising: (a) directing light of known intensity through the fiber(s) from the proximal to the distal end; (b) applying a pressure differential of a first magnitude across the inside and outside of the sensor tip; (c) continuously varying said pressure differential from said first magnitude to a second magnitude over a time period; (d) measuring the value of said pressure differential at a plurality of discrete times during said time period; (e) measuring the value of the intensity of light reflected back to the proximal end of the fiber(s) at said discrete times, thereby providing a plurality of values of pressure differential matched with corresponding values of reflected light intensity; and (f) storing said plurality of matched values, whereby an unknown value of pressure differential may be determined after calibration by matching a measured value of reflected light intensity with the corresponding stored value of pressure differential.

Claim 14

Independent Claim 230 words

The method of calibrating a pressure measurement system of the type having one or more optical fibers for conducting light from a proximal to a distal end within an enclosed sensor tip reflecting means within the sensor tip for directing at least a portion of the light back through the fiber(s) to the proximal end, and means for attenuating the intensity of the reflected light as a function of the pressure differential across the outside and inside of the sensor tip, said method comprising: (a) directing light of known intensity through the fiber(s) from the proximal to the distal end; (b) applying a pressure differential of a first magnitude across the inside and outside of the sensor tip; (c) continuously varying said pressure differential from said first magnitude to a second magnitude over a time period; (d) measuring the value of said pressure differential at a plurality of discrete times during said time period; (e) measuring the value of the intensity of light reflected back to the proximal end of the fiber(s) at said discrete times, thereby providing a plurality of values of pressure differential matched with corresponding values of reflected light intensity; and (f) storing said plurality of matched values, whereby an unknown value of pressure differential may be determined after calibration by matching a measured value of reflected light intensity with the corresponding stored value of pressure differential.

Claim 15

Dependent Claim 27 words

The method of claim 12 wherein said values of pressure differential and reflected light intensity are simultaneously sampled at said discrete times, and stored in a microcomputer.

Claim 16

Dependent Claim 30 words

The method of claim 13 wherein said pressure differential is applied by exposing the outside of said sensor tip to atmospheric pressure and the inside to a pressure below atmospheric.

Claim 17

Dependent Claim 42 words

The method of claim 14 wherein said pressure differential is applied by connecting vacuum pump means in essentially air-tight engagement with the inside of said sensor tip, thereby creating a pressure below atmospheric pressure in said one end and said sensor tip.

Claim 18

Dependent Claim 35 words

The method of claim 15 and further including connecting said vacuum pump means in essentially air-tight engagement with a high accuracy pressure transducer by which said pre sure differential is measured during said time period.

Claim 19

Dependent Claim 30 words

The method of claim 16 wherein said pressure differential is varied by permitting air to enter said one end of said cylinder at a controlled rate during said time period.

Claim 20

Dependent Claim 22 words

The method of claim 17 wherein said first and second magnitudes are at least about 300 mm Hg and substantially zero, respectively.

Claim 21

Dependent Claim 33 words

The method of claim 14 wherein the fiber(s) extend through a length of hollow tubing and the sensor tip is removably secured in essentially air-tight engagement with the distal end of said tubing.

Claim 22

Dependent Claim 25 words

The method of claim 19 and further including placing the system in use to measure unknown pressures substantially immediately upon completion of said calibration steps.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1992-08-14	1993-02-13	1993-08-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1996-08-14	1997-02-13	1997-08-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2000-08-14	2001-02-13	2001-08-15	$7700.00	Window Closed / Lapsed

Vacuum calibration system and method for fiberoptic pressure transducer

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