Method of monitoring pressure in a pneumatic tire
First Claim
1. Method of monitoring pressure in a pneumatic tire, comprising:
- sensing ambient temperature within the tire, and generating a first reading which is a linear function of ambient temperature only;
sensing ambient pressure within the pneumatic tire, and generating a second reading which is a hybrid, non-linear function of both ambient pressure and ambient temperature;
characterized by;
generating a reading which is a linear function of only the ambient pressure by dividing the first reading by the second reading.
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Accused Products
Abstract
A method for monitoring pressure with a transponder (200, 604) capable of measuring temperature data (NT) and pressure data (NP) in an object (e.g., a tire, (104)) and transmitting a data stream (FIG. 3C) to an external reader/interrogator (106, 400). The transponder includes a memory (238) for storing measurements, calibration data (662), transponder ID number and the like. Since the transponder combines temperature and pressure information in the “pressure” data, the ratio NT/NP is a direct indicator of pressure-only, and is also relatively insensitive to transponder power variations. The calibration method employs a calibration chamber (602) containing reference pressure (614) and temperature (612) sensors. The transducer to be calibrated is placed in the chamber and exposed (652) to a number of predetermined temperatures and pressures (as measured by the reference sensors) at a number of calibration points. At each calibration point, a temperature reading (NT) and a pressure reading (NP) sensed by the transponder are recorded along with the reference temperature and pressure. From these readings and reference measurements the calibration constants (NT25, mT, NT/NP700.25, mp) are calculated (658).
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Citations
11 Claims
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1. Method of monitoring pressure in a pneumatic tire, comprising:
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sensing ambient temperature within the tire, and generating a first reading which is a linear function of ambient temperature only;
sensing ambient pressure within the pneumatic tire, and generating a second reading which is a hybrid, non-linear function of both ambient pressure and ambient temperature;
characterized by;
generating a reading which is a linear function of only the ambient pressure by dividing the first reading by the second reading. - View Dependent Claims (2, 3, 4, 5, 6)
transmitting the first and second readings from a transponder within the tire to a reader/interrogator external to the tire.
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3. Method, according to claim 2, characterized by:
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calculating at least one calibration constant for use in an equation which characterizes pressure responsiveness of the transponder;
whereinthe at least one calibration constant is based on a ratio of a calibration temperature reading which is a function of ambient temperature sensed by the transponder, to a calibration pressure reading which is a function of both ambient pressure and ambient temperature sensed by the transponder.
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4. Method, according to claim 3, characterized by:
storing the at least one calibration constant in the transponder.
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5. Method, according to claim 4, characterized by:
subsequently providing from the transponder the at least one calibration constant along with a real-time ambient pressure reading.
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6. Method, according to claim 3, characterized in that:
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the equation is expressed in the form of a line equation;
the line equation is in a point-slope form characterized by a defining point and a slope which are the calibration constants; and
the calibration constants comprise;
the defining point of a pressure response line equation; and
the slope of the pressure response line equation.
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7. Method of measuring pressure within a pneumatic tire comprising:
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in a transponder, storing calibration data related to a ratioed response of a first reading divided by a second reading, as determined during a calibration of the transponder;
characterized in that;
the first reading is a linear function of ambient temperature within the tire only, and the second reading is a hybrid, non-linear function of both ambient pressure and ambient temperature within the tire. - View Dependent Claims (8, 9, 10, 11)
providing a radio frequency transponder within the tire, said RF transponder including a temperature sensor and a pressure sensor; and
transmitting the first reading and the second reading.
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9. Method, according to claim 8, further characterized by:
dividing the first reading by the second reading.
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10. Method, according to claim 7, characterized by:
transmitting the calibration data related to a ratioed response of the first reading divided by the second reading, as determined during a calibration of the transponder and which is stored in the transponder.
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11. Method, according to claim 8, further characterized by:
transmitting the calibration data related to a ratioed response of the first reading divided by the second reading, as determined during a calibration of the transponder and which is stored in the transponder.
Specification