Self-calibrating variable pressure touch key system employing transducers subject to parameter drift

Claim 2

A variable touch key system comprising: a pressure transducer device for producing an output signal having a value dependent on touch pressure applied to said transducer devices; means for periodically reading the output signal value to establish a calibration reference value; and means for periodically reading the output signal value and comparing the output signal to a comparison value determined by applying a predetermined change threshold value to the calibration reference value to recognize an operating condition.

Claim 3

Avariable pressure touch key system comprising: a pressure transducer device for producing an output signal having a value dependent on touch pressure applied to said transducer device; and means for periodically reading the output signal value to maintain a calibration reference value corresponding to a non-activated condition and to recognize at least one operating condition, said means functioning to re-establish the calibration reference value based on the output signal value when the output signal value differs from the calibration reference value by an amount which is within an expected drift range between calibration intervals, and said means functioning to recognize the operating condition when the output signal value differs from the calibration reference value by an mount which is outside the expected drift range.

Claim 4

Avariable pressure touch key system comprising: a pressure transducer device for producing an output signal having a value dependent on touch pressure applied to said transducer device; and means for periodically reading the output signal value to maintain a calibration reference value corresponding to a non-activated condition and to recognize at least one operating condition, said means functioning to re-establish the calibration reference value based on the output signal value when the output signal value differs from the calibration reference value by an amount which is within an expected drift range between calibration intervals, and said means functioning to recognize the operating condition when the output signal value differs from the calibration reference value by an mount which is outside the expected drift range.

Claim 5

Avariable pressure touch key system comprising: a functi8on select pressure transducer device for producing a function output signal having a value dependent on touch pressure applied to said function select pressure transducer device; a variable operation select pressure transducer device for converting touch pressure to an operation output signal having a value dependent on touch pressure applied to said operation select pressure transducer device; and calibration and operating decision means for periodically calibrating said system to compensate for any drift in characteristics of said transducer elements and for recognizing at least one operating condition, said calibration and operating decision means functioning to periodically read the function output signal value to maintain a function select calibration reference value corresponding to a non-activated condition of said function select pressure transducer element, and to recognize a function select operation by periodically re-establishing the function select calibration reference value based on the function output signal value, and by recognizing the function select operation when the function output signal value differs from the function select calibration reference value by an amount which is outside the expected drift range, and said calibration and operating decision means functioning immediately prior to an expected operation of said variable operation select pressure element as indicated by a recognized function select operation to establish a variable operation select reference value as the operation output signal value, and said calibration and operating decision means functioning thereafter to recognize a particular operation value by periodically reading the operation output signal value and comparing the operation output signal value to at least one of a plurality of comparison values respectively determined by applying each of a plurality of predetermined change threshold values to the variable operation select reference value.

Claim 6

Avariable pressure touch key system comprising: a functi8on select pressure transducer device for producing a function output signal having a value dependent on touch pressure applied to said function select pressure transducer device; a variable operation select pressure transducer device for converting touch pressure to an operation output signal having a value dependent on touch pressure applied to said operation select pressure transducer device; and calibration and operating decision means for periodically calibrating said system to compensate for any drift in characteristics of said transducer elements and for recognizing at least one operating condition, said calibration and operating decision means functioning to periodically read the function output signal value to maintain a function select calibration reference value corresponding to a non-activated condition of said function select pressure transducer element, and to recognize a function select operation by periodically re-establishing the function select calibration reference value based on the function output signal value, and by recognizing the function select operation when the function output signal value differs from the function select calibration reference value by an amount which is outside the expected drift range, and said calibration and operating decision means functioning immediately prior to an expected operation of said variable operation select pressure element as indicated by a recognized function select operation to establish a variable operation select reference value as the operation output signal value, and said calibration and operating decision means functioning thereafter to recognize a particular operation value by periodically reading the operation output signal value and comparing the operation output signal value to at least one of a plurality of comparison values respectively determined by applying each of a plurality of predetermined change threshold values to the variable operation select reference value.

Claim 7

A variable pressure touch key system in accordance with claim 3 wherein said function select pressure transducer device comprises a function select pressure sensitive element, and a function select transducer conditioning circuit connected to said function select pressure transducer element for producing the function output signal; and wherein said variable operation select pressure transducer device comprises a variable operation select pressure sensitive element, and a variable operation select transducer conditioning circuit connected to said function select pressure transducer element for producing the operation output signal.

Claim 8

A variable pressure touch key system in accordance with claim 1 or 2, wherein said means for periodically reading and comparing compares the output signal value to at least one of a plurality of comparison values respectively determined by applying each of a plurality of predetermined change threshold values to the calibration reference value to recognize a particular one of a plurality of potential operation values depending on the amount of touch pressure applied to said pressure transducer device.

Claim 9

A variable pressure touch key system in accordance with any preceding claim, wherein said pressure transducer device comprises: a pressure sensitive element; and transducer conditioning circuitry connected to said pressure sensitive element for producing the output signal.

Claim 10

A variable pressure touch key system in accordance with claim 5, wherein said pressure sensitive element comprises a pressure sensitive variable capacitance element, and wherein the output signal produced by said transducer conditioning circuitry has a value dependent on the capacitance of said element.

Claim 11

A variable pressure touch key system in accordance with claim 7, wherein said pressure sensitive variable capacitance element comprises; a fixed position capacitor plate; an apertured insulating spacer over said fixed capacitor plate; and a flexible electrically conductive overlay over said apertured spacer defining a variable position capacitor plate; whereby touch pressure applied to said flexible overlay decreases the spacing between said capacitor plates and increases the capacitance therebetween.

Claim 12

A variable pressure touch key system in accordance with claim 1 or 2 wherein said means for periodically reading the output signal value and comparing to recognize an operating condition reads the output signal value immediately prior to an expected operation of said pressure transducer device.

Claim 13

A variable pressure touch key system in accordance with claim 10, wherein said means for periodically reading the output signal value and comparing to recognize an operating condition repeatedly reads and compares the output signal value to the comparison value to recognize changes in the operating condition.

Claim 14

A variable pressure touch key system in accordance with claim 5, wherein the potential operation values comprise different slew rates for setting a data entry indicator.

Claim 15

A variable pressure touch key system in accordance with claim 12, wherein said data entry indicator indicates the value of an appliance function.