Self-calibrating variable pressure touch key system employing transducers subject to parameter drift
First Claim
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1. A variable 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;
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 value to 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.
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Abstract
A pressure sensitive touch pad system, for example employing variable capacitance touch pads, employs low cost transducers subject to parameter drift and periodically (e.g. once each second) re-calibrates each touch pad. The periodic re-calibration allows a low cost transducer to be used for multi-point operation, as well as for simple on/off operation, such as for function selection. One application is to provide different slew rates for setting a data entry indicator, for example indicating the value of an appliance function.
74 Citations
23 Claims
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1. A variable pressure touch key system comprising:
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a pressure transducer device for producing an output signal having a value dependent on touch pressure applied to said transducer device; 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 value to 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A variable pressure touch key system comprising:
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a pressure transducer device for producing an output signal having a value dependent on touch pressure applied to said transducer device; 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; said means for periodically reading the output signal value to establish a calibration reference value reading the output signal value immediately prior to an expected operation of said pressure transducer device when triggered by a recognized function select operation. - View Dependent Claims (9)
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10. A variable pressure touch key system comprising:
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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, said means functioning to recognize the operating condition when the output signal value differs from the calibration reference value by an amount which is outside the expected drift range, and said means further functioning, when the at least one operating condition is recognized, to compare the output signal value to 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 pressure applied to said pressure transducer device. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A variable pressure touch key system comprising:
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a function 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 function select pressure transducer and said variable operation select pressure transducer devices 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 device, 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 an the expected drift range, and said calibration and operating decision means functioning immediately prior to an expected operation of said variable operation select pressure device as indicated by a recognized function select operation to establish a variable operation select reference value corresponding to a non-activated condition of said 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. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification