Patent ID: 6047245
Filing Date: 2000-04-04
Classification: G01L

Abstract:
A method of maintaining an operating point of a resistive strain gauge force calculating system within a personal computer which resistive strain gauge force calculating system includes resistive strain gauge elements for producing signals upon manual manipulation by an actuator, which signals are a function of a power supply voltage applied across the resistive strain gauge elements, and including a digital filtering circuit having a pulse modulation counter with an amplifier and resistive and capacitive network providing a delay filter to reduce non-linearity resulting from different pulse modulation counter counts, comprising the steps of:generating signals across the resistive strain gauge in response to manual manipulation of the resistive strain gauge elements;setting a count from zero to one thousand in the pulse modulation counter;producing a fixed frequency digital signal in the pulse modulation counter where a ratio composed of up time and fixed period is proportional to the set count in the pulse modulation counter;providing a direct current offset voltage to the amplifier equal to one half of the power supply voltage;amplifying the fixed frequency digital signal from the pulse modulation counter and the direct current offset voltage to provide a direct current voltage proportional to the count set in the pulse modulation counter; andproviding analog signals for conversion to digital signals to the analog to digital converter which signals are generated as a function of the signals generated across the resistive gauge elements and the direct current voltage proportional to the count set in the pulse modulation counter.