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US 4,051,721 AGranted
Capacitive force-measuring system
AssigneeScope Incorporated
InventorRichard E. Williams
Life of this patent
Estimating the term…
Abstract
An applied force whose mangitude is to be measured is caused to change the spacing between a pair of conductive plates. The resulting variation in capacitance between the plates is employed in an RC oscillator circuit so as to produce a frequency that is reciprocally related to the capacitance. A neutralizing circuit serves to cancel the effect of stray capacitance, and a digital counting device converts the oscillator frequency to a scaled number indicating the magnitude of the applied force.
Claims7
A system for measuring force comprising:
- first means for producing electrical capacitance reciprocally responsive to said force including an electrical phase and amplitude positive feedback device for neutralizing stray capacitance;
- a resistance-capacitance oscillator responsive to said first means for generating an alternating electrical signal whose frequency is reciprocally responsive to said capacitance;
- second means responsive to the output of said oscillator for generating a signal indicative of said frequence whereby said signal is also indicative of said force.
A system for linearly measuring force comprising:
- a pair of electrically conductive surfaces spaced apart by a distance responsive to said force;
- a resistance-capacitance oscillator connected to said surfaces for generating a first alternating electrical signal having a period linearly responsive to said distance;
- an electrical phase and amplitude positve feedback device coupled between said surfaces and said oscillator for neutralizing stray capacitance;
- a third means resposive to the output of said oscillator for generating an output signal having a characteristic linearly porportional to said force.
1 more element
Dependencies are inferred from the claim text.