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US 6,472,887 B1Granted
Capacitive sensor for sensing the amount of material in a container
AssigneeHewlett-Packard Company
InventorsBarclay J. Tullis, Carl Picciotto, Jun Gao
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AssigneeHewlett-Packard Company
InventorsBarclay J. Tullis, Carl Picciotto, Jun Gao
Estimating the term…
One embodiment of the invention is a capacitive sensor for sensing the amount of material in a container. This embodiment includes an oscillator that generates an oscillating signal. This oscillator includes an integrating amplifier that is formed by (1) an operational amplifier that has a low-impedance output and a virtually-grounded input, and (2) a capacitor that has a capacitance which depends on the amount of material in the container. The capacitor connects between the low impedance output and the virtually-grounded input of the operational amplifier In some embodiments, the operational amplifier includes a first amplifier and a second amplifier that are connected in series, with an output of the second amplifier fed back through the capacitor to the input of the first amplifier.
A capacitive sensor for sensing an amount of a material in a container, said sensor comprising:
Dependencies are inferred from the claim text.