Detecting a level of printable fluid in a container
AssigneeHewlett-Packard Development Company, L.P.
InventorsDaryl E. Anderson, James Michael Gardner, Michael W. Cumbie, Scott A. Linn, Berkeley Fisher
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Abstract
A method of detecting a level of printable fluid in a container includes, with at least one sensing location on a die in thermal contact with the printable fluid in the container, sensing a voltage of a capacitor over time as current from the capacitor leaks through a field effect transistor (FET). The FET and capacitor are associated with the sensing location. The method may further include, based on the voltage of the capacitor over time and a threshold voltage, determining whether the printable fluid is present at the at least one sensing location.
Claims20
A fluid level sensor for detecting a level of fluid in a container comprising:
- an array of sensing locations associated with a plurality of fluid levels, each sensing location comprising:
- a heating element to heat a surrounding area of the sensing location;
- a capacitor to discharge a voltage through a field effect transistor (FET);
- and
- a voltage comparator coupled to the sensing locations to compare a voltage of the capacitor to a voltage threshold over time to determine a rate of the discharge of the capacitor which is indicative of a temperature decay rate at the FET which indicates whether fluid is present at the sensing location to determine a level of the fluid along the array of sensing locations.
A print cartridge that detects a level of printable fluid therein comprising:
- an array of sensing locations associated with a plurality of fluid levels, each sensing location comprising:
- a heating element to heat a surrounding area of the sensing location;
- a capacitor to leak current through a field effect transistor (FET);
- and
- a voltage comparator coupled to the sensing locations to compare, for any sensing location, a voltage of the capacitor to a voltage threshold over time to, based on a rate of current leakage from the capacitor through the field-effect transistor (FET), determine a level of the fluid along the array of sensing locations.
A method of detecting a level of printable fluid in a container comprising:
- with at least one sensing location on a die in thermal contact with the printable fluid in the container, sensing a voltage of a capacitor over time as the capacitor leaks through a field effect transistor (FET), the FET and capacitor being associated with the sensing location;
- based on the voltage of the capacitor over time and a threshold voltage, determining whether the printable fluid is present at the at least one sensing location.
Dependencies are inferred from the claim text.