Hewlett-packard Development Company, L.p.

Teck-Khim Neo

Joseph M Torgerson

Ning Ge

Trudy L Benjamin

George H Corrigan

Neel Banerjee

Lawrence H White

Chris Bakker

Paul I Mikulan

Reynaldo V Villavelez

Kenneth J Stewart

Lonnie Byers

Bjorn Warloe

Michael Allen Godwin

In some examples, a method of sensing an ink level includes applying a pre-charge voltage to a sense capacitor to charge the sense capacitor with a charge, sharing the charge between the sense capacitor and a reference capacitor, causing a reference voltage at a gate of an evaluation transistor, and determining a resistance from a drain to a source of the evaluation transistor that results from the reference voltage.

Ink level sensing

In some examples, an ink level sensor includes a sense capacitor between a first node and ground, a first switch to couple a first voltage to the first node and charge the sense capacitor, a second switch to couple the first node with a second node and share the charge between the sense capacitor and a reference capacitor, causing a second voltage at the second node, and a transistor having a drain, a gate coupled to the second node, and a source coupled to ground, the transistor to provide a drain to source resistance in proportion to the second voltage.

In an embodiment, a method of sensing an ink level includes applying a pre-charge voltage Vp to a sense capacitor to charge the sense capacitor with a charge Q, sharing Qbetween the sense capacitor and a reference capacitor, causing a reference voltage Vg at the gate of an evaluation transistor, and determining a resistance from drain to source of the evaluation transistor that results from Vg.

Ink level sensor and related methods

A thermal inkjet printhead may include a substrate and a resistive layer. A thermal resistor may be formed in the resistive layer. A first metal layer may be between the substrate and a resistive layer having a thickness to form a power bus. A dielectric layer may be between the first metal layer and the resistive layer.

Power distribution in a thermal ink jet printhead

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