Apparatus and method for detecting ink in a reservoir using an overdriven thermistor and an electrical conductor extending from the thermistor
First Claim
1. A method for monitoring an ink level in an ink reservoir comprising:
- dissipating heat in a thermistor positioned within an ink reservoir, the thermistor having an electrical conductor that extends from the thermistor, a length of the electrical conductor extending through and being exposed within at least a portion of the ink reservoir;
providing electrical power through the electrical conductor to the thermistor to maintain the thermistor at a predetermined temperature that is a fixed differential above a temperature of the ink reservoir;
measuring a parameter that corresponds to the heat dissipated from the thermistor and the length of the electrical conductor extending through and being exposed within the portion of the ink reservoir; and
correlating the measured parameter to a predetermined value corresponding to an ink level in the ink reservoir to detect a position of the ink level in the reservoir continuously along the length of the electrical conductor and the thermistor.
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Abstract
A method detects the level of ink in a print head reservoir by monitoring the power drawn by a thermistor positioned within the print head reservoir by an electrical conductor. The method includes dissipating heat in a thermistor positioned within an ink reservoir, the thermistor having an electrical conductor that extends from the thermistor, a length of the electrical conductor extending through at least a portion of the ink reservoir, providing electrical power through the electrical conductor to the thermistor to maintain the thermistor at a predetermined temperature that is a fixed differential above a temperature of the ink reservoir, measuring a parameter that corresponds to the heat dissipated from the thermistor and the length of the electrical conductor extending through the portion of the ink reservoir, and correlating the measured parameter to a predetermined value corresponding to an ink level in the ink reservoir to detect a position of the ink level in the reservoir continuously along the length of the electrical conductor and the thermistor.
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Citations
18 Claims
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1. A method for monitoring an ink level in an ink reservoir comprising:
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dissipating heat in a thermistor positioned within an ink reservoir, the thermistor having an electrical conductor that extends from the thermistor, a length of the electrical conductor extending through and being exposed within at least a portion of the ink reservoir; providing electrical power through the electrical conductor to the thermistor to maintain the thermistor at a predetermined temperature that is a fixed differential above a temperature of the ink reservoir; measuring a parameter that corresponds to the heat dissipated from the thermistor and the length of the electrical conductor extending through and being exposed within the portion of the ink reservoir; and correlating the measured parameter to a predetermined value corresponding to an ink level in the ink reservoir to detect a position of the ink level in the reservoir continuously along the length of the electrical conductor and the thermistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An ink level detection system for use in a printer comprising:
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a thermistor positioned with an electrical conductor within an ink reservoir of a printer, the electrical conductor being thermally exposed within the ink reservoir to enable the electrical conductor to dissipate heat into the ink reservoir; a switch configured to couple a voltage to the thermistor through the thermally exposed electrical conductor in response to a control signal being received at the switch; a comparator having one input coupled to a voltage across the thermistor and another input coupled to a threshold voltage, the comparator generating the control signal received by the switch; and a digital controller coupled to the comparator and configured to measure a parameter corresponding to a dissipation of heat from the thermistor and the thermally exposed electrical conductor during a predetermined time period and to correlate the measured parameter to a predetermined value that corresponds to an ink level in the ink reservoir to detect a position of the ink level continuously along a length of the thermally exposed electrical conductor and the thermistor. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification