Capacitive Ink Level Sensor with Exposed Ground Electrode
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Solution Overview
Problem
Existing printing systems face inaccuracies in ink level sensing, leading to premature replacement of ink cartridges and potential low-quality prints due to inadequate ink supply levels, as current methods are not sufficiently precise for determining fluid levels in reservoirs.
Innovation Solution
The integration of printhead-integrated ink level sensors (PILS) with a ground electrode exposed to the fluid chamber, utilizing a capacitive sensor and sample and hold technique to accurately measure ink levels by calculating resistance values based on capacitance changes, and employing multiple sensors and a shift register to enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ink level sensing methods are used, then device complexity is reduced, but measurement precision deteriorates leading to inaccurate ink level detection
Solution Approach 1:
The patent merges the ink level sensing function with the printhead assembly by integrating capacitive sensors directly into the printhead structure. The sense structure includes a sense electrode, reference electrode, and clearing electrode all formed within the printhead, eliminating the need for separate external sensing devices and achieving accurate ink level detection while maintaining manufacturing simplicity.
Solution Approach 2:
The printhead assembly is designed to perform multiple functions: fluid ejection for printing and ink level sensing. The same printhead structure that ejects ink also contains the capacitive sensing electrodes that measure ink levels, allowing a single component to serve dual purposes and improving measurement precision without adding separate dedicated sensing devices.
2Loss of information
If ink level sensing is not implemented, then device complexity is minimized, but loss of information occurs leading to premature cartridge replacement
Solution Approach 1:
The printhead assembly performs self-diagnosis by continuously monitoring its own ink level through integrated capacitive sensors. The sense structure measures the capacitance between the sense electrode and reference electrode, which changes with ink level, allowing the system to self-determine ink status without external intervention and prevent information loss about actual ink levels.
Solution Approach 2:
The system implements feedback by continuously measuring ink level through the capacitive sensors and providing real-time information about ink status. The measured capacitance values are processed to determine ink level, and this information feeds back to the printing system to control printing operations and prevent premature cartridge replacement, ensuring accurate information is maintained.
3Measurement precision
If multiple sensors are used to enhance precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The sensing function is segmented into three distinct electrodes within the printhead: a sense electrode for measuring capacitance, a reference electrode for providing a stable reference potential, and a clearing electrode for removing residual ink. This segmentation allows each electrode to perform its specific function optimally, improving measurement precision through multiple sensing points while keeping the overall structure integrated within the printhead.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides accurate ink level detection, preventing premature cartridge replacement and ensuring consistent print quality by accurately determining fluid levels, thereby optimizing ink usage and system performance.
Implementation Method 1
utilizing a capacitive sensor and sample and hold technique to accurately measure ink levels by calculating resistance values based on capacitance changes
Implementation Method 2
a ground electrode for the sensor(s) is exposed to the fluid chamber for directly contacting a fluid in the fluid chamber
Data Source
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AI summary
An example provides a fluid ejection device including a fluid feed slot, a fluid chamber between a nozzle layer and a passivation layer, and a printhead-integrated sensor to sense a property of a fluid in the fluid chamber. The sensor may include a ground electrode exposed to the fluid chamber through a via in the passivation layer.