Capacitive Fluid Level Sensing in Inkjet Supply Items
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Solution Overview
Problem
Existing fluid level detection methods in micro-fluid applications, such as inkjet printing, are inaccurate and complex, especially in networked environments, leading to issues like 'dry firing' and incorrect ink replenishment, and require external stimuli and complex calibration schemes.
Innovation Solution
A consumable supply item with capacitive sensing and on-board signal processing determines fluid levels, providing a digital data stream to the imaging device for accurate tracking, and includes a controller for processing signals, amplification, filtering, and analog-to-digital conversion, with modular construction for compatibility and ease of use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive sensing with on board processing is implemented in the supply item, then measurement precision and reliability are improved, but device complexity increases
Solution Approach 1:
The supply item performs self-measurement of fluid levels using onboard capacitive sensors and processing circuitry, eliminating the need for external measurement devices and complex calibration procedures. The supply item autonomously determines its own fluid status and communicates this information to the imaging device.
Solution Approach 2:
The measurement and processing functions are extracted from the imaging device and placed directly into the supply item. This separation allows the imaging device to receive ready-to-use fluid level information without implementing complex sensing or calibration systems itself.
2Device complexity
If algorithm-based fluid level tracking is used in the printer, then device complexity is reduced, but measurement precision and reliability deteriorate
Solution Approach 1:
The fluid level measurement function is extracted from the printer and relocated to the supply item. The printer receives accurate, ready-to-use fluid level information from the supply item without implementing complex measurement algorithms, thereby maintaining low device complexity while achieving high measurement precision.
Solution Approach 2:
The supply item continuously monitors its own fluid levels using capacitive sensors and provides real-time feedback to the printer through digital communication. This feedback mechanism enables the printer to accurately track fluid levels without implementing complex measurement systems.
3Measurement precision
If external stimuli and complex calibration schemes are implemented, then measurement precision is improved, but ease of operation and device complexity worsen
Solution Approach 1:
The supply item performs self-calibration using its own internal reference standards and characteristics, eliminating the need for external calibration equipment and complex calibration procedures. The supply item is simply installed and begins operation with accurate measurements from the first use.
Solution Approach 2:
The supply item is pre-calibrated during manufacturing with reference to its own internal characteristics. This preliminary calibration ensures accurate fluid level measurements from the moment of installation without requiring field calibration or external adjustment procedures.
4Device complexity
If fluid level detection is centralized in the printer, then device complexity is reduced, but adaptability to different supply items deteriorates
Solution Approach 1:
The fluid level detection capability is localized to each individual supply item rather than being centralized in the printer. Each supply item contains its own capacitive sensors and processing circuitry, enabling it to autonomously determine its fluid status. This localizes the intelligence to where it is most adaptable to different supply item variations.
Solution Approach 2:
The capacitive sensing approach used in the supply item is universally applicable across different supply item designs and imaging devices. The supply item communicates fluid level information through a standard digital interface, making it compatible with various imaging devices without requiring device-specific calibration or adjustment.
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 and simplified fluid level detection, preventing issues like 'dry firing' and ink spills, while allowing the supply item to be easily moved between devices, reducing variability and noise, and enabling proper pump operation based on fluid availability and installation.
Implementation Method 1
The electrodes define a capacitance that varies in response to an amount of liquid between them
Data Source
AI summary
A consumable supply item for an imaging device holds an initial or refillable volume of ink. A housing defines an interior having a pair of opposed electrodes. The electrodes have a capacitance that varies in response to an amount of liquid between them. A controller energizes one electrode and receives an output reading from the other. The controller processes the reading on board the housing and supplies it as a digital data stream to the imaging device during use. A memory stores calibration values for an empty and full housing. The controller writes back to the memory present fluid levels obtained from the output reading of the electrode. An enable output allows operation or not of a fluid pump in the imaging device. Materials, construction, modularity, and fluid communication ports are further embodiments, to name a few.