Capacitive Liquid Level Sensor with Integrated Electronics
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Solution Overview
Problem
Existing liquid level measurement devices for inkjet printers are bulky, require external evaluation electronics, and suffer from structural size issues and interference due to long connection lines, making them unsuitable for mass-produced articles with simple geometry.
Innovation Solution
A capacitive measurement device with integrated evaluation electronics, using an RC oscillator and demodulator to detect liquid levels directly at the output of the printing device, eliminating stray capacitance and interference by minimizing structural size and integrating the sensor and electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rod-shaped sensor with external evaluation electronics is used, then liquid level measurement is achieved, but the structural volume increases and susceptibility to interference increases
Solution Approach 1:
The patent integrates the evaluation electronics directly into the sensor housing, combining the sensor element and evaluation circuitry into a single compact unit. This eliminates the need for separate external electronics and long connection lines, thereby reducing overall structural volume while maintaining measurement precision.
Solution Approach 2:
The patent introduces a capacitive sensor that measures liquid level through the container wall without direct contact with the liquid. This intermediary measurement approach eliminates the need for rod-shaped sensors that extend into the liquid, reducing structural volume and minimizing interference from connection lines.
2Measurement precision
If a rod-shaped sensor with external evaluation electronics is used, then liquid level measurement is achieved, but susceptibility to electromagnetic interference increases
Solution Approach 1:
The capacitive sensor measures liquid level through the container wall as an intermediary, avoiding direct contact with the liquid and eliminating long connection lines that are susceptible to electromagnetic interference. The measurement is performed capacitively through the wall material, which acts as an intermediary medium.
Solution Approach 2:
The patent replaces traditional contact-based mechanical or electrical sensors with a capacitive measurement system that operates through the container wall. This substitution eliminates the need for physical connection lines that extend into the liquid, thereby reducing susceptibility to electromagnetic interference.
3Reliability
If a contact-less level detector through the container wall is used, then overflow prevention is achieved, but the structural size increases
Solution Approach 1:
The evaluation electronics are merged into the sensor housing, creating a compact integrated unit that performs contact-less measurement through the container wall. This integration eliminates the need for separate external electronics and large support structures, reducing overall structural size while maintaining overflow prevention capability.
Solution Approach 2:
The patent uses capacitive measurement parameters that can detect liquid level changes through the container wall material. By changing the measurement approach to capacitive coupling through the wall, the system achieves contact-less measurement without requiring large structural modifications or additional space.
4Loss of information
If long connection lines are used between sensor and electronics, then signal transmission is achieved, but transfer resistance variability and electromagnetic interference increase
Solution Approach 1:
The evaluation electronics are merged into the sensor housing, eliminating long connection lines between sensor and electronics. This integration ensures stable signal transmission by removing the variable transfer resistance and electromagnetic interference that would otherwise affect long connection lines.
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
Enables continuous, contactless liquid level monitoring with reduced structural size, ensuring reliable ink supply and preventing overflow, suitable for aggressive media and various fluid types, while maintaining operational efficiency and minimizing interference.
Implementation Method 1
The change in the liquid level in the chamber of the measurement device, that is, in the active measurement zone of the capacitive sensor, causes a change in capacitance of the capacitor
Implementation Method 2
The sensor is essentially made from an RC oscillator as a transducer, a demodulator, and an output stage. The change in the liquid level in the chamber of the measurement device, that is, in the active measurement zone of the capacitive sensor, causes a change in capacitance of the capacitor, by means of which the RC oscillator changes its oscillation frequency
Data Source
AI summary
The subject matter of the invention is a method for a printing machine with a printing device (5), in particular an inkjet printer, for applying liquid (22) onto a print material, with monitoring of the quantity of liquid in a liquid supply unit (1) by measuring the liquid level (23) with a sequential controller, wherein the measurement of the liquid level (23) is performed by a device (11), which detects the presence of liquid at the output of the printing device (5).Another subject matter of the invention is a liquid supply unit (1) for a printing machine with a printing device (5), in particular, an inkjet printer, for applying liquid (22) on a print material, with monitoring of the quantity of liquid in a liquid supply unit (1) by measuring the liquid level (23) with a sequential controller, wherein the measurement device (11) is suitable for measuring a fill level (23) and for controlling a liquid device (3).Furthermore, a measurement device (11), in particular, for a liquid supply unit (1), is the subject matter of the invention, in which at least one part of the measurement device (11) is made from circuit-board material.