Liquid Tank Stray Capacitance Detector Shielding
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Solution Overview
Problem
Existing methods for accurately measuring the remaining liquid fuel in fuel cell tanks, such as those using capacitance detection, face challenges like measurement inaccuracies due to temperature-dependent viscosity and external disturbances, making it difficult to estimate the remaining time for active and passive fuel cells, especially in portable devices.
Innovation Solution
A liquid tank with a detector system comprising a first board with detection electrodes that directly or indirectly contact the liquid and a second board with a shielding electrode, reducing external interference and allowing for accurate volume measurement by detecting stray capacitance, thereby improving measurement accuracy and convenience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If comb-shaped electrodes are patterned on a printed board to detect stray capacitance, then liquid volume detection is achieved, but detection results change when a hand or the like is brought close thereto
Solution Approach 1:
A shielding electrode is introduced that generates an opposing electric field to counteract the effect of external objects (such as a hand) brought close to the detector. The shielding electrode is configured to preemptively neutralize external electromagnetic interference, preventing it from affecting the stray capacitance measurement between the comb-shaped detection electrodes.
Solution Approach 2:
The shielding electrode acts as an intermediary element between the external environment and the detection electrodes. It mediates the electromagnetic field by absorbing or redirecting external disturbances before they can reach the sensitive detection electrodes, thus protecting the measurement from external influences.
2Measurement precision
If the volume V2 sent in liquid form per one time the pump is driven is kept constant, then accurate remaining amount measurement is achieved, but this is difficult due to temperature-dependent viscosity variation of methanol
Solution Approach 1:
The patent replaces the mechanical pump-based measurement method with an electrical capacitance detection system. Instead of relying on mechanical pumping and volume counting (which is sensitive to viscosity changes), the system uses comb-shaped electrodes to directly detect liquid volume through capacitance measurements, which are not affected by the fluid's viscosity or temperature variations.
Solution Approach 2:
The measurement approach changes from tracking mechanical pump operations (which depend on fluid properties like viscosity) to measuring electrical capacitance parameters. Capacitance is primarily influenced by the dielectric constant of the liquid and the geometry of the electrodes, making it much less sensitive to temperature-induced viscosity changes in methanol.
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
The solution enables precise estimation of the remaining liquid fuel volume, enhancing user convenience and accuracy, particularly for portable fuel cell systems by minimizing disturbance effects and maintaining measurement accuracy across varying conditions.
Implementation Method 1
a pair of detection electrodes for detecting a stray capacitance, in which the pair of detection electrodes directly or indirectly contact with the liquid inside the liquid container section
Implementation Method 2
a second board having a shielding electrode and arranged on a back face side of the first board. (B) A second board having a shielding electrode and arranged on a back face side of the first board, whereby, even when a hand or the like is brought close to the detector, the detection electrodes are prevented from sensing a stray capacitance generated as a result
Data Source
AI summary
Provided are a liquid tank capable of reducing an influence of disturbance on measurement results and measuring accurate volume, and a fuel cell using the same. One face of a liquid container section is structured by a detector in which a first board to a fourth board each configured of a printed board are stacked in order. A pair of detection electrodes 12A and 12B are provided on a front face of the first board, and this pair of detection electrodes 12A and 12B are allowed to contact directly or indirectly to a liquid fuel inside the liquid container section to detect a stray capacitance. A back face side of the first board is disposed with the second board having a shielding electrode 22. Even when a hand or the like is brought close to the detector, the detection electrodes 12A and 12B are prevented from sensing the stray capacitance generated as a result.