Piezoelectric Liquid Surface Sensor Natural Frequency Detection
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Solution Overview
Problem
Existing liquid surface sensors face challenges in measuring liquid levels with high precision due to acoustic mismatch between resonant elements and the gas within the tank, requiring large measurement spaces and limiting their use in narrow environments.
Innovation Solution
A liquid surface sensor with a hollow member and a sensor unit that includes a vibration plate and a piezoelectric element formed by laminating electrode and piezoelectric films, allowing the sensor to calculate the liquid surface position based on the natural frequency of the gas and vibration plate, without the need for a wide space for Helmholtz resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Helmholtz resonance is used for liquid surface detection, then the measurement can be performed in a tank environment, but a large measurement space is required and measurement precision is poor due to acoustic mismatch
Solution Approach 1:
The invention uses a vibration plate that vibrates in its natural frequency determined by the inertia of the gas in the hollow space and the rigidity of the vibration plate itself. This mechanical vibration approach replaces the Helmholtz resonance method, allowing the system to detect liquid surface position based on the vibration characteristics of the plate and gas column, thereby eliminating the need for a large measurement space while improving measurement precision.
Solution Approach 2:
The invention changes the detection parameter from Helmholtz resonant frequency to natural frequency of the vibration plate system. By measuring the natural frequency which depends on the gas inertia and plate rigidity, the system achieves accurate liquid surface detection without requiring a large tank volume, thus resolving the contradiction between measurement precision and measurement space requirements.
2Measurement precision
If Helmholtz resonance is used for liquid surface detection, then the measurement can be performed in a tank environment, but acoustic matching between resonant element and gas is poor
Solution Approach 1:
The vibration plate serves as an intermediary element that couples the piezoelectric actuator to the gas column. The plate's natural frequency vibration creates effective acoustic coupling between the solid actuator and the gas medium, resolving the acoustic mismatch problem inherent in direct Helmholtz resonance approaches where the resonant element and gas have poor acoustic compatibility.
3Adaptability or versatility
If buzzer is placed on side surface for Helmholtz resonance, then liquid surface can be detected, but device complexity increases and measurement environment is restricted
Solution Approach 1:
The invention merges the actuator and sensor functions into a single integrated sensor unit. The piezoelectric element both drives the vibration plate to generate natural frequency vibrations and detects the resulting vibrations to determine liquid surface position. This unified structure eliminates the need for separate buzzer and detection components, reducing device complexity and enabling use in diverse measurement environments including narrow spaces.
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 high-precision liquid surface measurement irrespective of the measurement environment, reducing the inertance of the sensor unit and improving measurement accuracy by matching the acoustic impedance of the sensor with the gas, allowing for precise detection of the liquid surface position.
Implementation Method 1
a piezoelectric element that is provided on the vibration plate and is formed by laminating a first electrode film, a piezoelectric film, and a second electrode film in order in a thickness direction of the vibration plate
Implementation Method 2
the vibration plate vibrates in the natural frequency determined by the inertia of the gas of the hollow space and the rigidity of the vibration plate, and thus, it is possible to calculate the distance from the sensor unit to the liquid surface based on the resonant frequency
Data Source
AI summary
A liquid surface sensor includes a hollow member having a first opening end and a second opening end, and a sensor unit provided so as to close the first opening end of the hollow member. The sensor unit includes a vibration plate, and a piezoelectric element which is provided on the vibration plate and is formed by laminating a first electrode film, a piezoelectric film, and a second electrode film in a thickness direction of the vibration plate.