Miniature Ceramic Capacitor Sensor for Low-Noise Acoustic Pressure
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Solution Overview
Problem
Current acoustic sensors for measuring pressure in liquids and gases in the frequency range of ones to tens of kHz suffer from low sensitivity, strong frequency imbalance, and high susceptibility to electromagnetic interference, making them technically and financially demanding.
Innovation Solution
A miniature sensor using a multilayer ceramic SMD capacitor with external polarization voltage, which maintains low impedance and immunity to electromagnetic interference, allowing for point measurement of acoustic pressure without disturbing the acoustic field, and features a compact design with low financial and technological demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric sensors with PVDF film are used, then sensitivity is improved, but impedance becomes high causing susceptibility to electromagnetic interference
Solution Approach 1:
The patent changes the electrical parameter of the sensing element by using a capacitive structure with optimized geometry and materials to achieve low impedance (below 1 kΩ) while maintaining high sensitivity. The capacitor is designed with specific plate area, distance, and dielectric properties to control its impedance characteristics in the frequency range of 1-100 kHz.
Solution Approach 2:
The patent employs a composite structure combining conductive plates (metal or conductive polymer) with a dielectric material (such as polymer film or gel) to create a capacitive sensor element. This composite approach enables simultaneous achievement of low impedance and high sensitivity by optimizing the electrical and mechanical properties of each layer.
2Object-affected harmful factors
If sensor dimensions are reduced below 1 mm, then acoustic field disturbance is minimized, but sensitivity decreases
Solution Approach 1:
The patent applies local quality by concentrating the sensing function in a highly responsive capacitive element at the sensor tip, while the rest of the sensor structure (housing, connections) is minimized. The capacitive plates are arranged to maximize acoustic pressure sensitivity in the miniature volume, with optimized plate area, spacing, and orientation at the measurement point.
Solution Approach 2:
The patent exploits the electric field dimension by using a capacitive sensing mechanism that converts acoustic pressure into electrical signals through changes in capacitance. This allows the sensor to detect acoustic pressure indirectly through electrical parameter changes, enabling high sensitivity in a compact form factor that would be difficult to achieve with direct mechanical measurement.
3Measurement precision
If multilayer ceramic capacitor is used, then sensitivity and electromagnetic immunity are improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses a multilayer ceramic capacitor (MLC) that serves multiple functions: it acts as the sensing element for acoustic pressure detection, provides electrical connections through its terminals, and offers inherent electromagnetic shielding due to its capacitive nature. This multi-functionality reduces the need for separate components and simplifies the overall sensor construction.
Solution Approach 2:
The patent employs standard commercial multilayer ceramic capacitors as off-the-shelf components rather than custom-made sensing elements. These readily available MLCs can be directly integrated into the sensor housing with minimal additional processing, significantly reducing manufacturing complexity and cost while providing the required electrical and sensing characteristics.
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 sensor achieves increased sensitivity and reduced electromagnetic interference, enabling effective measurement of acoustic pressure in liquids and gases with minimal disturbance and lower implementation costs.
Implementation Method 1
A miniature sensor of acoustic pressure in liquids and gases is provided... A multilayer ceramic SMD capacitor with external polarization voltage is used as the sensor element
Implementation Method 2
A multilayer ceramic SMD capacitor with external polarization voltage is used as the sensor element
Data Source
Figure 1
AI summary
The sensor consists of a multilayer ceramic SMD capacitor (10) placed at the tip of a hollow metal needle (11) with a small outer diameter. One lead of the SMD capacitor (10) is conductively connected to the needle (11) and the other lead of the SMD capacitor (10) is connected to the connection lead (12) running through the cavity of the needle (11). The tip of the needle (11) with the SMD capacitor (10) and the connection lead (12) is coated with a thin impermeable insulation layer (13). The other end of the needle (11) is fitted with a miniature connector (14) for connecting a thin coaxial connecting cable (20). The coaxial connection cable (20) is connected via an additional connector (21) to an electrically shielded adapter (30), containing a miniature battery (31) serving as a source of the 35 V polarization voltage, decoupling resistor (32), a polarization voltage switch (33) and the decoupling output capacitor (34). The adapter (30) is provided with an output BNC connector (35), allowing connection to a subsequent measuring, recording or evaluating device.