PCB Capacitive Sensor Circuit for Multi-Depth Media Detection
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Solution Overview
Problem
Existing medium detection methods require additional operational amplifiers for deep detection, leading to complex circuits and reduced sensitivity, especially at varying depths.
Innovation Solution
A method and circuit using a sensor with PCB copper foils, a depth detection signal that adjusts frequency with depth, and a self-calibration signal to adjust phase difference, eliminating the need for operational amplifiers and enhancing sensitivity through RC circuits and MCU processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed frequency detection signal is applied to the sensor, then the detection circuit is simple, but the penetrability becomes weaker and the signal becomes very weak when the detection depth is large
Solution Approach 1:
The patent applies dynamic frequency adjustment by changing the detection signal frequency according to detection depth. The control unit adjusts the frequency of the detection signal dynamically: using lower frequencies for deeper detection to maintain penetrability, and higher frequencies for shallower detection to improve resolution. This dynamic adaptation resolves the contradiction between circuit simplicity and signal reliability at varying depths.
Solution Approach 2:
The patent changes the frequency parameter of the detection signal based on detection depth requirements. By adjusting this key parameter, the system optimizes signal penetrability for deep detection while maintaining circuit simplicity, avoiding the need for additional operational amplifiers.
2Reliability
If additional operational amplifiers are added to amplify weak signals at large detection depths, then the signal strength is improved, but the circuit complexity increases and detection sensitivity is reduced
Solution Approach 1:
Instead of statically adding operational amplifiers, the patent dynamically adjusts the detection signal frequency to maintain adequate signal strength at different depths. This dynamic approach avoids the need for additional amplification hardware, keeping the circuit simple while maintaining sensitivity.
Solution Approach 2:
The patent changes the frequency parameter of the detection signal to optimize signal penetration and strength. By using lower frequencies for deep detection, the system maintains signal strength without requiring additional operational amplifiers, thus avoiding increased circuit complexity and sensitivity loss.
3Reliability
If the detection frequency is changed according to detection depth, then the penetrability and signal strength are improved, but the circuit and control complexity increase
Solution Approach 1:
The control unit serves multiple functions: it generates the detection signal, adjusts its frequency based on depth, and processes the output signal. This multi-functionality is achieved within a single integrated control unit, avoiding the need for separate dedicated circuits for each function, thus limiting the increase in overall system complexity.
Solution Approach 2:
The patent replaces complex analog signal conditioning circuits with digital signal processing within the control unit. The frequency adjustment and signal processing are performed through digital control, which simplifies the overall hardware architecture compared to traditional analog approaches.
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 simplifies the detection circuit, improves sensitivity, and allows for flexible function realization by omitting analog devices, achieving consistent large-scale production and high detection accuracy at different depths without additional operational amplifiers.
Implementation Method 1
A core component of a medium detector is a detection sensor consisting of parallel plate capacitors
Implementation Method 2
When a dielectric medium between the parallel plate capacitors changes, the capacitance of the parallel plate capacitors will also change
Implementation Method 3
applying the depth detection signal Ftest to the big and small polar plates of the sensor in the S01 to form an electromagnetic field between the big polar plate and the small polar plates
Data Source
AI summary
The method comprises the steps of: first, providing a sensor, the sensor consisting of a group of PCB copper foils; second, providing a depth detection signal Ftest which can change the detection frequency along with the change in detection depth, and applying the depth detection signal Ftest to the big and small polar plates of the sensor in the step S01 to form an electromagnetic field between the big polar plate and the small polar plates; third, providing a self-calibration signal Fcal acting on the big polar plate, to adjust a phase difference between the big polar plate and the small polar plates, thereby improving the detection sensitivity; and finally, performing shaping and phase comparison on signals output from the big and small polar plates driven by the depth detection signal Ftest, and processing signals output after filtering the phase-compared signals to judge the condition of a medium at the current detection depth.