SAW Sensor Differential Frequency Driving for Liquid Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensors for detecting substances in liquids using surface acoustic wave elements face challenges in reliably detecting the presence or absence and density of target substances due to small frequency differences between sensing and reference SAW elements when the target substance is present, leading to reduced precision.
Innovation Solution
A sensor design incorporating a sensing circuit with a reaction film-covered SAW element and a reference SAW element driven by independently controlled frequency signals, ensuring a differential output that enhances detection precision by amplifying the amplitude difference caused by the target substance's mass addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensing SAW element and reference SAW element are driven at the same frequency, then the detection precision is improved by comparing their outputs, but the oscillation frequencies may become substantially the same causing electromagnetic coupling and reducing detection reliability
Solution Approach 1:
The patent applies parameter changes by driving the sensing SAW element and reference SAW element at different frequencies. The frequency of the first signal source is set to be different from the frequency of the second signal source, ensuring that the oscillation frequencies of the two SAW elements are substantially different. This prevents electromagnetic coupling between the oscillation circuits while still allowing differential measurement, thus resolving the contradiction between detection precision and reliability.
2Quantity of substance
If the target substance is present in the liquid, then the mass on the sensing SAW element increases causing a frequency shift, but the frequency difference between sensing and reference elements becomes relatively small making detection difficult
Solution Approach 1:
The patent changes the operating frequency parameter of the reference SAW element to be different from that of the sensing SAW element. By setting the frequency of the second signal source differently from the first signal source, the patent ensures that even when the target substance is present and causes mass increase on the sensing element, the frequency difference between the two elements remains substantial, preventing detection difficulties.
3Adaptability or versatility
If a reaction film is added to the sensing SAW element to enable substance detection, then the detection capability is improved, but the device complexity increases due to additional components
Solution Approach 1:
The patent applies segmentation by separating the sensing function from the reference function. The sensing SAW element includes a reaction film for detecting target substances, while the reference SAW element excludes the reaction film. This segmentation allows the sensing element to have enhanced detection capability while the reference element provides a simplified baseline for comparison, thus improving detection capability without excessively increasing overall device complexity.
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
This design improves the sensitivity and reliability of detecting substances in liquids by ensuring a non-zero differential output, allowing for precise detection of the target substance's presence and density without oscillation coupling issues.
Implementation Method 1
a sensor for detecting a substance in liquid using a surface acoustic wave element (SAW element)
Implementation Method 2
The sensing SAW element 104 includes a piezoelectric substrate, an interdigital transducer (IDT) provided on the piezoelectric substrate
Implementation Method 3
The reaction film is made of a material that reacts with a detection-target substance in liquid and is coupled to the detection-target substance
Data Source
AI summary
A sensor for detecting a substance in liquid includes a sensing circuit including a sensing surface acoustic wave (SAW) element in which a reaction film to react with a substance in liquid, a reference circuit including a reference SAW element including an IDT and not including a reaction film, a first signal source driving the sensing circuit, a second signal source driving the reference circuit and being independent of the first signal source, and a differential circuit arranged to output a differential output between an output of the sensing circuit and an output of the reference circuit. The frequency of a first frequency signal output from the first signal source is different from the frequency of a second frequency signal output from the second signal source, thereby making a driving frequency for the sensing SAW element and a driving frequency for the reference SAW element substantially the same as or different from one another.