Crystal Oscillator Sensor Phase Shift Detection
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Solution Overview
Problem
Existing sensors, such as quartz crystal oscillator sensors, face challenges in detecting substances in small concentrations due to limitations in sensitivity and precision, particularly in measuring mass changes caused by accumulating substances.
Innovation Solution
A sensor configuration using a sensing crystal oscillator and a reference crystal oscillator arranged in a phase locked loop with a phase analyzer, allowing for highly sensitive detection of substances by monitoring phase shifts between the oscillators' output frequencies, enabling the detection of small concentrations of substances through a phase comparator and digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single quartz crystal oscillator is used to measure mass changes, then the sensor can detect substance accumulation, but the sensitivity and precision are insufficient for detecting small concentrations
Solution Approach 1:
The sensor is divided into two independent oscillators: a sensing crystal oscillator exposed to the environment and a reference crystal oscillator isolated from it. Each oscillator functions as an independent measurement unit, allowing the system to detect phase differences caused by mass changes on the sensing oscillator while using the reference oscillator to compensate for environmental variations, thereby improving detection sensitivity without excessive complexity
Solution Approach 2:
A phase-locked loop (PLL) circuit is introduced as an intermediary mechanism to compare the output frequencies of the sensing and reference oscillators. The PLL converts frequency differences into a measurable phase differential, enabling highly sensitive detection of substance accumulation while maintaining system stability and reducing noise interference
2Measurement precision
If the sensing crystal oscillator frequency is changed due to substance accumulation, then mass measurement is enabled, but noise interference reduces detection accuracy
Solution Approach 1:
The phase-locked loop acts as a noise-filtering intermediary that compares the sensing oscillator output with the reference oscillator output. By measuring only the phase differential between the two signals rather than absolute frequency changes, the system eliminates common-mode noise and environmental interference, achieving high-precision detection of substance accumulation
Solution Approach 2:
The system transitions from measuring absolute frequency changes to measuring relative phase differences. This parameter transformation allows the use of differential measurement techniques that inherently reject noise and interference, improving the signal-to-noise ratio and detection accuracy for trace substance detection
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 precise and sensitive detection of substances by converting frequency changes into phase shifts, allowing for the detection of minute traces of substances like explosives, maintaining high sensitivity and minimizing noise interference.
Implementation Method 1
Quartz crystal oscillator sensors have long been used to measure mass, e.g., in semiconductor fabrication environments. Operation of such sensors is based on the frequency of oscillation of an oscillating quartz crystal oscillator as a function of the mass of the crystal.
Implementation Method 2
The sensing crystal oscillator and the reference crystal oscillator can be arranged in a phase locked loop so that the oscillators oscillate at a common frequency... A phase analyzer comprising a phase comparator can be disposed at the output of the first crystal oscillator and the second crystal oscillator.
Data Source
AI summary
There is set forth herein a sensor for sensing of substances. The sensor can include a sensing crystal oscillator and a reference crystal oscillator. The sensing crystal oscillator and the reference crystal oscillator can be arranged in a phase locked loop so that the oscillators oscillate at a common frequency. The sensor can be configured so that there is a baseline phase differential between the oscillation frequencies of the sensing crystal oscillator and the reference crystal oscillator. Detectable substances accumulating on the sensing crystal oscillator will induce a phase shift between output frequencies of the reference oscillator and the sensing crystal oscillator to allow for highly sensitive sensing of substances in small concentrations.