Dual-band Fabry-Perot Interferometer Synchronization for Gas Analysis
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Solution Overview
Problem
Existing gas concentration-measuring devices using dual-band Fabry-Perot interferometers face challenges in achieving effective measurement rates for inhalation anesthetics, carbon dioxide, and alcohol concentrations due to hysteresis in wavelength transmission and limited modulation frequencies, which result in inadequate time resolution for distinguishing breath phases and increased noise levels.
Innovation Solution
The implementation of a dual-band Fabry-Perot interferometer with synchronized infrared radiation sources and a variable ramp function control voltage, where the radiation sources are switched on and off based on light control signals, and the control voltage ramps are delayed relative to the radiation source activation times to account for their time constants, allowing for simultaneous detection of multiple spectral ranges with improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dual-band Fabry-Perot interferometer is used to measure multiple gas concentrations simultaneously, then the measurement capability is improved, but hysteresis in wavelength transmission occurs which degrades measurement precision
Solution Approach 1:
The control voltage is applied as a ramp function that is synchronized with the radiation source activation. The ramp function is delayed relative to the radiation source switching to account for the thermal time constants, ensuring that the interferometer is tuned to the correct wavelength before measurement begins. This preliminary action eliminates hysteresis effects by establishing a predictable, monotonic relationship between control voltage and transmission wavelength.
2Productivity
If the measurement rate is increased to resolve individual breathing phases, then time resolution is improved, but noise levels increase which degrades signal quality
Solution Approach 1:
The radiation sources are switched on and off periodically in synchronization with the ramp function of the control voltage. This periodic action allows for coherent integration of signals over multiple measurement cycles, improving the signal-to-noise ratio while maintaining high measurement rates. The synchronized switching ensures that measurements are taken at optimal points in the interferometer tuning cycle.
3Productivity
If radiation sources are switched rapidly to achieve high measurement rates, then productivity is improved, but the thermal inertia of the sources causes wavelength drift which degrades measurement precision
Solution Approach 1:
The ramp function of the control voltage is delayed relative to the radiation source switching to account for thermal time constants. This preliminary action ensures that the interferometer has sufficient time to stabilize at each wavelength before measurement begins, eliminating wavelength drift caused by thermal inertia while maintaining high measurement rates through synchronized periodic operation.
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 approach enables higher measurement rates, resolving gas concentrations for individual breathing phases with improved time resolution and reduced noise, effectively addressing the limitations of previous technologies.
Implementation Method 1
a dual-band Fabry-Perot interferometer with a first infrared radiation source for a first wavelength range from 4 μm to 6 μm and with a second infrared radiation source for a second wavelength range from 8 μm to 12 μm
Implementation Method 2
a first infrared radiation source for a first wavelength range from 4 μm to 6 μm and with a second infrared radiation source for a second wavelength range from 8 μm to 12 μm
Implementation Method 3
Infrared optical systems with optical interference filters are frequently used to measure the gas concentrations of anesthetic gases such as inhalation anesthetics, carbon dioxide and laughing gas
Data Source
AI summary
A gas concentration-measuring device makes it possible to measure gas components in a gas sample. An interferometer, based on a dual-band Fabry-Perot interferometer (1), is provided with a transmission spectrum that can be set by a control voltage (38). The control voltage (38) of the dual-band Fabry-Perot interferometer (1) is synchronized over the course of time with the activation and deactivation of the radiation sources (11, 12).