LED Gas Analyzer Temperature Compensation
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Solution Overview
Problem
Conventional non-dispersive infrared (NDIR) gas sensors face challenges with high power consumption, complexity, and accuracy issues due to temperature dependencies and the need for additional components, particularly in single-channel designs using LEDs and photodiodes.
Innovation Solution
A low power, single-channel optical absorption gas analyzer employing a light emitting diode (LED) and photovoltaic radiation detector pair with an integrated temperature sensor and memory storing baseline data, effectively acting as a virtual reference channel to compensate for temperature variations, allowing for accurate gas concentration measurement without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single-channel NDIR design using LED and photodiode is used, then power consumption is reduced and device complexity is lowered, but measurement accuracy deteriorates due to temperature dependencies
Solution Approach 1:
The patent applies preliminary action by pre-storing baseline optical absorption data at multiple temperatures in memory during device operation. The temperature sensor continuously monitors current temperature, and the processor retrieves the appropriate baseline data from memory to compensate for temperature variations in real-time, eliminating the need for a reference channel while maintaining measurement accuracy
Solution Approach 2:
The patent uses copying by creating a virtual reference channel through digital storage of baseline absorption characteristics at different temperatures. Instead of using a physical reference channel with additional optical components, the system copies and stores reference data in memory, then retrieves and applies the appropriate baseline data computationally to compensate for temperature effects
2Measurement precision
If a two-channel NDIR sensor with reference channel is used, then measurement accuracy is improved by compensating for source and detector drift, but power consumption increases and device complexity increases
Solution Approach 1:
The patent replaces the physical reference channel with a digital copy of baseline absorption data stored in memory. The processor retrieves pre-stored baseline data corresponding to the current temperature and uses it to compensate for drift, achieving reference channel functionality without additional optical components or increased complexity
Solution Approach 2:
The patent substitutes the mechanical/optical reference channel system with an electronic/computational solution. Instead of using a second photodetector and optical path to provide reference measurements, the system uses a temperature sensor, memory storage, and processor to digitally compensate for drift, replacing physical reference components with electronic processing
3Adaptability or versatility
If incandescent lamp is used as radiation source, then broad bandwidth radiation is produced covering signal and reference wavelengths, but power consumption increases and response time decreases
Solution Approach 1:
The patent changes the operating parameters of the radiation source by using an LED that operates at a specific wavelength matching the absorption peak of the target gas, rather than using an incandescent lamp that emits broad spectrum radiation. This parameter change in wavelength selection improves power efficiency while the temperature-compensated baseline approach maintains accuracy across the measurement range
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 solution achieves high measurement accuracy with minimal power consumption, eliminating the need for complex chamber designs and reducing power requirements, enabling a portable, low-cost gas analyzer with improved stability and accuracy.
Implementation Method 1
an optopair, comprising a light emitting diode (LED) arranged to emit radiation into the chamber and a photovoltaic radiation detector arranged to detect radiation transmitted through the chamber from the LED
Implementation Method 2
a photovoltaic radiation detector arranged to detect radiation transmitted through the chamber from the LED and to output a corresponding detection signal
Implementation Method 3
the selective absorption of infrared radiation by certain gas species of interest is measured to determine the concentration of the target gas in a sample
Data Source
AI summary
An optical absorption gas analyzer is provided for determining the concentration of a target gas in a sample, comprising: a chamber for containing the sample in use; an optopair, comprising a light emitting diode (LED) arranged to emit radiation into the chamber and a photovoltaic radiation detector arranged to detect radiation transmitted through the chamber from the LED and to output a corresponding detection signal SS; a temperature sensor arranged in thermal contact with the LED and the photovoltaic radiation detector, and to output a temperature signal T representing the temperature of the optopair; a memory having stored therein data representative of the baseline detection signal ST output by the optopair in the absence of the target gas as a function of the temperature of the optopair across a range of temperatures; and a processor adapted to generate a differential detection signal SA indicative of the concentration of target gas in the sample by retrieving from the memory the baseline detection signal ST corresponding to the temperature signal T and calculating the difference between the detection signal SS and the baseline detection signal ST.