Compact Photoacoustic Gas Sensor Layout for Precise Detection
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Solution Overview
Problem
Conventional photoacoustic gas sensors are large in size and complex to assemble, and they require a long optical path length for sufficient infrared absorption, making them less practical for accurate and compact gas detection.
Innovation Solution
A compact photoacoustic gas sensor device with a substrate and measurement cell body that includes a reflective measurement cell, a bottom port microphone, and a narrow-band electromagnetic radiation source, allowing for efficient absorption and measurement of pressure variations within a small form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long optical path length is used for sufficient infrared absorption, then measurement precision is improved, but device volume increases
Solution Approach 1:
The patent transitions from a linear optical path to a three-dimensional measurement volume where infrared radiation can propagate in multiple directions. The measurement cell with its specific geometry (length, width, height) allows the radiation to traverse the gas component sample in three dimensions, effectively increasing the absorption path length without proportionally increasing the device volume. This dimensional approach resolves the contradiction by achieving sufficient absorption in a compact form factor.
Solution Approach 2:
The measurement volume is nested within the measurement cell body, which is integrated with the substrate. The infrared source, measurement volume, and microphone are closely integrated in a nested arrangement, with the measurement volume positioned within the cell body that sits on the substrate. This nesting allows efficient use of space while maintaining the required optical path length for accurate measurements.
2Measurement precision
If a complex three-dimensional assembly is used for measurement cell, infrared source and pressure transducer, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the measurement cell body with the substrate by positioning the cell body on the substrate and integrating the infrared source and microphone within this combined structure. The measurement volume is formed within the cell body that is directly mounted on the substrate, creating an integrated assembly. This merging reduces the number of separate components and simplifies the overall device structure while maintaining measurement precision.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support for the measurement cell body, acts as a mounting platform for the infrared source and microphone, and contributes to the overall structural integrity of the device. The measurement cell body simultaneously contains the measurement volume and provides the optical path for infrared radiation. This multi-functionality reduces device complexity by eliminating the need for separate structural components.
3Volume of moving object
If a compact design is used to reduce device size, then device volume is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent optimizes the geometric parameters of the measurement volume (length, width, height) to achieve the best balance between compact size and measurement precision. By carefully selecting the dimensions of the measurement cell body and positioning the infrared source and microphone at specific locations, the device achieves sufficient infrared absorption in a compact form factor. The parameters are tuned to maximize the optical path length within the available volume while maintaining accurate measurements.
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 device achieves accurate and compact gas detection with a small size, improved mechanical stability, and reduced sensitivity to mechanical instabilities, while maintaining high measurement accuracy and reducing the impact of ambient conditions.
Implementation Method 1
Photoacoustic gas sensors rely on the physical effect that e.g. infrared radiation is absorbed by molecules of a component of interest in a gas, e.g. CO2, thereby transferring the molecules to an excited state. Subsequently heat is generated due to non-radiative decay of the excited state, e.g. by collisions of the molecules, which leads to an increase of pressure.
Implementation Method 2
The electromagnetic radiation source is an infrared radiation source for emitting infrared radiation. Infrared radiation preferably is defined as radiation having a wavelength in a range between 700 nm and 1 mm.
Implementation Method 3
Such pressure variation may be measured by a pressure transducer. The concentration of the component is proportional to an amplitude of the pressure variation.
Data Source
Figure 1a~1c
Figure 2~3
AI summary
A photoacoustic gas sensor device is proposed for determining a value indicative of a presence or a concentration of a component in a gas. The photoacoustic gas sensor device comprises a substrate (1), and a measurement cell body (2) arranged on a first side (11) of the substrate (1). The substrate (1) and the measurement cell body (2) define a measurement cell enclosing a measurement volume (3). The measurement cell comprises an aperture (4) for a gas to enter the measurement volume (3). The device further comprises an electromagnetic radiation source (7) for emitting electromagnetic radiation (8), and a microphone (6) for measuring a sound wave (9) generated by the component in response to an absorption of electromagnetic radiation (8) by the component. The electromagnetic radiation source (7) and the microphone (6) are arranged on the first side (11) of the substrate (1) and in the measurement volume (3). The microphone (6) has a bottom port (61) facing the substrate (1), and the measurement volume (3) is communicatively coupled to the bottom port (61).