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Method for detecting concentration of trace steam by using photoacoustic spectrometry method

A photoacoustic spectroscopy and water vapor technology, which is applied in the measurement of color/spectral characteristics, measuring devices, and material analysis by optical means, can solve the problems of inability to detect trace amounts of water vapor, inaccurate detection results, etc. High detection accuracy and excellent stability

Active Publication Date: 2012-09-19
江苏舒茨测控设备股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method is widely used, but it is necessary to pay attention to the interference factors that affect the measurement accuracy during measurement. Among them, condensation of water vapor will cause inaccurate test results, and this method cannot detect trace water vapor with a concentration as low as 20000ppm

Method used

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  • Method for detecting concentration of trace steam by using photoacoustic spectrometry method
  • Method for detecting concentration of trace steam by using photoacoustic spectrometry method
  • Method for detecting concentration of trace steam by using photoacoustic spectrometry method

Examples

Experimental program
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Effect test

Embodiment

[0022] A beam of monochromatic light with adjustable intensity is modulated by a chopper, and then the spectrum passes through an optical filter to irradiate a trace amount of water vapor sample sealed in a photoacoustic cell. The trace amount of water vapor absorbs light energy and releases heat energy In the way of de-excitation, the released heat energy causes periodic pressure fluctuations of trace water vapor molecules, which can be detected by a sensitive microphone and amplified to obtain a photoacoustic signal, which is the photoacoustic effect. The use of photoacoustic spectroscopy sensors to detect trace water vapor concentrations is based on the photoacoustic effect after gas absorption spectroscopy.

[0023] please see Figure 1 to Figure 3 , the method for detecting trace water vapor concentration using photoacoustic spectroscopy of the present invention is the method for detecting trace water vapor concentration using photoacoustic spectral sensor, and this photo...

Embodiment 2

[0044] The infrared light source 1 cooperates with the optical filter 3 to emit 2.5-3μm mid-infrared spectrum, which is irradiated on the chopper 2, and the chopper 2 is controlled by the chopper control unit 4, so that the precise 2.5-3μm light source is incident on the In the resonant photoacoustic cell 8, since the photoacoustic cell 8 is filled with a trace amount of water vapor gas to be measured, the trace amount of water vapor absorbs light energy and releases the absorbed energy thermally through intermolecular collisions, and then passes through the released The energy enables trace water vapor gas molecules to convert light energy into heat energy through non-radiative transitions, and the heat energy changes the local temperature of trace water vapor gas and causes pressure fluctuations. This pressure fluctuation is detected by the electret capacitive microphone 11 configured outside the photoacoustic cell 8 with a capacitance of 10PF, a signal-to-noise ratio of 56dB...

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Abstract

The invention discloses a method for detecting concentration of trace steam by using a photoacoustic spectrometry method, belonging to the technical field of trace gas detection. The method comprises the steps of: firstly, emitting an adjustable light to a chopper by an infrared light source, and enabling stream and reference gas to enter a photoacoustic cell; and secondly, radiating a mid infra-red spectrum to gas trace stream in the photoacoustic cell, absorbing light energy at a place with wavelength of 2.5-3mu m, and releasing the absorbed energy, wherein the energy enables the light energy to be converted into heat energy, the heat energy enables the temperature of the trace stream to change and cause pressure fluctuation for generating sound waves, the sound waves are detected by a rheomicrophone, a photoacoustic signal is obtained, the photoacoustic signal is converted into a digital electric signal through an analog-to-digital conversion circuit of a peripheral analog-to-digital signal converter, and the photoacoustic signal is converted into an industrial analog signal through a digital-to-analog conversion circuit of a digital-to-analog signal converter to be supplied to a user. The method has the advantages of capability of detecting the concentration of PPM-level trace stream, no need of any chemical materials, no need of re-regulation after marked regulation, capability of preventing stream from condensing, high detection precision, good sensitivity and excellent stability.

Description

technical field [0001] The invention belongs to the technical field of trace gas detection, and in particular relates to a method for detecting trace water vapor concentration by photoacoustic spectroscopy, which is suitable for such as environmental monitoring and detection of food packaging materials. Background technique [0002] Under conditions such as industrial environment and laboratory environment, it is necessary to judge the condition of equipment and product performance by detecting the concentration of trace water vapor. For example, in the power industry, it is necessary to monitor the concentration of trace water vapor in high-voltage switchgear to determine whether there are potential safety hazards in high-voltage switchgear; for example, in the food packaging industry, it is necessary to detect trace water vapor transmission rates of food packaging materials to analyze The reliability and airtightness of packaging materials. In these applications, the conc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/25G01N21/01
CPCG01N21/1702G01N2021/1704
Inventor 陈默李茂安德里亚斯·何安德
Owner 江苏舒茨测控设备股份有限公司
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