CS206187B1 - Method of measuring the concentration of the carbon dioxide - Google Patents

Description

The present invention relates to a method for measuring the concentration of carbon dioxide in a gaseous medium by an infrared spectrum analyzer.

Infrared spectral analyzers of both oxygen and carbon dioxide work on the principle of absorption of radiation by gas molecules in a certain wavelength range. The carbon dioxide molecule acts as a rotational-vibrating oscillator with an appropriate absorption band in the region of 4.26 µm. Absorption reduces the intensity of the radiation beam propagating through the absorbing gas environment. The rate of absorption depends on the concentration of the absorbing molecules. The concentration of the gas to be examined can be determined from the decrease in the radiation intensity, at a known beam path length in the absorbing medium.

Radiation in the 4 to 5 µm wavelength range is possible; detect, for example, broadband bolometers, ί thermocouples and pyroelectric detectors, highly selective semiconductor-based detectors with a narrow bandwidth Wg of 0.3 eV. The detectors used in this area either have a lower sensitivity or are too expensive and unavailable, leading to an even proportional increase in the cost of the analyzer. Some types of detectors need to be cooled.

These disadvantages are eliminated by the method of measurement! the concentration of carbon dioxide in the gaseous medium by the infrared spectrum analyzer of the invention. Its essence lies in the fact that 206187 determines the concentration of carbon dioxide in the gaseous environment from the absorption of radiation in the second or third harmonic zone. It is preferred that the infrared spectrum is also within the radiation range of 2.05 to 2.2 µm, or 1.4 to 1.5 µm.

| The spectral curves of radiation in the area of the second or third harmonics of the basic spectrum of carbon dioxide are also measured and compared with the normal concentration of carbon dioxide.

An advantage of the method of the invention is that a lead simulator with relatively high sensitivity and lower cost can also be used, although the upper limit and its spectral sensitivity do not exceed 2.5 µm to 3.0 µm. In fact, the molecular oscillator is generally non-linear and there are also higher harmonics corresponding to the respective absorption bands. Belts second resp. the third harmonic therefore lies in the region of 2.13 pm and the second harmonic respectively. 1.42 pm. Concentration of carbon dioxide can then be determined from the absorption in the mentioned and harmonic bands. In particular, a second harmonic band lying in the region of the maximum spectral sensitivity of the lead resistance photoresist may be used. J Absorption in the region of the third harmonic band can also be detected by a germanium photodiode.

The lead simulator detector can be used to replace the detector for most design types of spectrum analyzers ^

206187 _______ Selective characteristic has to be adjusted for the respective absorption harmonic strip. Due to the significantly higher signal, the electronic part can be significantly simplified.

Said use of a lead-based simulator in infrared carbon dioxide analyzers allows for a much simpler design of existing ana | lysers and their price reduction.

The invention is described in more detail on the basis of the accompanying infrared radiation density diagram in the 0.5 to 2.5 µm gaseous zone in which the carbon dioxide was found at 24 ° C.

The diagram was generated using a lead simulator sensor that was used as a photoresistor connected to a recording apparatus and was in the 0.5 to 2.5 µm infrared spectrum.

The lows on are clearly apparent

Claims (2)

SUBJECT Method for measuring the concentration of carbon dioxide in a gaseous medium by an infrared spectrum analyzer, characterized in that the concentration of carbon dioxide in the gaseous medium is determined from the absorption of radiation in the region of the second or third harmonic zone. ______________________________ 2.13 pm second harmonic and 1.42 pm third harmonic baseline wavelength of the 4.26 pm carbon dioxide spectrum. i The magnitude of the minima is then compared to the magnitude of the minima i of the normal and the ratio of the minima of the carbon dioxide in the measured gaseous medium is then calculated from their ratio. • In this case, the natural ones were surveyed; The concentration of carbon dioxide was about 0.01% and the sensitivity of the instrument at this concentration was determined. The accuracy of the data for a given device is better than 5%. ' The method of measuring the concentration of carbon dioxide is very suitable for the response rate of the ms order, especially for medical analyzers, as it can capture the breathing dynamics and further for measurement in air heavily polluted by industrial fumes. OF THE INVENTION 2. The method of item 1 characterized by tan. 2. The method of claim 1, wherein the infrared spectrum delimits from 2.05 to 2.2.