Nondispersive Infrared Gas Analyzer Research Articles

Seasonal, latitudinal, and secular variations in the abundance and isotopic ratios of atmospheric carbon dioxide: 1. Results from land stations

Between March 1977 and February 1982, 517 samples of air were collected in 51 glass flasks at four stations in the northern hemisphere near the Pacific ocean and at the South Pole. First, the CO2concentration of each sample was determined by nondispersive infrared gas analysis, and then the 13C/12C and 18O/16O ratios of the cryogenic extracted CO2 were determined with a triple collector mass spectrometer. For each station the secular trend and seasonal variation in 13C/12C ratio have been established as a function of CO2 concentration. The seasonally adjusted 13C/12C ratio is found to have decreased at a rate of about 0.02‰ per ppm increase in the seasonally adjusted CO2 concentration and to vary with latitude as expected if CO2 is being released by fossil fuel combustion in the northern hemisphere and from ocean water near the equator. At the three northernmost stations (La Jolla, California, at 33°N and two Hawaiian stations near 19°N) the 13C/12C ratio of the CO2 added to and withdrawn from the atmosphere during one annual cycle is circa −29‰ with respect to standard PDB, as expected from the exchange of atmospheric CO2 with the carbon of terrestrial plants. Near the equator at Fanning Island (4°N) the similarly computed 13C/12C ratio is −21‰, while at the South Pole it is about −13‰. This suggests that the seasonal variation in the southern hemisphere and tropics is partially a result of oceanic CO2 exchange.

Calculations of carrier gas effects in non-dispersive infrared analyzers. II. Comparisons with experiment

A numerical model for calculating carrier gas effects in non-dispersive infrared gas analyzers was presented in the preceding paper. This model is applied here to sets of data from several analyzers used in measuring atmospheric CO 2 concentrations at a world-wide network of baseline stations. The agreement between the model and the experimental results is generally satisfactory, and the model can be used to better understand the behaviour of non-dispersive analyzers.DOI: 10.1111/j.2153-3490.1982.tb01828.x

Calculations of carrier gas effects in non-dispersive infrared analyzers I. Theory

A theory and method of calculation is presented for determining changes in instrument response and hence apparent gas concentration which arise in non-dispersive infrared gas analyzers when gas mixtures with varying carrier gases are analyzed. The theory is based on variations in pressure-broadening in the sample cell of the analyzer and initial comparisons with experimental values for CO 2 -in-air and CO 2 -in-N 2 indicate good agreement between theory and experiment. DOI: 10.1111/j.2153-3490.1982.tb01827.x

Calculations of carrier gas effects in non-dispersive infrared analyzers. II. Comparisons with experiment

A numerical model for calculating carrier gas effects in non-dispersive infrared gas analyzers was presented in the preceding paper. This model is applied here to sets of data from several analyzers used in measuring atmospheric CO 2 concentrations at a world-wide network of baseline stations. The agreement between the model and the experimental results is generally satisfactory, and the model can be used to better understand the behaviour of non-dispersive analyzers.DOI: 10.1111/j.2153-3490.1982.tb01828.x

Chamber Systems for Measuring Nitrous Oxide Emission from Soils in the Field

AbstractRecent concern over N2O losses from soils has highlighted the need for new techniques for measuring N2O exchange in the field. Two systems are described, in which nondispersive infrared gas analysis is used to measure the change in N2O concentration of air passing through a cylindrical chamber driven 0.1 m into the ground. When interfering gases are removed from the air stream, the infrared analyzer has a resolution of ± 12 ppb N2O.In one system, air circulates in a closed loop between the chamber air space and the gas analyzer; in the other, open system, outside air is drawn continuously through the chamber space and its N2O enrichment or depletion measured.Two operational problems (common to many emission chambers) were encountered: the development of a low pressure in the chamber when air is withdrawn, which induces a mass flow of N2O from the soil in addition to the diffusive flow; and a readjustment of the N2O concentration in the soil air whenever the N2O concentration in the chamber air changes from ambient. These can lead to incorrect estimates of the flux. The former problem was overcome by chamber design. The latter appeared to be insurmountable in the closed system, but could be reduced to acceptable proportions in the open system by choice of air flow rate.The open system permits relatively rapid equilibration, automatic and continuous operation, a discrimination less than 2 ng N m−2 sec−1, and the maintenance of environmental conditions within the chamber close to those in the field.

Non-Dispersive Infra-Red Gas Analysers for Industrial Processes and the Protection of the Environment

Non-Dispersive Infra-Red Gas Analysers for Industrial Processes and the Protection of the Environment

Pressure Effect of the Nondispersive Infrared Gas Analyser

Abstract Based on the Elsasser model, a formula for the mean absorption applicable to the pressure effect of the nondispersive infrared gas analyser has been derived. The formula is generalized by removing the assumption in the Elsasser model that the total absorption coefficient, the half width and the spectral distance are constant.

Errors in atmospheric CO2concentration measurements arising from the use of reference gas mixtures different in composition to the sample air

Comparisons have been made between the URAS 2, UNOR 2 and Grubb Parson's SB2 non-dispersive infra-red gas analysers, involving the measurement of CO 2 concentration in gas mixtures containing N 2 and O 2 in varying proportions. The results imply that the CO 2 concentration in air when using CO 2 /N 2 mixtures as references, is under-estimated by 3.7 and 2.3 ppmv for the URAS and Grubb Parson's instruments respectively and over-estimated by 4.5 ppmv by the UNOR. The measurement of CO 2 concentration in air is not affected if CO 2 /air mixtures are used as references. The indicated CO 2 concentration of air relative to a CO 2 /N 2 reference mixture is found to depend on ambient pressure for both the UNOR and URAS analysers. Thus aircraft or high altitude in situ measurements need an additional correction, to be comparable with measurements made relative to the same CO 2 /N 2 reference mixtures at a standard (near sea-level) pressure of 1 000 mb. The results are similar to those obtained by Bischof (1973) and have important implications on the interpretation of carbon dioxide concentration measurements made at monitoring stations. DOI: 10.1111/j.2153-3490.1975.tb01656.x

A correction for the effect of drying of air samples and its significance to the interpretation of atmospheric CO<sub>2</sub> measurements

Non-dispersive infrared gas analysers used for the measurement of atmospheric carbon dioxide concentration are influenced by water vapour in the air sample. It has thus become common practice to dry the air prior to analysis. The subsequent measurement must be corrected by multiplying the indicated concentration by (1 + 1.61<em>r</em>)⁻¹, where r is the water vapour mass mixing ratio of the undried air. The correction is of the order 1% near the surface, varying in both space (e.g. with latitude) and time (e.g. day-today and seasonally), and of the same order of magnitude as the measured but uncorrected horizontal, vertical and seasonal CO₂ variations. Thus serious doubt is thrown on previous comparisons of global CO₂ measurements. Ideally each CO₂ analysis of an air sample should be corrected using knowledge of the water vapour concentration of the undried air. For data obtained in the past, appropriate correction may be possible after consideration of the water vapour conditions in the atmosphere at each of the monitoring stations. This should be done by the research personnel involved with each monitoring programme, together with a consideration of the effects of carrier gas composition on the gas analyser(s) employed.

ChemInform Abstract: PRESSURE EFFECT DETERMINED WITH USE OF THE NONDISPERSIVE INFRARED GAS ANALYSER

Chemischer InformationsdienstVolume 5, Issue 8 Physical Inorganic Chemistry ChemInform Abstract: PRESSURE EFFECT DETERMINED WITH USE OF THE NONDISPERSIVE INFRARED GAS ANALYSER EIJI NIKI, EIJI NIKISearch for more papers by this authorTSUTOMU YONEZAWA, TSUTOMU YONEZAWASearch for more papers by this author EIJI NIKI, EIJI NIKISearch for more papers by this authorTSUTOMU YONEZAWA, TSUTOMU YONEZAWASearch for more papers by this author First published: February 26, 1974 https://doi.org/10.1002/chin.197408495Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue8February 26, 1974 RelatedInformation

Pressure Effect Determined with Use of the Nondispersive Infrared Gas Analyser

Abstract The pressure effect of nitrous oxide and nitric oxide due to nitrogen gas was investigated with use of a nondispersive infrared gas analyser. The results are in line with the theoretical curves derived from the Elsasser theory. The calculated expression is partly improved and the error of calculations is estimated in regard to carbon dioxide.

非分散形赤外線ガス分析計の圧力効果の研究

Based on the Elsasser model, a formula for the mean absorption applicable to the pressure effect of the nondispersive infrared gas analyser has been derived. The formula is generalized by removing the assumption in the Elsasser model that the total absorption coefficient, the half width and the spectral distance are constant.

Book Review: Non-Dispersive Infra-Red Gas Analysis in Science, Medicine and Industry

Book Review: Non-Dispersive Infra-Red Gas Analysis in Science, Medicine and Industry

Concentration of CO2 in the Upper Troposphere and Lower Stratosphere

DURING a number of flights of commercial aircraft over the polar route from Frankfurt/Main to Tokyo via Copenhagen the concentration of CO2 in the atmosphere was continuously recorded using a non-dispersive infrared gas analyser. The flights took place between April 1967 and February 1968. The recorded concentration of CO2 from all flights shows a remarkable change when the aircraft enters and leaves the stratosphere. A quite sudden change of about 3–5 p.p.m. CO2 is usually observed at the transition from tropospheric into stratospheric air and vice versa. The striking difference between the CO2 content of the upper troposphere and the stratosphere was clear enough on the record for the crew of the aircraft to use our CO2 analyser as an indicator of the position of the aircraft relative to the tropopause. Fig. 1 shows the record obtained during the flight from Tokyo to Copenhagen on May 29–30, 1967, together with the position of the aircraft and the tropopause. Sections of the flight within the stratosphere are marked. They clearly show a drop of the CO2 content in the stratosphere. The sudden peak at 70° N 145° W during the flight through the stratosphere may be explained by influx of tropospheric air into the stratosphere. The relative accuracy of our measurements is about ±0.3 p.p.m. CO2, which gives confidence in the reality of the observed fluctuations. The accuracy of the absolute values of the CO2 concentration amounts to ±1.5 p.p.m. due to difficulty in calibrating the reference gases. The marked decrease of the CO2 concentration in the lower stratosphere compared with the upper troposphere suggests that, contrary to previous practice, it is wrong to assume a constant mixing-ratio of CO2 in the troposphere and stratosphere. Exact knowledge of the CO2 concentration with altitude is needed for many calculations of the radiation budget of the atmosphere.

Paper 9: The Sampling and Measurement of Exhaust Emissions from Motor Vehicles

The development of apparatus and systems to reduce exhaust air pollution from motor vehicles was hampered initially by the lack of suitable quantitative measuring apparatus. Great improvements have taken place and accurate measurement of pollutants can now be made, either in the form of continuous records, or of an average value, over a period of time or cycle. The principal instrument in current use is the rapid response non-dispersive infrared gas analyser. Apart from carbon compounds it can also detect with accuracy oxides of nitrogen. Future trends in pollution measurements are orientated towards the evaluation of the mass emitted during a predetermined cycle instead of the average concentration. With this in view, new sample collection methods have been developed, such as total bag sampling, and variable dilution sampling. The B.T.C. Analytical Committee was formed four years ago to advise on and discuss exhaust gas measurement techniques. Amongst its achievements have been the establishment of gas and car correlation schemes and the laying down of instrument specifications.

The frequency response characteristics of some condenser microphone infra-red detectors

The frequency response characteristics for interrupted infra-red radiation are described for four condenser-microphone type detectors as used in nondispersive infra-red gas analysers. Three of the detectors are of conventional dimensions. The fourth is a subminiature type, and its use is described with a field-effect transistor amplifier. It is shown that markedly increased optical modulation frequencies can be used with infra-red pneumatic detectors, without radical reductions in output signal, if the dimensions of the device are drastically reduced. This has been accounted for on theoretical grounds. The frequency responses obtained are examined and shown to correlate adequately with mathematically predicted profiles. Low frequency attenuation is explained on the grounds of thermal conductivity effects and leakage paths across the transducer diaphragm, whereas a high frequency maximum for one detector is shown to arise from Helmholtz resonation due to the chamber configuration.

Cross-sensitivity effects in non-dispersive infra-red gas analysers using condenser microphone detectors

A pair of precision gas mixing pumps has been used to investigate the effect of spectral overlap and collision broadening by sample diluents on the accuracy of three commercial non-dispersive infra-red gas analysers, sensitized for carbon dioxide and having a condenser microphone type of transducer. These effects were investigated in respect of the composition of the sample mixture and the filling mixture of the condenser microphone chamber. The results are given as the ratio `actual%CO2 in sample/indicated%CO2 in sample'. In the case of broadening by helium, argon, oxygen and nitrogen this ratio is typically 1.125 ± 0.005, 1.030 ± 0.008, 1.000 and 0.950 ± 0.006, respectively, for the range 0-10% v/v CO2. This has been shown to be in accord with available spectroscopic data. Broadening by nitrous oxide indicates a value of 1.32 ± 0.06 for the foreign broadening coefficient F for this gas on the 2349 cm-1 band of carbon dioxide. Results for the vapours ether and halothane suggest a broadening ability similar to that of nitrous oxide.