Odor Sensor Research Articles

Breath odor characteristics after drinking and identification of sake quantity

Alcohol concentration in the expiration of a subjective person after drinking was examined. Beer, Japanese sake, red wine and shochu were adopted as the alcoholic subjects. The concentration grade was indicated using three metal oxide odor sensors. It became obvious that the alcoholic component in the expiration could remain over 3 h after drinking. Japanese elderly people mostly prefer beer and sake according to a questionnaire survey. In this study, the sensor output characteristic as a function of passage time after drinking sake was investigated and the suitable amount could be indicated by a proposed technique. This means an amount of alcohol from which the subject feels refreshment of mind and body. The sensor outputs after 1 and 2 h of drinking were adopted in the technique. In the questionnaire, it became obvious that 61% of aged men habitually drunk and 18% of females drunk. Women also preferred wine, plum liquor and shochu cocktails. This system was developed to survey the aged life style and identify whether they moderately drunk or not.

The fabrication and characterization of a formaldehyde odor sensor using molecularly imprinted polymers

The fabrication and characterization of odor sensors based on molecularly imprinted polymers is reported as the first case of imprinting formaldehyde. A quartz crystal microbalance is employed as a sensitive apparatus of a sensor for the determination of odor formaldehyde. An equation is deduced to characterize the interaction between molecularly imprinted films and the template. A linear relationship between the frequency shifts and the concentration of analyte in the range of 1.25 to 14.25 μM is found. The detection limit is about 20.5 μM. The sensor can selectively distinguish gaseous formaldehyde. It is envisaged that this novel and handy method could be employed to determine formaldehyde gas in the atmosphere.

Sensory based quality control utilising an electronic nose and GC-MS analyses to predict end-product quality from raw materials

The objective of the present study was to investigate if an electronic nose, comprising six metal oxide sensors (MOS) could predict the sensory quality of porcine meat loaf, based on measuring the volatiles in either the raw materials or the meat loaf produced from those raw materials. A multivariate data analysis strategy involving analysis of variance partial least squares regression (APLSR) and principal component analysis (PCA) was used to determine causal and predictive relationships between the raw material and meat loaf samples, sensory analysis, electronic nose, and GC-MS measurements. The results showed that the six MOS sensors in the Danish odour sensor system (DOSS) could detect the raw materials that led to unacceptable products, as determined by sensory profiling and in-house sensory quality control (QC), and separate those raw materials from each other, based on the volatile composition, as determined by GC-MS. However, the electronic nose was unable to detect all the sensory unacceptable meat loaf samples themselves due to changes in the volatile composition after cooking. Analysis of the GC-MS compounds identified from raw materials and meat loaf samples indicate that two MOS sensors mainly responded to alcohols and to a lesser degree to aldehydes and alkanes, whereas two other sensors most likely responded to low molecular weight sulphur compounds. Thus, the results indicate that measuring volatiles with the MOS sensors in the DOSS system, on raw materials for processed meat products, may be a feasible strategy in sensory based quality control, and may also have potential in predicting the sensory quality of the end product.

Determination of the dynamics of the odour release from a pig house, using an electronic odour sensor

The widely fluctuating operating conditions in pig husbandry, due to climatic and biological changes (changes in temperature and air flowrate between day and night, as well as between summer and winter, increasing animal mass during the fattening process, etc.) exert a significant influence on the amount of actual odour emission. The project presented here comprised the measurement of seasonal (fattening course), daytime-related, and short-term (feeding) dynamic effects of odour release, as well as the identification of potential factors which influence the amount of odour emitted. In parallel with "classic" olfactometry, an electronic odour sensor with a chemosensor array of ten metal oxide sensors was employed. The highest odour emissions are measured on hot summer days, while the lowest emissions were determined on cold winter days. On the one hand, the sensor signals of the electronic odour sensor exhibited considerable differences on days with large volume flow alterations. On the other hand, continuous measurement with the electronic odour sensor allowed changes in the gas- and odorant composition of the exhaust air during feeding times to be shown. From the measurement results, recommendations for odour sampling, the consideration of seasonal odour emission fluctuations, and the use of electronic odour sensors for the evaluation of odour emissions have been derived.

A new method for measuring emission of odour from a rendering plant using the Danish Odour Sensor System (DOSS) artificial nose

This paper presents Danish experiences with measurement of odour from a rendering plants bio-filter by use of a recently developed Danish Odour Sensor System (DOSS). A rendering plant produces numerous odorous compounds and might cause annoyance in the environment. The plant management wants to minimize the amount of odour components released into the surroundings. The intention of the DOSS project is to develop a so-called electronic nose with a fast response time for use as an on-line odour-monitoring tool in the exhaust from bio-filters. The main DOSS objective is to develop and evaluate gas sensors and sensor systems (collectively called electronic noses) for industrial applications, specifically a system for on-line process control. The sensors should provide real-time measurement assessment of odours at the source and possibly at the receptor location. Bio-filter outlet is estimated to be less than 5000 OU/m 3 (Odour Units). The DOSS uses six QMB sensors, six MOS sensors and four chemical/infrared/capacitive sensors for measuring O 2, H 2O, CO, CO 2. The data during instrument development is gathered from sample bags and compared with reference odour concentrations (OU/m 3). Results from experiments are presented. Principal components analysis (PCA) and partial least squares (PLS) regression plots indicate good classification and prediction expectation. Preliminary results on interfering compounds, e.g. H 2O, H 2S and CO 2 are shown. The method was thus far developed and evaluated under laboratory conditions. Generally, the results obtained with the electronic nose measurement method showed a good repeatability and a potential to get useful results comparable with odour emission over the range 1000–30,000 OU/m 3. Experiments with the DOSS have shown that the method has a high potential as fast, reliable odour-monitoring tool for rendering plant emission monitoring.

Improvement of odor-recorder capability for recording dynamical change in odor

A new method of recording rapid dynamical change in odors using quartz crystal microbalance (QCM) odor sensor arrays is proposed in this study. Two identical sensor arrays were used to simultaneously measure target and blended odors so that the composition of the blended odor could be adjusted in real time to reproduce the same odor as that of the target. As a result of the increased speed of determining the target-odor recipe, odor that changes over 5 s was successfully recorded. Furthermore, ambient odors were also successfully recorded despite the rapid changes in odors due to turbulent airflows.

Odor sensor with water membrane using surface polarity controlling method and analysis of responses to partial structures of odor molecules

A novel odor sensing system which imitates the process of reception of odorants in biological olfactory system had been developed, utilizing surface polarity controlling method as a transducer of the sensor. In biological system, odorants are received by a large number of receptors, which recognize not whole structures but partial structures of molecules. The present sensor responded partial structures of odorants and adsorption interaction of the partial structures were controlled by the surface polarity of the electrode. Sensor output signals were analyzed on the stand point of partial structures of odorants. As a result, the responses to alcohols, aromatic compounds and aromatic alcohols as odorants could be discriminated by similar molecular structures, with principal component analysis (PCA). In addition, regression models of the response to partial structures of odorants were developed by multiple regression analysis, and odor qualities of aromatic alcohols could be evaluated quantitatively by partial structures of odor molecules.

Evaluation of odour from portable toilets in a four-bed hospital ward

Objective. Unpleasant odours in hospital wards arising from patients’ use of portable toilets is a significant problem. The odours in a four-patient hospital ward were evaluated by using semiconductor odour sensors to evaluate the ambient odour. All the patients in the ward used a conventional portable toilet for four successive days, and then an odourless portable toilet for six successive days. Method. Four semiconductor odour sensors were used. They were mainly sensitive to hydrogen sulphide, ammonia, chemicals of light molecular weight (A sensor), and chemicals of heavy molecular weight (B sensor), respectively. Air was collected from near the ceiling of the hospital ward and transported to the sensors via Tygon® tubes. Result. In comparison with the conventional portable toilet, the odourless portable toilet resulted in a decrease of 14% in levels of hydrogen sulphide, 30% in ammonia, 58% in chemicals of light molecular weight and 44% in chemicals of heavy molecular weight. Conclusion: The ambient odour in the hospital ward was significantly improved by using the odourless portable toilet.

Fundamental study of odor recorder for multicomponent odor using recipe exploration method based on singular value decomposition

A new method for the odor recorder, electronically recording the recipe of odors or scents made up of many components, was proposed. Although apple flavors have been recorded with a mixture of five components using the odor recorder in previous work, the number of odor components should be increased to expand the applicable range of odors. Since the collinearity problem of the odor sensor array became apparent with the increase of components, a new method based on variable transformation using singular value decomposition was developed in this paper, to extract the effective subspace of the sensor outputs for recipe exploration. As a result, the sensor-array response pattern of the reproduced odor, with the eight-component recipe, almost agreed with that of the target apple flavor. Furthermore, human sensory tests revealed that the smell of the approximated odor was identical to that of the target flavor.

Proposition of a survey device with odor sensors for an elderly person

Three types of metal oxide gas sensors were adopted to detect the degree of breath odor. Various sorts of information are included in the odor. Each sensor has different sensitivities to gaseous chemical substances and the sensitivities also differ according to human behaviors, for example taking a meal, teeth brushing and drinking something. There is also a possibility that the sensor can detect degrees of daily fatigue. Sensor sensitivities were low for the expiration of the elderly when the subject drank green tea. In this study, it is thought that the odor system can be incorporated into a healing robot. The robot can communicate with the elderly using several words and also by connecting to the Internet. As for the results, the robot can identify basic human behaviors and recognize the living conditions of the resident. Moreover, it can also execute a kind of information retrieval through the Internet. Therefore, it has healing capabilities for the aged, and can also receive and transmit information.

Study of recording apple flavor using odor recorder with five components

The odor recorder has been developed using the odor sensing system based on the active sensing method to electronically record odors and reproduce them anytime and anywhere. The recorder developed in this paper has capability of recording the target odor, the mixture of five odor components, using the odor sensor array composed of quartz crystal microbalance sensors. The difference between the sensor response patterns of the recipe and target odors was minimized so that the recipe of the five components for the target odor was determined. In this paper, the method of selecting the most appropriate sensors to record odors was investigated based on the condition number of the sensor array sensitivity matrix. Moreover, the method of determining the parameters of the odor-recording algorithm was studied. As a result, several apple flavors composed of the five components were successfully recorded. Furthermore, the typical apple flavor composed of nine components was approximated using the mixture of the five components. The approximation result by the sensing system was successfully verified by the human sensory test.

Odor recorder for multi-component odor using two-level quantization method

A new algorithm to electronically record an odor composed of the mixture of many components using the odor sensing system was proposed. Since the human impression on the odor mostly depends on the kinds of key components rather than the accurate mixture composition, the odor was approximated with the combination of several components. Moreover, the efficient method to explore the recipe for the odor approximation with the combination of many components was established. Then, the recipe of an apple flavor was recorded using the proposed method and was evaluated by the human sensory test. As a result, it was found that the odor approximated with up to eight components was close to the target apple flavor. Furthermore, it was confirmed that the response pattern of the QCM (quartz crystal microbalance) odor sensor array was a good indicator of the odors detected by human olfaction. The proposed method was useful to realize the odor recorder with many odor components.

Non-destructive egg freshness determination: an electronic nose basedapproach

An electronic nose (EN) based system, which employs an array of four inexpensivecommercial tin-oxide odour sensors, has been used to analyse the state offreshness of eggs. Measurements were taken from the headspace of four sets ofeggs over a period of 20–40 days, two ‘types of egg data’ being gathered using ourEN; one type of ‘data’ related to eggs without a hole in the shells and the othertype of ‘data’ related to eggs wherein we made tiny holes in the shells. Principalcomponent analysis, fuzzy C means, self-organizing maps and 3D scatter plotswere used to define regions of clustering in multisensor space according tothe state of freshness of the eggs. These were correlated with the ‘useby date’ of the eggs. Then four supervised classifiers, namely multilayerperceptron, learning vector quantization, probabilistic neural networkand radial basis function network, were used to classify the samples intothe three observed states of freshness. A comparative evaluation of theclassifiers was conducted for this application. The best results suggest thatwe are able to predict egg freshness into one of three states with up to95% accuracy. This shows good potential for commercial exploitation.

QCM Odor Sensor Noticed by Boilling Point of Odor Substances

QCM Odor Sensor Noticed by Boilling Point of Odor Substances

Landfill odour: assessment of emissions by the flux footprint method

This paper will focus on the development of an innovative method for estimating odour fluxes and the contributing source areas from a Municipal Solid Waste (MSW) landfill site. A micrometeorological model has been developed based on the estimation of footprints of scalar odour concentration measurements in the atmospheric surface layer. The model is based on an analytical solution of the Eulerian advection-diffusion equation for vertical diffusion; model parameters include the location of the odour sensor and standard surface layer scaling factors. Lindvall Hoods are commonly used for measuring odour fluxes from ground based fugitive sources. However these cannot replicate the real atmospheric conditions. Common micrometeorological techniques for determining fluxes, such as vertical gradient measurements or eddy correlation methods, yield a flux magnitude but give practically no information about the source location. On the other hand the flux footprint describes the expansion and contraction of the required fetch under varying atmospheric stabilities. Preliminary results from the model are quite encouraging and agree well with those from Lindvall hood measurements. The accuracy of Lindvall hood measurements depends on how tightly the hood is positioned on the uneven landfill surface. It should prevent any air escaping out from the sides of the hood open to the atmosphere. Typical results show an average odour flux of ±25.91 (ou m −2 s −1) from freshly tipped wastes for an upwind fetch of 45.0 m and with the sensor at a height of 1.5 m from the ground. The hood results have a geometric mean of ±29.35 (ou m −2 s −1) based on the inlet air volume and a shade air temperature of 22.5 °C.

Distributed odor source localization

This paper presents an investigation of odor localization by groups of autonomous mobile robots. First, we describe a distributed algorithm by which groups of agents can solve the full odor localization task. Next, we establish that conducting polymer-based odor sensors possess the combination of speed and sensitivity necessary to enable real world odor plume tracing and we demonstrate that simple local position, odor, and flow information, tightly coupled with robot behavior, is sufficient to allow a robot to localize the source of an odor plume. Finally, we show that elementary communication among a group of agents can increase the efficiency of the odor localization system performance.

Functional imaging and molecular technology of olfactory cells and odorant sensor

Functional imaging and molecular technology of olfactory cells and odorant sensor

味と匂いセンサの研究·開発動向

味と匂いセンサの研究·開発動向

実時間参照方式による匂い記録·再生システムの環境変化に対するロバスト性向上

The new type of odor recorder called real-time reference system is proposed to improve robustness against environmental changes, especially humidity and temperature changes. Since an odor sensor depends on humidity and temperature, these conditions have to be precisely controlled in a general odor sensing system. However, the odor recorder we developed in this paper does not need those requirements because of the real-time relative measurement based on the active sensing method, where a target odor and the reproduced odor were alternately exposed to the sensor array to reduce the influence of the dynamic environmental changes. We describe the design of the feedback controller for the real-time reference system and the experimental results of recording odors using the system. The recipes of apple flavors made up of four components were successfully recorded under the varying environments of humidity and temperature. Once the recipe for the target odor is recorded electronically by the odor recorder, it can be reproduced anytime and anywhere using an odor blender.

水晶振動子匂いセンサ用マルチチャンネル高速周波数変化計測回路

Frequency shift measurement circuit with high sampling rate using reciprocal method for QCM odor sensor is proposed. Although the circuit including an analog-type mixer achieved the high sampling rate, the digital mixer in place of analog one is required since all the circuits can be implemented into one chip. The proposed digital mixer helped us achieve 128ms time resolution, 8 times faster than the conventional one, without the deterioration of the frequency resolution. Then, it was found that its introduction into the gas odor visualization system enabled us to have clear image. After the successful implementation into a FPGA, its ASIC version was fabricated. The increase in the mixer performance brought us further increase in the sampling rate of the frequency shift.