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Non-dispersive infrared (NDIR) gas sensors applied in an environmental field are considered. Disadvantages of the non-dispersive infrared (NDIR) gas sensors include spectral interference and high detection limit. Efforts to improve these disadvantages are reviewed in this paper. Interference caused by water vapor and gas matrix has been partially solved using optical filters and interference correction factors. Limitations such as accuracy and sensitivity of the sensor were overcome by the improvements of inlet gas concentrations, infrared sources, optical designs (including optical filter and gas chamber) and detectors. These improvements are limited to a few gases, in particular, carbon dioxide. Drawbacks related to water vapor still remain and need to be addressed.

Methane is the primary constituent of natural gas and is used in many industrial processes. Detection of the presence of methane is important, especially before it reaches explosive concentrations. Earlier sensor types are based on catalytic adsorption (which may limit the sensor lifetime) at elevated temperatures (requiring additional power and possibly compromising safety). Recently, optical sensors based on infrared (IR) absorption by hydrocarbon molecules have become an important research focus. One unsolved problem when using solid-state IR sources is that of optical flux variation due to heating. This paper introduces a novel power compensation approach for IR LEDs employed in gas detection, which accounts for variations in the optical flux of the source. The contribution of this paper is threefold. First, we propose the idea of compensating for emitted IR flux by means of pulsed junction voltage measurement and explain why this is effective. Second, we introduce a compensation algorithm which shows how to take advantage of this concept. Third, experimental results demonstrate that the discrimination algorithm is at least six times better than the uncompensated measurements. The convergence of the algorithm results in a stabilized measurement in less than 1 s.

This work describes the implementation and the modeling of an infrared gas sensor with pulse delta-sigma sensing architecture. Beyond the conventional technique of constant periodic heating of infrared light source, our proposed delta-sigma architecture with closed-loop feedback system is built with the hybrid combination of a CO2 infrared sensor with a specific wavelength filter, an infrared MEMS heater, a chopper amplifier, threshold comparator, ARM based MPU and discrete electronic devices. After a modeling of system, we built a model for the description of relationship between gas concentration and sensor by the duty of heating. The measurement results show a good linear behavior of signal and it proves to be a practical for all the NDIR measuring techniques and this work also gives a new approach not only to measure gas concentration fast but also obtain the high resolution.

The development of high resolution, low cost, infrared/thermal imaging systems is one of the critical challenges in infrared photonics. This paper highlights the design, simulation, fabrication, and characterization of a thermo-optic sensor based on a resonance waveguide grating structure. The sensor has been realized using polymer materials on a glass substrate. Detailed characterization of the thermal response of the structure has been performed and the experimental results show close correspondence with the simulations. The thermal response of the sensor was measured within the temperature range of 25 °C–45 °C and the measured sensitivity was found to be 0.268 nm/°C. The resonance of the structure undergoes a blue shift with respect to applied temperature. This observed displacement of the resonance is due to the thermo-optic properties of the sensor’s waveguide material. Based on 2-D structure, the sensor can be implemented as a thermal imaging sensor array. The simplicity of fabrication and high thermal sensitivity of the resonance structure enable low cost, infrared/thermal imaging applications.

Many gas molecules absorb electromagnetic radiation at characteristic wavelengths in the infrared region. This absorption can be used to identify defined substances like CO2, ammoniac, and so far. This study presents a comparative analysis of parameters of infrared radiation source and detector hardware that are most important for the creation of portable optical nondispersive infrared (NDIR) gas sensors. One of the central issues in the design of this kind of sensors is the geometry of the sensor cell. In this paper we investigate an asymmetry sensor cavity and predict the performance using Tracepro software. Then, the CO2 sensor is made and tested.

Detection of C2H2 gas in transformer oil is significant for diagnosing the operating state assessment of power equipment. The paper develops an infrared laser gas sensor to detect the C2H2 gas in transformer oil, and also introduces the system structure in detail. A gas-absorbed laser cell that contains a series of laser reflectors is designed and used in our detection system, which adds the optical path without changing the volume of the cell. 1529.16nm is chosen as the characteristic spectrum line of C2H2 gas, and concentration of C2H2 gas is quantitatively analyzed based on least square method. The experiment result shows that in certain volume fraction range of acetylene, the absorbance has a good linear relationship with the acetylene concentration, and the minimum detection limit for acetylene is 10μL/L. In general, the developed infrared laser gas sensor can detect C2H2 gas in transformer oil effectively.

The hardware and software is described for a traffic flow system based on infrared sensors. Ultrasonic ranging and the infrared sensor-based speed measurement programs are compared. The selection of infrared sensors and the application of a Fresnel lens are described. A pyroelectric sensor is used in the infrared detection system to monitor vehicle information and convert it into an electrical signal. Using an amplifier circuit and a window comparator, external interrupt signals of a microcontroller are triggered to characterize traffic-flow and vehicle velocity. The system has adjustable sensitivity and a simple design and includes automatic threshold adjustment circuit, an adjustment scheme for a digital potentiometer, and an interrupt function program. In addition, the traffic-flow and vehicle-velocity are displayed. An application of the system is reported.

As a fire detection device, flame detector has the advantages of short reaction time and long distance. Based on pyroelectric infrared sensor working principle, the passive pyroelectric infrared alarm system is designed, which is mainly used for safety of tunnel to detect whether fire occurred or not. Modelling and Simulation of the pyroelectric Detector Using Labview. An attempt was made to obtain a simple test platform of a pyroelectric detector which would make an excellent basis for the analysis of its dynamic behaviour. After many experiments, This system has sensitive response, high anti-interference ability and safe and reliable performance.

This paper presents the effects of infrared energies on dual elliptical nondispersive infrared (NDIR) ethanol gas sensors for preventing drunken drivers and the advantages of using dual ethanol detectors for temperature compensation algorithm. In order to achieve long-term reliability according to the aging of infrared source, two ethanol detectors are placed at the two foci of ellipsoids and the averaged voltage ratios of two ethanol detectors are used to establish the compensation methods.

The noise performance of infrared detectors can be improved through utilization of thinner detector layers which reduces thermal and generation-recombination noise currents. However, some infrared detector materials suffer from weak optical absorption and thinning the detector layer can lead to incomplete absorption of the incoming infrared photons which reduces detector quantum efficiency. Here, we show how subwavelength metallic nanoantennas can be used to boost the efficiency of photon absorption for thin detector layers, thereby achieving overall enhanced detector performance.

MEMS tunable Fabry-Perot filters are a key component for infrared microspectrometers and miniature gas sensors. Compared to other technologies, they have several advantages particularly with regard to miniaturization and optical throughput. This paper gives a short summary of the technology, packaging, system integration and closed loop operation. Several types with different spectral ranges and resolutions will be presented. Possible applications in gas analysis, based on own work and with reference to the literature, are also discussed.

The non-uniformity response in infrared focal plane array (IRFPA) detectors has a bad effect on images with fixed pattern noise. At present, it is common to use shutter to prevent from radiation of target and to update the parameters of non-uniformity correction in the infrared imaging system. The use of shutter causes „freezing‟ image. And inevitably, there exists the problems of the instability and reliability of system, power consumption, and concealment of infrared detection. In this paper, we present an efficient shutter-less non-uniformity correction (NUC) method for infrared focal plane arrays. The infrared imaging system can use the data gaining in thermostat to calculate the incident infrared radiation by shell real-timely. And the primary output of detector except the shell radiation can be corrected by the gain coefficient. This method has been tested in real infrared imaging system, reaching high correction level, reducing fixed pattern noise, adapting wide temperature range.

The infrared detector is the kernel of an infrared thermal imager. Usually it is the most expensive device. This paper describes a new infrared thermal design, based on an uncooled infrared detector with high performance and low price. It describes the specifications of the infrared detector and illustrates detailed the circuit to driver the infrared detector, include pivotal functions like TEC control and bias-voltages generation. The software to obtain image, correct non-uniformity and enhancement image is discussed also. At last, some infrared images prove the correctness of this design.

In this paper, infrared data correction algorithm is suggested when the environmental conditions such as air temperature or detector substrate temperature are varying. To correct the infrared data, infrared detector measurement model is described by a parameter-dependent first-order input-output equation and the relations between infrared data and model environmental parameters are investigated first. By determining the parameters which dominate the influence on the infrared data, the coefficients of a model are obtained. By using only the measurements of ambient temperatures and detector substrate temperatures, infrared detector output data corrupted by environmental temperature variations are compensated based on the model instead of using any target temperature source equipments. It is shown through experiments that the proposed algorithm can reduce the influence of environmental temperatures on the infrared data.

Based on the analysis of infrared detection technology and Lambert-Beer law a new kind of quad-channel non-dispersive infrared (NDIR) gas concentration analyzer is designed by applying the modulated IR light source and a quad thermopile sensor into automobile exhaust gases concentration detection. The emphasis is paid on the analysis of modulated light source, gas chamber, sensor and the acquisition and processing circuit of the signal. The result of simulation and analysis of the designed circuit proved the feasibility of the design.

We report a Fabry-Perot interferometer (FPI)-based multi-channel micro-spectrometer used for multi-gas measurement in the spect ralrange of 3-5 Im and its gas sensing performance. The fabricated infrared (IR) spectrometer consists of two parts: an FPI on the top sidefor selective IR filtering and a V 2 O 5 -based IR detector array on the bottom side for the detection of the filtered IR. Experimental resultsshow that the FPI-based multi-channel gas sensor has reliability and selectivity for simultaneously detecting environmentally harmfulgases such as CH 4 , CO 2 , N 2 O and CO in the spectral range of 3-5 Im. The fabricated FPI-based multi-channel gas sensor alsodemonstrated that a reliable and selective detection of gas concentrations ranging from 0 to 500 ppm is feasible. In addition, the electricalcharacteristics demonstrate a superior response performance in regards to the selectivity in the multi-target gases. Keywords : Fabry-Perot interferometer, Multi-channel infrared gas sensor, MEMS

In this study, we developed an embedded infrared fiber-optic temperature sensor for thermometry in high temperature/pressure and water-chemistry environments by using two identical silver-halide optical fibers. The performance of the fabricated temperature sensor was assessed in an autoclave filled with an aqueous coolant solution containing boric acid and lithium hydroxide. We carried out real-time monitoring of the infrared radiation emitted from the signal and reference probes for various temperatures over a temperature range from 95 to 225 °C. In order to decide the temperature of the synthetic coolant solution, we measured the difference between the infrared radiation emitted from the two temperature-sensing probes. Thermometry with the proposed sensor is immune to any changes in the physical conditions and the emissivity of the heat source. From the experimental results, the embedded infrared fiber-optic temperature sensor can withstand, and normally operate in a high temperature/pressure test loop system corresponding to the coolant system used for nuclear power plant simulation. We expect that the proposed sensor can be developed to accurately monitor temperatures in harsh environments.

Alcohol concentration measurement becomes very important in mixing a chemical solution. The measurement in general uses a conventional method that requires direct contact and a long time of measurement period, such as using a capacitive sensor. Another method is Non-Dispersive Infrared (NDIR) which is capable of measuring the concentration of alcohol without any direct contact and within relatively short test period. In NDIR system, infrared light generated by an infrared source passes through the sample tube. Then, the infrared light that can be absorbed by the hydrocarbon particles of the alcohol is sensed by an infrared detector. In this paper, the infrared source is made of inexpensive 19 Gauge nichrome wire heated at different temperatures to find the best alcohol absorption. PID controller system is employed to maintain constant temperature of the infrared source. The infrared light absorbed is then detected by a thermopile sensor. The result showed that the best alcohol absorption is at 60 °C, and it is proportional to the magnitude of the concentration, the greater the concentration, the higher the value of its absorbance. Absorbance value for distilled water is 0 while the absorbance value for 20% alcohol is at 0.15 and for 60% alcohol is 0.26. This proves that the higher the concentration of alcohol, the infrared light absorbed will be higher. Overall, the inexpensive NDIR system is capable of observing and detecting alcohol that may be used for other solutions in further research.

The IR source, gas chamber, optical filter and detector of nondispersive infared (NDIR) gas sensor are the components which interact directly with IR radiation, so they are called optical system of sensor. The design of optical system is one of the keys of NDIR gas sensor development, but manufacturing prototype of sensor is very expensive and timeconsuming, this limits the number of design variants to be considered. To slove this problem, a simulation method of optical system is presented, response of optical system can be obtained by using this method. The agreement between simulated and measured response proves the feasibility of simulation.

In this work, design method for fabricating optical gas chamber of infrared gas sensor was introduced in detail. IRL715 infrared source, PYS3228 pyroelectric detector with double filters and optical gas chamber were assembled into the optical gas chamber, and then the Nor-infrared (NDIR)gas sensor was produced. After tested in specific methane environment, the performance of optical gas chamber was verified. Meanwhile, optical gas chamber was processed with dustproof and waterproof measures. Experimental results show that response sensitivity of optical gas chamber is good.

An icing rate sensor based on infrared spectrum absorption is researched in this paper, which two infrared laser diodes are used in. Two laser diodes are driven by pulse circuit, and the key technology of the icing rate sensor based on infrared spectrum absorption is put forward. The icing rate sensor is smaller cubage, easier to extend and more steadfast components than the traditional circumvolving filter project.

A new dual-wavelength optic-fiber temperature sensor is introduced in this paper. Transmitted probe of this sensor system is designed. LED IR880 and LED IR940 which peak wavelength is 880nm and 950nm are used as the survey light source and the reference light source of the sensor system. So the infection from the changes of the optical fiber transmission loss, the temperature effect of the temperature probe and the optical detector excursion of the sensor can be eliminated. The accuracy and stability of the temperature sensor can be improved and the cost of temperature sensor can be reduced.

A portable methane gas monitor based on an infrared spectrum absorption principle has been developed using a dual-channel and dual-wavelength pyroelectric infrared detector, active filters around the overtone absorption lines of methane at 3.31 μm, reference filters around the non-absorption lines of methane at 3.93 μm, mid-IR LEDs, a miniature gold-filled cell structure, temperature sensors for gas concentration calibration and compensation, an electrical modulation source, and a highly integrated intelligent controller. A detailed investigation has been carried out to design a low-cost portable IR optical sensor for methane detection that can operate in harsh environments with temperature variations between −10 °C and 40 °C. The infrared detection optics principle used in developing this system is mainly analyzed. A prototype based on this design showed an accuracy of ±0.05%, which meets the technology requirements of lower-power consumption, reduced volume, and wide measurement range.

The present study investigated the ability of a system using a carbon infrared emitter (CIE) and an infrared (IR) camera to detect a combustible gas, propane. The CIE transmitted infrared at wavelengths ranging from 1 to 5 μm, and the infrared absorption band of propane gas (3.37 μm) was obtained using a bandpass filter to remove other infrared wavelengths. The intensity of infrared radiation passing through the propane gas decreased as a result of infrared absorption. A clear, real-time image of the gas leak was also obtained using this system. Furthermore, a hazard evaluation of the leakage propane gas was made from a correlation between infrared intensity and the concentration–pathlength product.

A miniaturized sensor for measuring carbon dioxide (CO 2 ) gas concentration is developed based on infrared absorption. A novel space-double-beam optical probe is designed, which consists of an infrared source, an air chamber, an infrared receiving device, and two sapphire windows. The air chamber is modified by incorporating a parabolic-shaped receiving-light cone to effectively improve the signal-to-noise ratio of the sensor. Four rectangle holes are arranged around the air chamber, and diffusive sampling is adopted to collect gas into the air chamber. The infrared source works between ON and OFF states. The interference of background light is eliminated by subtracting the measured value in the ON state from the OFF state. The measurement model of the sensor is established based on the Lambert–Beer law and the working principle of the sensor. The partial least squares method is applied to calibrate the measurement model. The sensor has a volume of 80 mm ( L )×78 mm ( W )×35 mm ( H ), a weight of 200 g, a power consumption of 1.5 W, and a response time of 2.5 s. The experimental results show that the measurement accuracy of the sensor is 0.026% with a measurement range of 0–3% for CO 2 gas concentration.

In the paper, the principle, the preparation and the performance of the dual-color infrared HgCdTe detector is introduced. The detector is a combination of different wave band filter and different respond wave band element. The application of the dual-color infrared HgCdTe sensitive element for methane gas detection sensor is developed. A two-element HgCdTe methane detector which responds between 3.13~3.53μm and 3.91~4.09μm wave bands respectively was reported. The performance of each detection channel was presented. The experiment test and analyze are fulfilled. The experiment result indicates that under the refrigeration temperature the dual-color HgCdTe detector not only has a favorable response ability and repetition but also can realize the response and distinguish ability to methane gas through integrate narrow band filter on the front of the detector sensitive element.

Many gas molecules absorb electromagnetic radiation at characteristic wavelengths in the infrared region. This absorption can be used to identify defined substances like CO2, ammoniac, and so forth. A lot of different types of gas sensors are based on the principle of infrared absorption like photoacoustic sensors (e.g., Golay cells), dispersive infrared instruments (e.g., utilizing a diffraction grating), or Fourier transform infrared (FTIR) spectrometers. However, the most commonly used types of infrared absorbing gas sensors are nondispersive infrared (NDIR) sensors. Such a NDIR gas sensor consists of some basic function blocks, i.e., an IR-source, the sensor cell or optical path containing the sample gas, a gas specific filter, and an IR-detector. One of the central issues in the design of this kind of sensors is the geometry of the sensor cell. In this paper we investigate the use of statistic ray tracing to predict the efficiency of 3-D cell geometries for NDIR gas sensors. We demonstrate the feasibility of the method and show examples on how to apply it on given 3-D sensor models where we illustrate the agreement between simulated and measured gas response data.

In this paper, the design, fabrication and experimental results of the thermopile infrared detector, with a single layer of low-stress SiNx membrane, instead of thin sandwich layer membrane of SiO2–Si3N4 are presented. Thermal isolation is achieved by using back etching of bulk silicon. Thermopiles are consisted of serially interconnected p-poly-Si/Al thermocouples supported by the single layer of SiNx membrane with low stress. Au/Ti reflective coating was evaporated on the surface of cold junctions of the thermopile to block incident radiation. In the measurement, we find that infrared absorbance of SiNx membrane to different wavelength is diverse and less than 100%, which has great influence on calculating the actual absorbing power of the detector, so the infrared (IR) transmission spectrum is measured to calibrate the actual infrared absorbing amount of the detector. The analysis result shows that only 43.72% infrared radiation is absorbed by the detector. Based on the measurement of IR transmission spectrum and output voltage of the detector, the response sensitivity of the detector is calculated as 31.65 V/W, detectivity of the detector is 1.16 × 108 cmHz(1/2)W−1, and response time of the detector is 126 ms.

This study presents a comparative analysis of parameters of infrared radiation source and detector hardware that are most important for the creation of portable optical nondispersive infrared (NDIR) gas sensors. An analytical model of the optical gas sensor is proposed. The notions of an instrument and transfer functions of the sensor as a measurement device are introduced. Capabilities of the model have been demonstrated by the example of carbon dioxide sensor based on immersion diode optopairs. Validity of the model is proved by good coincidence of calculated and experimental data. Analytical description of the transfer function of a NDIR carbon dioxide sensor allowed us to carry out the comparative analysis of potential sensitivity of sensors based on different hardware produced by basic fabricators of IR components.

Explosion caused by gas is one of the major coal mine accident, and real-time detection of the coal mine gas is becoming more and more important. In this paper we introduce a method based on near infrared spectrum coal mine gas sensor systems aiming at the errors caused by background-interference in detection on the concentration of methane gas in the past. We choose equal-absorption method in the experiment to eliminate the inaccuracy caused by spectrum of other gas absorbed at the same time. Also, we make use of a absorption cell to eliminate inaccuracy caused by different absorption parameters and interference caused by background. The experiment shows that the effect is very good.

This paper describes a Non-Dispersive Infrared (NDIR) CO 2 gas sensor with auto-temperature compensation in order to apply HVAC systems. The developed gas sensor amplifies differentially both the output of thermopile and output of temperature sensor that has linear output characteristics. With differential amplification circuits, the output voltage of sensor module according to the CO 2 concentration shows the independent temperature output characteristics from 10 ∘ C to 40 ∘ C. The developed sensor module shows ±30 ppm error at 1,000 ppm and ±50 ppm error at 2,000 ppm CO 2 concentration regardless of temperature variations.

Prepared by a sol-gel process, the lead zirconate titanate (PZT) (PbZr"0"."3Ti"0"."7O"3) thin film, which is chosen as an infrared sensing film, uses lead acetate trihydrate, zirconium acetylacetone, acetylacetone, and titanium isopropoxide as starting materials. The pyroelectric infrared sensor with the PZT thin film has been successfully fabricated. The fabrication process of the device is discussed in detail. A new Au Pt-PZT-Pt infrared detecting structure on silicon substrate with a micro bridge is designed. Under the response and reference dual-element configuration, undesirable signals, caused by vibration, ambient temperature change, and sunlight, are cancelled out at the input of the preamplifier circuit. The dual-element structural design of the device is discussed and analyzed in detail. In order to realize our purpose to use this detector to monitor gas concentration, we designed a detection set-up in the light of a certain gas which absorbs infrared radiation at specific wavelengths. The gas concentration is obtained by designing a weak signal detect circuit and data arithmetic. The first measurement for methane is reported. Experimental result shows the ability of methane detection of the detector based on the infrared sensor element.

To improve the sensitivity of a non-dispersive infrared optical gas sensor, diffractive Fresnel lenses have been designed, fabricated with silicon microtechnologies, and tested. The target gases (for fruit storage applications) determine the wavelengths for the lens design: 10.6 μm, 9.7 μm, 3.5 μm, and 3.9 μm for ethylene, ammonia, ethanol, and the reference band, respectively. Four lenses are fabricated on the same silicon substrate in a combined multi-lens. In order to reduce the number of photolithographic steps, a new design based on sharing up to sixteen quantization steps by the four lenses is done. Due to the high reflection losses at the silicon–air surfaces, some multi-lenses have been coated with zinc sulphide antireflection layers. The difference between the measured and the target focal length is smaller than 5%. Alignment fixtures have been fabricated to assemble the Fresnel lenses chip on the detector lid in the correct orientation.

In industry, a vast variety of processes can be optimized by means of online measurement of chemical properties of fluids in order to reduce costs for maintenance or increase productivity as well as production quality. In this contribution, we report on the design of a fully integrated infrared absorption sensor, which is capable to determine chemical properties by investigating infrared absorption at selected distinct wavelengths in the mid-infrared region. For example, in order to reduce the frequency of scheduled maintenance of lubrication oil, e.g., in combustion engines, the quality of the deteriorated oil has to be determined, which has been selected as pilot application for our development. Based on results of transmission spectroscopy, we show that by means of a properly designed optical waveguide structure, a sensitivity similar to that obtained by transmission spectroscopy, as used in the laboratory, can be achieved. To achieve a highly sensitive absorption element, a planar mono-mode waveguide is utilized which requires an appropriate coupler to couple the infrared light into the waveguide. The employed grating couplers have been modeled in order to derive a design yielding the desired sensor performance. As the targeted wavelength is located in the mid-infrared region, a suitable infrared source or detector, respectively, can be fabricated by thermal components. Finally, we report on the ongoing technological development to establish the required thin-film processes.

Fourier transform infrared (FTIR) spectrometry is an indispensable laboratory measurement method for the evaluation of the condition of lubricating oils. This technique allows the determination of several oil properties, e.g., degree of oxidation, nitration, and soot content. One of the most important parameters is the oxidation number, which is a measure for the oxidative degradation of the oil, in particular of the base oil. The utilisation of a sensor assembly consisting of an IR source, IR detector, oil measurement cell, and narrowband IR filters enables the detection of significant oil parameters at selected characteristic bands within the IR spectrum. The applicability of the sensor concept described above is illustrated by evaluating the oxidation number from the absorption of a significant IR band and a reference band. Our investigations showed that the implementation of an IR sensor for on-site or even online oil condition monitoring is possible. An appropriate choice of IR filters and the development of a sensor signal algorithm enable the determination of further oil properties, which can be derived from the infrared absorption spectrum.

The paper presents a spectroscopic gas sensor system for measuring carbon dioxide (CO 2 ). The Bi-Source design consists of two infrared (IR) sources with one common detector and maintains high accuracy in the entire range of the harsh automotive environmental conditions over 6000 h operating lifetime. The influence of the atmospheric pressure on the gas sensor output data is compensated with an implemented MEMS piezo resistive pressure sensor.

Numerical model of a gas sensor based on the ring multi-wavelength fiber laser is discussed to detect gas such as methane (CH4), which has multi-line absorption in near infrared. The schematic of the gas sensor is given, and its detecting principle of multiple windows is demonstrated in detail. The detecting methods based on the differential method and the second harmonic wave method in the sensor are analyzed, and the optimal information syncretions are used to process the information of the detected gas. The analyzing results show the sensor has advantages over the traditional sensor, and can be expanded to detect other gas such as acetylene (C2H4).

We have developed multi-point bad-smell sensing system for monitoring living environment. Although there are a variety of gas sensors, it is difficult to detect ppb-order gas without interference. Our previous system was able to detect methyl mercaptan, hydrogen sulfide, propion aldehyde and toluene with the concentrations down to a few tens of ppb by using a gas detector tube combined with a CCD image sensor. A gas detector tube with color change caused by the chemical reaction between the analyte and the reagent system was implemented into our low cost wireless portable measurement system. This portable system called a sensor node consists of a gas detector tube, one-dimensional CCD image sensor, LVDS interface, microcomputer, and wireless LAN module. We report experiment on gas-distribution measurement under actual environments such as paint factories. It was found that the gas distibution around paint factories could be measured using this sensor network. Moreover, the dynamical change of gas distribution was clearly observed.

A multi-element double ring infrared detector based on InSb p-n photodiodes is presented. The presented detector includes an outer ring detector and an inner ring detector. Each ring consist 10 detector elements, five mid-wave infrared detector elements and five short wave infrared detector elements. Two wavebands of 3.5–5 μm and 1.5–3 μm in mid-wave infrared and short wave infrared are adopted. The mid-wave infrared and short wave infrared detector elements are arranged alternately and close to each other to form detection pair. Between the adjacent detector elements, there is an interval to avoid cross talk. Dual band filter thin films are directly coated on the photodiode surface to form a dual band infrared detector. The double ring detector which can perform dual band IR counter-countermeasures can track target effectively under infrared countermeasure conditions.

Recently, we can find news about toxic and combustible gas accident. So, we have to develop gas detector that can measure gas safely at dangerous area and be possible to monitor gas detection at remote area. In this paper, we analyze and estimate gas sensor modules and combustible gas detectors that is already developed, by using standard gas sample manufactured Korea Gas Safety. We apply result analyzed data from experience for developing next generation combustible gas detector.

Development of the new light sources for middle infrared region opened new perspectives for methane detection. Possibilities of non-dispersive infra-red open path methanedetector operating at 2.3 µm wavelength are discussed. Analytical model of NDIR methane sensor is considered and detector calibration curve for LEDs is presented. The effects of the influence of the methane concentration and the atmospheric precipitations on detector sensitivity are discussed.