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Next Generation Gas Detection. | |||
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Axetris AG Schwarzenbergstr. 10 6056 Kägiswil, Switzerland  Phone: +41 41 662 76 76 Fax: +41 41 662 75 25 |
Compact Laser Gas Detector OEM Modules for Process Control and Safety |
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| Changes in Microray/LVF Spectrometer Supply |
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IR Microsystems has ceased the small series production and commercialization of the Microray/LVF Spectrometer product lines of all window/filter types. Further orders may be accepted on the basis of several hundred units per year and will be discussed on a case-to-case basis. IR Microsystems is currently seeking a buyer for the activity related to these products and will keep customers informed on any further developments. Please contact us in case you have further questions. |
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| Application Examples - Gases | |
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| Low-Cost Spectrometry for Near and Mid-Infrared Enables In-Situ Process Control | ||||
| ®IR MICROSYSTEMS range of LVF Spectrometers is targeted toward OEM's providing process control solutions for a wide range of industrial sectors. Our sub-systems facilitate continuous process monitoring and quality control directly on the process line, leading to substantial savings for end customers. |
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| The combination of IR MICROSYSTEMS unique low-cost ®µray64 IR detector arrays with linear variable filter (LVF) technology enables simple und rugged in-situ process control for gases, liquids and solids in chemical, petrochemical, biochemical, nutrition, medical and a wide range of other industries. The device is very compact as the LVF represents the dispersive optical component and is glued directly into the metal cap above the detector. This means that the printed circuit board as shown to the right is a complete IR-spectrometry sub-system. Such a LVF spectrometer is extremely easy to operate, has no adjustable parts, requires no cooling, is insensitive to vibrations or shocks and delivers one complete spectrum of a substance per second. A LVF spectrometer needs a relatively intense light-source because it allows only a certain wave-length to pass at a certain position. Resolution for most LVF's is 1.5 % of the passing wave-lengths; for some LVF's the resolution can be 0.75 %. The additional systems components needed to operate a LVF Spectrometer are:
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To obtain optimal results it is best to use collimated light, either by using a parabolic reflector for the light-source and/or by using mirrors or lenses to collimate the beam. As shown to the right, more collimated light results in better resolution with the LVF. In this measurement a narrow band pass filter was placed on top of the LVF and the light source was gradually removed further away to achieve collimation. For a light-source at a distance of 150 mm, the collimation is sufficient and the transmittance curve approaches the one theoretically possible for this LVF. For comparison the transmittance curve of the narrow band-pass filter, as measured by FTIR is shown (black curve). The wavelengths covered by the LVF Spectrometers can be chosen from various standard ranges: 1.4-2.5 µm (7143-4000 cm-1), 2.5-4.9 µm (4000-2041 cm-1), 2.9-4.8 µm (3448-2083 cm-1), 5.5-10.5 µm (1818-952 cm-1), 9.0-11.0 µm (1111-909 cm-1) and 7.0-14.0 µm (1428-714 cm-1). |
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| Application Examples Gases | ||||
| To demonstrate the potential of LVF Spectrometers, IR MICROSYSTEMS has conducted a series of feasibility demonstrations on different gases. All the measurements were carried out with simple set-ups using the IR MICROSYSTEMS EVALUATION KIT, either equipped with a LVF or with a wide band-pass filter (in case the measurement was performed with an optical grating). The configuration details for each application example are given below. |
No additional optical components or engineering were applied. Data treatment was limited to calculations of peak heights and integrated intensities to show basic results. It is obvious that PLS, PCR and multi-variant analysis data treatment, as well as optical engineering will significantly improve measurement precision and detection limits in comparison to what is shown below. | |||
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| Spectrometry on CO2 and CO for Security & Process Control Applications: | ||||
| A test measurement was carried out to evaluate the ability of a spectrometer to resolve CO and CO2 absorption peaks in various mixtures of these two gases, keeping in mind that for high CO2 concentrations, cross sensitivity is caused by the high CO2 absorption coefficient. The results show that the resolution of such an instrument is sufficient to resolve the two peaks, and to even show the twin-structure of the CO peak. System used :
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 Spectrometry across the CO2 and CO absorption bands |
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| Spectrometry on CO2 for Capnography in Patient Monitoring Systems: | ||||
| Capnography is the continuous non-invasive measurement of CO2 concentration in exhaled breath, providing an immediate indication of adequate ventilation of a patient. For example, in anesthesia, the primary goal is to prevent hypoxia and capnography helps to identify situations that can lead to hypoxia if uncorrected. The purpose of this measurement was the integration over the area of the CO2 absorption peak rather than doing NDIR measurements. The integration yields a significantly higher precision of the measurement which in turn enables the system to run on less electrical power for the light source - a major request from systems integrators in medical technology. The picture to the right shows the set up with an aluminium tube as a gas cell. The light source is placed at the upper end of this tube. System used :
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| Spectrometry across the CO2 absorption band. | Precision: 2000 ± 30 ppm (from peak area integration) |
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| N2O & NH3: | ||||
| This measurement was carried out to demonstrate the ability of a LVF spectrometer module to measure NH3, relevant to security in refrigeration and process control applications, as well as N2O in medical anesthesia applications, using a small path-length of only 2 cm. System used :
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| N2O for anesthesia gas measurements LVF Spectrometer 7-9 µm (1429-1111 cm-1) |
NH3 at 3 vol.% LVF Spectrometer 9-11 µm (1111-909 cm-1) |
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| Volatile Organic Compounds (VOC's) for Security & Process Control Applications: | ||||
| This measurement demonstrates the ability of the ®µray64 detector unit to identify and measure volatile organic compounds in the fingerprint region of 8 - 14 mm. Mixtures of VOC's were produced by a gas mixing device and different concentrations of analytes were produced by mixing zero-TOC air with analyte saturated air. For the measurements a 200 sccm gas stream of the analyte at concentrations from 200 to 800 ppm (in zero-TOC air) was applied to the spectrometer which has an internal absorption path of 0.48 m. After purging for 15 minutes with the analyte, a measurement was recorded, assuming that the analyte concentration in the spectrometer reached its maximum. In order to determine the noise of the sensors, reference and blank measurements were recorded with pure air resulting in a noise-level of less than 0.2% (this also includes speed variations of the DC-motor driven chopper wheel of about 0.3% and the chopper driver electronics' hysteresis of about 0.5%). The light source was a-non focused 5 W IR-source from CalSensor, operated at 3.1 V and 1.64 A. Due to the non-focused light beam, only about 10% of the light intensity was transmitted through the monochromator slit. The spectra of all analytes at concentrations of 600 ppm are shown in the first graph below. The spectra for 1-propanol, methoxybenzene and cyclohexanone were recorded at the same wavelengths. Because toluene has an absorption peak at about 14.3 µm (699 cm-1), the spectrometer was adjusted to another wavelength range. |
For an evaluation of the sensitivity of this set-up, the depths of the calibration spectra at the wavelengths of maximum absorption were plotted (see second figure) and a linear regression was applied in order to determine the slope. Because the calibration curves showed a non-linear behavior, only data points at analyte concentrations of 200 - 800 ppm were fitted. This non linear behavior, which may be attributed to insufficient and too short purging times. The obtained sensitivities are listed below this graph. The following graphs show the spectra of the individual analytes at concentrations of 200, 400, 600 and 800 ppm, as well as their reference NIST spectra. System used :
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| Different VOC's at 600 ppm concentration Grating-based spectrometer with 0.5 m path. |
Limit of detection (LOD) - 3 fold value of the measured noise level: Toluene : 33 ppm m 1-Propanol : 36 ppm m Methoxybenzene : 32 ppm m Cycolhexanone : 78 ppm m |
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| Cyclohexanone at different concentrations | Cyclohexanone, gas phase spectrum. Conc. : not available Source : NIST, EPA |
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| Methoxybenzene at different concentrations | Methoxybenzene, gas phase spectrum. Conc. : not available Source : NIST, EPA |
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| 1-Propanol at different concentrations | 1-Propanol, gas phase spectrum . Conc. : saturated, path 12.5 cm Source : NIST, The Coblentz Society (No.10490) |
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| Toluene at different concentrations | Toluene, gas phase spectrum. Conc. : 26300 ppm, path 5 cm Source : NIST, The Coblentz Society (No.8882) |
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| Ethylene and Ethanol Gas for Fruit Storage Applications: | ||||
| Ethylene and ethanol play an important role in controlled atmosphere storage (CA Storage) of fruit. For example, in apple storage, ethylene must be avoided because it triggers the ripening of the fruit and monitoring of ethylene content is crucial. Additionally, in dynamic CA Storage, which allows for extended storage times, the oxygen content in the warehouse is lowered below the normal 2 %. However, if oxygen levels become too low, anaerobic fermentation takes place in the fruit and ethanol evolves. It is therefore necessary to monitor both, the ethanol as well as the ethylene content in the atmosphere. In this case the cross-sensitivity of the strong ethanol absorption peak with the weak ethylene peak makes IR spectrometry mandatory. The measurements in the graphs below show that a relatively simple instrument, based on a ®µray64 LVF spectrometer module is capable of analyzing mixtures of the two gases with a resolution which is appropriate for the application. With this system a detection limit of approximately 20 ppm for ethylene and 0.3 ppm for ethanol were determined by peak-height measurements. Improvements should be possible by applying additional optical engineering as well as a more refined data treatment software using multivariant analyis. System used :
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 Ethanol and ethylene, gas phase spectra. Conc. : not available Source ethylene : NIST, Coblentz Society. (No.8869); Source ethanol : NIST/EPA |
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| Spectrometry for ethylene and ethanol. High ethanol concentrations | Spectrometry for ethylene and ethanol. High ethylene concentrations |
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| Spectrometry for ethylene, high concentrations. | Spectrometry for ethylene, low concentrations. | |||
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| The examples illustrated above are only a small selection of applications in a wide range of industrial sectors where many OEM's are active in bringing low-cost analysis systems, as well as application specific process control solutions to their end customers.
If you have further questions or if you want to talk to us about your application, please contact us at:
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Axetris AG 2000-2013 | General Terms & Conditions |
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