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Gas Analyzers Meet Stringent Requirements of Respiration Calorimeters
MEI Research is an engineering firm based in St. Louis Park, MN, that develops technologies to support research in nutrition and weight management.
One of MEI's goals is to improve the design and construction of whole-body respiration calorimeters. These instrumented systems calculate energy expenditure by precisely measuring the amount of oxygen that the body converts by metabolism to carbon dioxide during periods from minutes up to several days. Calorimeters comprise sealed living areas, atmosphere controls and gas analyzers. Because the living areas contain thousands of times more air than respiratory volume the accuracy of the analytical systems that measure carbon dioxide (CO2) and oxygen (O2) concentrations is critical to overall performance.
Highly precise gas analyzers are at the heart of respiration calorimeters. Six Siemens analyzers will be installed at the Translational Research Institute (TRI) for Metabolism and Diabetes, a partnership between Florida Hospital and Sanford- Burnham, in Orlando, Florida. These rooms are actively ventilated using ‘medical' air and two mass flow controllers. The analyzers have dedicated sample lines plumbed to each room outlet, allowing them to rapidly capture changes in the concentration of O2 and CO2.
Engineers at MEI chose Siemens ULTRAMAT/ OXYMAT 6 after reviewing several process analyzers. The oxygen channel is capable of measuring to an accuracy of +/- 50 ppm. The customer stated that precision was paramount to their application and found that the Siemens system was superior. The menu-driven user interface was substantially easier to use and troubleshoot than other devices used in the past. Further, the ULTRAMAT/OXYMAT 6 can combine O2 and CO2 cells into one rack mount enclosure, which allowed MEI to dramatically reduce the size of the analytical rack. Additionally, the increased reliability of the flow-through paramagnetic cell design contributes to the long planned life of the laboratory.
In addition to the product features and performance, MEI was impressed with the excellent support provided by Siemens and the local representative. After purchasing the six analyzers for TRI and additional units for internal use, a Siemens service engineer went to the customer's site for an entire day of training. During that time, he tore a unit entirely apart and reassembled it with the customer, explaining preventative maintenance procedures and answering all questions to a high level of detail.
Additionally, the service manager and the Siemens product manager helped MEI get in touch with the engineering team in Germany to answer a series of highly technical and specific questions related to the analyzer signal processing system. MEI, the local Siemens representative and the engineering team in Germany rewrote open source code for Labview software so that it can query up to 10 analyzer channels each second through the ELAN network used by the analyzers for serial communication. This allowed the analyzers to communicate with the computer system at a higher resolution than would be possible using the standard analog outputs, and prevented the possibility of electrical noise affecting readings in long cable runs. Because LabVIEW is the control system platform MEI has chosen at the beginning of the project, integration with the Siemens ULTRAMAT/ OXYMAT 6 analyzers was critical.
About the ULTRMAY/OXYMAT 6 Analyzers
Most frequently used for demanding applications, the ULTRAMAT 6 must meet high standards with regard to reliability and measuring quality. The ULTRAMAT 6 Series analyzers can measure up to four infrared active components in a single unit. The use of optical couplers and the optional use of optical filters to increase the selectivity mean that, in many cases, the analyzers can be used for measurements even in complex gas mixtures. This also guarantees measurements of lower concentrations and lower detection limits. Appropriate materials in the gas channel allow the analyzers to be used even for measurements in gas mixtures with corrosive elements or corrosive measuring components.
Most frequently used for demanding applications, the OXYMAT 6 must meet high standards with regard to reliability and measuring quality. The OXYMAT 6 measures oxygen using the paramagnetic alternating pressure method. This guarantees perfect linearity and allows parameterization of minimal measuring ranges of 0 to 0.5 % (detection limit 50 ppm) up to 0 to 100% in a single device, and even 99.5 to 100%.
The sensor in the detector does not come into contact with the sample gas thus allowing the measurement of corrosive gases. Corrosive resistant materials are used in the gas path.
For further information visit www.siemens.com
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