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- 2017 (3) (entfernen)
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- Chemical reaction (1)
- Coulometric sensors (1)
- Coulometrische Sensoren (1)
- Hydrogen sensor (1)
- Response behavior (1)
- Response time (1)
- Spurenfeuchte (1)
- Technische Gase (1)
- Temperature influence (1)
- Test facility (1)
Planar coulometric sensors were tested in humidified synthetic air at various gas temperatures. Generated frost point temperature in the gas ranged from -30 °C to -60 °C and were measured by coulometric sensors and in addition by a calibrated dew point hygrometer. The gas temperatures, which were measured by a calibrated Pt100 sensor, were set to -20 °C, 0 °C, 23 °C, 40 °C, 50 °C, and 60 °C during the experiments. Empiric nonlinear functions were calculated between the generated humidity and the sensor signals. In comparison to the measured signals at 23 °C, the sensor signals were lower at the other gas temperatures. The measurements at 60 °C showed indistinct results due to a great signal noise. The response behavior of the sensors was similar at 23 °C, 40 °C and 50 °C. In contrast to that, the sensors reacted slowly at a gas temperature of -20 °C and 0 °C. In summary, with coulometric sensors it was possible to measure continuously trace humidity with an expanded uncertainty below 2 K.
Die Messung der Gasfeuchte im Spurenbereich in unterschiedlichen technisch und medizinisch relevanten Gasen erfolgte mit Sensoren, die auf dem coulometrischen Messprinzip basieren. Die verwendeten planaren coulometrischen Sensoren wurden im Frostpunkttemperaturbereich von -70 °C bis -30 °C in synthetischer Luft, Wasserstoff, Stickstoff und Distickstoffmonoxid (Lachgas) untersucht. Als Referenz für die Messungen wurde ein Präzisionstaupunktspiegel-Hygrometer verwendet. Die Gasfeuchte kann mit Hilfe der Sensoren in allen untersuchten Gasen, aber mit geänderten Kalibrierfunktionen, mit einer erweiterten Unsicherheit von kleiner als 2,1 K bestimmt werden. Für die Messungen in unterschiedlichen Gasen muss also der Einfluss der Gasmatrix auf das Sensorsignal berücksichtigt werden. So ist zum Beispiel bei Messungen in befeuchtetem Wasserstoff, aufgrund von Rekombinationseffekten, ein signifikant geändertes Sensorsignal zu beobachten.
The efficiency of gas sensor application for facilitating the safe use of hydrogen depends considerably on the sensor response to a change in hydrogen concentration. Therefore, the response time has been measured for five different-type commercially available hydrogen sensors. Experiments showed that all these sensors surpass the ISO 26142 standard; for the response times t90 values of 2 s to 16 s were estimated. Results can be fitted with an exponential or sigmoidal function. It can be demonstrated that the results on transient behaviour depend on both the operating parameters of sensors and Investigation methods, as well as on the experimental conditions: gas change rate and concentration jump.