Temperature modulated direct thermoelectric gas sensors : thermal modeling and results for fast hydrocarbon sensors

Titelangaben

Rettig, Frank ; Moos, Ralf:
Temperature modulated direct thermoelectric gas sensors : thermal modeling and results for fast hydrocarbon sensors.
In: Measurement Science and Technology. Bd. 20 (2009) Heft 6 . - 065205.
ISSN 0957-0233
DOI: https://doi.org/10.1088/0957-0233/20/6/065205

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Abstract

Direct thermoelectric gas sensors are a promising alternative to conductometric gas sensors. For accurate results, a temperature modulation technique in combination with a regression analysis is advantageous. However, the thermal time constant of screen-printed sensors is quite large. As a result, up to now the temperature modulation frequency (20 mHz) has been too low and the corresponding principle-related response time (50 s) has been too high for many applications. With a special design, respecting the physical properties of thermal waves and the use of signal processing similar to a lock-in-amplifier, it is possible to achieve response times of about 1 s. As a result, direct thermoelectric gas sensors with SnO2 as a gas-sensitive material respond fast and are reproducible to the propane concentration in the ambient atmosphere. Due to the path-independent behavior of the thermovoltage and the temperature, the measured thermopower of two sensors is almost identical.