A3.4 - Measuring Flow Velocity and Gas Concentration in Binary Gas Mixtures Using Thermal Sensors
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- A3 - Flow Measurement
- C. Hepp, F. Krogmann, J. Polak, M. Lehmann - Innovative Sensor Technology AG, Wattwil (Switzerland), G. Urban - Universität Freiburg (Germany), G. Urban - Universität Freiburg (Germany)
- 84 - 88
An enhanced thermal flow sensor is under development at IST AG in cooperation with IMTEK (Freiburg) measuring simultaneous thermal gas properties and flow velocity. Simultaneous measurement of thermal gas properties and flow velocity is necessary for gas mixtures where gas concentration is fluctuating by time, enabling a more accurate flow speed measurement. This is achieved by using an AC signal as excitation and analyzing phase shift and amplitude of the returned signal.
Here, the AC characterisation and the fabrication process of the sensor element are presented. The sensor consists of platinum temperature sensors and a platinum heater in between located on a thin membrane. The time to flight method allows - in contrast to state-of-the-art DCreadouts - more information like phase shift and amplitude.
The results show that amplitude and phase shift depend on thermal conductivity of the gas as well as on the gas’ humidity. Phase shift is nearly constant within a certain flow range. This range can be used to determine the thermal conductivity of the gas. In a next step the accurate flow speed can be calculated with this information.