Towards thermal flowsensing with pL/s resolution


Tas, N.R. and Lammerink, T.S.J. and Leussink, P.J. and Berenschot, J.W. and Bree, H-E. de and Elwenspoek, M. (2000) Towards thermal flowsensing with pL/s resolution. In: Micromachined Devices and Components VI, 18 September 2000, Santa Clara, CA, USA (pp. pp. 106-121).

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Abstract:This paper focuses on the development of highly sensitive calorimetric flow sensors. Both the hydrodynamics of the flow channel, as well as the heat transfer are analyzed in detail. With the expressions for the hydraulic resistance of the flow channel and the hydraulic system requirements for the flow sensor, it is possible to optimize the design of the flow channel. It is theoretically shown why for small v the calorimetric flow sensor output is linear in v. Also it follows from theory that for a symmetrical configuration, in this linear regime the heater temperature is independent of v for constant heating power. This suggests that for low Reynolds Number King's Law has t obe modified. Different configurations and methods are analyzed: absolute, differential, two beam, three beam, CPA, CTA and TBA. The latter is a real thermal balance measurement and allows the use of non-linear sensing elements. From our experience with acoustical measurements it is possible to estimate practical attainable sensitivity. In combination with proper flow channel design, and a fabrication technology for narrow channels, it is shown that pL/s sensitivity is in reach
Item Type:Conference or Workshop Item
Copyright:© 2000 SPIE
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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