Low-drift flow sensor with zero-offset thermopile-based power feedback

Author

Dijkstra, M. ; Lammerink, T.S.J. ; de Boer, M.J. ; Berenschot, J.W. ; Wiegerink, R.J. ; Elwenspoek, M.

Author_Institution

MESA+ Inst. for Nanotechnol., Univ. of Twente, Enschede

fYear

2008

fDate

9-11 April 2008

Firstpage

247

Lastpage

250

Abstract

A thermal flow sensor has been realised consisting of freely-suspended silicon-rich silicon-nitride microchannels with an integrated Al/poly-Si⁺⁺ thermopile in combination with up- and downstream Al heater resistors. The inherently zero offset of the thermopile is exploited in a feedback loop controlling the dissipated power in the heater resistors, eliminating inevitable influences of resistance drift and mismatch of the thin-film metal resistors. The control system cancels the flow-induced temperature difference across the thermopile by controlling a power difference between both heater resistors, thereby giving a measure for the flow rate. The flow sensor was characterised for power difference versus water flow rates up to 1.5 mul-min^-1, being in good agreement with a thermal model of the sensor, and the correct low-drift operation of the temperature-balancing control system has been verified.

Keywords

aluminium; flow sensors; microchannel flow; silicon; silicon compounds; thermopiles; SiN-Al-Si; feedback loop; heater resistors; low-drift flow sensor; power feedback; silicon-nitride microchannels; thermal flow sensor; thermopile; Cogeneration; Control systems; Feedback; Resistors; Sensor phenomena and characterization; Sensor systems; Temperature control; Temperature sensors; Thermal resistance; Thermal sensors;

fLanguage

English

Publisher

ieee

Conference_Titel

Design, Test, Integration and Packaging of MEMS/MOEMS, 2008. MEMS/MOEMS 2008. Symposium on

Conference_Location

Nice

Print_ISBN

978-2-35500-006-5

Type

conf

DOI

10.1109/DTIP.2008.4752993

Filename

4752993