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arXiv · 0805.0891

Low-Drift Flow Sensor with Zero-Offset Thermopile-Based Power Feedback

M. Dijkstra·T. S. J. Lammerink·Meint De Boer·J. W. Berenschot·Remco Wiegerink·M. Elwenspoek
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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 ul/min, 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.

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M. Dijkstra, T. S. J. Lammerink, Meint De Boer, J. W. Berenschot, Remco Wiegerink, M. Elwenspoek. 2008-05-07. Low-Drift Flow Sensor with Zero-Offset Thermopile-Based Power Feedback. https://arxiv.org/abs/0805.0891

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