Thermal-wave balancing flow sensor with low-drift power feedback

Marcel Dijkstra, Theodorus S.J. Lammerink, O. Pjetri, Meint J. de Boer, Johan W. Berenschot, Remco J. Wiegerink, Michael Curt Elwenspoek

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Abstract

A control system using a low-drift power-feedback signal was implemented applying thermal waves, giving a sensor output independent of resistance drift and thermo-electric offset voltages on interface wires. Kelvin-contact sensing and power control is used on heater resistors, thereby inhibiting the influence of heater resistance drift. The thermal waves are detected with a sensing resistor using a lock-in amplifier and are mutually cancelled by a thermal-wave balancing controller. Offset due to thermal gradient across the chip and resistor drift are eliminated by the lock-in amplifier and power controller, and therefore do not influence the sensor output signal. A microchannel thermal-wave balancing flow sensor with integrated Al resistors has successfully been fabricated. The thermal flow sensor is capable of measuring water flow rates with nl· min−1 precision, up to about 500 nl· min−1 full scale. Measurement results are in good agreement with a dynamic model of the flow sensor. Drift measurements show the sensor output signal to be ompensated for resistance drift and thermal gradient across the chip.
Original languageUndefined
Pages (from-to)055016
Number of pages7
JournalJournal of micromechanics and microengineering
Volume24
Issue number5
DOIs
Publication statusPublished - 11 Apr 2014

Keywords

  • EWI-25635
  • IR-93844
  • METIS-309854

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