Low-Drift U-Shaped Thermopile Flow Sensor

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

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    7 Citations (Scopus)
    92 Downloads (Pure)

    Abstract

    A thermal flow sensor has been realised consisting of a freely-suspended U-shaped microchannel. The structure is symmetrically heated by a heater at the top of the U-shape. The thermal imbalance caused by liquid flow is sensed by an integrated Al/poly-Si++ thermopile. The U-shape microchannel facilitates the integration of a large number of thermocouple junctions, resulting in a highly-sensitive calorimetric flow sensor (40 mV/μlmin−1 at 2 mW heating power). The heating power is controlled accurately by forcing a current, while measuring the voltage over the heater resistor. Influences of thermal gradients across the chip are minimised by the freely-suspended microchannel ends being fixed to the substrate over a small distance. The inherently zero-offset of the thermopile can furthermore be exploited in a control system cancelling temperature imbalance by liquid flow using additional heaters. This makes the flow sensor independent of heater resistor values and thermopile output characteristics. Accurate measurements up to 400 nl-min−1 water flow have been obtained applying a temperature-balancing control system.
    Original languageUndefined
    Title of host publicationSensors, 2008 IEEE
    PublisherIEEE
    Pages66-69
    Number of pages4
    ISBN (Print)978-1-4244-2580-8
    DOIs
    Publication statusPublished - 26 Oct 2008
    Event2008 IEEE Sensors - Hotel Tiziano, Lecce, Italy
    Duration: 26 Oct 200829 Oct 2008

    Publication series

    Name
    PublisherIEEE
    Number2008/16200
    ISSN (Print)1930-0395

    Conference

    Conference2008 IEEE Sensors
    CountryItaly
    CityLecce
    Period26/10/0829/10/08

    Keywords

    • TST-SENSORS
    • METIS-255044
    • IR-65250
    • EWI-14707

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