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MEMS Flow Sensors Based on Self-Heated aGe-Thermistors in a Wheatstone Bridge.

Talic A, Cerimovic S, Beigelbeck R, Kohl F, Sauter T, Keplinger F - Sensors (Basel) (2015)

Bottom Line: The analyses include electrothermal feedback effects of current driven NTC thermistors.Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements.The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrated Sensor Systems, Danube University Krems, Viktor-Kaplan Straße 2, A-2700 Wiener Neustadt, Austria. almir.talic@donau-uni.ac.at.

ABSTRACT
A thermal flow transduction method combining the advantages of calorimetric and hot-film transduction principles is developed and analyzed by Finite Element Method (FEM) simulations and confirmed experimentally. The analyses include electrothermal feedback effects of current driven NTC thermistors. Four thin-film germanium thermistors acting simultaneously as heat sources and as temperature sensors are embedded in a micromachined silicon-nitride membrane. These devices form a self-heated Wheatstone bridge that is unbalanced by convective cooling. The voltage across the bridge and the total dissipated power are exploited as output quantities. The used thin-film thermistors feature an extremely high temperature sensitivity. Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements. Two sensor configurations with different arrangements of the membrane thermistors were examined experimentally. Moreover, we investigated the influence of different layouts on the rise time, the sensitivity, and the usable flow range by means of two-dimensional finite element simulations. The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach.

No MeSH data available.


Related in: MedlinePlus

Contour plot of the simulated velocity vpeak [m/s], which marks the boundary of the monotonous transduction characteristic. The available region for possible designs is plotted using the position of inner and outer thermistors as design parameters. The designs of implemented devices are indicated by respective numbers (designs 1 and 2).
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sensors-15-10004-f011: Contour plot of the simulated velocity vpeak [m/s], which marks the boundary of the monotonous transduction characteristic. The available region for possible designs is plotted using the position of inner and outer thermistors as design parameters. The designs of implemented devices are indicated by respective numbers (designs 1 and 2).

Mentions: Figure 11 shows a contour plot of simulation results for the range of monotonous transduction vpeak as a function of the position of the inner and outer thermistors. The locations of Th2 or Th3 (vertical axis) and Th1 or Th4 (horizontal axis) are measured from the middle of the membrane and indicated as open circles. The contour plot is based on an interpolation of 30 simulated design variants and also illustrates the available design space for thermistor positioning on the membrane area (Figure 3).


MEMS Flow Sensors Based on Self-Heated aGe-Thermistors in a Wheatstone Bridge.

Talic A, Cerimovic S, Beigelbeck R, Kohl F, Sauter T, Keplinger F - Sensors (Basel) (2015)

Contour plot of the simulated velocity vpeak [m/s], which marks the boundary of the monotonous transduction characteristic. The available region for possible designs is plotted using the position of inner and outer thermistors as design parameters. The designs of implemented devices are indicated by respective numbers (designs 1 and 2).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481909&req=5

sensors-15-10004-f011: Contour plot of the simulated velocity vpeak [m/s], which marks the boundary of the monotonous transduction characteristic. The available region for possible designs is plotted using the position of inner and outer thermistors as design parameters. The designs of implemented devices are indicated by respective numbers (designs 1 and 2).
Mentions: Figure 11 shows a contour plot of simulation results for the range of monotonous transduction vpeak as a function of the position of the inner and outer thermistors. The locations of Th2 or Th3 (vertical axis) and Th1 or Th4 (horizontal axis) are measured from the middle of the membrane and indicated as open circles. The contour plot is based on an interpolation of 30 simulated design variants and also illustrates the available design space for thermistor positioning on the membrane area (Figure 3).

Bottom Line: The analyses include electrothermal feedback effects of current driven NTC thermistors.Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements.The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrated Sensor Systems, Danube University Krems, Viktor-Kaplan Straße 2, A-2700 Wiener Neustadt, Austria. almir.talic@donau-uni.ac.at.

ABSTRACT
A thermal flow transduction method combining the advantages of calorimetric and hot-film transduction principles is developed and analyzed by Finite Element Method (FEM) simulations and confirmed experimentally. The analyses include electrothermal feedback effects of current driven NTC thermistors. Four thin-film germanium thermistors acting simultaneously as heat sources and as temperature sensors are embedded in a micromachined silicon-nitride membrane. These devices form a self-heated Wheatstone bridge that is unbalanced by convective cooling. The voltage across the bridge and the total dissipated power are exploited as output quantities. The used thin-film thermistors feature an extremely high temperature sensitivity. Combined with properly designed resistance values, a power demand in sub-1mW range enables efficient gas-flow transduction, as confirmed by measurements. Two sensor configurations with different arrangements of the membrane thermistors were examined experimentally. Moreover, we investigated the influence of different layouts on the rise time, the sensitivity, and the usable flow range by means of two-dimensional finite element simulations. The simulation results are in reasonable agreement with corresponding measurement data confirming the basic assumptions and modeling approach.

No MeSH data available.


Related in: MedlinePlus