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Passive Hybrid MEMS for High-Temperature Telemetric Measurements
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Passive Hybrid MEMS for High-Temperature Telemetric Measurements


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  • 1.
  • 2.
    • High temperature measurements are needed in industrial applications .
    • High temperature sensors capable of operating in harsh environments are needed to prevent disasters .
    • Most existing temperature sensors do not satisfy the needs.
  • 3.
    • A contactless passive sensing device(Hybrid MEMS) is described for high temperature measurements.
    • Inductive telemetric measurement systems is used for contactless measurement using passive sensors.
  • 4.
  • 5.
    • Passive autonomous sensors - those that are just passive elements, interrogated wirelessly by a readout unit.
    • Self-powered autonomous sensors - those that have a power-harvesting module or are supplied power by an electromagnetic field.
    • Hybrid MEMS temperature sensor is a Passive autonomous sensor.
  • 6.
  • 7.
    • Sensing element is placed in harsh/remote area.
    • Read out unit in safety zone.
    • Two elements are connected by a wireless communication channel.
    • Most passive sensors use telemetric communication consisting of 2 inductors.
    • Measured quantity is usually read as reflected impedance.
  • 8.
  • 9. Components of MEMS
  • 10.
  • 11. Image of the hybrid telemetric MEMS.
  • 12.
    • Developed using Metal MUMPs process.
    • Layout is organized into 36 cells having capacitive behavior and connected in parallel.
    • Built over a silicon nitride isolation layer with a 1µm air gap.
    • Working principle –structural deformation due to increase in temperature.
  • 13. Microscope image of interdigitated capacitor
  • 14.
    • A single cell is based on a cascade of bent beam structures.
    • Consist of V-shaped beam anchored at 2 ends.
    • Thermal expansion induces displacement of central apex.
    • Central apex is connected to an interdigitated comb.
  • 15. Bent Beam structure .
  • 16.
    • Movement of central apex causes displacement one electrode towards the fixed one.
    • Change in capacitance occurs.
    • Maximum temperature 623K
    (left) at 298 K and (right) at 500 K .
  • 17. Equivalent model of the interdigitated capacitor and an impedance diagram measured at 270 ◦C [(a) modulus and (b) phase].
  • 18. Impedance module of the interdigitated capacitor measured at different Temperatures(100 ◦C to 330 ◦C.)
  • 19.
    • 3 different zones has been identified,
    • In the lower frequencies, an increase in the parasitic resistance.
    • In the middle frequency, the increasing
    • of the capacitance.
    • In the higher frequencies, as the temperature increases, the resonant frequency decreases.
  • 20.
  • 21. Microscope image of the inductor A1 realized by thick-film deposition on alumina.
  • 22. Microscope image of the inductor B1 realized by photolithography
  • 23. Equivalent model of the planar inductor and impedance diagrams at different temperatures.(23 ◦C to 340 ◦C)
  • 24.
    • 3 different zones have has been identified
    • A resistive behavior is shown at lower frequencies.
    • At higher frequencies, a resonant frequency is visible due to capacitance behavior.
    • In middle frequencies purely inductive behavior is obtained
  • 25.
  • 26.
    • Hybrid telemetric MEMS is placed in harsh environment.
    • Conditioning electronics is into the safe zone.
    • Readout inductor, is placed close to the hybrid MEMS.
    • Two inductors constitute a telemetric coupled system.
    • Readout inductor is a planar spiral fabricated in thick-film technology.
  • 27.
    • It has 30 windings, each of 250 μm width and spaced 250 μm.
    • External diameter is 50 mm wide.
  • 29.
    • Link wirelessly two devices through inductive coupling.
    • Measurement information is acquired by the sensing element.
    • Sent through the communication channel using the magnetic coupling.
    • Read as reflected impedance by the conditioning electronics and elaborated by the readout unit.
  • 30.
  • 31. Modulus and phase of the impedance measured from the terminals of the readout inductor.
  • 32.
    • Min-Phase method measures a frequency fo.
    • Impedance of the terminals of the readout inductor is also measured.
    • Capacitive value of the sensor is related to the frequency at which the phase, in a short frequency interval, is at its minimum value.
  • 33.
  • 34.
    • An IR heater of 500 W is provided to rise temperature upto 350 ◦C.
    • Pt100 thermo resistance measure the internal temperature at different points.
    • PC is connected to multimeter , impedance analyser through IEEE-488 bus.
    • PC is also connected to power control.
    • It monitors the temperature inside and controls it.
    • Two MEMS sensors are placed, one to impedance analyzer, one for telemetric measurement.
  • 35. Modules of hybrid sensor measured using impedance analyzer at different temperatures.
  • 36. Phase of hybrid sensor measured using impedance analyzer at different temperatures
  • 37.
    • Observed that increase in temperature generates a decrease of the values of the resonant frequencies, since the sensor capacitance value increases.
    • Capacitances measured using 2 methods shows a quasi linear relationship.
  • 38. Capacitance sensor values directly measured and compared with the calculated ones.
  • 39. Temperature values measured with the Pt100 and compared with the Min-Phase and 3-Resonances calculated values.
  • 40.
    • Passive wireless sensor is capable of operating in harsh environments for high-temperature measurements.
    • The values measured by the two techniques have demonstrated good agreement with the reference values.
    • Inductive telemetric systems offer solutions to specific applications for contactless measurement.
  • 41.
    • “ Passive Hybrid MEMS for High-Temperature Telemetric Measurements” Daniele Marioli, Member, IEEE, Emilio Sardini, Member, IEEE, and Mauro Serpelloni
    • Y. Wang, Y. Jia, Q. Chen, and Y. Wang, “A passive wireless temperature sensor for harsh environment applications”
    • D. Marioli, E. Sardini, M. Serpelloni, B. Andò, S. Baglio, N. Savalli, and C. Trigona, “Hybrid telemetric MEMS for high temperature measurements into harsh industrial environments,”
    • Bruno Andò, Salvatore Baglio, Senior Member, IEEE, Nicolò Savalli, and Carlo Trigona Cascaded “Triple-Bent-Beam” MEMS Sensor for Contactless Temperature Measurements in Non accessible Environments.
    • “ Inductive Telemetric Measurement Systems for Remote Sensing”, Daniele Marioli, Emilio Sardini and Mauro Serpelloni
    • “ Passive and Self-Powered Autonomous Sensors for Remote Measurements”, Emilio Sardini and Mauro Serpelloni