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I.V.Anudeep Kumar Redd Parne Saidi Redd G.R.C.Redd

SIMULTANEOUS MEASUREMENT OF TEMPERATURE AND PRESSURE SENSOR USING BRAGG GRATINGS. I.V.Anudeep Kumar Redd Parne Saidi Redd G.R.C.Redd INDIA. Presentation Outline . Introduction Research Approach Temperature sensor head

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I.V.Anudeep Kumar Redd Parne Saidi Redd G.R.C.Redd

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  1. SIMULTANEOUS MEASUREMENT OF TEMPERATURE AND PRESSURE SENSOR USING BRAGG GRATINGS I.V.Anudeep Kumar Redd ParneSaidiRedd G.R.C.Redd INDIA.

  2. Presentation Outline Introduction Research Approach Temperature sensor head Pressure sensor head Combined sensor Conclusions Applications

  3. Introduction

  4. Introduction Fabrication of Fiber Bragg Gratings using phase mask method Fiber gratings are made by laterally exposing the core of a single-mode fiber to a periodic pattern of intense ultraviolet light. The exposure produces a permanent change in the refractive index of the fiber core, creating a fixed index modulation according to the exposure pattern. This fixed index modulation is called a grating. At each periodic refraction change a small amount of light is reflected

  5. Structure of Fiber Bragg Gratings Bragg wavelength Refractive index wavelength Effective refractive index Contd…

  6. Introduction Sensing principle of FBG • The effective Bragg wavelength shift due to strain and temperature is given by • The strain response arises due to both the change in the fiber index due to photo elastic • coefficients and the elongation of the sensor . • The thermal response due to the temperature depends of the refractive index and inherent • thermal elongation of the fiber material .

  7. Research Approach • To design sensor heads for temperature and pressure measurement. • 2. To study the individual response of Temperature and Pressure sensors. • 3. To design combined sensor head and study the characteristics of FBG.

  8. Temperature Sensor Head • A bimetallic strip is used to convert a temperature change into mechanical displacement. • The strip consists of two strips of different metals which expand at different rates as they are heated, usually steelandcopper, or in some cases brass instead of copper. • The strips are joined together throughout their length by riveting, brazing or welding. • The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. • The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled.

  9. Deflection of Bimetallic Cantilever

  10. Experimental Setup using single Bimetallic strip

  11. Experimental Setup using two Bimetallic strips

  12. Theoretical support

  13. Results

  14. Pressure Sensor Head • The sensor head is a hallow cylinder with dimensions of 4cm x 2cm which can be held in palm. • It is made of stainless steel so that sensor head is anti-corrosive. • The diaphragm is made of silicon rubber with maximum Young’s modulus of 5Mpa. • A small copper foil is placed to fix the fiber. • The 0.3cm hole made to allows water inside the sensor head and sensor is maintained under a varying pressure. • Due to the pressure variations FBG gets strained and shift is noticed. This shift is used to measure the pressure at that particular place.

  15. Design A 4cm x 2cm Sensor head with 0.3cm hole :

  16. For more sensitivity :-

  17. Mathematical Support When water enters into hallow cylinder, silicon rubber gets elongated

  18. According to Hooke’s law, the radial strain is calculated as follows: The tangential strain is calculated accordingly: ) Length () of circle with height with peak height wo and base length 2RM

  19. Analyzing the above fig. we get : By approximating we get : Now the length of the arc of the circle is: Now strain produced in silicone rubber is calculated as follows:

  20. If tangential strain is assumed to be zero everywhere: The total stress of the thin circular membrane is obtained from the sum of the residual stress and the stress generated by the deflection of the membrane : Here residual stress is neglected as it is very low for silicone rubber and if it seems to matter we can eliminate it by coating with very small amount of copper and the equation is reduced to:

  21. Finally the equation for pressure is equal to: If we neglect the approximation sin we get the following equation Therefore elongation is equal to: where Y=

  22. Bragg wavelength shift

  23. Combined Sensor Head The temperature sensor is combined with pressure sensor in series and we can monitor temperature and pressure change simultaneously.

  24. Questions??

  25. Thank you

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