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Microwave Calorimeter

Microwave Calorimeter. Sponsor: Chris Leach Merlyn Bluhm Chris De La Cruz Ben Schaefer. High Power M icrowaves (HPM). ~2-5GHz, ~1GW Compare to 783GW Used in High resolution radar Military “soft kill” of electronics IED’s. Calorimeter Overview. Used to measure microwave power

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Microwave Calorimeter

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  1. Microwave Calorimeter Sponsor: Chris Leach Merlyn Bluhm Chris De La Cruz Ben Schaefer

  2. High Power Microwaves (HPM) • ~2-5GHz, ~1GW • Compare to 783GW • Used in • High resolution radar • Military “soft kill” of electronics • IED’s

  3. Calorimeter Overview • Used to measure microwave power • Traditionally used to measure endo- and exo-thermic chemical reactions • Container of alcohol • Absorbs microwave power • Expands into capillary tube • Gives energy change

  4. Subcomponents • Physical housing • Microwave-transparent case • Capillary tube • Microcontroller • Sensors • Heating/calibration coils • Feedback • Signal/LCD output

  5. Physical Housing - Case

  6. Physical Housing–Capillary Tube • Coaxial capillary • Height measured via resistance • Wheatstone bridge

  7. Microwave Source • ~1GW • ~14J

  8. Goals of System • Accurately measure power • Provide method of calibration • Output scaled signals to oscilloscope and computer

  9. Roles of Team Members and Sponsor • Chris Leach (Sponsor) • Calorimeter Body Design and Assembly • Physics Guru • Merlyn • Software Development / Signal Processing • Chris • Cap Tube Instrumentation, Temp Measurement • Ben • Amplifiers, DAC, Sample and Hold, Heater Coil

  10. Microcontroller Block Diagram

  11. Arduinovs PIC • $30 • C++ Programming • 14 Digital I/O ports (6 PWM) • 6 Analog input ports • Stackable thermocouple module • Free multiplatform software, tons of sample code • No direct access to digital I/O ports • Multiplexed analog ports • Complications with installed software

  12. Project Deliverables • Calorimeter Body • Control Unit • Capillary Tube • Heater / Calibration Coils • ? Temp Sensor / Feedback • Power System • MCU • Software • Signal Scaling / Displaying • Calibration Controller • Data Archiving • Calibration Phase • Experimental Data

  13. Calorimeter Specifications • Physical Dimensions • 4cm deep X 40cm diameter. Driven by: • source aperture diameter • attenuation profile of source • Material • Aperture: HDPE/PiezoGlass • Body: HDPE/PiezoGlass or different material • Absorbing Material: Ethyl alcohol. (5,027 cm3) • Machining capabilities will play a major role

  14. Calorimeter Specifications Cont… • Removable Sensor Interface • Different tube sizes or additional thermocouples • Our Idea • Source and calorimeter specs will yield: • ΔT = 6.25 x 10-3°C • ΔV = 0.0325 cm3

  15. Capillary Tube • Physical Dimensions • Tube: 0.0314” (0.08 cm) dia X 4.0” (10.2 cm) length • Wire: 0.010” (4e-3 cm) dia • Predicted fill level during experiment: 3.5” (8.9 cm) • Must hold off main alcohol volume • Resistance • Conductivity of alcohol: 5.63e-8 S/m? => 17.8 MΩ/m • For coaxial geometry: R’ = 3.11 MΩ/m • Experiment • For 1cm initial fill level: R0 = 31 kΩ • For 8.9 cm displacement at 14 J: delta R = 278 kΩ • Wheatstone bridge should not be required • Must know voltage breakdown specs of alcohol to optimize detection circuit

  16. Temperature Measurement • Expected Temperature Change: 6.25 x 10-3 °C • Very, very low and atypical • Thermocouple • Sensitivity: 40 μV/°C , Accuracy: 1°C • Expected output: 0.24 μVw/o amplification • Not feasible • RTD – Resistance Temperature Detector • Sensitivity: 1.8 mΩ/°C , Accuracy: 30 x 10-3°C • Current constraint: 1mA • Expected output w/ Wheatstone bridge: 1 μVw/o amplification • Viable option but is accuracy adequate? • May forgo temperature measurement • Physics say the capillary tube should be adequate

  17. Heater Circuit • 300W DC Power Supply • PID algorithm to control temp • NiChrome Wire • Ohms/ft • Use IGBT for switching • Fast response time • Large power rating (1KW)

  18. Amps, DAC, S&H • Amplify small voltages from capillary tube and temp sensor • -mV => 0-5V Scaled • DAC: Generate analog data from MC • - TBD • S&H: Closed loop system between MC and S&H • - Collect data when we want it

  19. Software Development • Implement sample code for analog voltage mapping • Read-in capillary tube resistance via voltage change • Extrapolate total energy deposition from calorimeter dynamic equations • Implement PWM signal to calibration power system • Display / record experimental data

  20. Challenges and Concerns • Current Issues • ΔT, 6.25 x 10-3 °C • Resolved Issues • MCU choice • Alcohol Volume

  21. Milestones for End of Fall Semester • Cap Tube Bench Test • Prototype Software for Functional I/O • Heater System Spec’ed • Power • NiCr • Other components • Calorimeter Fab Complete

  22. Major Schedule Milestones • Calorimeter Fab – Dec 2011 • Controller Development – Dec 2011 • Calibration – Feb 2012 • Experiment/Testing – Apr 2012

  23. Why This is a Good Senior Design Project • Entrenched in all phases from initial design to final testing. • Combination of digital, analog, software, power. • Project emulates real world job scenario. • Team effort

  24. Questions?

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