Sponsor: Chris Leach Merlyn Bluhm Chris De La Cruz Ben Schaefer

bendembarrassΗλεκτρονική - Συσκευές

2 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

76 εμφανίσεις

Sponsor: Chris Leach

Merlyn
Bluhm

Chris De La Cruz

Ben Schaefer


~2
-
5GHz, ~1GW


Compare to 783GW


Used in


High resolution radar


Military “soft kill” of
electronics


IED’s


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


Physical housing


Microwave
-
transparent case


Capillary tube


Microcontroller


Sensors


Heating/calibration
coils


Feedback


Signal/LCD output


Coaxial capillary


Height measured
via resistance


Wheatstone bridge


~1GW


~14J


Accurately measure power



Provide method of calibration



Output scaled signals to oscilloscope
and computer


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


$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


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




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 cm
3

)


Machining capabilities will play a major role



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 cm
3


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 M
Ω
/m


For coaxial geometry: R’ = 3.11 M
Ω
/m


Experiment


For 1cm initial fill level: R
0

= 31 k
Ω


For 8.9 cm displacement at 14 J: delta R = 278 k
Ω


Wheatstone bridge should not be required


Must know voltage breakdown specs of alcohol to optimize
detection circuit



Expected Temperature Change:
6.25
x 10
-
3

°
C


Very
, very low and atypical




Thermocouple


Sensitivity
: 40
μ
V
/
°
C , Accuracy
: 1
°
C


Expected
output: 0.24
μ
V

w/o amplification


Not
feasible



RTD


Resistance Temperature Detector


Sensitivity
: 1.8
m
Ω
/
°
C , Accuracy
:
30

x 10
-
3

°
C


Current
constraint: 1mA


Expected
output w/ Wheatstone bridge: 1
μ
V

w/o amplification


Viable
option but is accuracy adequate?



May forgo temperature measurement


Physics say the capillary tube should be adequate



300W DC Power Supply



PID algorithm to control temp



NiChrome

Wire


Ohms/
ft




Use IGBT for switching


Fast response time


Large power rating (1KW)



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









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


Current Issues


ΔT,
6.25 x 10
-
3

°
C



Resolved Issues


MCU choice


Alcohol Volume


Cap Tube Bench Test



Prototype Software for Functional I/O



Heater System
Spec’ed


Power


NiCr


Other components



Calorimeter Fab Complete


Calorimeter Fab


Dec 2011



Controller Development


Dec 2011



Calibration


Feb 2012



Experiment/Testing


Apr 2012


Entrenched in all phases from initial design to final
testing.



Combination of digital, analog, software, power.



Project emulates real world job scenario.



Team effort