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Indium-Tin Indium-Tin Oxide SensorsOxide Sensors
Measuring Atmospheric OzoneMeasuring Atmospheric Ozone
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GeneralGeneral
• The primary goal of the ITO sensor project is to measure the concentration of Ozone (O3) as a function of altitude.
• The concentration of these gases will specify the current situation of ozone depletion.
• These measurements will be compared to past measurements made by other payloads.
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ScienceScience
• The measurement from the sensors depend greatly on temperature conditions, which must remain relatively constant (24 – 30 deg C).
• The obtained measurements are compared with various experiments showing the precise concentration of Ozone.
• Indium-Tin Oxide Sensors have been chosen for this flight.
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TechnicalTechnical
• The concentration of Ozone is calculated as the function of voltage produced across the sensor.
• As the resistance in the ITO sensor varies with the concentration of these gases, different voltages are produced with the same amount of input current in the circuit board.
• The Real Time Clock will be utilized as a counter and a timestamp will be printed for each measurement so that it can be related by time to altitude.
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Electrical Design and Electrical Design and DevelopmentDevelopment
Sensors/Sensor InterfacingSensors/Sensor InterfacingControl ElectronicsControl Electronics
Power SupplyPower SupplyPower BudgetPower Budget
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Power BudgetPower Budget
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Supply Component Current Drawn Suffi cient Power?10.5V
BalloonSat 53 mA YESITO 1 - 8 8 mA YESThermistor 0 - 0.3 mA YES
3VRTC < 1 micro amp YES
13.5VHeater 173 mA YES
Software DesignSoftware Design
Data Format and StorageData Format and Storage
Flight SoftwareFlight Software
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Data Format and StorageData Format and Storage
• EEPROM will store all data collected on flight
• EEPROM stores addresses for flight software
Byte # Data Stored0 Original Address1 Current Address
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Byte # Data Stored ADC ADC Channel1 - 8 ITOs 2 CH1 - CH8
9 THERM 1 CH110 HOUR N/A N/A11 MINUTE N/A N/A12 SECOND N/A N/A
Flight SoftwareFlight Software
• Read “original address” from EEPROM Address $0000
• Read RTC – 3 bytes
• Read all ITO sensors and Thermistor– 9 bytes
• Store all data from reading • Store current address in
EEPROM Address $0000• Repeat loop until current
address equals 8170– (current_address =
original_address)– LED flashes once per second
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Thermal DesignThermal Design
• ITO Sensors must maintain temperatures between 24 and 30 degrees Celsius
• Kapton Heater• Requires
approximately 1W
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Mechanical DesignMechanical Design•A hollow regular hexagonal A hollow regular hexagonal prismprism
•FOAMULAR Insulating FOAMULAR Insulating SheathingSheathing
External Design:External Design:•Each side of the base = 94 Each side of the base = 94 mmmm
•The height of the prism = 193 The height of the prism = 193 mmmm
•51mm X 49mm rectangular 51mm X 49mm rectangular hole for the ITO sensorhole for the ITO sensor
•The ITO sensor attached The ITO sensor attached from the inner walls; minimal from the inner walls; minimal area of the ITO sensor is area of the ITO sensor is exposedexposed
The external design of ITO sensor payload (in m) 17 of 25
Internal Design:
• Rectangular- shaped foam (thickness = 18 mm) bisects the internal payload in two– Heater Batteries,
Heater, ITO sensors, BalloonSat
– BalloonSat Batteries, Sensor Interfacing Board
• Kapton Heater attached to the back of the sensor with thermal paste
Internal Divider with BalloonSAT (in m)
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a) Side where ITO sensor is attached (in m)
b) Side where ITO sensor is attached with ITO sensor (in m)
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Weight Budget:
• Balloon payload should be less that 500 g
• Density of The FOAMULAR Insulating Sheathing = .029 g/ cm3
S.N.
Components Weight (gram) Clearance (g)
1. BalloonSAT 60 +/- 5
2. FOAMULAR Insulating Sheathing 110 +/- 20
3. Power Supply (Battery) 240 +/- 15
4. ITO sensor and PCB 70 +/- 5
5. Components for Sensor Interface 15* +/- 5
6.7.8.
Mass of cable for ITO sensorKapton Heater/ThermistorTape, Glue and other structure
15*10*10*
+/- 500
Total: 530.00 +/- 50
* Approximated within 0.1g 20 of 25
Ground SoftwareGround Software
• Save into text file
• Use Microsoft Excel
• Algorithms pre-programmed
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Risk ManagementRisk Management
User BacklashMalfunctioning of
ITO sensor
Cold Solder JointUnexpected
Weather
Software Malfunctioning
System Freezing
Bad Landing (Not on ground) Batteries DrainedHardware
Malfunctioning
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PROBABILITY
SEVERITY