Thermal Investigation for Accurate Temperature Measurement

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Thermal Investigation for Accurate Temperature Measurement

Team TCTJTruc Le

Cedric ToguemJonathan Newman

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Overview•Mission Goal•Objectives•Science Background•Technical Background •Payload Design

• Electrical• Software

• Mechanical•Payload Development

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Mission GoalThe goal is to determine why previous LaACES payloads failed to correctly measure temperature in comparison to NOAA.

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ObjectivesDetermine the effect of the thermal boundary layer on temperature measurementsDetermine the effects of material and coating of temperature sensors on temperature measurementHave the measurements of the control temperature sensor be similar to NOAA measurements

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Temperature change in the Atmosphere

• Troposphere (0 to 12km) : lowermost atmosphere where temperature decreases from 30 to -80°C• Stratosphere (12 to 48km): second lowermost part of the atmosphere where temperature increases from -80 to 0°C

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/vert_temp_all.html

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Boundary LayerThin layer of fluid in contact with a solid

body that flows more slowly than the rest of the fluid

As the payload gains altitude in fluid air, the boundary layer around it will be affected by heat transfer processes

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/vert_temp_all.html

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Heat Transfer ModesHeat can be transferred in three

different ways:- Conduction- Convection- Radiation

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RadiationElectromagnetic radiation emitted from the

surface of an object in the form of heat due to the objects temperature

If an object is warmer than its surrounding environment, it will emit more radiation in the form of heat into the surrounding environment than it will absorb in order to attain thermal equilibrium

http://www.tsc.com/irgen/Image7.gif

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Test 1: Radiation Test 1Radiation test:

Sun →Electromagnetic radiation → Space →Sensors

The test will consist of different color shielding to reflect the electromagnetic radiation from the sun

http://image.tutorvista.com/content/dispersion

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Test 2: Radiation Test 2Radiation Test:The payload circuitry will emit radiation

to the sensor.Distance from the radiation source will

determine the amount of heat dissipated

http://images.google.com/imgres?imgurl=http://www.uos.harvard.edu/images/ehs/radiation

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Test 3: Boundary Layer Test

Sensors are placed at different distance from the exterior surface of the payload

Determine how much effect the boundary layer has on the measured temperature

http://www.google.com/imgres?imgurl=http://www.engineering.leeds

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Sensors7 temperature sensorsModel: 44003RC Precision Epoxy NTC Thermistor -80 °C to 50 ° C 1kΩat 25 ° C

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Sensors 1µA constant current from LM134Output voltage will then vary from

1mV to 190.8mV (Value based on device’s datasheet – Resistance V. Temperature Table)

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Sensor InterfacingSensors’ output voltage will vary

from 1mV to 190.8 mV

Payload ADC, from 0 to 3V

Will use AD820 op-amp to amplify each sensors’ output

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Sensor Interface

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Sensor Interface

Vref = 1V, R6 = 1kΩR4 = 0.94MΩR5 = 14.806kΩ

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Control Electronics

Program from Basic Stamp

Editor

Basic Stamp

Sensors Op-Amp ADC EEPROM

Control Electronics

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Power Supply6 x 1.5V Energizer L92 Ultimate

Lithium (AAA)9V to BalloonSat 9V to Op-Amps pin 7 1V from BalloonSat’s Voltage

regulator to Op-Amp Vref9V Current sources positive

voltage terminal

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Power Supply

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Power budget

Component Current (mA) Duration CapacityBalloonSat 51 (measured) 4 204mA-hThermistors (x7)

≤ 0.7 (desired) 4 2.8mA-h

AD820 op-amp (x7)

≤ 25 E-9 4 0.001mA-h

LM134 ≤0.7 (desired) 4 2.8mA-hMax Total 53.4 4 213.6mA-h

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Data Format TableDescription ByteExtra variables 2Time-Hour 1Time-Minute 1Time-Seconds 1Sensor-Inside wall 1Sensor-Outside wall 1Sensor-Control sensor 1Sensor-Inside B.L. 1Sensor-Outside B.L. 1Sensor-Black coating 1Sensor-White coating 1Total per Loop 12Total Estimated Bytes 2880 bytes

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Flight and Post-Flight Software

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Programming Flow Chart

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Flow Chart During Flight

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Exterior Mechanical Design

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Interior Mechanical Design

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Weight BudgetComponent Weight (g)Batteries ~91BalloonSat 60.4Op amp Board ~30.2Foamular structure 64.1BalloonSat/Op-amp board attachments ~9

Wiring ~10Booms (Plexiglas Straws) ~20Boom attachments ~25Sensors ~1.5Total ~311.2

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Payload Development PlanMechanical

Thermal TestingBoom TestingAttachment prototypingImpact test to find best design to

store componentsMaintain payload within regulation

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Payload Development PlanElectrical

Design the circuitry of the systemDetermine how well the components

will function in flight climateDetermine methods of calibration of

the sensors

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Payload Development PlanSoftware

Determine if extra memory will be needed and how to access it

Determine how to access ADC Determine methods of calibration

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Reference1. Clavius: Environment - heat transfer.

http://www.xmission.com/~jwindley/heatxfer.html. November 24, 2009

2. Anne E. Egger "Earth's Atmosphere: Composition and Structure," Visionlearning Vol. EAS 2003. http://www.visionlearning.com/library/module_viewer.php?mid=107

3. Sad Dr Rodrigue – Introduction to physical Geaography. http://www.csulb.edu/~rodrigue/geog140/lectures/thermalstructure.html

4. BASIC Stamp 2p 24-Pin Module. http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/ProductID/7/List/1/Default.aspx?SortField=UnitCost,ProductName. November 25, 2009

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Questions?