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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•Tests •Overall Design•Payload Design

• Electrical• Software • Mechanical

•Payload Development•Projected Budget•Schedule and Status

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Mission GoalThe goal is to determine why previous LaACES payloads temperature measurements are different in comparison to NOAA temperature measurement.

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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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Science Background • 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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Science : 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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Science: 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

Science: Previous Data

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Test 1: Radiation Test 1

Radiation 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 2

Radiation 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

Overall Design

Control Subsystem 1BalloonSat

Main PowerSubsystem

Power Source(9V DC)

ControlSubsystem 2

(BASIC Stamp2p 24-PinModule)

Data ArchiveSubsystem

Memory(EEPROM)

Analog to digitalconverters(ADC0834)

ElectricalSubsystem 2

Op Amps(AD820)

Sensors(44003RC

Precision EpoxyNTC Thermistor)

ElectricalSubsystem 1

Current Sources(LM134)

AnalogAnalog

Digital

9V DC

Real Time Clock

1 μA

Dig

ital

RS

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Ground ControlSubsystem(PersonalComputer)

Backup PowerSubsystem

(2) AA batteries

MechanicalSubsystem

Foam Enclosure

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

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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 = 1.5V, R6 = 1kΩR4 = 0.94MΩR5 = 14.806kΩ

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Power Supply6 x 1.5V Energizer L92 Ultimate

Lithium (AAA)9V to BalloonSat 9V to Op-Amps9V Current sources positive

voltage terminal1.5V Battery to Op-Amps Vref

Supplemental ADC ChipTeam will use 7 sensors4 Channel on BallonSat ADCTeam will add another ADC0834

chipNew chips’ pin connection will

follow the original’s.Ohmmeter will test pin

connections

Supplemental ADC Chip (cont.)

ADC pin Connection

2 P0

3 CH4

4 CH5

5 CH6

6 CH7

7 GND

8 GND

10&13 P13

12 P14

14 Vcc

Added ADC Pin Connection

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Power budget

Component Current (mA) Duration Capacity

BalloonSat 51 (measured) 4 204mA-h

Thermistors (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-h

Max Total 53.4 4 213.6mA-h

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Software: Data Format Table

Description 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 1

Total per Loop 12Total Estimated Bytes 2880 bytes

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Software: Flowchart

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Software: Flight Flowchart

Software: Ground System

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Exterior Mechanical Design

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Interior Mechanical Design

Mechanical/electronics interface

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Weight Budget

Component Weight (g)

Batteries ~91

BalloonSat 60.4

Op amp Board ~30.2

Foamular structure 64.1

BalloonSat/Op-amp board attachments ~9

Wiring ~10

Booms (Plexiglas Straws) ~20

Boom attachments ~25

Sensors ~1.5

Total ~311.2

Thermal TestActivity Time (min)

1. Acquire dry ice and place it in a cooler 2

2. Initialize software 1

3. Place payload in refrigerator 5

4. Place payload in freezer 15

5. Place payload in dry ice cooler 30

6. Place payload in freezer 60

7. Place payload in dry ice cooler 15

8. Return payload to room temperature .5

9. Run program to ensure payload worked 5

Vacuum TestActivity Time (min)

1. Initialize software 2

2. Place payload in vacuum chamber .25

3. Begin evacuating chamber (10 mb/min) 1

4. Allow chamber to reach 5mb ~100

5. Begin re-pressurizing chamber (35mb/min) ~30

6. Run program to ensure payload worked 5

Impact TestActivity Time

(min)

1. Initialize software 2

2. Go outside with a tape measure and the payload 2

3. Put payload at a height of 3 meters and drop .5

4. Analyze damage to determine if current structure is sufficient 20

BudgetItem Part Retailer Qty. Unit

PriceTotal Price

Sensors x7 44003RC Precision Epoxy NTC Thermistor

http://www.newark.com/measurement-specialties

10 $15.17 $152.00

Batteries Energizer L92 Ultimate Lithium (4 pack)

www.Zbattery.com or local Wal-Mart or Radio Shack

4 10.00 $40.00

Constant Current x7

LM234 In house 7 ---------- ---------

ADC ADC0834 In house 1 ---------- ---------

Op-amp AD820 In house 10 ---------- --------

Resistors Varying values In house ???? ---------- --------

Booms Plexiglas straws http://www.amazon.com 1 pack

$20.00 $20.00

Op-amp Board Stripboard http://www.futurlec.com/ProtoBoards.shtml

1 $2.00 $2.00

Payload Structure

Foamular In House ------ ---------- --------

Total $214.00

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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?