team philosoraptors: temperature, humidity, pressure hannah gardiner joe valieant bill freeman randy...
TRANSCRIPT
Team Philosoraptors:Temperature, Humidity, Pressure
Hannah GardinerJoe ValieantBill Freeman
Randy Dupuis
Goals and Objectives
• Goals
• Objectives
Science Objectives
• Layers of the atmosphere
• Time dependence
Technical Objectives
• Payload• Money and Weight• Measurements• Documentation
PDRPDR
CDRCDR
FRRFRR
Earth’s Atmosphere
Overview
• Troposphere– Clouds
• Stratosphere• Mesosphere• Thermosphere
Troposphere
• Atmospheric Conditions
• “Stirring”
Clouds
Stratosphere
• Atmospheric Conditions
• Ozone Layer
Mesosphere
• Atmospheric Conditions
• Measuring
Thermosphere
• Atmospheric conditions
• Start of “space”
Review
• Atmospheric layers
Weather Balloons
http://www.ehow.com/about_5050060_history-weather-balloons.html
Science Background
US Model Atmosphere 1976
• Produced by NOAA, NASA, and USAF– NOAA: National Oceanic and Atmospheric
Administration– NASA: National Aeronautics and Space
Administration– USAF: United States Air Force
US Model Atmosphere 1976
• Theoretical model of the atmosphere using:– Ideal gas law• p = DRT
– Hydrostatic Equilibrium law• dp/dh = -gD
p = Pressure of airD = Density of airR = Universal Gas ConstantT = Temperatureg = Acceleration due to gravity
US Model Atmosphere 1976
• Assumes:– Dry Air– Temperature is linear with altitude
• Can calculate properties of the atmosphere– Pressure– Temperature– Density– Speed of sound
Measured Temperature profile of the atmosphere
0 5 10 15 20 25 30 35-80
-60
-40
-20
0
20
40Temperature vs Altitude
Altitude [km]
Temperature[C]
Troposphere Tropopause Stratosphere
Measured Lapse Rate of the atmosphere
0 20000 40000 60000 80000 100000 1200000
1
2
3
4
5
6
7
8
9
10
Change in Temperature vs Altitude
Altitude [feet]
ΔTemp/alt[°C/km]
Troposphere Tropopause Stratosphere
Measured and theoretical pressure as a function of altitude
0 5 10 15 20 25 30 350.001
0.01
0.1
1
Pressure vs Altitude
MeasuredTheory
Altitude [km]
Pressure[atm]
Troposphere Tropopause Stratosphere
Measured humidity as a function of altitude
0 5 10 15 20 25 30 350
20
40
60
80
100
120
Humidity vs Altitude
Altitude [km]
Humidity[%rel]
Troposphere Tropopause Stratosphere
Measured humidity rate of change as a function of altitude
0 5 10 15 20 25 30 35-30
-20
-10
0
10
20
30
40
50
Humidity rate of change vs Altitude
Altitude [km]
ΔHum/alt[%rel/km]
Troposphere Tropopause Stratosphere
Temperature error and humidity as a function of altitude in the Troposphere
0 2 4 6 8 100
10
20
30
40
50
60
70
80
90
100
HumidityTdiff
Science Requirements
• Temperature
• Pressure
• Humidity
-70 °C
30 °C
10Pressure Sensor(atm)
0% 100%
Technical Requirements
• Payload must cost less than $500 and weigh less than 500 grams.
• Payload must have separate sensors to measure pressure, temperature, and humidity and a real time clock to timestamp data.
• Signal conditioning is required to transform the signal from the sensor to a signal that spans the range of the ADC on the BalloonSat.
• The payload must have enough memory available to take data every 10 seconds.
Sensor Information
• The payload must have temperature sensors that to measure temperatures between 30 and -70 °C on the inside and outside of the payload with a standard deviation of ± 1.7 °C
• The payload must have a pressure sensor to measure pressures between 1 and 0.008 atm with a standard deviation of ± 0.002 atm
• The payload must have a humidity sensor to measure humidity between 100 and 0 %rel with a standard deviation of ± 0.5 %rel
Temperature Sensors
• There are 2 different types contact and noncontact.• Contact Sensors function by producing an electrical
output based on the temperature of the sensor. These sensors are placed in contact with the target and if the sensor and target are in thermal equilibrium (no heat flow between the sensor and target) the target’s temperature can be measured
• Noncontact Sensors measure temperature using the thermal radiant power of the infrared or optical radiation from the targets surface.
• Some examples are Thermocouples, thermistor, RTD’s
Pressure Sensors
• Pressure sensors are mechanical elements that are designed to deflect when pressure is applied. The deflection can be measured and transduced to produce an electrical output.Examples include poteniometric, piezoressistive, capacitive, and piezoelectric sensors
Humidity Sensors
• There are three main types: capacitive, resistive, and thermal conductive.
• Capacitive sensors consist of a substrate with a thin film placed in between two conductive electrodes, as the relative humidity changes the capacitance changes.
• Resistive sensors measure the change in the impedance of a hygroscpoic medium.
• Thermal Conductive sensors measure the absolute humidity by using the difference of the thermal conductivity of dry air and air containing water vapor