LaACES Program
Preliminary Design Review Document
for the
Air Mass Flow Rate
Experiment
by
Team
Team Fly Boys
Prepared by:
David Branch
Team Spokesperson
Date
Jared Pellegrin
Team Member
Date
Team Member (replace with name)
Date
Team Member (replace with name)
Date
Team Member (replace with name)
Date
Institution Signoff (replace with name)
Date
Institution Signoff (replace with name)
Date
LAACES Signoff
Date
Submitted:
Reviewed:
Revised:
Approved:
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TABLE OF CONTENTS
Cover ............................................................................................................................................. i
Table of Contents ......................................................................................................................... ii
List of Figures ............................................................................................................................. iii
List of Tables .............................................................................................................................. iv
1.0 Document Purpose ................................................................................................................. 1
1.1 Document Scope .............................................................................................................. 1
1.2 Change Control and Update Procedures .......................................................................... 1
2.0 Reference Documents ............................................................................................................ 1
3.0 Goals, Objectives, Requirements ........................................................................................... 5
3.1 Mission Goal .................................................................................................................... 5
3.2 Objectives ........................................................................................................................ 5
3.3 Science Background and Requirements .......................................................................... 6
3.4 Technical Background and Requirements ....................................................................... 9
3.5 Previous Methodologies and Measurements.....................................................................9
3.6 Expected Results.............................................................................................................12
4.0 Payload Design .................................................................................................................... 17
4.1 Principle of Operation .................................................................................................... 17
4.2 System Design ............................................................................................................... 17
4.3 Electrical Design ............................................................................................................ 21
4.4 Software Design ............................................................................................................. 28
4.5 Thermal Design .............................................................................................................. 31
4.6 Mechanical Design......................................................................................................... 32
5.0 Payload Development Plan .................................................................................................. 34
8.0 Project Management ............................................................................................................ 35
8.1 Organization and Responsibilities ................................................................................. 35
8.2 Configuration Management Plan ................................................................................... 35
8.3 Interface Control ............................................................................................................ 36
9.0 Master Schedule ................................................................................................................... 37
9.1 Work Breakdown Structure (WBS) ............................................................................... 37
9.2 Timeline and Milestones ................................................................................................ 38
11.0 Risk Management and Contingency .................................................................................. 40
12.0 Glossary ............................................................................................................................ 43
PDR Note: Sections 6, 7 and 10 will be provide in a later document. In addition, for PDR
some sections of 4 and 9 need to be partially completed (see details in sections 4 & 9).
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LIST OF FIGURES
1. Plot of density and specific volume of air versus altitude ....................................................... 6
2. Psychometric chart ................................................................................................................... 6
3. Plot of Pressure versus Altitude ............................................................................................... 7
4. Plot of Temperature versus Altitude ........................................................................................ 8
5. Schematic of a hot wire anemometer ....................................................................................... 9
6. Photo of sonic anemometer .................................................................................................... 10
7. Sonic anemometer in water test for flow distortion ............................................................... 10
8. Picture of UVW anemometer................................................................................................. 11
9. Photo of vane mounted anemometer...................................................................................... 12
10. Flight profile for ACES-23.................................................................................................. 13
11.Balloon Velocity................................................................................................................... 14
12. Mean mass air flow versus altitude...................................................................................... 17
13. BalloonSat system diagram.................................................................................................. 18
14. MA40S4R/S......................................................................................................................... 22
15. Two vertically aligned ultrasonic sensors ........................................................................... 23
16. Temperature sensor system diagram................................................................................... 24
17. Pressure sensor system diagram.......................................................................................... 24
18. Humidity integrated circuit system diagram........................................................................ 25
19. Ultrasonic sensor system diagram........................................................................................ 25
20. Payload system diagram....................................................................................................... 26
21. Power system diagram.......................................................................................................... 26
22. Battery discharge curve......................................................................................................... 27
23. Flight software flow chart..................................................................................................... 29
24. Air velocity sensor flow chart................................................................................................30
25. ¾ View of payload................................................................................................................ 32
26. Section of payload................................................................................................................. 32
27. Work Breakdown Schedule................................................................................................... 37
28. Gant Chart………………..................................................................................................... 38
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LIST OF TABLES
1. Group Interfaces..................................................................................................................... 19
2. Requirements ......................................................................................................................... 19
3. Power budget ........................................................................................................................ 27
4. Weight budget ....................................................................................................................... 33
5. Risk detection ........................................................................................................................ 40
6. Risk severity matrix ............................................................................................................... 41
7. Contingency plan per risk ...................................................................................................... 42
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1.0 Document Purpose
The purpose of this document is to provide the preliminary design for a payload that will
measure the mass flow rate of air as a function of altitude by Team Fly Boys for the LaACES
project. This document fulfills the LaACES project requirements for the Preliminary Design
Review (PDR) to take place on February 7, 2012.
1.1 Document Scope
The scope of this PDR document covers the scientific and technical background of measuring air
flow. This document also serves as an outline for the development, design, and operation of the
payload under the LaACES project. This includes what and how the payload will measure and
calculations for analyzing these measurements. In addition, this document will address team
objectives - both technical and scientific – and provide project management, timelines, word
breakdown, and risk management in order to achieve these objectives. This document is a
precursor to the Critical Design Review (CDR) and its contents are preliminary and are not
finalized.
1.2 Change Control and Update Procedures
Changes to this document shall only be made after the approval of both members of Team Fly
Boys and LaACES staff. Document changes should follow the same version control guidelines
established in team contract and members shall be notified of any changes made.
2.0 Reference Documents
200-81000 Ultrasonic anemometer. (n.d.). NovaLynx Corporation - Professional Quality
Weather Instruments and Systems. Retrieved November 18, 2011, from
http://www.novalynx.com/200-81000.html
Aber, J. S., & Aber, S. W. (2005, January). High-altitude kite aerial photography.
Geospectra.net. Retrieved November 13, 2011, from
http://www.geospectra.net/kite/weather/h_altit.htm
Air - altitude, density and specific volume. (n.d.). The Engineering ToolBox. Retrieved
November 14, 2011, from http://www.engineeringtoolbox.com/air-altitude-densityvolume-d_195.html
The atmosphere. (n.d.). Structure of the Earth's Atmosphere. Retrieved November 15, 2011,
from http://www.ux1.eiu.edu/~cfjps/1400/atmos_struct.html
Brooks, Cassidy, & Huff, Isabel (2006) The Effect of Altitude on Relative Humidity. Retrieved
February 7, 2012, from
http://www.physics.umt.edu/borealis/RH%20Lab%20Report_06.pdf
Busch, N. E., & Kristensen, L. (1976). Cup anemometer overspeeding. Journal of Applied
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Meteorology, 15(12), 1328-1332. Retrieved November 12, 2011, from
http://journals.ametsoc.org/doi/pdf/10.1175/15200450%281976%29015%3C1328%3ACAO%3E2.0.CO%3B2
Campbell, G. S., & Unsworth, M. H. (1979). An inexpensive sonic anemometer for eddy
correlation. Journal of Applied Meteorology, 18(8), 1072-1077. Retrieved November 17,
2011, from http://journals.ametsoc.org/doi/pdf/10.1175/15200450%281979%29018%3C1072%3AAISAFE%3E2.0.CO%3B2
Comte-Bellot, G. (1976). Hot-wire anemometry. Annual Review of Fluid Mechanics, 8(1), 209231. Retrieved November 11, 2011, from http://www.annualreviews.org/doi/abs/
10.1146/annurev.fl.08.010176.001233
Coppin, P. A., & Taylor, K. J. (1983). A three-component sonic anemometer/thermometer
system for general micrometeorological research. Boundary-Layer Meteorology, 27(1),
27-42. Retrieved November 12, 2011, from http://www.springerlink.com/content/
l2u347j2p1021610/fulltext.pdf
Downs, R. J., & Krizek, D. T. (1997). Air movement, chapter 6 (R. W. Langhans & T. W.
Tibbitts, Eds.). Plant Growth Chamber Handbook, 94-96. Retrieved November 11, 2011,
from www.controlledenvironments.org/Growth_Chamber_Handbook/Ch06.pdf
Dyer, A. J. (1981). Flow distortion by supporting structures. Boundary-Layer Meteorology,
20(2), 243-251. Retrieved November 17, 2011, from http://www.springerlink.com/
content/w641p226pm257518/fulltext.pdf
Fox, R. W., McDonald, A. T., & Pritchard, P. J. (2009). Introduction to fluid mechanics.
Hoboken, NJ: Wiley.
Hicks, B. B. (1972). Propeller anemometers as sensors of atmospheric turbulence. BoundaryLayer Meteorology, 3(2), 214-228. Retrieved November 11, 2011, from
http://www.springerlink.com/content/k45444g0w4214t13/fulltext.pdf
Horst, T. W. (1973). Corrections for response errors in a three-component propeller anemometer.
Journal of Applied Meteorology, 12(4), 716-725. Retrieved November 11, 2011, from
http://journals.ametsoc.org/ doi/pdf/10.1175/15200450%281964%29003%3C0194%3ADFFSAI%3E2.0.CO%3B2
Miyara, J. (1971). Measuring air flow using a self-balancing bridge. Analog Dialogue, 5(1).
Retrieved November 12, 2011, from http://www.analog.com/library/
analogdialogue/archives/38-12/reader.html
Morris, P. S. (n.d.). Air pressure and circulation. SMC Homepage. Retrieved November 20,
2011, from http://homepage.smc.edu/morris_pete/physical/main/notes/pgcirculation.html
Murnan, J. (2011, April 15). Flight of the weather balloons. NOAA Weather Partners. Retrieved
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November 27, 2011, from http://www.norman.noaa.gov/2011/04/flight-of-the-weatherballoons/
Nawi, Mohd. (n.d.). Current development of MEMS flow sensor. Underwater Robotics Research
Group. Retrieved February 6, 2012, from http://urrg.eng.usm.my/index.php?option=
com_content&view=article&id=191:current-development-of-mems-flow-sensor-&catid=
31:articles&Itemid=70
Pidwirny, M. (2009, May 07). Atmospheric Pressure. Geography : Physical Geography.
Retrieved November 19, 2011, from http://www.physicalgeography.net/fundamentals
/7d.html
Quashning, V. (n.d.). Photo gallery: Solar and wind measurements. Erneuerbare-Energien-undKlimaschutz.de. Retrieved November 17, 2011, from http://www.volkerquaschning.de/fotos/messung/index_e.php
Ritter, M. E. (n.d.). The physical environment: An introduction to physical geography. National
Council for Geographic Education. Retrieved November 19, 2011, from
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/ title_page.html
Russell, R. (n.d.). Layers of the earth's atmosphere. Windows to the Universe. Retrieved
November 20, 2011, from
http://www.windows2universe.org/earth/Atmosphere/layers_activity_print.html
Shelquist, R. (n.d.). Equations - Air Density and Density Altitude. Wahiduddin's Web. Retrieved
December 29, 2011, from http://wahiduddin.net/calc/density_altitude.htm
Sonntag, R. E., Borgnakke, C., & Van, W. G. (2003). Fundamentals of thermodynamics. New
York: Wiley.
Surridge, A. D., (1982). On the measurement of atmospheric winds. Boundary-Layer
Meteorology, 24(4), 421-428. Retrieved November 12, 2011, from
http://www.springerlink.com/content/j03756ljr0861123/fulltext.pdf
Urieli, Israel, (2011). Engineering Thermodynamics – A Graphical Approach. Retrieved
February 07, 2012, from
http://www.ohio.edu/mechanical/thermo/Applied/Chapt.7_11/Chapter10b.html.
Williams, J. (2005, May 17). Understanding air density and its effects. USATODAY.com.
Retrieved November 14, 2011, from http://www.usatoday.com/weather/wdensity.htm
Wood, R. C. (1964). Direct-flow filter sampler: An improved large-volume collector of
radioactive stratospheric debris. Journal of Applied Meteorology, 3(2), 194-197.
Wyngaard, J. C. (1981). Cup, propeller, vane, and sonic anemometers in turbulence research.
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Annual Review of Fluid Mechanics, 13(1), 399-423. Retrieved November 12, 2011, from
http://www.annualreviews.org/doi/abs/10.1146/
annurev.fl.13.010181.002151?journalCode=fluid
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3.0 Goals, Objectives, Requirements
3.1 Mission Goal
Team Fly Boys’ mission goal is to design and construct a high altitude balloon sensor payload to
measure the pressure, temperature, relative humidity, and flux of air as a function of altitude up
to 30,480 meters in order to calculate the mass flow rate of air as a function of altitude.
3.2 Objectives
3.2.1 Technical Objectives
Team Fly Boys will:
• Comply with all LaACES requirements.
• Complete PDR, CDR, FRR, and science presentation in accordance with requirements
and deadlines.
• Construct a payload that passes thermal, pressure, and shock testing before completion of
FRR.
• Operate within the given time constraints and budget allocated from LaACES
management.
3.2.2 Science Objectives
Team Fly Boys’ payload will:
• Calculate the mass flow rate of air up to 30,480 meters.
• Include sensors that measure the pressure, temperature, air velocity, and relative humidity
of air during balloon ascent.
• Be able to detect changes in the pressure, temperature, air velocity, and relative humidity
of air to accurately calculate the air mass flow rate.
• Be structurally sound and insulated to protect electrical components during ascent,
descent, and impact.
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3.3 Science Background and
Requirements
This portion of the report provides an
overview of atmospheric properties that
will affect our experiment as well as an
introduction to buoyancy. There are
several properties of the atmosphere that
impact the ascent rate of a balloon, such
as air density, pressure, and temperature.
3.3.1 Airflow and Atmospheric
Properties
The study of how the mass flow rate of
air changes as a function of altitude is an
examination of how the properties of air
change with altitude and its relationship
to air velocity. One of the main properties
of air that we will be studying is density.
The density of air is essentially the
measurement of how many molecules of
air are present in a given area and is
expressed in units of mass per unit
volume (J. Aber & S. Aber, 2005).
Density is dependent upon the relative
humidity, pressure, and temperature of the
air that is being taken into consideration.
While all of these variables independently
affect the density of air, Figure 1 shows
that the density of air decreases at a near
linear rate as altitude increases. In order
to accurately determine the density of air,
the effects that relative humidity,
pressure, and temperature create must be
understood and modeled.
Figure 1: Plot of density and specific volume of air versus altitude (“Air altitude, density and specific volume,” n.d.)
Figure 2: Psychometric chart (Urieli, 2011).
Relative humidity or the amount of water vapor present in air compared to what the air can hold
and plays a significant role in calculating the density of air. Water vapor molecules are less dense
than air molecules and their presence results in an air density that is less dense than “dry air”
(Williams, 2005). In order for humidity to be included in any air density calculations, a
measurement of the percentage of water vapor molecules present in the air must be made. The
relative humidity of air can range from 0-100% and can be dependent upon temperature. Figure 2
shows a Psychometric Chart used for determining relative humidity from wet and dry bulb
temperatures. Although this method of calculating relative humidity will not be used for the
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mission, Figure 2 shows that warm air
molecules are more capable of holding a
higher percentage of water vapor than cooler
air molecules (C. Brooks & I. Huff, 2006).
This relation to temperature provides an
explanation as to why humidity levels drop as
altitude increases.
The pressure of air is also an important
variable to consider when calculating air’s
density. The pressure of air decreases as
altitude increases and is expressed in terms of
force per unit area (J. Aber & S. Aber, 2005).
Higher air pressure compresses air molecules
closer together and causes the air’s density to
increase. Gravity plays a significant role in the
Earth’s air pressure. It is worth noting that
atmospheric pressure is reduced by nearly half
as altitude is increased by 5,486 meters. To
put this in perspective, the Exosphere, or the
outer layer of the Earth’s atmosphere, is
Figure 3: Plot of Pressure versus Altitude
nearly 10,000 kilometers high. This equates to
(Pidwirny, 2009)
half of the Earth’s air pressure existing in 18
percent of the atmosphere. This is due to gravity pushing air molecules on top of one another
near the Earth’s surface and causing a higher force per unit area. Figure 3 show the exponential
decrease in air pressure as attitude increases. Team Fly Boy’s payload will ascend into the
bottom of the Stratosphere (30,480 meters) where the pressure is expected to be very low.
A reasonable question one could now ask is that if pressure decreases exponentially with
altitude, then why does density remain linear? Temperature, the third variable in density
calculations that we will be considering, will help answer this question. Warm air molecules
have more thermal energy in them and therefor are more excited than cooler air molecules. This
excitement allows air molecules to move around their environment more freely while cooler air
molecules remain more stationary. This freedom of movement is why temperature should be
considered when calculating air density. Near the surface of the Earth air is warmer. As
discussed before, this air can hold more water vapor and can move around more freely. While the
pressure is highest at the surface, humidity and higher temperatures counter balance the pressure
and what results is what humans consider “normal” air density (which we have calculated to be
around 1.2 kilograms per meter squared. As altitude rises, pressure, temperature and humidity
decreases. Figure 4 shows how temperature changes with altitude. Although air pressure
decreases and air molecules move further apart, they also become less energized and become
more stationary. This explains why air density increases on a near linear scale. As Figure 4
shows, air temperature does begin to increase as altitude rises into the Stratosphere, or around 20
kilometers. This is a result of the amount of ozone present in this atmospheric layer. Ozone
absorbs energy from the Sun, and the air molecules become more energized (Russel, n.d.).
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Although ozone has a much higher enthalpy
than air and can absorb more energy, the air
pressure is very low at this altitude and air
temperature only raises a few tens of degrees
Celsius.
The density of air can affect airflow, or the
movement of air. Wind is the result of a
pressure gradient force from uneven heating of
the air from the Sun (Ritter, n.d.). This force
varies along latitudinal lines due to surface
exposure to the Sun. Because the air in lower
latitudinal regions has more exposure to the
Sun, it is warmer and is less dense with a lower
pressure. This difference between low-pressure
areas and high-pressure areas at the same
altitude in the atmosphere causes the gradient
force, which results in horizontal winds.
Coriolis forces affect the direction of airflow
Figure 4: Plot of Temperature versus Altitude ("The
Atmosphere," n.d.)
from high to low pressure systems. This is a
result of the rotation of the Earth as air is
deflected off of its linear path. The concept of the Coriolis force dictating the path of the wind is
illustrated in Figure 4. The magnitude of this deflection is a result of its latitudinal distance from
the equator and the particle’s velocity (Morris, n.d.). The farther away the air particle is from the
equator and the faster the particle is moving, the more the Coriolis force will deflect it. Another
force that affects the speed and direction of airflow is friction. Frictional forces exist in the lower
atmosphere and resist the direction of the wind’s magnitude. As altitude increases, frictional
forces become less prevalent as the density of air decreases. The amount of friction to the airflow
is related to the density of the surrounding air. Although an understanding of how and why air
moves is important, our study is focused on how many air molecules are available to be moved
by atmospheric forces. The movement of air can also be nearly impossible to predict and
expensive to measure. With this in mind, our payload will use the balloon’s vertical ascent to
measure the amount of air it passes through.
3.3.2 Overview of Buoyancy
The principle of buoyancy is the core science behind why helium balloons rise in air. The
knowledge of buoyancy is therefore critical to modeling the ascent rate of a balloon, which is an
important variable in calculating our expected results. Buoyancy was first defined by
Archimedes around 220 B.C.E. ( Fox, McDonald, and Pritchard, 2009). Archimedes’ principle
states that an object completely immersed in a fluid will experience an upward buoyant force
equal to the weight of the displaced fluid (Fox et al., 2009). The buoyant force that gives a
balloon lift is due to the displacement of the air that the balloon is occupying. Further discussion
of how buoyancy and the aforementioned atmospheric properties affect the vertical ascent rate of
helium filled balloons is to follow in the expected results portion of this report.
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3.3.3 Scientific Requirements
•
•
•
To design and implement circuitry and sensors to measure the humidity, pressure, and
temperature of air (in order to calculate the air’s density) as well as the air’s flow rate.
Implement sensors that can detect small changes in the environment and produce accurate
measurements.
To determine how the air mass flow rate changes as a function of altitude and how the
properties of air affect this change.
3.4 Technical Background and Requirements
3.4.1 Technical Requirements
•
•
•
•
•
•
The payload circuitry must be able to operate in temperatures ranging from -70°C - 25°C
or be insulated enough to operate within manufacturer’s suggested temperatures.
The payload must record the following every 20 seconds: Air pressure, temperature,
relative humidity, and the minimum, maximum, and average air velocities during 20
second event.
The power budget must support all circuitry contained in the payload for at least four
hours.
The payload must be capable of connecting to flight strings that are separated by 17 cm
and not exceed 500 grams.
The payload must be able to withstand an impact of 6.1 meters per second.
The payload’s EEPROM must be able to survive payload impact for download to
external software.
3.5 Previous Methodologies and Measurements
3.5.1 Hot Wire Anemometers
A hot wire anemometer is a device consisting of a metal
wire that is heated up by an electrical current to
temperatures above the ambient air temperature. Figure 5
shows a schematic of a common hot wire anemometer.
The device measures air speed by the air’s cooling effect
on the wire. Different arrangements of hot wire
anemometers with respect to air flow provide different
information about the wind speed. For instance, to strictly
measure the longitudinal component of the wind speed a
single wire is used and is oriented normal to the direction
of air flow. To measure both the longitudinal and
transverse components, two wires are placed a small
distance apart and form an “X” along their common
Figure 5: Schematic of a hot wire anemometer
normal plane (Comte-Bellot, 1976). The arrangement
(Nawi, n.d.)
of hot wire anemometers is important since they are
directional devices, meaning they do not measure air
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velocity equally from all directions. The measured value can vary as much as 50% depending on
the orientation of the hot wire (Downs and Krizek, 1997).
There are three types of hot wire anemometers: constant-current anemometers, constant-voltage
anemometers, and constant-temperature anemometers. In constant-current and constant-voltage
anemometers, the air flowing over the heated wire causes a decrease in temperature and an
increase in electrical resistance. This change in resistivity is then used to measure the wind
speed. The anemometers differ in that constant-current anemometers have the potential of
burning themselves up at low wind speeds due to natural convection currents generated by their
own heat and constant-voltage anemometers increase the resistance with the temperature change
making them safe to operate, but they are relatively insensitive at low air speeds (Downs and
Krizek, 1997). Both constant-current and constant-voltage anemometers depend on the
temperature of the wire to change in order to detect a change in air speed. This dependence
results in a delay in detecting the wind speed, resulting in slow response to changes and small
temperature changes to be undetected (Miyara, 1971). Air temperature changes will cause
outputs that are not related to the velocity in upper altitudes, resulting in some error as well
(Downs and Krizek, 1997). However, keeping the wire temperature high relative to the air
temperature can minimize this error. The third type of hot wire anemometer is the constanttemperature anemometer. In this device, resistance is held constant by altering heater current or
voltage to maintain constant temperature of the wire. The change in current or change in voltage
is then used to indicate the wind speed. In general, this method has a greater sensitivity than both
the constant-current and constant-voltage methods described above (Downs and Krizek, 1997).
3.5.2 Sonic Anemometers
Sonic anemometers are designed to measure wind speed by using
the speed of sound. A photo of one such anemometer is shown in
Figure 6. The device injects sound waves into the atmosphere and
measures the time it takes for the waves to be carried over a fixed
distance. The variation in the travel time of the sound wave is
dependent upon the wind speed. The travel time of the sound
wave may also be obtained by measuring a phase-shift, either by
using two pairs of transducers transmitting sound waves in
opposite directions or a single pair of transducers and switching
their functions (Coppin & Taylor, 1983). Since this method
measures the time of flight, the output is a linear response. This
method measures wind speed along all three axes (u, v, w)
providing good directional characteristics (1983). There are no
moving parts in sonic anemometers, and they can reverse sound
direction around 60 times a second. This allows for the
Figure 6: Photo of sonic anemometer
anemometer to be capable of measuring rapid vibrations in
("200-81000 Ultrasonic anemometer,"
wind, hence, at high wind speeds (Campbell & Unsworth,
n.d.)
1979).
Although very accurate, commercial sonic anemometers are expensive. Campbell and Unsworth
(1979) designed a new sonic anemometer that would be less expensive and have low power
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consumption. Their anemometer consists of a
phase-lock loop integrated circuit as well as a
voltage controlled operator. The operator
automatically adjusts its frequency to maintain
a phase shift of 90 degrees between signals
(1979). Sonic anemometers of this type have
a maximum sensitivity to wind speed when
they are operated at the instruments resonant
frequency. Changes in temperature result in
changes in frequency of the operator shifts.
As the operator deviates from the resonant
frequency, the efficiency decreases, limiting
the range of temperatures where the
instrument can operate effectively. While
operating at the resonant frequency, this
anemometer has a high sensitivity for wind
speed with a maximum resolution of one
centimeter per second (1979).
Figure 7: Sonic anemometer in water test for flow distortion
(Dyer, 1981)
A downside to using a sonic anemometer for measuring vertical wind speed is the structure of
the device. To investigate flow distortion of wind speed measurement, A.C. Dyer conducted an
experiment in a water tank using a die tracer on a sonic anemometer. As shown in Figure 7, the
supporting structure of the sonic anemometer distorted the flow, causing the horizontal flow to
interfere with the vertical flow (Campbell & Unsworth, 1979). When utilizing sonic
anemometers for measuring vertical winds, an error may be introduced into the measurement as
a result of this distortion. The structure disrupts the horizontal component of flow, resulting in
an upward flow that is not a part of the vertical component of the wind speed (1979). They may
also fail when water or ice is present. The speed of sound is a varying function of atmospheric
pressure, temperature, and humidity, and an instrument that uses the speed of sound for
measurement may show error in these parameters (Coppin & Taylor, 1983).
3.5.3 Force and Drag Anemometers
The amount of force or drag caused by wind is directly related to the
speed of the wind. From this relationship, wind speed can be calculated
from a known drag force. Two types of anemometers that use this
method to measure wind speed are propeller and cup anemometers.
Propeller anemometers are a propeller connected to a tachometer
through a shaft. The rotation of the propeller turns a shaft, which is
monitored by the tachometer. The tachometer provides an analog signal
directly proportional to the rotation speed, thus measuring the air
velocity. There are two types of mountings for a propeller anemometer:
on a fixed axis and on a vane. The UVW propeller anemometer is a
fixed array of three propeller anemometers, each on an axis of rotation
oriented on one of the three orthogonal directions (u, v, w) of the wind
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Figure 8: Picture of UVW
anemometer (Campbell &
Unsworth, 1979)
Team Fly Boys
speed (Horst, 1973). A UVW anemometer is pictured in Figure 8 and shows how the propellers
are oriented. Since each propeller is positioned in one direction, the wind speed of each
propeller is proportional to the component of the wind speed along the axis of the propeller. A
vane mounted propeller anemometer orients the propeller to the wind, making the propeller
omnidirectional. This also allows the wind speed vector to be resolved into horizontal
components, giving both wind speed and direction (Wyngaard, 1981). A vane mounted propeller
is shown in Figure 9.
The angle at which the air flow hits the propeller is
important. When a propeller anemometer’s axis is normal to
the wind flow, the anemometer does not give an accurate
result (Hicks, 1972). Corrections need to be made in the
output data of the tachometer for this error of the instrument.
If no corrections are made, then errors may result in up to
four degrees in wind direction and 12% in wind speed
(Surridge, 1982). Sudden increases in wind speed also may
induce errors. The larger the magnitude of fluctuation of
Figure 9: Photo of vane mounted
wind speed, the longer it takes for a propeller anemometer
anemometer (Quashning, n.d.)
to respond. A cup anemometer is a smaller version of a
propeller anemometer consisting of three to six conical cups in place of a propeller. Cup
anemometers are used because they are simple in design, sturdy, and require little maintenance.
Contrary to propeller anemometers, cup anemometers do not need to be aligned into the wind
direction, making them ideal for continuous measurements (Busch & Kristensen, 1976).
However, over speeding may occur with fluctuating winds and induce error in the measurement
of the wind speed. This is due to the fact that cup anemometers respond faster to an increase in
wind speed than to a decrease in wind speed of the same magnitude.
An example of a previous measurement performed using a propeller anemometer is the study
performed by Woods, which was discussed in the filters section of this report. The direct-flow
filter sampler is a device that was designed to collect particles in the air at high altitudes. It
utilizes a high-volume blower to pull air through filter paper at high velocities and a propeller
anemometer as a flow meter to measure the total volume of air sampled (Wood, 1964). The next
section of the report includes the results we expect to obtain from the data measured using one of
the aforementioned methods.
3.6 Expected Results
There are several published studies with information pertaining to our experiment, which provide
an idea of what to expect from our results. The expected average vertical wind speed can be
found by determining the rate of ascent of the high altitude balloon. Our sensor will be attached
to our balloon payload and thus the vertical speed of the payload will equal the vertical wind
speed measured by the sensor. A plot of the flight profile from ACES- 23 is shown in Figure 10.
This figure shows the balloon’s vertical displacement versus time. By differentiating the
displacement with respect to time, the velocity is obtained. The instantaneous velocity is
represented graphically by the slope of the tangent line at any point on Figure 10. The vertical
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Team Fly Boys
ascent velocity has approximately two constant values shown by the two unique slopes shown in
the ascending portion of Figure 10.
Figure 10: Flight profile for ACES-23
3.6.1 Balloon Ascent
A theoretical approximation of the ascent rate can be calculated by assuming the balloon ascent
rate is the terminal velocity (Fox et al., 2009). Terminal velocity is reached when the upward
and downward forces acting on a falling or rising object are equal. By the neglecting the vertical
wind forces, the forces acting on a high altitude balloon are the buoyant force, FB, drag force, FD,
and the force of gravity, FG. For terminal velocity to be reached, Equation 1 must be satisfied.
𝐹! = 𝐹! + 𝐹!
Equation 1
Where, assuming a spherical balloon profile, the values of 𝐹! , 𝐹! , and 𝐹! are given in Equations
5, 6, and 7 (Fox et al., 2009).
!
𝐹! = ! 𝜋𝑅! 𝜌!"! 𝑔
Equation 2
Where 𝑅 is the radius of the balloon, 𝜌!"# is the density of the surrounding air, and 𝑔 is the
acceleration due to gravity.
Equation 3
Where 𝑅 is the radius of the balloon, 𝜌!!"#$% is the density of the helium in the balloon, 𝑔 is the
acceleration due to gravity and 𝑚!"#$ is the total mass of the balloon material and payload.
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Team Fly Boys
!
𝐹! = ! 𝜌!"# 𝑉 ! 𝐶! 𝐴
Equation 4
Where 𝜌!"# is the density of the surrounding air, V is the velocity of the balloon, 𝐶! is the
coefficient of drag, and 𝐴 is the surface area of the balloon. Substituting Equations 5, 6, and 7
into Equation 4 and solving for V yields an approximate expression, Equation 5, for the ascent
speed of the balloon.
Equation 5
This theoretical approximation for the rate of ascent for the balloon is dependent upon several
values that vary with increasing the altitude. In order to model the velocity as a function of
altitude, our group must know how the variables in Equation 5 vary with altitude. In Figure 11
Team Fly Boys has constructed a graph that will estimate the balloon velocity as a function of
altitude. This balloon velocity will be close but not exact to the air velocity that will be seen in
vertical ascent.
Balloon Velocity 14 Velocity (m/s) 12 10 8 6 Balloon Velocity 4 0 0 304.8 609.6 914.4 1219.2 1524 2133.6 2743.2 3657.6 5181.6 6705.6 8229.6 9753.6 11277.6 12801.6 14325.6 16764 19812 25908 28956 2 Al:tude (Meters) Figure 11: Balloon velocity as a function of altitude.
3.6.2 Density, Pressure and Humidity versus Altitude
With a theoretical balloon ascent we can now incorporate different variables to ensure accurate
calculations. In order to model the velocity as a function of altitude, Team Fly Boys must know
the density of the air. Air is composed of 78.1% Nitrogen, 20.95% Oxygen, and .95% of other
components (Sonntag, Borgnakke, & Van, 2003). These base values are given at a low altitude
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Team Fly Boys
and vary with altitude; this density will also vary with altitude. Density of air is the mass per unit
volume of the earth’s atmosphere (Equation 6).
Equation 6
The composition of air is not solely responsible for the changes of air’s density. The ideal gas
law (Equation 7) helps to further evaluate the variables that affect a change in air density with a
change in altitude.
Equation 7
In which P is the absolute pressure, V is unit volume, m is the mass of gas, R is the specific gas
constant, and T is the temperature of the gas (Sonntag et al., 2003). With the arrangement of
these equations an equation relating density with pressure and temperature is derived (Equation
8).
Equation 8
This equation is used for the dry air of the standard atmospheric conditions. However, for realworld situations it is necessary to understand how the moisture in the air affects the density. The
density of a mixture of dry air molecules and water vapor molecules is taken into consideration
in Equation 9 (Shelquist, n.d.).
Equation 9
In which Pd is the pressure of the dry air, PV is the pressure of water vapor, P is total air pressure,
and Rd is the gas constant for dry air. For this equation to be useful, the dry air and water vapor
pressures must be known. These can be measured through the use of sensors and data can be
collected and used to determine relative density.
In order to calculate water vapor pressure, we must first calculate the saturation vapor pressure
(Shelquist, n.d.). To do this we use Equation 10.
Equation 10
Where Es is the saturation vapor pressure, Tc is the temperature in Celsius, C0=6.1078, C1=7.5,
and C2 =237.3. Being able to calculate the saturation vapor pressure one can now determine the
vapor pressure. In Calculating the vapor pressure it is often more accurate the use the dew point
temperature instead of the relative humidity, which is strongly affected by the ambient
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Team Fly Boys
temperature. The dew point temperature is much more stable and close to constant for a given air
mass. Relating the dew point as the measurement of humidity allows for a more accurate and
stable result (Shelquist, n.d.).
To determine the actual vapor pressure using the dew point, one must first know the temperature.
Using that temperature in Equation 10 produces the saturation vapor pressure (Es). At the dew
point the pressure of the water vapor equals the saturation vapor pressure. Once the pressure of
water vapor is known one can use Equation 11 to determine the dry air pressure. Because the
total air pressure is known, the derivation calculations just become algebraic.
Equation 11
Once the variables in Equation 9 are known, the derivation of density is also known. With an
accurate measurement of density one can compare the ideal behavior of density at an ideal
temperature and pressure with the gathered data. Figure 1 shows the normal density of air versus
altitude behavior.
3.6.3 Mass Flow Rate of Air
From our experimental velocity data, we will calculate the two unique constant velocities to use
in further calculations of mass flow rate of air. The mass flow of a fluid is related to the fluid’s
density, velocity, and cross sectional area through which it is flowing by Equation 12 (Fox et al.,
2009).
𝑚 = 𝐷𝑉𝐴
Equation 12
Where 𝑚 is the mass flow rate, 𝐷 is the density of the fluid, 𝑉 is the velocity of the fluid, and 𝐴
is the cross sectional area through which the flow is moving. Since we do not know the area
through which the fluid is flowing, we will find the mass flow rate per unit area, which is shown
in Equation 13.
𝑚
= 𝑚! = 𝑉𝐷
𝐴
Equation 13
Where 𝑚! is the mass flow rate per unit area, 𝑉 is the velocity of the fluid, and 𝐷 is the density
of the fluid.
Our calculated value of 𝑚! can then be used to find the total mass flow rate through a known
area by multiplying 𝑚! by the cross sectional area of interest. Using a constant vertical velocity
and a decreasing density model in Equation 12, we anticipate our results to show a continuous
decrease in the mass flow of air as the balloon acends higher into the atmosphere. Figure 12 is
the mean mass air flow that was calculated from these equations and from know data given to us
from the LaACES staff.
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Mean mass air flow 0.12 Velocity (m/s) 0.1 0.08 0.06 0.04 Mean mass air flow 0 0 304.8 609.6 914.4 1219.2 1524 2133.6 2743.2 3657.6 5181.6 6705.6 8229.6 9753.6 11277.6 12801.6 14325.6 16764 19812 25908 28956 0.02 Al:tude (Meters) Figure 12: Mean mass air flow versus altitude.
4.0 Payload Design
4.1 Principle of Operation
Team Fly Boys’ payload will determine the mass flow rate of air as a function of altitude. To
achieve this goal the payload will incorperate various sensors to measure air temperature,
pressure, velocity and relative humidity. With the use of the BalloonSat’s Basic Stamp
Microcontroller and Analog to Digital Converter (ADC), analog data from the sensors will be
gathered at pre-determined times kept by the Real Time Clock (RTC), converted to digital data,
and stored, along with the corresponding time, to the Electrically Erasable Programmable ReadOnly Memory (EEPROM). After flight and payload retrieval, data stored on the EEPROM can
be interfaced with external software via the RS-232 Serial Port located on the BalloonSat. Once
data is compiled onto the external software, it is then arranged in a spreadsheet in which the rows
correspond to the altitude where the time of the data point matches the time of the altitude. The
LaACES beacon payload will measure the altitude and store that information with its
corresponding time. The beacon time and altitude will be used to compare data point times to
determine the altitude where data points were taken. After all data is collected and arranged on
the spreadsheet, formulas from the Technical Background and Requirements will be used to
determine the mass flow rate of air.
4.2 System Design
The main component for the payload is the BalloonSat, which is a custom design prototyping
board. The BalloonSat board contains the Basic Stamp Microprocessor, the RTC, the EEPROM
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Memory Storage, the RS-232 Serial Port, the four channel ADC, the four Light Emitting Diode
(LED) indicators, voltage regulator, and a prototyping area.
EEPROM
+12 V
RS-232 Seriel Port
Microcontroller
ADC
Real Time Clock
Figure 13: BalloonSat system diagram
4.2.1 Functional Groups
Central processing unit (CPU): The BS2P24 Basic Stamp Microprocessor is a programmable
microcontroller that will execute the commands of the software design and control all data
reading and storing. The Basic Stamp editor software from parallax will be used to write
programs with the language PBASIC. The Basic Stamp on the BalloonSat features four free
digital Input/Output (I/O) pins.
Real time clock (RTC): The DS1302 RTC is a time keeping integrated circuit that interconnects
with the CPU via synchronous serial interface. The RTC can registers the year, month, day, hour,
minutes, seconds, but for Team Fly Boys requirements only the time stamp HH/MM/SS is
needed. The RTC includes on-chip 31 x 8 bit RAM for scratchpad data storage. The RTC will be
calibrated before take-off and will be set with beacon on the LaACES flight vehicle. Data entries
will be put into context with the time-stamp so the altitude of data collection is known.
Memory (EEPROM): The 24LC64 series CMOS Serial EEPROM is an integrated circuit that
interconnects with the CPU via synchronous serial interface. The 24LC64 provided is a 64K chip
organized as 8 blocks of 1K x 8-bits. The EEPROM will store all data entries collected during
flight and store a time-stamp with each entry.
Connection to computer: The RS-232 Serial Port connection from the BalloonSat allows the
computer, loaded with the Basic Stamp editor software, to write to the CPU. The Serial Port also
allows flight data to be loaded onto external software and analyzed after flight completion.
Analog to digital converters (ADC): The BalloonSat includes a 4 channel ADC, ADC0834
MICROWIRE synchronous serial interface, with selectable 2.50 or 3.00 VDC reference. The
ADC will convert analog sensor data to digital data to be processed by the CPU and stored in the
EEPROM. The ADC will convert measurements to a binary number in a range of 0 to 255.
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LED indicators: Team Fly Boys will use the LED’s as visual components that will help denote
whether a process has or will commence.
Power: The BalloonSat requires a voltage supply range of 9-15VDC, which is then regulated by
a precision voltage reference AD780. With the use of a voltage reference the components of the
BalloonSat are supplied with 5V. The power source will be a DC battery that will supply power
to the sensor boards as well as the BalloonSat board.
Prototyping Area: The BalloonSat board features a prototyping area that will be used by Team
Fly Boys to interface the humidity integrated circuit as well as supply power to the circuit.
4.2.2 Group Interfaces
Table 1: Group interfaces.
Interface Serial Data Analog Data Digital Data Timing Information Power Mechanical Description Data sent from the serial port.
Data sent from the sensors.
Data from the ADC that is stored.
Information stored with measurements
DC power source.
Structural integrity between payload and
components.
Quality control of parts and building supplies
to handle low temperatures.
Thermal 4.2.3 Traceability
Table 2: Requirements
Objectives Accurately measure the mass flow rate of air up to 32,480 meters. Design and construct a payload that can measure PDR vFINAL
Requirements Design circuitry for sensors to
measure the pressure,
temperature, humidity, and air
velocity.
Incorporate sensors that can
detect small changes in the
environment and provide
19
Functional Components The accuracy of the pressure,
temperature, and humidity
sensor shall be within 3%.
The accuracy of the air
velocity sensor shall be within
5%.
All sensors will be powered
during ascent and controlled
by the CPU
The accuracy of the pressure,
temperature, and humidity
sensor shall be within 3%.
Team Fly Boys
measurements accurately.
data accurately, survive flight conditions and impact, and remain within weight budget. Payload sensors and circuitry
must be able to operate within
a temperature range of -70˚C
to 25˚C or payload housing
must insulate interior enough
to stay within manufacturer’s
specified operational
temperature.
Payload must be able to attach
to flight strings.
The accuracy of the air
velocity sensor shall be within
5%.
The pressure sensor has an
operating temperature down to
-40˚C. Payload shall be
insulated such that interior
does not go below -20˚C.
The temperature sensor has an
operating temperature down to
-65˚C.
The humidity sensor has an
operating temperature down to
-40˚C. Payload shall be
insulated such that interior
does not go below -20˚C.
The air velocity sensors have
an operating temperature
down to -40˚C. This sensor
will be located on the exterior
of payload; therefor sensor
housing will need to be heated
by at least 30˚C for
compensation.
Payload exterior will be
designed to withstand the
impact speed and will be
shock tested with force tests to
simulate the impact.
Holes for flight strings must
be 17 cm apart.
Present measurements Data storage must not and calculations of exceed 64 kilobits (8 findings from ground level kilobytes). to 32,480 meters. Data must be able to be
downloaded to external
software.
Design circuitry for sensors to
Gather data on air mass flow from ground level up measure the pressure,
temperature, humidity, and air
to 32,480 meters velocity. Design software to
control sensors.
The CPU will gather and store data onto EEPROM. Data storage will not exceed
4.2 kilobytes
RS2 Serial port will be used to
connect BalloonSat to
computer for data download.
Air pressure, temperature, and
humidity will be measured
every 30 seconds during
balloon ascent and stored with
time-stamp.
Payload must withstand an
impact of 6.1 m/s.
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Air velocity sensors will send
and receive an ultrasonic pulse
every second during ascent.
After 30 second increments,
the maximum, minimum, and
average velocity will be
determined by CPU and then
stored along with time-stamp.
4.3 Electrical Design
4.3.1 Sensors
Temperature Sensor
The temperature sensor shall be the 1N457 silicon p-n junction diode. A p-n diode consists of ptype and n-type semiconductors that are joined together. This construction allows current to flow
easily in only one direction. As current flows through the diode, the voltage decreases linearly at
the rate of about 0.0022V for each degree increase in temperature. The magnitude of voltage
change depends on the current through the diode and the temperature at the junction of p-type
and n-type semiconductors. The voltage will range from 240 to 300 millivolts (mV) during
flight. This change in voltage versus changes in temperature makes the diode a useful and
inexpensive temperature sensor. The temperature range of the diode is -65 C to 200 C.
To ensure accurate calibration Team Fly Boys must take a series of careful measurements using
both the prototype temperature circuit as well as a know-accurate reference instrument. To
calibrate the temperature measuring circuit Team Fly Boys will utilize the WBEE sensor test set
provided by the LaACES staff. The first step in calibration is to record the ambient temperature
as value TA. Next plug the temperature sensor into the sensor interface board and use a digital
multimeter to measure the voltage from the circuit at the same ambient temperature record, at TA,
value as VA. With TA and VA known Equation 14 can be solved for Vo.
Equation 14
Equation 14 is also needed to predict the diode voltage at the highest expected temperature (25C)
and the lowest (-70C) expected temperature. Knowing the range of temperature, the WBEE
sensor test set, in conjunction with calibration software, can be used to set the TEMP HIGH until
the ADC count is 5 and the TEMP LOW until the ADC count is 250. Once calibration is
completed the ADC value should be consistent with the ambient room temperature TA.
Pressure Sensor
The pressure sensor shall be the ICS1230. This device employs a piezoresistive strain gauge in a
Wheatstone bridge configuration. Pressure changes applied to the internal strain gauge produce
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Team Fly Boys
resistance changes that result in a differential output voltage of 0-100 millivolts. The device’s
operating temperature is -40 C to +125 C. Although this temperature is out of the desired range
specified in the requirements, the pressure sensor will be housed inside the payload and thus
insulated. The device has an accuracy of 0.5% if and only if the temperature doesn’t drop below
-20 C. A variety of pressure ranges exist for this product. The range that Team Fly Boys will
need is the 0 to 15 pounds per square inch (0 to 103 kilopascals (kP)).
To calibrate the pressure sensor, Team Fly Boys will analyze the data given from LaACES staff
to set a binary number for the highest pressure our payload should encounter. Knowing the
analog to digital converter (ADC) will convert measurements to a binary number in a range of 0
to 255, we will set the binary number 250 to the highest pressure. Using the WBEE sensor test
set interfaced with the pressure sensor, adjustment to the GAIN trimmer on the sensor interface
board, in conjunction with the calibration software, until the count is 250.
Humidity Sensor
The humidity sensor shall be the HIH-4031. This sensor is a covered condensation-resistant
integrated circuit. This circuit can measure relative humidity (RH) from 0% to 5% with ±3.5%
accuracy. The operating temperature is -40 C to +85 C. This does not meet our requirements but
will be housed inside the payload with a probe located outside the payload. This integrated
circuit has three pins that need to be connected in order to function, a 5V power supply, a 0V
ground, and and
a Vo that
will be connected
to the ADC.
Construction
Operation
Principles
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ales representatives or product engineers before ordering.
This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
2
In order to calibrate the relative humidity sensor, the manufacture measures the characteristics of
each sensor and supplies that documentation with the sensor. Team Fly Boys will use data the
data from the manufacture to set up the WBEE sensor test set to simulate the humidity sensor.
2. Enclosed
type
The gain
willUltrasonic
be adjusted to Sensor
the manufactures relative humidity measurements.
Ultrasonic sensors
for outdoors use are sealed to protect
Air Velocity
them from dew, rain and dust.
Piezoelectric ceramics
arethat
attached
toused
the top
inside ofthe air
The sensor
shall be
to measure
the metal case.velocity
The entrance
of the case isascovered
is the MA40S4R/S
seen inwith
Figure 14.
resin. (See Fig.This
4.) sensor is a transducer that is surrounded in a
Metal Case
Piezoelectric
Ceramic
metal case to protect against weather. When a
voltage is supplied or received, the piezoelectric
ceramics will induce mechanical distortion,
which is generated according to the voltage and
frequency. For transmitting circuits mechanical
distortion creates an ultrasonic wave and for
receiving circuits mechanical distortion from the
ultrasonic wave produces an electric charge. By
applying this principle, the transducers can either
receive or transmit an ultrasonic wave.
Lead Wire
Base
Shielding
Material
Cable
Fig. 4 Construction of Enclosed Type Ultrasonic Sensor
Figure 14: MA40S4R/S
3. High Frequency Ultrasonic Sensors
For use in industrial
robots, accuracy as precise as 1mm
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and acute radiation are required. By flexure vibration
of the conventional vibrator, no practical characteristics
22
Team Fly Boys
Ultrasonic Radiation Surface
Acoustic Matching
Layer
S15E.p
08.10.
The use of two vertically aligned sensors shall be used in the
payload to detect changes in air velocity, as seen in Figure 15.
To detect a change in air velocity, one sensor will be an
ultrasonic pulse transmitter and the other will be ultrasonic
pulse receiver. The exact characteristics of these sensors are
unknown until further testing but the main characteristics of
the sensor are known. The operating temperature range is -40
C to +85 C. Although the temperature range does not meet the
0
0
requirements of our mission, we plan to heat the housing of the
sensor to stay within the manufacturer’s suggested temperature
range.
Figure 15: Two vertically aligned
ultrasonic sensors.
The theory behind the sonic anemometer used in Team Fly Boy’s payload is that a constant
ultrasonic pulse of 40kHz will be transmitted from the south transmitting transducer to the north
receiving transducer. The mass flow rate of air will pass downward through the open-air tunnel
and produce a hesitance to the amplitude of the ultrasonic wave. This hesitance will be measured
by the decrease or increase in electric charge on the receiving transducer.
Team Fly Boys can calibrate the circuit using the WBEE sensor test set interfaced with the air
velocity circuit to set the ADC counts. When there is no resistance the circuit should produce the
maximum voltage, so the GAIN trimmer on the sensor interface board is adjusted until the
calibration software’s count is 125. A wind tunnel can then be made measure the exact velocity
of air and the value of the voltage from the receiving circuit. This data can be compiled into a
graph and with the use of data analysis determine a function to calculate the velocity with known
voltage.
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Team Fly Boys
4.3.2 Sensor Interfacing
Temperature Sensor
The p-n junction forward voltage will vary over a range of 240 to 300 millivolts (mV) due to
flight temperatures. Due to this small change, a voltage gain will need to be incorporated into the
design.
+12 V
Constant Current
+ 12 V
Temperature
Temperature
Sensor
Signal Conditioning
ADC 2
Figure 16: Temperature sensor system diagram.
Pressure Sensor
This device results in a differential output voltage of 0-100 millivolts. This signal must be
amplified in order to meet ADC requirements.
+12 V
Constant Current
+ 12 V
Pressure
Pressure Sensor
Signal Conditioning
ADC 3
Figure 17: Pressure sensor system diagram.
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Team Fly Boys
Humidity Sensor
The humidity sensor is an all in one sensor that only needs five volts to operate. No additional
amplifiers are needed.
+5 V
Humidity Integrated
Circuit
Humidity
ADC 4
Figure 18: Humidity integrated circuit system diagram.
Air Velocity Sensor
The Air velocity sensor measures the voltage of the ultrasonic wave that is transmitted. The
magnitude of the decrease in voltage determines the velocity of the air in the opposing direction.
I/O
ADC 1
+12 V
Oscillating
Circuit
Signal Conditioning
Ultrasonic Sensor
(Transmitter)
Ultrasonic Sensor
(Reciever)
+12 V
Medium
Figure 19: Ultrasonic sensor system diagram.
4.3.3 Control Electronics
The main electrical components will be housed in the payload as seen in Figure 21. The RS-232
serial port will interact with the microcontroller on the BalloonSat board. With this
communication the data stored onto the EEPROM can be collected and transferred to external
software. From the equations in Technical Background and Requirements as well as Electrical
Design section the data can be calculated into useable data and graphs.
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Team Fly Boys
Payload
Mechanical Support
System
Thermal Support
System
BalloonSat Board
Ch 4
Pressure
Sensor
Humidity
Sensor
Data Archive
(EEPROM)
ADC
RTC
Ch 3
Ch 2
Temperature
Sensor
Serial
Air Velocity
Sensor
CPU
Microprocessor
Ch 1
Power
Ground Control
Data Processing
and Analysis
Figure 20: Payload system diagram.
4.3.4 Power Supply
The BalloonSat, temperature sensor, pressure sensor, and air velocity sensor requires 10V to 12V
to operate properly. With the use of 8 AAA lithium batteries, 12V can be sufficiently supplied to
these circuits. For the humidity integrated circuit the voltage needs to drop to a range of 4V to
5.5V. The BalloonSat features a voltage regulator that supplies the range needed for the humidity
circuit (Figure 21).
12V Lithium Battery
Temperature
Sensor
Pressure Sensor
V out (10-12)
BalloonSat
V out (4-5.5)
Air Velocity Sensor
Humidity Integrated
Circuit
Figure 21: Power system diagram.
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Team Fly Boys
The power source for prototyping will be the bench power supply. This power supply should
have a range from 0V to 15V perfect for simulating the 12V battery that will be used for flight.
4.3.5 Power Budget
Table 3: Power budget.
Component
BalloonSat
Temperature Sensor
Pressure Sensor
Humidity Integrated Circuit
Air Velocity Sensor
Total
Required Amperes
60 mA
2 mA
2 mA
0.2 mA
15 mA
94.2 mA
The total pre-flight and flight time is estimated to be four hours. To achieve data collection and
storage throughout the entire flight a power budget with every component in the payload taken
into account. The required amperes for Team Fly Boys payload is 94.2mA. The use of AAA
batteries rated at 1100mA/h will ensure that the four hour operation requirement is
accomplished.
PRODUCT DATASHEET
US/CAN
With a load of approximately 100mA discharge time will decrease with faster1-800-383-7323
with
a decrease
in
www.energizer.com
temperature as seen in Figure 22.
ENERGIZER L92
AAA
Typical Discharge Curve Characteristics
Constant Current Discharge at 21°C (low and high drains)
Low Drain Performance
High Drain Performance
50mA Continuous (21°C)
AAA Lithium
1.4
1.2
1.0
0.8
0
6
12
18
AAA Lithium
1.6
24
AAA Alkaline
1.4
Voltage (CCV)
Voltage (CCV)
1.6
600mA Continuous (21°C)
AAA Alkaline
1.2
1.0
0.8
30
0.0
Service (hours)
0.5
1.0
1.5
2.0
Service (hours)
Figure 22: Battery discharge curve.
Constant Power Performance
Constant Current Performance
Typical Characteristics to 1.0 Volts (21°C)
Typical Characteristics to 1.0 Volts (21°C)
AAA Lithium
Service, Hours
Service, Hours
AAA Lithium
1000
1000
100
10
100
10
1
1
10
100
10
1000
Application Tests (21°C)
oltage (CCV)
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1.6
1.4
1.2
1.0
REMOTE
24 ohm 15 sec/min 8 hrs/day
REMOTE
AUDIO
1000
Industry Standard Tests (21°C)
27
oltage (CCV)
ELECTRONIC GAME / DIGITAL AUDIO
100 mA 1 hr/day
100
Discharge (mA)
Discharge (mW)
1.6
1.4
1.2
1.0
DSC 1CAMERA (DSC)
DIGITAL STILL
.9/.4K mW 2/28 sec 10x per hour
Team Fly Boys
4.4 Software Design
4.4.1 Data Format & Storage
The EEPROM on the BalloonSat provided to Team Fly Boys by LaACES has 8 kilobytes of
available space for data storage. An Analog to Digital Converter (ADC) is also available on the
BalloonSat and converts analog data into an 8 bit digital signal. The pressure sensor, temperature
diode, and relative humidity circuit require a byte each of storage space and shall measure its
environment every 20 seconds once the payload flight software begins. The air velocity sensors
will have a subroutine for collecting air velocity during a 20 second increment. During this
interval, the ultrasonic sensor set up to receive frequencies will collect data in pulses every
second. These data points will be temporarily stored onto the Basic Stamp Microcontroller RAM
along with corresponding time. The Basic Stamp Microcontroller has 128 bytes of scratch pad
RAM and the velocity data and associated time stamp will use 80 bytes of memory during the 20
second time interval. After twenty seconds, the highest, lowest, and average wind velocity data
during this time interval will be computed by the microcontroller and stored onto the EEPROM.
All data points taken after 20 seconds will have a time stamp stored in the format HH:MM:SS,
and will require three bytes of storage. For an estimated ascent rate of 304.8 meters per minute,
6000 seconds shall be a sufficient amount of time for the sounding balloon to reach 30,480
meters. For 8 kilobytes of available data storage, roughly 533 data intervals can be taken. Taking
data every 20 seconds will result in a data acquisition time of almost three hours. This timeframe
should be sufficiently long enough for the balloon to make a complete ascent to 30,480 meters
and also leave enough time for any launch delays.
4.4.2 Flight Software
The flight software for the payload will be written and downloaded onto the BalloonSat using the
Basic Stamp programming software. A flow chart of the flight software can be found in Figure
23. Once the payload is powered up, the internal flight software will initialize sensors, the Basic
Stamp Microcontroller, and Real Time Clock. The microcontroller will then determine if the
EEPROM used memory is equal to 7995 bytes. If the memory is not equal to 7995 bytes, a 20
second loop will begin for data acquisition. At the end of the event loop the microprocessor will
acquire data from the temperature, pressure, and relative humidity sensor to be stored on the
EEPROM after analog to digital conversion. In addition to temperature, pressure, and relative
humidity data that is stored at the end of the event loop, three data values will be stored to the
EEPROM from the air velocity sensors. These values are a result of a subroutine that takes place
during the 20 second time interval. The flow chart for this subroutine can be found in Figure
24.During this subroutine, air velocity data will be acquired every second during the event loop.
The ultrasonic sensor dedicated to transmitting will transmit a constant frequency aimed towards
the receiving dedicated ultrasonic sensor, which will be controlled by the Basic Stamp
Microcontroller to receive data every second. Data received from the receiving dedicated
ultrasonic sensor will be temporarily stored onto the Basic Stamp Microcontroller scratch pad
RAM along with a time stamp from the RTC. At the end of the 20 second subroutine loop, the
maximum and minimum velocity readings during the event loop will be stored onto the
EEPROM with its corresponding time stamp. In addition, the microcontroller will compute the
average air velocity during the event loop and store value onto the EEPROM. Velocity data
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Team Fly Boys
from subroutine will be removed from Basic Stamp Microcontroller scratch pad RAM. Data for
the temperature, pressure, relative humidity, and average air velocity will have a common time
stamp associated with the values. After data is stored to the EEPROM, the microcontroller will
determine if the EEPROM’s used memory is equal to 7995 bytes. If the used memory is not
equal to 7995 bytes, the event loop will begin again. If the used memory is equal to 7995 bytes,
the flight program will end. After the payload has landed and is retrieved, it will be powered up
(if necessary) and connected to a computer so that collected data can be downloaded and
analyzed.
Start Flight Program
Set Variables, Initialize
Hardware
Set Real Time Clock
YES
Does Stored
Memory on
EEPROM =
7995 Bytes?
Store Final Data
End Flight
Program
NO
Request Data from
Pressure Sensor
Request Data from
Temperature
Sensor
Pause 20 seconds
Request Data from
Humidity Sensor
Request Data from Air
Velocity Sensors
Request Data from
RTC
Store Data to
EEPROM
Figure 23: Flight software flow chart.
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Request Data from Air Velocity Sensors - Subroutine
Transmitting Ultrasonic
Sensor Transmits Constant
40 kHz Frequency
Note Time T1 from RTC
Request Data from
Receiving Ultrasonic
Sensor
Request Data from RTC
Pause 1 Second
Send Data to BASIC Stamp
Microcontroller RAM
NO
Does T2 = T1 +
20 seconds?
YES
Request Highest Velocity
During 20 Second Interval
and Associated Time from
BASIC Stamp
Microcontroller
Request Lowest Velocity
During 20 Second Interval
and Associated Time from
BASIC Stamp
Microcontroller
Request Average Velocity
During 20 Second Interval
from BASIC Stamp
Microcontroller
Figure 24: Air velocity sensor flow chart
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Team Fly Boys
4.5 Thermal Design
The payload will encounter a decrease in pressure from 101 to 10 kilopascals, temperature
ranging from -70 C to 35 C, and relative humidity from 0% to 100%. Because of these harsh
environment conditions certain precautions must be taken to ensure mission success.
The shell of the payload will be constructed of polystyrene, a composite foam board that has
been used in tested in many LaACES flights. This material is also used to insulate the payload’s
components from low temperatures in order to ensure that electrical systems remain in working
order. The shell will be glued together with any of the following: Gorilla Glue ®, Elmer‘s ®
High- Performance Glue, Elmer‘s ® Carpenter‘s Wood Glue, or a glue similar to hot glue. All
glues have been used in previous payloads and are rated for low temperatures.
Components for the payload have been selected to work properly in low temperatures. If a
component is not capable of withstanding the low temperatures of flight, heating elements will
be incorporated to ensure the device will work properly. Some sensors will be inside the payload
with a probe outside that can operate in low temperatures.
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Team Fly Boys
4.6 Mechanical Design
4.6.1 External Structure
The payload housing will consist of two separate rectangular tubes. The reasoning for this
construction design is to keep the electrical compartment separate from the open-air tunnel in
order to reduce condensation exposed to the circuitry.
The electrical compartment of the payload will be a rectangular cube that has the dimensions 18
cm long, 13 cm wide, and 18 cm high. These dimensions have been chosen to give enough room
for the BalloonSat board, the humidity integrated circuit, and the three sensor interface boards.
The sides will be constructed with 2cm polystyrene and glued together. There will be a
removable top that will allow access to the components inside. Temperature, pressure, and
humidity sensors will be wired outside the payload.
The open-air tunnel of the payload will be a rectangular cube that has the dimensions 10cm long,
7cm wide, and 22cm high. These dimensions have been chosen because the ultrasonic sensors
need to be spaced face to face by 20cm. The ultrasonic sensors will be mounted inside the tube
vertically with the transmitter at the bottom and the receiver at the top. At the top and bottom of
open-air tunnel, noise deadening foam will be glued around the perimeter of the square hole to
eliminate any whistles that horizontal wind may create. The reason for this is to reduce any
frequencies caused by the whistle that may affect the readings of our air velocity sensors.
Figure 26: Section of payload
Figure 25: ¾ Veiw of payload
4.6.2 Internal Structure
On the inside of the payload the bottom will house the battery. A battery compartment will be
surrounded by extra insulation that will help the battery store the thermal energy loss and keep
the battery warmer than its surroundings. A top for the battery compartment will also be
constructed to separate the battery box from the electronic box. The electronic boards will be
mounted vertically above the battery box in the payload via a wood board that will fit into
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vertical slots on the payload so that the electrical boards can be removed easily. The electrical
boards will then be screwed onto the wood board on either side. The electrical wires for the
external sensors will be connected to the board via color-coded connectors.
4.6.3 Weight Budget
Table 3: Weight budget.
Components
Payload Structure
Temperature board
Pressure board
Humidity circuit
Ultrasonic Anemometer
BalloonSat
Total Weight
Weight Approximation
150g
75g
75g
5g
100g
80g
485g
The total weight budget comes out to be 485 grams (g), which is under the 500g requirement.
This approximation includes: wires, connectors, and sensors. Because the payload structure is
large the majority of the weight will come from its design.
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Team Fly Boys
5.0 Payload Development Plan
5.1 Electrical Design Development
In order to determine circuit schematics for the CDR, Team Fly Boys must finalize the power
budget and all choices of sensors. To do this each sensor will be tested and calibrated to
determine actual accuracy and measurement capabilities, as well as undergo cold and pressure
tests. From this prototyping we can further determine current and voltage supplies. Using the
system level diagrams from the PDR we can determine the circuits by knowing the desired
output and the voltage supplied. Further research will be necessary to determine various
components
5.2 Software Design Development
The details of the software design shall follow the software flowchart in the PDR. This flowchart
gives the necessary information to successfully write the outline of the program. As the program
is written it will be tested to make sure the newly added code will function properly. This data
retrieved from the program will then be compared to determine accuracy.
5.3 Mechanical Design Development
For the mechanical design Team Fly Boys will follow the construction outline provided in the
PDR this includes dimension, materials, and sensors. The decision of where to place each sensor
and circuit is unknown but will be determined before the CDR. Mechanical engineering
drawings will completed in detail showing the complete placement of circuits and sensors.
5.4 Mission Development
Circuit prototyping will be utilized as well as thermal, shock, and vacuum testing to ensure
mission success. A calibration process will be needed along with sensors testing for accuracy to
determine measurements within a certain range. The use of external software such as excels and
PBASIC will be used to collect data and calculate such data into corresponding graphs.
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Team Fly Boys
8.0 Project Management
8.1 Organization and Responsibilities
David Branch
• Team Lead – Contact point for LaACES staff and management of project goals
• Software Design Lead – Design and write software for payload hardware
• Report Editing Lead – Quality control of documentation.
Jared Pellegrin
• Payload Design Lead – Thermal and structural design and construction of payload housing.
• Hardware Design Lead – Design and construct working circuitry for sensor readings.
Due to limited staff, the members of Team Fly Boys will work simultaneously on different tasks
throughout the research, design, and construction of the payload in order to reach time sensitive
goals.
Team Fly Boys contact information:
David Branch
(318) 344-8580
dbb1231@lsu.edu
Jared Pellegrin
(985) 852-0651
pellegrinjared@yahoo.com
8.2 Configuration Management Plan
•
Because decisions cannot be determined by majority vote, the primary system designer
will determine final decisions. If issues are deemed detrimental to the success to the
payload, Team Fly Boys will seek advice from an advisor.
•
Meetings will take place every Monday and Wednesday between seven and eight Post
meridiem.
•
Additional meetings may be required in order to accomplish team goals. No less than
four hours’ notice must be given to team for any previously unscheduled meeting.
•
Meetings will take place in the LaACES lab unless otherwise specified. Meetings will
begin and end promptly.
•
Any unresolved issues at the end of a meeting will be documented and discussed at the
beginning of the next meeting.
•
If any member cannot attend a meeting or believes he will be late, he must give prior
notice of no less than three hours.
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Team Fly Boys
•
A team notebook will be used to record team notes, general ideas, and meeting agendas
and will remain in LaACES lab at all times.
•
All data sheets will be stored in team binder and will remain in LaACES lab at all times.
•
All calculations will be made using the International System of Units.
•
Electronic data will be shared via the QNAP Web File Manager provided by LaACES.
•
Electronic data files will also be kept on LaACES computers in organized folders and
personal USB jump drives for backup purposes and at-home access.
•
When documentation and software versions are updated, a maximum of four versions
must be saved at all times. For example: Versions 1.0, 1.1, 1.2, and 1.3 have been created
during the drafting process.
8.3 Interface Control
Upon the first meeting, Team Fly Boys will set short and long term goals within a Work
Breakdown Schedule that must be met on time. Short-term goals will change upon completed
milestones throughout the semester in order to micromanage the project. Tasks will be assigned
by the Team Lead during scheduled meeting times; however subtasks may be assigned via any
form of communication at any time. All reports are to be completed five days before the hard
deadline and submitted to Jennifer Hay for review. All presentation slides are to be completed
three days before the hard deadline and submitted to Jennifer Hay for review. Each member is to
be accountable for his obligations throughout the semester. This includes, but is not limited to
school and the LaACES program.
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Team Fly Boys
9.0 Master Schedule
9.1 Work Breakdown Structure (WBS)
Figure 27: Work breakdown schedule.
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Team Fly Boys
9.2 Timeline and Milestones
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Figure 28: Gant chart
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Team Fly Boys
11.0 Risk Management and Contingency
Table 4: Risk Detection.
System
Electrical
1
2
3
4
5
Software
6
7
8
Mechanical
9
10
11
Other
12
13
14
15
Risk
Likelihood
Impact
Detection
Difficulty
When
Condensation in
electrical area
Components failure
Sensor failure
Power failure
Loose solder connection
2
4
1
During Flight
1
1
3
1
5
5
5
5
2
3
3
2
Before Flight
Before Flight
During Flight
Before Flight
Forgot to load correct
program
Didn’t factor in enough
time for data retrieval
and ground calibrations
Didn’t test new
programs modifications
1
5
2
Before Flight
1
3
2
Before Flight
1
3
1
Before Flight
Loss of Payload
Payload breaks during
testing
Lid is not secured
properly
2
3
5
2
5
1
After Flight
Before Flight
2
3
1
During Flight
Interface expenses
exceed budget
Team deadlines not met
on time
LaACES deadlines not
met on time
Team cooperation
issues
2
2
1
Before Flight
1
3
1
Before Flight
3
4
1
Before Flight
1
4
1
Before Flight
Key:
Likelihood – 5 is very likely, 1 is not likely
Impact – 5 is most impact, 1 is least impact
Detection Difficulty – 5 is difficult to detect, 1 is easy to detect
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Team Fly Boys
Table 5: Risk Severity Matrix.
5
Likelihood
4
10
14
4
11
1
9
7
8
13
6
15
2
3
5
6
3
4
5
3
12
2
1
1
2
Impact
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Team Fly Boys
Table 6: Contingency Plan per Risk.
System
Electrical
1
Risk
2
Condensation in
electrical area
Components failure
3
Sensor failure
4
Power failure
5
Loose solder connection
Software
6
7
8
Mechanica
l
9
10
11
Other
12
13
14
15
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Contingency Plan
Trigger
Who is
responsible
Make Final Report
Engineering
Jared
See other teams who
used similar
See other teams who
used similar
See other teams who
used similar
See other teams who
used similar
Weather
Jared
Bad Part
Jared
Bad Part
Jared
Bad Work
David
Forgot to load correct
program
Didn’t factor in enough
time for data retrieval
and ground calibrations
Didn’t test new
programs modifications
Reload
Engineer
David
Use measurements
up until no data
Engineer
David
Hope they work
Engineering
Jared and
David
Loss of Payload
Payload breaks during
testing
Lid is not secured
properly
Failure analysis
Failure analysis
Engineering
Engineering
Jared
Jared
Re-secure
Engineering
David
Interface expenses
exceed budget
Team deadlines not met
on time
LaACES deadlines not
met on time
Team cooperation issues
Downsize
Bad Leading
David
Downsize
Bad Leading
David
Pray and downsize
Bad Leading
David
Resolve
Bad Leading
David and
Jared
42
Team Fly Boys
12.0 Glossary
Term
Definition
LaACES
CDR
FRR
PDR
WBS
Component
Sensor
Interface
WBEE sensor test set
Binary
Analog
Digital
HIGH TEMP
Physics & Aerospace Catalyst Experiences in Research
Critical Design Review
Flight Readiness Review
Preliminary Design Review
Work breakdown structure
Systems, circuit boards, and integrated circuits
An electrical device used to measure
An interconnection between systems
LaACES provided circuit board used to calibrate sensors
Digits or numbers used in the binary system
Represents data by measurement of a continuous physical variable
Data measured in binary
Potentiometer integrated into the WBEE sensor test set used to adjust
the high temperature
Potentiometer integrated into the WBEE sensor test set used to adjust
the low temperature
Potentiometer integrated into the WBEE sensor test set used to adjust
the gain voltage
LOW TEMP
GAIN trimmer
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Team Fly Boys