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\begin_body

\begin_layout Title
AguaClara Turbidimeter Team
\end_layout

\begin_layout Author
Julia Morris, Andrew Gorodetsky, Heidi Rausch
\end_layout

\begin_layout Abstract
This report will cover all the work that has been done by Cornell's AguaClara
 program on turbidimeters.
 Research first started on creating a new, low cost turbidimeter at Cornell
 in the Spring of 2011.
 Since then several different prototypes have been created and ten turbidimeters
 have been sent to Honduras for use by communities who are considering building
 an AguaClara plant.
 The reason that a low cost turbidimeter needs to be developed is so that
 communities who may be in need of water treatment facilities can test their
 water without  incurring the high expense of other turbidimeters currently
 on the market.
 The most current complete turbidimeter prototype can read NTU values down
 to 15 NTU.
 The research discussed in this report details new turbidimeter designs
 with which it may be possible to read NTU values down to approximately
 seven NTU.
 The most promising design includes the use of a blue LED light and a large
 HDPE block, which is used for diffusing the light.
 However, this design will need to be tested more thoroughly for accuracy
 before it can be fabricated for use in the field.
 In the future if research continues to be done to try to create a turbidimeter
 that can read turbidity values below 5 NTU the length of the lowering rod
 may have to be made longer than the current prototype, which is only 60
 cm long.
 Without adding length to the lowering rod current research suggests that
 it may be impossible to read the turbidity of any water with an NTU value
 lower than seven.
 
\end_layout

\begin_layout Abstract
\begin_inset Newpage pagebreak
\end_inset


\end_layout

\begin_layout Section*
Introduction
\end_layout

\begin_layout Standard
The turbidimeter is a vital part of the AguaClara design.
 The turbidimeter helps AguaClara determine the type of water treatment
 processes that are needed for a particular source water.
 The final goal of the Turbidimeter team is to build a device that can accuratel
y measure turbidities down to <5NTU.
 The device will be distributed to any community that is looking into having
 an AguaClara plant built.
 Next, the community would use the device for approximately a month until
 it can be accurately determined whether or not a plant should be built
 for them.
 Some communities may only require chlorination, while others may need the
 flocculation, sedimentation, filtration, and chlorination.
 The turbidimeter should also be user friendly.
\end_layout

\begin_layout Standard
There are many different turbidimeters on the market for use by labs and
 scientific experimentation, however there is no such device available at
 a low cost for 
\begin_inset Quotes eld
\end_inset

home
\begin_inset Quotes erd
\end_inset

 use.
 It would be impractical to give all the communities in Honduras that are
 considering building an AguaClara plant a turbidimeter that costs hundreds
 of dollars.
 The community would not be willing or able to pay for it.
 One of the most important design parameters of the turbidimeter is that
 it can not cost more than $20.
 The latest prototype that was built and is currently be used in Honduras
 is under $5; it is the hope of AguaClara that all future designs will remain
 this affordable.
 It is possible that in the future one of the turbidimeters designed at
 Cornell will make it onto the market so that others can take advantage
 of this technology as well.
 
\end_layout

\begin_layout Section*
Background 
\end_layout

\begin_layout Subsection*
How Traditional Turbidimeters Work
\end_layout

\begin_layout Standard
Turbidity is defined as an expression of the optical property that causes
 light to be scattered and absorbed rather than transmitted in straight
 lines through a sample.
 If light were to travel through 
\begin_inset Quotes eld
\end_inset

pure
\begin_inset Quotes erd
\end_inset

 water, the light beam should travel relatively undisturbed, but if there
 are other particles, such as suspended solids, present then the light will
 be scattered and absorbed as it interacts with these molecules.
 Traditional turbidimeters contain a light source, sample container or cell,
 and photodetectors to sense the scattered light.
 The most basic turbidimeter design, seen in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Single-Beam-Design"

\end_inset


\begin_inset Foot
status collapsed

\begin_layout Plain Layout
Basic Nephelometer.
 1999.
 Graphic.
 EPA Guidance Web.
 6 Dec 2011.
 <http://water.epa.gov/lawsregs/rulesregs/sdwa/mdbp/upload/2001_01_12_mdbp_turbidi
ty_chap_11.pdf>.
 
\end_layout

\end_inset

, consists of a light source that is projected through a sample.
 The detector is located at a ninety degree angle to the light source.
 Therefore, the light that is scattered at a ninety degree angle is detected.
 The amount of light detected is then related to the turbidity of the water.
 
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\begin_inset Graphics
	filename Single-Beam Turbidimeter.jpg

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\begin_inset space \hfill{}
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\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Single Beam Design Turbidimeter 
\begin_inset CommandInset label
LatexCommand label
name "fig:Single-Beam-Design"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection*
Past Research
\end_layout

\begin_layout Standard
Research on the turbidimeter began in the spring of 2011 and was continued
 during the summer.
 During the spring of 2011 a relationship between depth and turbidity was
 confirmed and a first prototype with a turbidity scale was designed.
 During Summer 2011 the turbidimeter design was improved and a more accurate
 relationship between depth and turbidity was found.
 A number of different LED designs were tested (See Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:First-12-Designs"

\end_inset

 and 
\begin_inset CommandInset ref
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reference "fig:Last-12-Designs"

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 ) 
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\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
First set of 12 Designs
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name "fig:First-12-Designs"

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\begin_layout Plain Layout
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Second set of 12 Designs
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name "fig:Last-12-Designs"

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\end_layout

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\end_layout

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\begin_layout Standard
Design #14 did not have the best total percent error but it did have the
 best ﬁt to a power function, therefore, it was chosen to be the ﬁnal design.
 Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Log-log-plot-for"

\end_inset

 is a Log Log plot of Depth vs Turbidity for the ﬁnal design.
 As seen in this plot, an excellent fit for the data was achieved; the R
\begin_inset script superscript

\begin_layout Plain Layout
2
\end_layout

\end_inset

value for this fit was 0.99472.
 The power law function for this set of data was as follows:
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
Depth=1463.7*Turbidity^{-1.29}\label{eq:PowerLaw}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
Using this formula, the scale for the ﬁnal turbidimeter was developed by
 marking desired turbidities such as 15, 16, 50, 100, 400 NTU etc.
 on the rod at the distance specified by Equation 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:PowerLaw"

\end_inset

 above the light source.
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
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status open

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\begin_inset space \hfill{}
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\begin_inset Graphics
	filename log log plot final design.PNG
	scale 40

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\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Log-log plot for Design 14
\begin_inset CommandInset label
LatexCommand label
name "fig:Log-log-plot-for"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The latest design for the turbidimeter can be seen below in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Latest-Turbidimeter-Design"

\end_inset

.
 Ten of these turbidimeters were sent to Honduras to be used as seen in
 Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Turbidimeter-being-used"

\end_inset

.
 
\end_layout

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\begin_layout Plain Layout
\begin_inset Caption

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Latest Turbidimeter Design
\begin_inset CommandInset label
LatexCommand label
name "fig:Latest-Turbidimeter-Design"

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\end_inset


\end_layout

\end_inset


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\begin_inset Float figure
wide false
sideways false
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	filename Turbidimeter in Honduras.jpg
	scale 50

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	filename Turbidimeter in Honduras 2.jpg
	scale 50

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\begin_inset space \hfill{}
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\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Turbidimeter being used in Honduras
\begin_inset CommandInset label
LatexCommand label
name "fig:Turbidimeter-being-used"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section*
Methods 
\end_layout

\begin_layout Subsection*
Mirror Component Design
\end_layout

\begin_layout Standard
Current research focuses on creating a turbidimeter which can measure turbiditie
s as low as 5 NTU.
 One idea to achieve this was to extend the range of the turbidimeter by
 placing the light source at the top of the water column (facing down) and
 then attaching a mirror to the end of the lowering rod.
 The first design task was to figure out how to attach the LED (light source)
 at the top of the PVC pipe (water column) facing down.
 The LED light was secured with a screw (including light diffuser and pattern)
 to the inside of a PVC coupling, as seen in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Mirror-Component-Design"

\end_inset

.
 There is a slit in the coupling so that the operator can attach and remove
 it as needed.
 The mirror is glued to a L-shaped piece of metal (see Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Mirror-Component-Design"

\end_inset

).
 The metal attachment piece (again as seen in Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Mirror-Component-Design"

\end_inset

) is then attached to the end of a lowering rod.
 
\end_layout

\begin_layout Standard
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wide false
sideways false
status open

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\begin_inset space \hfill{}
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\begin_inset Graphics
	filename Mirror Component Design.JPG
	scale 30

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Mirror Component Design
\begin_inset CommandInset label
LatexCommand label
name "fig:Mirror-Component-Design"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection*
Colored LED Design
\end_layout

\begin_layout Standard
The next design idea for possibly extending the range of NTU values that
 could be measured was to use colored LED lights, however none were immediately
 available.
 Therefore colored cellophane was bought at a local craft store (blue, green,
 red) to be used as a replacement for colored LED lights.
 A small piece of cellophane was cut and placed between the LED light and
 the light diffuser (HDPE block) as seen in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:LED-light-with"

\end_inset

.
 To get the cellophane to the right size we simply placed a large piece
 of cellophane between the light and the HDPE block and then cut around
 the edges of the block.
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename Blue LED Design.JPG
	scale 30

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
LED light with colored cellophane
\begin_inset CommandInset label
LatexCommand label
name "fig:LED-light-with"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
For more accurate testing colored LED lights were ordered and received;
 the colors ordered were red, green and blue.
 Testing with the blue LED light (seen in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Blue-LED-light"

\end_inset

) has proved most successful.
 The blue LED light was attached to the lowering rod in the same way that
 the colorless LED light was attached in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Latest-Turbidimeter-Design"

\end_inset

.
\end_layout

\begin_layout Standard
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wide false
sideways false
status open

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\begin_inset Graphics
	filename Blue LED light.jpg
	scale 30

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Blue LED light
\begin_inset CommandInset label
LatexCommand label
name "fig:Blue-LED-light"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection*
Double HDPE Block
\end_layout

\begin_layout Standard
It was decided to try to increase the thickness of the HDPE block to see
 if a lower NTU could be measured.
 When first using the double HDPE block, it was noticed that a large quantity
 of light was escaping from the sides of the block.
 Therefore, black electrical tape was wrapped around the HDPE to block out
 as much light as possible.
 Tests were done using two different patterns (Design 14 from Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Last-12-Designs"

\end_inset

 and light slit design made from electrical tape) and two different color
 LEDs (blue and white).
 Both of these designs can be seen in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Design-for-the"

\end_inset

.
 
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

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\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename double hdpe, slits 1.JPG
	scale 34

\end_inset


\begin_inset Graphics
	filename double hdpe, slits 2.JPG
	scale 20

\end_inset


\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename double hdpe, original pattern.JPG
	scale 50

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Design for the double HDPE block.
 First two pictures are of the light slits pattern and the third picture
 contains the original pattern.
 
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LatexCommand label
name "fig:Design-for-the"

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout

\end_layout

\end_inset


\end_layout

\begin_layout Section*
Experimental Design
\end_layout

\begin_layout Standard
As in previous semesters, a pump (with a ﬂow rate of 1.4 L/min) was used
 to continuously stir the water sample.
 A PVC pipe with holes drilled at the top and bottom was used to hold the
 water.
 Using tubing, the bottom hole connects to an electronic turbidimeter, from
 there to a pump and ﬁnally to the top of the PVC (See Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Contiuous-mix-experimental-turbi-1"

\end_inset

).
 The electronic turbidimeter is connected to a computer in the lab and using
 a Process Controller the NTU was recorded into an excel ﬁle every second.
 This program proved extremely useful in that it was possible to write notes
 directly into the excel ﬁle at any given point in time.
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\begin_inset Graphics
	filename Contstant Mix Schematic.png
	lyxscale 25
	scale 50

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Continuous-mix experimental schematic
\begin_inset CommandInset label
LatexCommand label
name "fig:Contiuous-mix-experimental-turbi-1"

\end_inset

 
\end_layout

\end_inset


\end_layout

\end_inset

 
\end_layout

\begin_layout Enumerate
Turn on Process Controller 
\end_layout

\begin_layout Enumerate
Add initial amount of clay 
\end_layout

\begin_layout Enumerate
Run pump system for four minutes 
\end_layout

\begin_layout Enumerate
Unplug pump, make a mark in data log as to show when pump was ﬁrst unplugged
 
\end_layout

\begin_layout Enumerate
First team member takes depth reading 
\end_layout

\begin_layout Enumerate
Plug pump in 
\end_layout

\begin_layout Enumerate
Wait 60 seconds 
\end_layout

\begin_layout Enumerate
Unplug pump 
\end_layout

\begin_layout Enumerate
Second team member takes depth reading 
\end_layout

\begin_layout Enumerate
Repeat steps 6-8 
\end_layout

\begin_layout Enumerate
Third team member takes depth reading
\end_layout

\begin_layout Enumerate
Wait 60 seconds
\end_layout

\begin_layout Enumerate
Add the next amount of clay, make mark in data log with the new total amount
 of clay in the system
\end_layout

\begin_layout Enumerate
Repeat steps 3-13 until you reach the ﬁnal amount of clay/NTU desired
\end_layout

\begin_layout Section*
Results and Conclusions
\end_layout

\begin_layout Subsection*
Mirror Component Design
\end_layout

\begin_layout Standard
After first testing out the mirror design it was determined that aligning
 the mirror so the operator could see the reflection of the LED light pattern
 was very difficult.
 Even after brainstorming a few ideas to improve the design, it was decided
 to reject the mirror concept and focus solely on improving the LED design.
 
\end_layout

\begin_layout Subsection*
Colored LED Tests
\end_layout

\begin_layout Subsubsection*
Blue Cellophane Covered LED
\end_layout

\begin_layout Standard
The first colored LED light tests were run using the blue cellophane covered
 LED.
 After the first test, the relationship found resulted in a R-squared value
 of 0.6419.
 This value was too low.
 In general the goal is to achieve an R-squared value in the 0.9 range.
 This low R-squared value was probably due to the fact that our range of
 turbidity was not large enough (13-30 NTU) and that only a few measurements
 have been taken (see Table 
\begin_inset CommandInset ref
LatexCommand ref
reference "tab:Blue-LED-light-1"

\end_inset

).
 Tests on the blue cellophane covered light were continued and more data
 points were aquirred.
 Following these tests the R-squared value increased to 0.9409.
 Using the equation of the line given in the log-log plot (see Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Log-log-plot-of"

\end_inset

) a relationship was found between turbidity and depth using a LED light
 covered with blue cellophane.
 This relationship can be seen below:
\end_layout

\begin_layout Standard
\begin_inset Formula 
\[
Depth=385.56*Turbidity^{-0.824}
\]

\end_inset


\end_layout

\begin_layout Standard
\begin_inset Float table
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
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\begin_inset Tabular
<lyxtabular version="3" rows="14" columns="3">
<features tabularvalignment="middle">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Mass of Clay (mg)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Average Height (cm)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Average Turbidity (NTU)
\end_layout

\end_inset
</cell>
</row>
<row>
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0 
\end_layout

\end_inset
</cell>
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Bottom (120 cm)
\end_layout

\end_inset
</cell>
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3.9
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0
\end_layout

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</cell>
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55.7
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13.6
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5
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105.7
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8.3
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5
\end_layout

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46 
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\end_inset
</cell>
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\begin_inset Text

\begin_layout Plain Layout
18.1 
\end_layout

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<row>
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10
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_layout Plain Layout
87.7
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
9.1
\end_layout

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</row>
<row>
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10
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40 
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\begin_layout Plain Layout
22.1
\end_layout

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<row>
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15
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</cell>
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\begin_layout Plain Layout
37.3 
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_layout Plain Layout
22.6
\end_layout

\end_inset
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<row>
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20
\end_layout

\end_inset
</cell>
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\begin_layout Plain Layout
58.3
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
12.2
\end_layout

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<row>
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20
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35 
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\begin_layout Plain Layout
21.7 
\end_layout

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</cell>
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30
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_layout Plain Layout
43.7
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_layout Plain Layout
15.4
\end_layout

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30
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29.7 
\end_layout

\end_inset
</cell>
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\begin_layout Plain Layout
23.2 
\end_layout

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50
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26.3 
\end_layout

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</cell>
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\begin_layout Plain Layout
25.6 
\end_layout

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</cell>
</row>
<row>
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\begin_layout Plain Layout
100
\end_layout

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</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
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\begin_layout Plain Layout
19 
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
29.9 
\end_layout

\end_inset
</cell>
</row>
</lyxtabular>

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Blue cellophane covered LED light test data
\begin_inset CommandInset label
LatexCommand label
name "tab:Blue-LED-light"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename log log plot blue cellophane.PNG
	scale 50

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Log-log plot of depth as a function of turbidity for the blue cellophane
 covered LED light
\begin_inset CommandInset label
LatexCommand label
name "fig:Log-log-plot-of"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection*
Blue Colored LED
\end_layout

\begin_layout Standard
After the blue LED lights were acquired, testing using these lights began
 immediately.
 The turbidities tested with the blue LED ranged from about 7 NTU to 53
 NTU, as seen in Table 
\begin_inset CommandInset ref
LatexCommand ref
reference "tab:Blue-LED-light-1"

\end_inset

.
 The log-log plot regression analysis produced an R-squared value of 0.9964
 (See Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Log-log-plot-of-1"

\end_inset

).
 Because this value is higher than the R-squared value found with the blue
 cellophane covered LED data, the relationship between turbidity and depth
 using the blue LED light is more accurate.
 Therefore, testing using the cellophane covered LED light design will cease
 and only further testing with the colored LED lights will continue.
 Whether the colored LED light will be able to measure turbidities less
 than 5 NTU accurately has yet to be determined.
 
\end_layout

\begin_layout Standard
Using the trend line equation given in the log-log plot a relationship between
 turbidity and depth was determined.
 This relationship can be seen below:
\end_layout

\begin_layout Standard
\begin_inset Formula 
\[
Depth=715.22*Turbidity^{-1.112}
\]

\end_inset


\end_layout

\begin_layout Standard
Using this equation, theoretically, a turbidity of 5 NTU could be measured
 at a depth of 119 cm.
 Currently, the turbidimeter being used to do testing is 120 cm.
 Therefore, measuring turbidity less than 5 NTU might not be possible.
 Further testing, will either prove or nullify this hypothesis.
 
\end_layout

\begin_layout Standard
\begin_inset Float table
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Tabular
<lyxtabular version="3" rows="10" columns="3">
<features tabularvalignment="middle">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Mass of Clay (mg)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Average Depth (cm)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Average Turbidity (NTU)
\end_layout

\end_inset
</cell>
</row>
<row>
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0 
\end_layout

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</cell>
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\begin_layout Plain Layout
81.7
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
6.9
\end_layout

\end_inset
</cell>
</row>
<row>
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5
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_layout Plain Layout
67.3
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
8.8
\end_layout

\end_inset
</cell>
</row>
<row>
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10
\end_layout

\end_inset
</cell>
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51.3
\end_layout

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</cell>
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\begin_layout Plain Layout
10.3
\end_layout

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20
\end_layout

\end_inset
</cell>
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38.7
\end_layout

\end_inset
</cell>
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\begin_layout Plain Layout
13.2
\end_layout

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\begin_layout Plain Layout
30
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
33.7
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
16.4
\end_layout

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50
\end_layout

\end_inset
</cell>
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\begin_inset Text

\begin_layout Plain Layout
24.7
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
20.8
\end_layout

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100
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16.3
\end_layout

\end_inset
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
29.7
\end_layout

\end_inset
</cell>
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150
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\end_inset
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\begin_inset Text

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12.3
\end_layout

\end_inset
</cell>
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\begin_inset Text

\begin_layout Plain Layout
40.8
\end_layout

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\begin_inset Text

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200
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
8.3
\end_layout

\end_inset
</cell>
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\begin_inset Text

\begin_layout Plain Layout
52.3
\end_layout

\end_inset
</cell>
</row>
</lyxtabular>

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Blue LED light test data
\begin_inset CommandInset label
LatexCommand label
name "tab:Blue-LED-light-1"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename log log plot blue LED.PNG
	scale 60

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Log-log plot of depth as a function of turbidity using blue LED light
\begin_inset CommandInset label
LatexCommand label
name "fig:Log-log-plot-of-1"

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout

\end_layout

\end_inset


\end_layout

\begin_layout Subsection*
Double HDPE Block
\end_layout

\begin_layout Standard
Three different tests were done using a HDPE block that is double the length
 of the original HDPE block.
 A log log plot of these tests can be see in Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Log-log-plot-HDPE"

\end_inset

.
 Using the equations given by a power law fit to the data, a minimum NTU
 value can be determined for a turbidimeter length of 60 cm.
 It was found that for the white LED and light slit pattern, the minimum
 turbidity that can be measured (at 60 cm) is 8.233 NTU.
 For the blue LED and light slit pattern, a minimum turbidity of 7.73 NTU
 can be measured.
 For the blue LED and original design, a minimum turbidity of 5.89 NTU can
 be measured.
 Therefore, if the turbidimeter was to be redesigned, the double HDPE block
 with the blue LED and the original design (Design 14) would be used.
 Though the white LED and light slit pattern had a better R-squared value,
 the blue LED and original design was chosen because a lower NTU value can
 be measured and it had less variability between user readings.
 
\end_layout

\begin_layout Standard
The goal this semester was to be able to measure turbidities down to 5 NTU.
 Based on the double HDPE block tests, if the turbidimeter was lengthened
 from 60 to 65 cm, it may be possible to accomplish this goal.
 Further testing with the double HDPE, blue LED, and original design should
 be done to verify this result.
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename log log plot double hdpe.PNG
	scale 50

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Log log plot of all double HDPE block designs
\begin_inset CommandInset label
LatexCommand label
name "fig:Log-log-plot-HDPE"

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout

\end_layout

\end_inset


\end_layout

\begin_layout Section*
Future Work
\end_layout

\begin_layout Standard
There are still many different options that can be tested to improve the
 accuracy of the turbidimeter.
 Though we have already dismissed the idea of using mirrors for the design
 this semester, the use of mirrors could be revisited in the future.
 To get the mirrors to work well, the design would need more specialized
 components and most likely be more expensive.
\end_layout

\begin_layout Standard
This semester, experiments in which the color of the light has been changed
 have been performed.
 Due to the inaccuracy of the cellophane covered lights, the team will only
 continue using the colored LED lights.
 
\end_layout

\begin_layout Standard
Using lights other than LEDs is another possibility.
 This could possibly reduce the disparity between different users readings.
 The LEDs have proved to be a problem as they often turn off with the slightest
 movement.
 Sometimes a light could be on and then after setting down the light somewhere
 it will suddenly turn off.
 Another situation that has happened many times is that a user will be attemptin
g to take a reading but the light will go dim; this could clearly influence
 the accuracy of readings if the user did not realize the change in brightness.
 More research needs to be done into substitutes for LED tea-candle type
 lights.
 
\end_layout

\begin_layout Standard
In past semesters the idea of using humic acid had been discussed.
 It would be a good idea to experiment with humic acid because it would
 better estimate natural waters.
 Humic acid would change the color of the water without changing its turbidity.
 This is something that people are often confused about, the idea of turbidity
 vs.
 color.
 Running experiments where we could change both would help to clear up this
 confusion.
 
\end_layout

\end_body
\end_document
