a multi-channel fiber optic phosphorescent sensor …...1 a multi-channel fiber optic phosphorescent...
TRANSCRIPT
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A multi-channel fiber optic phosphorescent sensor for
monitoring dissolved oxygen M.S. Final Exam
Manasi S. Katragadda
Advisor: Dr. Kevin L. LearCommittee: Dr. Diego Krapf
and Dr. Kenneth Reardon
Department of Electrical and Computer Engineering Colorado State University
February 23, 2009
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OutlineIntroduction and motivationBackgroundDesign and fabrication of multi-channel source and integration with detection systemMeasurements taken with multi-channel sensor instrumentMonitoring dissolved oxygen using multi-channel sensor instrumentConclusions and future work
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OutlineIntroduction and motivationBackgroundDesign and fabrication of multi-channel source and integration with the detection systemMeasurements taken with multi-channel sensor instrumentMonitoring dissolved oxygen using multi-channel sensor instrumentConclusions and future work
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toluene (source: paint solvents, thinners)
trichloroethylene (source: metal degreasing)
dichloroethylene, perchloroethylene (source: dry cleaning products)
vinyl chloride (source: PVC products)
http://www.epa.gov/
ApplicationIn-situ, real-time, simultaneous monitoring of multiple but chemically similar contaminants in ground water, such as
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OutlineIntroduction and motivation
BackgroundDesign and fabrication of the multi-channel source and integration with the detection systemMeasurements taken with the multi-channel sensor instrumentMonitoring dissolved oxygen using the multi-channel sensor instrumentConclusions and future work
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Chemical sensing mechanism
470 nm (blue) LED light excites the dye
Optical fiber (optode) tip
Phosphorescence signal (615 nm peak emission) quenched by oxygen
Oxygen sensitive phosphorescent dye [Ru(dpp)3
]2+
E.Coli
cells with enzymes consume diffused dissolved oxygen to metabolize analyte
oxygen
GROUND WATER
analyte
(e.g. toluene)
Monitoring contaminants with genetically engineered enzymes via indirect monitoring of DO in water
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Absorption and emission spectrum of [Ru(dpp)3
]2+
Reproduced from Gao
et. al, Biotech. and Bioengr. 86, 425-433 (2004)
Absorption peak at ~470 nm Emission peak at ~620 nm
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Transduction mechanisms in the multi-channel sensor
Phosphorescence detection by PMT
Analog to Digital conversion
Phosphorescence Amplification
by TIA
Data collection of digital signal
Voltage output
Phosphorescence optical power emission (620 nm)
Current output
Phosphorescence excitation by light source (470 nm LED)
Transducer Ru complex
Phosphorescence quenching by diffused O2
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Multi-channel sensor architecture
A multiple source-single detector system based on time-division multiplexing
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Other options for channel switching
Configuration #1: A switched system
Fiber-optic switch
Source
Detector
O ptodesSource
Detector
Source
Detector
O ptodes
Commercial plastic fiber optic switches: highly expensive, approx. five thousand dollars)
Glass fiber optic switches that have been used for telecommunication purposes available readily commercially
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Configuration #2: A single source-single detector replicated option
Multiple detectors are highly expensive
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Time-division multiplexing for monitoring multiple optodes
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Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6Channel 7
Channel 8
Time (ms)
Voltage (V)
Phosphorescence signal
LED excitation pulse
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Trace of the superposition of phosphorescence signals at the PMT
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Time
Anal
og C
hann
el 0
Vol
tage
(V)
Channel 1 Channel 2Channel 3
Channel 4Channel 5
Channel 6
Channel 7
Channel 8
Phosphorescence signal (V)
Time
Anal
og C
hann
el 0
Vol
tage
(V)
Channel 1 Channel 2Channel 3
Channel 4Channel 5
Channel 6
Channel 7
Channel 8
Phosphorescence signal (V)
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OutlineIntroduction and motivationBackgroundDesign and fabrication of multi-channel source and integration with detection systemMeasurements taken with multi-channel sensor instrumentMonitoring dissolved oxygen using multi-channel sensor instrumentConclusions and future work
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Design and fabrication of the multi- channel sensor
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Multi-channel sensor
Acquisition Software written in LabVIEW
Instrument
Excitation sourcesystem
Detection system
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Internal schematic of the multi-channel instrument
C O M P U TE R
A/D
MUXCIRCUIT
LEDs 1-8
450/60 nm band pass filter 2× 2 50:50 fiber-optics Coupler/ splitter
PMTTIA
Light dump box
Optodes 1-8
POF
Detection systemSource system
DAQ
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Circuit schematic of the excitation source
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The excitation source: Top & Front view
S T c onne cto rs fo r op to des
C us tom f i lter H older w ith 450 /60 m fi lter
F ib er-opt ic coup le rs
L ight du m p box
D C P ow e r con nector ja ck LE D sou rce s
cir cui t ry b oard
E u ro sty le term in al st rip
D A Q (m oun te d below th e circ ui try boa rd ) P las tic
op tical f ib ers
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The detection system: Top & front viewFiber holder for coupling fibers into PMT
PMT Voltage output
Photomultiplier tube (PMT) module
620/100 nm filter
TIA electronics
PMT Voltage outputdisplay
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Front panel of multi-channel LabVIEW
vi
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Electronic channel switchingOur approach
o Electronic switching & no moving partso Economical as costs only one-half as much as a switched
system
A software program was written in LabVIEW as interface with the DAQ
o Multiplex and demultiplex signals to and from the PMT o Take traces of phosphorescence (V) versus time for every
channelo
Save data at the time of collection o Collect dark voltage after each cycle of measurement
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Outline
Introduction and motivationBackgroundDesign and fabrication of multi-channel source and integration with detection systemMeasurements taken with multi-channel sensor instrumentMonitoring dissolved oxygen using the multi-channel sensor instrumentConclusions and future work
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LED power drop measurements
Analog inputDAQ
Analog gnd1M VR9V
Power supply(Radioshack)
Channels 1-8
Average power of the LEDs was studied for a few random channels with the ST connectorized photodiode (PDB 504-ST)
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Results indicate a 4-5 minute warm up time
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Summary of data taken for LED average power drop and noise
Case #
% drop in LED photo voltage
Vpp (mV)
LED dwell time (ms)
Power supply
LED location
Drive current (mA)
Supply voltage (DC)
Resistor (ohm) ICs
Long Electri cal connection
Shielded against EMI
1 4.46 1 100 radio shack
in multi-channel sensor 28.6 5 V 1M present no yes
4.47 1 500
4.57 1 1000
2 4.6 1 100 radio shack
in multi-channel sensor 28.6 5 V 1M absent no yes
3 0.9 1 100 radio shack
in multi-channel sensor 9.9 5 V 1M present no yes
4 5.75 1 100 radio shack
in multi-channel sensor
not measured<28.6 7.5 V 1M absent no yes
5 4 20 100 HP 6216A
in multi-channel sensor ~28.6 5 V 1M present no yes
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5 4 20 100 HP 6216A
in multi-channel sensor ~28.6 5 V 1M present no yes
4 20 500
3.2 20 1000
6 0.22 1 100 battery external 9.6 9 V 100k present no yes
0.36 1 500
0.295 1 1000
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Conclusions from the experiment LED drive current directly proportional to percent drop in LED powerPresence/absence of other variables had no effect on the percent drop in LED power Minimal noise amplitude of 1mV in photovoltage was observed due to minimum resolution of DAQPresence/absence of variables had no effect on 1 mV noise amplitude
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Effect of duration of turn-off times on LED power drop
Smaller the turn-off time, smaller the power drop
0.695
0.697
0.699
0.701
0.703
0.705
0.707
0.709
0.711
0.713
0 50 100 150 200 250 300
Cha
nnel
5 L
ED
pho
tovo
ltage
(V
)
Elapsed time (s)
10s turn off time30s turn off time
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Monitoring long-term stability of LED power
Measurement taken over 15 hours Stable, with negligible fluctuations of 0.3%
between 100-700 minutes
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Analysis of source insertion loss channel by channel
Insertion loss (dB) = 10 * log 10 (Launched photocurrent / Received photocurrent)
Results: Insertion loss varied from 14.5 dB to 18.5 dB for the channels
Multimeter
Case-2Multimeter
Measuring launched photocurrent
Measuring received photocurrent
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Detector insertion lossInsertion loss (dB) = 10 * log 10 (Optical power launched into the channel from the front panel / Optical power received by PMT)
where optical power launched into the channel from the front panel = photocurrent (nA) from fiber coupled red LED measured by photodiode / responsivity of PD @645 nm (A/W)
optical power actually received by PMT= TIA Voltage (V) measured from the front panel/ effective response of TIA & PMT
and effective response of TIA & PMT= (TIA gain of 120 kV/A) * (PMT responsivity of 2* 107 mA/W at 645nm)
Results: Insertion loss measured to be between 11 dB to 14.9 dB
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Summary of insertion loss measurements
CHANNEL 1 CHANNEL 2 CHANNEL 3 CHANNEL 4 CHANNEL 5 CHANNEL 6 CHANNEL 7 CHANNEL 8
17.79±.. 0.24
16.36 ± 0.34
17.34 ± 0.05
18.42 ± 0.23
18.53 ±1.32
14.54 ± 0.05
18.8 ± 0.09
17.5 ± 0.1
14.07 ± 0.16
13.79 ± .09
14.18 ± .03
14.54 ± 0.06
12.02 ± 0.04
14.88 ± 0
11.62 ± .04
11 ± 0.12
Detector insertion loss[Avg
(dB) ±
Stdev
(dB)] Source insertion loss [Avg
(dB) ±
Stdev
(dB)]
Source insertion loss: ~4 dB difference between strongest and weakest channelDet. insertion loss:~4.5 dB difference between strongest and weakest channel
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Studying optodes
to determine if they are the cause of non-repeatibility
ST connectors on front panel of McFOFI source
ST-ST 1mpatchcords
Water continuously bubbled withcompressed air
Optodein air
Channels 1-8
O #4
O #8 O #1 O #7
O #2 O #5 O #3 O #6
O=optode
1,2,3,4= optodes prepared in August and September2008
5,6,7,8= optodes freshlyprepared on Dec 162008
Channels 1-8 turned on, LED dwell time=3s
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Observation: All optodes drop by approximately 0.3 V.
Can be concluded that these fluctuations were due to a common system issue and not due to aging of optodes.
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ST connectors on front panel of McFOFI source
Experimental set-up
Optodein air
Channels 1-8
O #4
O #8 O #1 O #7
O #2 O #5
O #6
O=optode
1,2, 4=optodesprepared in August and September2008
5,6,7,8= optodes freshlyprepared on Dec 162008
9V
10K
Channels 1-8 turned on,LED dwell time= 3s
Red LED (640 nm)
Monitoring blue LEDs to check if they are the cause of non-repeatability
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Since red LED remains on all the time, it is present in all channels.
It could be possible that fluctuations between 4200-6000s were due to a common system component.
Not understood if the power of the blue LEDs was actually drifting.
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Testing of transimpedance
impedance amplifier (TIA) stability
0.83
0.84
0.85
0.86
0.87
0.88
0.89
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Elapsed time (s)
Cha
nnel
1 T
IA o
utpu
t vol
tage
A percentage drop of only 0.2% in the TIA output voltage observed at the end of the two hours. TIA not cause of non-repeatability.
DAQ didn’t cause any fluctuations either.
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Monitoring drift in dark voltage of the multi-channel system
Plot of dark voltage output of the multi-channel system measured by the PMT, with a dwell time of 3s
Optode tips wrapped in aluminum foil
Optode tips wrapped in black plastic
Dark voltage a significant source of non-repeatibility
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Studying attenuation in a ST-ST POF patchcord
Channel 1 (V)
Channel 2 (V)
Channel 3 (V)
Channel 4 (V)
Channel 5 (V)
Channel 6 (V)
Channel 7 (V)
Channel 8 (V)
With 1m ST‐ST Patchcord
0.48 0.46 0.44 0.44 0.39 0.39 0.39 0.31
Without 1m ST‐ST Patchcord
0.84 1.04 1.01 0.93 0.85 0.90 0.86 0.95
Conclusion: Phosphorescence signal (no 1m patchcord
connected to optode) was two to three times larger than phosphorescence when a 1m patchcord
was connected to optode
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Measurement of system crosstalk
Channels 1-8
Optodein air
Crosstalk for channels: -8.4 dB to -12 dB.
Cross talk not symmetric.
Crosstalk= 10* log (Undesired signal from neighboring channel/desired signal)
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Measurement of Uniformity
Uniformity = (1-
RSD) *100%
Uniformity calculated to be 89.4%.
Uniformity = [(Min+Max)/2] ±
difference
where difference= Max-
[(Min+Max)/2] =[(Min+Max)/2] –
Min
Uniformity= 0.987 V ±
0.274 V
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Outline
Introduction and motivationBackgroundDesign and fabrication of multi-channel source and integration with the detection systemMeasurements taken with multi-channel sensor instrumentMonitoring dissolved oxygen using multi-channel sensor instrumentConclusions and future work
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Experimental set-up for taking measurements with Cole-Palmer DO meter
Glass Flask
Ru(dpp) 3
OptodeHot Plate and stirrer
Dissolved oxygen meter Cole - Parmer
Model # 001971
Nitrogen/air outlet
Excitation source
Detection system
Dissolved oxygen
electrode
Nitrogen/air inlet
Water
To computer
Glass Flask
Ru(dpp) 3
OptodeHot Plate and stirrer
Dissolved oxygen meter Cole - Parmer
Model # 001971
Nitrogen/air outlet
Excitation source
Detection system
Dissolved oxygen
electrode
Nitrogen/air inlet
Water
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Measurement Set 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 1 2 3 4 5 6 7 8 9 10
Dissolved oxygen (ppm)
Phos
phor
esce
nce
sign
al (V
)
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
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0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3 4 5 6 7 8 9 10
Dissolved oxygen (ppm)
Phos
phor
esce
nce
sign
al (V
)
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Measurement
Set 2
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46Modified from http://www.artisan-scientific.com
DO display
DI Water
Optode Air inlet
Nitrogen inlet
Multi-channel phosphorescent sensor system
Experimental set-up for taking measurements with BioFLO-III DO meter
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Measurement Set-3
0.21
0.23
0.25
0.27
0.29
0.31
0.33
0 2 4 6 8 10Dissolved oxygen (ppm)
Phos
phor
esce
nce
signa
l (V
)
Channel 1 (V)Channel 5 (V)Channel 6 (V)Channel 8 (V)
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Front panel connections to multichannel source
No optode;black capon STconnector
Channels 1-8
Water in the fermentor reaction chamber
Optodes in air
Beaker with water
Inlet for mixed gas
Source system
Optodes with 1 m ST-ST patch cords
Optodes with 1 m ST-ST patch cords absent
Covered tightly with black plastic
Covered tightly with a black shroud
No optode;black capon STconnector
Channels 1-8
Water in the fermentor reaction chamber
Optodes in air
Beaker with water
Inlet for mixed gas
Source system
Optodes with 1 m ST-ST patch cords
Optodes with 1 m ST-ST patch cords absent
Covered tightly with black plastic
Covered tightly with a black shroud
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Data obtained after shielding experimental apparatus, Set-4
y = -0.0208x + 0.6352R2 = 0.9473
y = -0.025x + 0.592
y = -0.0197x + 0.4939R2 = 0.9511
R2 = 0.9265
0.310
0.360
0.410
0.460
0.510
0.560
0.610
0.660
0 1 2 3 4 5 6 7 8 9 10
Dissolved oxygen (ppm)
Phos
phor
esce
nce
sign
al (V
)
Channel 2Channel 3Channel 4Linear (Channel 2)Linear (Channel 3)Linear (Channel 4)
Sensitivity approx. 0.02 V/ppm
Limit of detection measured to be 2 ppm
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Experimental set-up for taking measurements with YSI 5100 DO meter
Hot plate stirrer
Air inlet
Nitrogen inlet
Deionized
water
Multichannel phosphorescent sensor system
Optode
Dissolved oxygen Meter (YSI 5100)
Dissolved oxygen probe
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0.150
0.170
0.190
0.210
0.230
0.250
0.270
0.290
0.310
0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000
Oxygen concentration (ppm)
Phos
phor
esce
nce
sign
al (V
)
Channel 2 Channel 3 Channel 4
Data points had R2=0.3 to 0.7. Not completely linear as expected
Data obtained with the YSI meter, Set-5
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OutlineIntroduction and motivationBackgroundDesign and fabrication of the multi-channel source and integration with the detection systemMeasurements taken with the multi-channel sensor instrumentMonitoring dissolved oxygen using the multi-channel sensor instrumentConclusions and future work
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ConclusionsA multi-channel fiber optic sensor for dissolved oxygen monitoring was fabricated and tested
Cost –effective electronic time division multiplexing technique was used instead of fiber optic switches
Future Application: Ground water quality monitoring
Parameters like cross talk, uniformity, sensitivity, LOD were investigated
LOD: 2 ppmSensitivity: 0.02 V/ppm
Source insertion loss: between 14.5 dB to 18.8 dB Detector insertion loss: between 11 dB to 14.9 dB
System crosstalk: -8.4 dB to -12 dB
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Future workContinuous monitoring of oxygen over long period is suggested with multiple optodes and calculation of parameters like LOD, sensitivity
Limited literature on these aspects: only single optodes discussed
Optoelectronic system modeling and simulation
Optodes integrated with biosensors in the future
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AcknowledgementsThanks to
o
Dr. Kevin Lear o
Students, Optoelectronics Group, ECE Sean Pieper, Weina Wang, Rashid Safaisini, Rongjin Yan, Bob Pownall, Santano Mestas, Wesley
o
Dr. Diego Krapf, ECEo
Bob Adame, Physics
o
Dr. Ken Reardon, Dr. David Dandy, CBEo
Zhong
Zhong, Tara Schumacher, Tim Gonzalez,
Prafulla
Shede, CBE
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Thanks……..
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