optical attenuation sensor for process...
TRANSCRIPT
-
Optical Attenuation Sensor forProcess Control
Eric A. Borisch
Jeremy D. Protas
Scott D. Ruppert
Christopher J. Spiek
Francis L. Merat, Advisor
April 21, 1999
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Project Background
Originated by a company in theCleveland area
Robotic binary epoxy sprayer Currently using an optical spectrum analyzer
for process control
Looking for an inexpensive alternative
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Project Goals
Decreased cost
Wide dynamic range
Strong correlation
Stability
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Our Solution
Frequency source Light emitting diode phototransistor
pair Amplify & rectify the detected signal Take the DC value of the AC component
DC OUTPUTLNA AD630
OSCILATOR LED PHOTO-NPN DC BLOCK LOCK-IN LPF
REFERENCE SIGNAL
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Design Considerations
Oscillator design
Optical transmission and detection
Attenuation measurement
Output
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Oscillator Design
Onboard
Sine wave orsquare wave
Wien Bridgeoscillator -6V
+6V
450p 330k
+
- LM741N1.5k
2.7k
50500
330k
450p
Wien Bridge oscillator
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Optical Transmission
High output infraredLED
Separate AC & DCdrive controls
+6V
Q2N3904Q2N3904
10027
1M10k
10k
LED
10mH
AC CONTROL DC OFFSETCONTROL
LED Drive
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Optical Detection
Phototransistorinstead of photodiode
Low noise amplifier
Variable gain
Over-amplificationdetection
-6V
+6V
+
- CLC425
100n
4.7u
PHOTO NPN1
51
2n
100k
100n
4.7u
JP3JP2JP1
51 510 5.1k 51k
AMPLIFICATION JUMPERS
JP4
Photoreceiver/Amplifier
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Attenuation Measurement
AD630 - Lock-in amplifier
Reference & received signals compared
Low pass filter
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Output
DC value
Output circuit Adjustable set points
Easy to read
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Results
Over 50 dB dynamic range
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
ResultsOutput Voltage
0
100
200
300
400
500
600
700
800
900
1000
0.00001% 0.00010% 0.00100% 0.01000% 0.10000% 1.00000% 10.00000% 100.00000%
Transmission
Vo
ltag
e (m
V)
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Results
Over 50 dB Dynamic Range
DC output linearly correlated with opticalattenuation
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
ResultsLow Amplification
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Transmission %
Ou
tpu
t (V
)
50 Ohm
FIT
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Results
Over 50 dB Dynamic Range
DC output linearly correlated with opticalattenuation
Crosstalk
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Results
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Recommendations
Better sine wave oscillator
Auto-ranging or application specific
Packaged for industrial environment
Multiple circuits with neural network
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Demonstration
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Conclusions
Goals Decreased cost
Wide dynamic range
Strong correlation
Stability
Results Under $50
Over 50 dB
Repeatability &Linearity
Unaffected byTransients
-
April 21, 1999 Optical AttenuationSensor for Process Control
EEAP 398/399
Any Questions?