Optical Sensors. Introduction Fundamentals of EM Radiation Standing waves Speed of light spectrum PIN Diode CCD’s, Digital Cameras and scanners Photodetectors Turbidity & other photosensors Phototransistors Rise and Fall times Optocouplers A laser measurement system
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Optical Sensors Introduction Fundamentals of EM Radiation Standing waves Speed of light spectrum PIN Diode CCD’s, Digital Cameras and scanners Photodetectors Turbidity & other photosensors Phototransistors Rise and Fall times Optocouplers A laser measurement system Pyrometry
Breadth and Depth of subject http://www.wiley.com/cda/product/0,,3527267727%7Cdesc%7C2643,00.html • Convenient Pistol Grip Design • Safe Non-Contact Operation to Three Feet and 45 Degrees from Target • Autoranging 5 to 100,000 RPM • Accuracy & Resolution ±1 RPM • 4½ Digit LED or LCD Display • Available with Remote Sensor $304 from Omega Engineering Optical Tachometer http://www.omega.com/ppt/pptsc.asp?ref=HHT20
Manufacturersof Optical Sensors http://www.sensorsportal.com/HTML/SENSORS/OptoSens_Manufacturers.htm http://www.lpc-uk.com/suppliers/
http://empl.ksc.nasa.gov/emfund.htm Fundamentals of EM Radiation λ is the wavelength in meters f is the frequency in Hz=1/sec λ Distance http://electron9.phys.utk.edu/135/modules/m10/emwaves.htm
c=fλ or v=fλ where v is the velocity of the waveform. Standing Waves L First 3 modes of standing waves on a string and their calculated frequencies. http://www.cord.edu/dept/physics/p128/lecture99_35.html#topic1
Speed of light in Copper Wire or in Fiberoptic cable Is approximately 2/3=.667c v=.997c c= Speed of Light Cobalt Green, A pigment 40% Titanium White, A pigment http://acept.la.asu.edu/PiN/rdg/refraction/refraction.shtml
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html c=fλ EM Spectrum Wp =hf=hc/λ
EM Spectrum of Eye 750E12 Hz 429E12 http://acept.la.asu.edu/PiN/rdg/color/color.shtml
How diodes work Current flows http://hyperphysics.phy-astr.gsu.edu/hbase/solids/diod.html#c3 No current
PIN Diodes http://hyperphysics.phy-astr.gsu.edu/hbase/solids/diod.html#c3 avalanche photodiodea photodiode that uses avalanche breakdown to achieve internal multiplication of photocurrent. Phototransistor A photo-sensitive region with transistor amplification.
This picture shows an electronic detector called a charge-coupled device, or CCD. The small central rectangle contains a closely packed array of 320 by 512 light sensing diodes, each of which individually record the brightness of light and send the information to a computer. At the focus of a large telescope this device allows astronomers to "see" objects millions of times fainter than the unaided eye! How Digital Cameras & Scanners Work http://violet.pha.jhu.edu/~wpb/spectroscopy/measure.html In a digital camera or scanner, this device enables you to capture great pictures or scan in detailed material.
A photodetector lab Collimator: a device used for producing a beam of parallel rays of light or other radiation Photodetectors Lab at Stanford
Photodetector as a photoconductor (Bayonet Neil-Concelman, or sometimes British Naval Connector) connector is used to connect a computer to a coaxial cable in a 10BASE-TEthernet network. The wiring in this type of Ethernet is thin, 50 ohm, baseband coaxial cable. The BNC connector in particular is generally easier to install and less expensive than other coaxial connectors.
Connectors BNC etc
http://www.seapoint.com/products.htm Optical Sensors Very low power requirements & Small size 6000 m depth capability Optically confined sensing volume Insensitive to ambient light Linear output over more than 5 decades Four programmable ranges Optical feedback compensates for temperature coefficient and aging of optical components Very low offset voltage does not require adjustment Interfaces easily with data acquisition systems APPLICATIONS Pollution Monitoring Water and Wastewater Quality Sediment Transport Ocean Profiling River and Stream Monitoring
Seapoint specs • Power Requirements: 7-20 VDC, 3.5 mA avg., 6 mA pk. • Output 0-5.0 VDC • Output Time Constant 0.1 sec. • RMS Noise< 1 mV • Power-up Transient Period < 1 sec • Light Source Wavelength 880 nm • Sensing Distance (from windows) < 5 cm (approx.) • Linearity < 2% deviation 0-750 FTU • Sensitivity/RangeGainSensitivity (mV/FTU)Range (FTU)100x2002520x401255x105001x2**(** output is non-linear above 750 FTU) • Temperature Coefficient < 0.05%/°C • Depth Capability 6000 m (19,685 ft) • Weight (dry) 86 g (3.0 oz)• Operating Temperature0°C to 65°C (32°F to 149°F) • Material ABS plastic, epoxy
Other Seapoint sensors • Ocean Profiling or Moored Measurements • Water Quality • Biomass and Nutrient Measurements • Environmental Stress Tolerances • Dye Trace Studies • Leak Detection • Ocean color research • Wastewater discharge quality • Radiative transfer studies • DOM (Dissolved Organic Matter) cycle studies
NTE3031Phototransistor DetectorNPN-Si, Visible & IR http://www.nteinc.com/specs/3000to3099/NTE3031.html
90% Rise & Fall Time Calculation T90% T10% Rise Time=Time from 10% to 90% Fall Time = Time from 90% to 10% 10% Time Rising Exponential equation Falling Exponential equation
http://www.taosinc.com/pdf/til300.pdf Optocouplers ac or dc Signal Coupling Wide Bandwidth . . . >200 kHz High Transfer-Gain Stability . . . ±0.005%/°C 3500 V Peak Isolation Typical Applications – Power-Supply Feedback – Medical-Sensor Isolation – Opto Direct-Access Arrangement (DAA) – Isolated Process-Control Transducers
Laser Measurement System • Key Features • Zero to 50 feet operating range for most surfaces. • 0.1 in (2.5mm) accuracy, 0.02 in (0.5mm) short-term repeatability. • RS-232 serial output standard. • Optional RS-485/422, 4-20 mA current loop, and pulse width outputs. Reflected signal amplitude output for grayscale Images. • Fast response time: 50 KHz max sample rate. • Lightweight, compact, low power design. • Tightly collimated output beam for small spot size. • Three output beam configurations available: Visible, infrared, or eye safe infrared Ideally suited to level and position measurement, • machine vision, autonomous vehicle navigation, and 3D imaging applications.
Pyrometers (Pyro means fire in Greek) Any non-contact device that measures thermal radiation to determine temperature • Requires no physical contact and provides an instant reading up to 750 degress. • Great for brake surface temperature, exhaust pipes to find a dead cylinder, hot spots on firewalls and floor pans, oil pans, trans and rear ends, tire temperature, track surface, and many other things. • 50615 - Standard Infrared Pyrometer - $169.00 • 50617 - Laser Infrared Pyrometer - $249.00 http://www.teegardenmotorsports.com/long5.htm http://www.omega.com/literature/transactions/volume1/historical1.html
Summary • Introduction • Fundamentals of EM Radiation • Standing waves • Speed of light • spectrum • PIN Diode • CCD’s, Digital Cameras and scanners • Photodetectors • Turbidity & other photosensors • Phototransistors • Rise and Fall times • Optocouplers • A laser measurement system • Pyrometry