Page 338 - Sensors and Control Systems in Manufacturing

294
Cha p te r
S i x

6.9 Other Sensors
Many other types of sensors exist. These include avalanche photodi-
odes, APD, bolometers, self-scanned arrays, and photon drag detec-
tors. A sensor manufacturer can provide information about these
devices and can discuss the physics and advantages of each detector
technology.

6.10 Selecting a Sensor
Reviewing a few key design aspects generally provides enough infor-
mation for making an optimum choice of detector for a given applica-
tion (Fig. 6.15).

6.11 Infrared Light Domain
For sensing wavelengths below 1100 nm, photoconductive cells or a
silicon-based detector should be appropriate. At wavelengths above
1100 nm, the costs and technology options are not straightforward,
and a detector vendor consulted at the beginning of a design pro-
gram will provide the most effective guidance.

Photo Avoid Costly
Detect Visible
Are No No Is the No Counting or No Photo
Wavelengths Light with Application High Noise Multiplier,
Start >1100 nm? Moderate 350-1100 nm Immunity Optical IC’s -
Precision?
Required Hybrids
Yes Yes Yes Yes
Guidance?

Consider
Final Photo- Consider Consider Final
Selection Conductive Photo-resistor Photo Diode Selection
Cell

Electronic Assembly
End

FIGURE 6.15 Selecting appropriate detectors for specifi c sensing applications.