Block 3 - lecture 9

Question 1

EM frequencies commonly used in process control?

Answer 1

visible and infrared

Question 2

Optical sensor?

Answer 2

converts light to electronic signals

Question 3

Photoelectric sensor?

Answer 3

can detect distance, absence/presence

Question 4

example of optical transduction?

Answer 4

temperature measurement by EM radiation

Question 5

Photoresistor/LDR?

Answer 5

resistance decreases with light intensity

• moderate response time
• low cost
• rugged/strong
• continually changing
• bidirectional

Question 6

PIN photodetector?

Answer 6

• in reverse bias

- the depletion region widens until its potential = applied voltage, then current stops

Question 7

equation for a photodiode?

Answer 7

R=Ip/Po

responsivity = photocurrent/optical power

Question 8

APD photodetector?

Answer 8

a photodiode with internal gain

Question 9

MSM photodetector?

Answer 9

composed of schottky diodes:

• low voltage drop (efficient)
• fast low to high transition
• large bandwidth
• good stability

Question 10

name for current produced when photovoltaic cell is unloaded?

Answer 10

short-circuit current

Question 11

phototransistors?

Answer 11

transistor with base current supplied by light

Question 12

motion sensor requirements

Answer 12

• high sensitivity
• fidelity (faithful reproduction)
• detection area (range/field of view)
• short response time
• minimum noise