Chapter 3

Question 1

Motion sensor examples

Answer 1

1) CCTV
2) doors
3) lights
4) car park barriers

Question 2

Active motion sensor

Answer 2

• emits energy into environment
• microwave sensor
• emit microwave, detect change in reflection, bounce off
• security
• work in harsh environments
• prone to false alarm (e.g object gets blown by wind)

Question 3

Passive motion sensor

Answer 3

• reads energy in room, detect changes caused by movement
• no work in harsh environment
• no detect slow motion
• passive infrared sensor
• security

Question 4

Pressure sensor

Answer 4

• use piezoresistance
• specific level of pressure to a level of charge in a substance (crystal)
• change in level of charge is a change in level of pressure

Question 5

Pressure sensor: uses

Answer 5

1) Airbag safety system
2) Liquid/ gas pipes , not flow too fast (nuclear plant), safety
3) pressure placed on accelerator / brake
4) aviation/ marine : atmosphere, breathing condition
5) touch screen , signal tell where pressure is applied

Question 6

Uses of humidity sensor

Answer 6

• agriculture
• allergy
• manufacturing
• meteorological station

Question 7

Uses of temp sensor

Answer 7

• washing machine
• dish washer
• dryer
• fridge
• AC

Question 8

Uses of light sensors

Answer 8

Photoresistor: change its resistance based on intensity of light

• street light
• camera
• phone

Question 9

Sensor application: traffic

Answer 9

Induction loop

• detect car overhead
• metal changes magnetic field induced in the loop