Sensors

Question 1

Define a sensor (2)

Answer 1

input devices

read physical properties from surroundings

Question 2

Temperature sensor description (2)

Answer 2

measures temperature of surroundings by sending signals

temperature changes = signals change

Question 3

Examples of temperature sensors (3)

Answer 3

control central heating system

control chemical process

control temperature in greenhouse

Question 4

Moisture sensor description

Answer 4

measures water levels

Question 5

Examples of moisture sensors (2)

Answer 5

control soil moisture levels in greenhouse

monitor moisture levels in food processing factory

Question 6

Description of humidity sensor

Answer 6

measures amount of water vapour in air sample

Question 7

Examples of humidity sensors (2)

Answer 7

monitor humidity levels in building

monitor humidity levels in greenhouse

Question 8

Description of light sensors (2)

Answer 8

use photoelectric cells

produce output depending on light brightness

Question 9

Examples of light sensors (2)

Answer 9

switching street lights on/off

switching car lights on/off

Question 10

Description of pressure sensors (2)

Answer 10

transducer

generates different electric currents depending on pressure applied

Question 11

Examples of pressure sensors (2)

Answer 11

weighing of lorries

measuring gas pressure in nuclear reactor

Question 12

Description of proximity sensor

Answer 12

detect presence of nearby object

Question 13

Examples of proximity sensors

Answer 13

detect when face is close to mobile phone

Question 14

Description of infrared active sensors (2)

Answer 14

use invisible infrared beam

beam broken = change in amount of infrared reaching detector

Question 15

Examples of infrared active sensors (2)

Answer 15

security alarm system

activating windscreen wipers

Question 16

Description of infrared passive sensors

Answer 16

measure heat radiation given by object

Question 17

Examples of infrared passive sensors (2)

Answer 17

security alarm system

monitor temperature

Question 18

Description of acoustic/sound sensors

Answer 18

microphones that convert sound into electric signals/pulses

Question 19

Examples of acoustic/sound sensors

Answer 19

pick up noise in security

Question 20

Description of gas sensors

Answer 20

detect gas being monitored and produce outputs

Question 21

Examples of gas sensors (2)

Answer 21

monitor pollution levels

monitor gas levels in greenhouse

Question 22

Description of pH sensors

Answer 22

measure acidity through changes in voltage

Question 23

Examples of pH sensors (2)

Answer 23

acidity in soil

acidity in chemical processes

Question 24

Description of accelerometer sensor

Answer 24

measure motion of object

Question 25

Examples of accelerometer sensors (2)

Answer 25

apply air bags in car

mobile phones = change between landscape and portrait

Question 26

Description of flow sensor

Answer 26

measure flow rate of liquid/gas and produce output

Question 27

Examples of flow sensor (2)

Answer 27

measure gas flow in pipes

respiratory devices

Question 28

Description of level sensor

Answer 28

detect changing liquid levels

Question 29

Examples of level sensors (2)

Answer 29

petrol tank

pharmaceutical process

Question 30

7 mark sensor answer (7)

Answer 30

Sensor name

Sensor send signal which converts analogue to digital using ADC

Microprocessor compares digital value (ADC value) with stored value (in the question)

If it’s within range nothing happens

If it’s outside ange signal is sent to actuator

does something (according to question)

system operates in a continuous loop