Sensors (Cambridge (CIE) IGCSE Computer Science)

Revision Note

James Woodhouse

Written by: James Woodhouse

Reviewed by: Lucy Kirkham

Sensors

  • Sensors are input devices

  • They measure a physical property of their environment such as light levels, temperature or movement

  • Sensors can be used for monitoring systems and control systems

    • A monitoring system tracks the state of a system, it gathers data and may issue warning messages

    • A control system will control the system based upon the input from sensors

    • For example, if the water temperature in a fish tank fell below the acceptable level, a control system would start up a heater

    • The system will then continue to check the water temperature readings (outputs) and when they are within the acceptable range it will switch off the heater

  • A process where outputs are recycled and used as inputs, creating a continuous cycle is called a feedback loop

Examiner Tips and Tricks

  • You are likely to be given a scenario and asked to identify the sensors that would be used.

  • The 14 sensors you need to be aware of are in the table below

Sensor type

What it measures

Typical use

Acoustic

Sound levels

To detect changes in sound levels of industrial machinery

To monitor noise pollution

In security system to detect suspicious sounds

Accelerometer

Acceleration rate, tilt, vibration

Detecting sudden changes in vehicle movement and deploy safety features if needed

In mobile phones to detect orientation of the device

Flow

Rate of gas, liquid or powder flow

Detect changes in the flow through pipes in water system

Gas

Presence of a gas e.g. carbon monoxide

Detect levels of gas in confined spaces

Detect gas levels when fixing gas leaks

Humidity

Levels of water vapour

Monitor humidity in greenhouses

Infra-red

Detecting motion or a heat source

Security systems detecting intruders who break the beam

Measures heat radiation of objects - used by emergency services to detect people

Level

Liquid levels

Detects levels of petrol in a car tank

Detect levels of water in a water tank

Detect a drop in water levels due to a leak

Light

Light levels

Automatically switching on lights when it gets dark (street lights, headlights)

Magnetic field

Presence and strength

Anti-lock braking system

Monitoring rotating machinery such as turbines

Moisture

Presence and levels of moisture

Monitoring moisture in the soil

Monitoring dampness in buildings

pH

Acidity or alkaline

Monitoring soil to ensure optimum growing conditions

Monitor ph levels in chemical processes

Pressure

Gas, liquid or physical pressure

Monitoring tyre pressure

Monitoring pressure in pipes during the manufacturing process

Proximity

Distance

Monitoring the position of objects in robotics

Used in safety systems to prevent objects from colliding

Temperature

Temperature in Celsius, Fahrenheit or Kelvin

Used to maintain temperature in swimming pools

Used to control temperature in chemical processes

Worked Example

What type of sensor would be used to help drivers when reversing?  [1]

A

Motion

B

Infra-red

C

Light

D

Proximity


Is this a monitoring system or a control system? [1]

A

Monitoring

B

Control

Answer

A

Motion

B

Infra-red

C

Light

D

Proximity

A

Monitoring

B

Control

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James Woodhouse

Author: James Woodhouse

Expertise: Computer Science

James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.

Lucy Kirkham

Author: Lucy Kirkham

Expertise: Head of STEM

Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.