Sensors are input devices that record data about the physical environment around it.

Sensors send data to a microprocessor (computer).  They do not make judgements, decisions or control any output devices.

There are many types of sensors used in a variety of household, commercial and industrial applications.

Advantages of using computer sensors

  • Sensors are reliable
  • Sensors are accurate
  • Sensors don’t get tired
  • Sensors work well in places where humans would rather not be

Common sensors and their applications

Magnetic Field

Detect changes in magnetic fields.
Can measure the strength and direction of a magnetic field.

  • Mobile phones
  • Anti-lock braking
  • Detection of cars at traffic lights
  • Reading magnetic ink characters on cheques

Motion (infra-red)

Detects movement / heat from objects.

  • Automatic doors
  • Burglar alarm systems
  • Gaming systems, inc accelerometer
  • Counting, e.g. people or cars


Measures heat generated by an object or system. By measuring the change in heat, the sensor can detect changes in temperature.

  • Chemical process or reaction
  • Central heating (thermostat) / air-con
  • Greenhouses
  • Ovens, refrigerators and freezers


Measures the presence of sound.

  • Burglar alarm systems
  • Leak detection system

Moisture / Humidity

Moisture sensors measures the amount of moisture in a certain material whilst humidity sensors measure the amount of moisture in the air, along with its temperature.

  • Clothes dryer
  • Environmental control / greenhouse, air-con


Measures pressure.

  • Burglar alarm systems
  • Traffic light controls
  • Chemical processes
  • Liquid through pipes


Detects the presence of gas in a certain area.

  • Pollution monitoring (river)
  • Greenhouse environments
  • Confined areas (space craft, aircraft)
  • Fish tanks / aquariums
  • Carbon monoxide alarms


Can detect the ambient light level, meaning how bright or dark it is.

  • Controlling street lighting
  • Burglar alarms (beams of light)
  • Automatic doors
  • Greenhouse


Measures how acidic or alkaline a material is.

  • Water treatment plants
  • Pollution monitoring (river)
  • Aquariums
  • Greenhouse