Sensors

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.

Sensors are reliable, accurate, and don’t get tired; working well in places where humans would rather not be.

Common sensors and their applications

Sensor	Description	Application
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
Temperature	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
Sound	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
Pressure	Measures pressure.	Burglar alarm systems Traffic light controls Chemical processes Liquid through pipes
Gas	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
Light	Can detect the ambient light level, meaning how bright or dark it is.	Controlling street lighting Burglar alarms (beams of light) Automatic doors Greenhouse
pH	Measures how acidic or alkaline a material is.	Water treatment plants Pollution monitoring (river) Aquariums Greenhouse