Sensors

Sensor is a-

•  Device that senses a physical quantity 
• This physical quantity becomes input to the sensor 
• In the present context, the output of the sensor should be an electrical quantity 
•  Sensor output is a function of sensor input 
• Input is called measured quantity or “measurand”

Examples of the measurand are: Temperature  Pressure and force  Torque  Displacement, velocity and acceleration  Strain  Flow, level  pH value  Humidity  Gas concentration  Voltage and current  Power and power factor  Frequency

The electrical output of a sensor can be one of the two types: 

•  Variation of an electrical parameter 
•  An electrical signal

Variation of electrical parameter means 

•  Variation of resistance (delta R), or 
• Variation of inductance (delta L), or 
• Variation of capacitance (delta C) 

Electrical signal means 

• Voltage signal, or 
• Current signal

Hence  Sensors are the ways of getting information into your device, finding out things about your surroundings. Pushbuttons and switches, which are probably the simplest sensors

Actuators: Actuators are the outputs for the device—the motors, lights, and so on, which let your device do something to the outside world.most useful actuators is light,LED