sensors

** Sensors **  by Ulemu & Zainab A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. they are three types of sensors :
 * temperature sensor
 * pressure sensor
 * light sensor
 * Motion sensor


 * **Temperature sensor**:


 * A temperature sensor is specially designed to detect temperature. Temperature sensors are found in many things in order to sound an alarm when a certain temperature has been exceeded. e.g. thermometer


 * Temperature is when an instrument of some sort determines the sensation of warmth or coldness felt from contact with it.

A **pressure sensor** measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer it generates a signal as a functionn of the pressure imposed.   **Light sensor**: A light sensor is used to detect the level of ambient light and to produce an output signal representative of the detected amount or level of such ambient light. A light sensor includes a light transducer for converting light into an electrical signal and may also include electronics for signal conditioning, compensation for cross-sensitivities such as temperature, and output signal formatting .
 * **Pressure sensors**:
 * Pressure sensors are used for control and monitoring in thousands of everyday applications.
 * Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude.
 * Pressure sensors can alternatively be called **pressure transducers**, **pressure transmitters**, **pressure senders**, **pressure indicators** and **piezometers**, **manometers**
 * It is used to provide information on distance, shape, speed, dimensions, and even types of substances contained in a wide array of objects.
 * Within industries ranging from architecture to offset printing light sensors are essential tools used for their high level of precision.
 * Used to automatically on street lights.

Movement sensors


 * Movement sensors are very similar in design to tilt switches; in fact, some tilt switches are used as motion sensors. The sensor will be in one condition (open or closed) at rest. When it is subjected to motion it will continually change state as long as it remains in motion.
 * Used for night time lights when it sensors darkness or other lights which also sense movement when you walk and they automatically switch on.