Sensors and its types

Broadly a sensor can be defined as an electronic device which reads the physical property of one form and converts into another form. Basically a senor reads on format of signals and converts into another format. Best and simple example of sensor can be illustrated in thermometer. A thermometer reads the temperature of the body and converts into the raise of mercury in calibrated capillary tube, using which temperature can be measured easily. 

Sensors can be of many types like proximity sensors, temperature sensors (RTD sensor), pressure sensors, chemical sensors, optical sensors, image sensors, bio sensor etc. Depending on the applications, sensors are classified like above. 

Proximity Sensors

 A proximity sensor is an electronic instrument used to detect the nearby objects and its distance from the certain point. They will be able to measure the exact distance from the point. To better understand this let us take an example of automatic opening and closing of door in an office, without manual intervention. The door will be in closed position always. When the person comes close to the door, the proximity sensors installed on the door senses the object and passes electromagnetic signal to the door controller, which in turn opens the door. When the person enters inside, the door will close.  

Proximity sensors can be of two major types, one is inductive proximity sensors and the other one is capacitive proximity sensors.  Capacitive proximity sensors works on the principle of capacitor. These sensors contain the capacitor plate. The capacitance of this capacitor will vary as the object moves near the sensor, which in turn used to measure the distance of the object. Capacitive sensors can detect both metallic and non-metallic objects. The working principle of Inductive proximity sensors is completely different. These sensors have a magnetic coil which generates magnetic field upon passing electric current. Whenever a metallic object comes near the inductive sensor, the magnetic field changes and this will be recorded by the detector. Inductive sensors can be used only to detect metallic objects. 

RTD Sensors

RTD senor also called as temperature sensors are used to measure the temperature. RTD sensors contains a resistor, the resistance of which changes with temperature. The change in resistance is correlated to the temperature reading. RTD sensors are used to measure the temperature of the element, temperature of fluid, heat generated in a system, liquid measurement, air and gas stream measurement etc.

Optical Sensors (Photo Electric Sensors)

Optical sensors are used to detect the presence of light. The light is converted into electro electronic signals by these sensors.  The strength of electronic signals is in turn used to measure the presence of light.  It works similar to photo resistor. They can be used in applications like automatic switching on/off of lights based on the darkness of the room.

SRI Electronics is the most well known electronic instruments manufacturers and suppliers. Their products include inductive type proximity sensor, temperature controllers, optical sensors, thermocouples etc. They are also well reckoned RTD sensor manufacturers of all types and specifications.