Distance/Proximity Sensors

1.What are Proximity Sensors?

• These are sensor devices that detect the presence of nearby objects without any physical contact. PR sensors emit an electromagnetic field or a beam of electromagnetic radiation and look for changes in the field or return signal.

2.What are Proximity Sensors used for?

• These sensors can be used for a wide range of applications:
  • Can be used as parking sensors in cars. Here the sensors are integrated to the bumpers of the cars, and alerts the driver when the car is in close contact with another vehicle.
  • Are used in Ground Proximity Warning systems that are designed to alert pilots if their aircraft is in immediate danger of flying into the ground or an obstacle. 
  • They are also used in measuring vibrations of rotating shafts in machinery.
  • Are also used in roller coasters. This sensor precedes the trim brake in order to identify the current speed of the passing train. 

3.What are the types of proximity sensors?

• Inductive Proximity Sensors
  • These sensors follow the principles of electromagnetic induction to detect and measure objects. They detect magnetic loss due to eddy currents that are generated on a conductive surface by an external magnetic field. An AC magnetic field is generated on the detection coil, and changes in the impedance due to eddy currents generated on a metallic object are detected.
• Capacitive Proximity Sensors
  • This sensor works is that one of the conductive elements, or plates, is inside the sensor itself while the other one is the object to be sensed. These sensors detect changes in the capacitance between the sensing object and the Sensor. The amount of capacitance varies depending on the size and distance of the sensing object.
• Magnetic Proximity Sensors
  • These sensors are used for non-contact position detection beyond the normal limits of inductive sensors. Since magnetic fields penetrate all non-magnetizable materials, these sensors can detect magnets through walls made of non-ferrous metal, stainless steel, aluminum, plastic or wood.
• Ultrasonic Proximity Sensors
  • These sensors are a common type of pr sensor used in many manufacturing and automation applications. They work by using sound frequencies higher than the audible limit of human hearing, which is typically in the range of 25 to 50 kHz.
• Photoelectric Proximity Sensors
  • These sensors detect objects directly in front of them by detecting the sensor's own transmitted light reflected back from an object's surface. When the light beam is able to reflect back, this registers as no object being present.