Can anyone explain why these proximity sensors are the best for detecting objects on conveyor belt. We have more sensors like IR sensor, PIR sensor But why are proximity sensors used in more and more systems.

How do you select the sensor for your design?

 

Can anyone explain why these proximity sensors are the best for detecting objects on conveyor belt.

What proximity sensors? You say "these" with no reference as to what these actually is.

I choose sensors based on application much the same way I choose anything else. If I want to detect small white cardboard boxes containing a plastic part I certainly would not choose an inductive proximity sensor. A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. They come in a wide range of types. Inductive, IR, Optical, Capacitive and many more. Some types, for instance Optical may use a beam or be reflective. IR sensors as well as PIR sensors meet the definition of proximity sensor.

Proximity Sensor:

"A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation, and looks for changes in the field or return signal".

Again, you choose a sensor based on the application. Some are better for some applications while others for other applications.

Ron

 

To add, Proximity sensors can take many forms, as Ron noted.
For example there are some that detect ferrous metal, some non-ferrous, some are used in pneumatic cylinders to detect the piston location by using a small embedded magnet in the piston itself.
It all depends on the application, they have been commonly used for some decades now as they are generally small, rugged and compact, such as the cylindrical type.
Max.

 

Can anyone explain why these proximity sensors are the best for detecting objects on conveyor belt. We have more sensors like IR sensor, PIR sensor But why are proximity sensors used in more and more systems.

How do you select the sensor for your design?

For a conveyor belt the logic is to fill the belt or to detect if it is empty so that the preceding or successive conv-belts may slow or speed up. usually inductive prox sensors with small levers on the side guide of the conveyors detect the presence of accumulation or sense empty depending upon the condition

 

For conveyor belt object detection useage , often the infra red light versions are used, there is retro-reflective or just light source-receiver.
Max.

 

You can get inductive proximity detectors that can detect metal. The sensing distance depends on the type of metal and the diameter of the inductive coil on the sensor. Ferrous metals (with iron content) are easier to detect so can be detected at greater distance. Most industrial proximity detectors only detect in the millimeter range. Larger coil for longer distances.

Capacitive proximity detectors can detect non-metallic objects but work best on dense materials or materials that contain water (conductive). Once again, fairly short distance.

Optical sensors can detect objects at long distances and are very accurate if the beam is very thin (like a laser). Can be "through beam" with separate emitter and detector devices, retro-reflective that use a special reflector (like a bicycle reflector), or sensitive devices that will detect the reflection from a surface. Transparent objects like empty bottles can be detected by reflection from the surface or by deflection of a through-beam.