By: OMRON Automation, India
The term “Proximity Sensor” indicates all those sensors that perform non-contact detection of target objects that are close by or within the general vicinity of the sensor, in comparison to other sensors, such as limit switches, that detect objects by physically contacting them. These Sensors convert information on the movement or presence of an object into an electrical signal.
There are three types of detection systems that do this
– systems that use the eddy currents that are generated in metallic sensing objects by electromagnetic induction,
– systems that detect changes in electrical capacity when approaching the sensing object, and
– systems that use magnets and reed switches.
OMRON Proximity Sensors are available in models using high frequency oscillation to detect ferrous and non-ferrous metal objects and in capacitive models to detect non-metal objects. Models are available with environment resistance, heat resistance, resistance to chemicals, and resistance to water.
The portfolio comprises of the following categories :
– Rectangular : These Proximity Sensors use high-frequency oscillation. There are available in a wide range of sizes to enable selection to match the installation location.
– Cylindrical : These Proximity Sensors use high-frequency oscillation. They resist heat, chemicals, and water better than Rectangular Sensors. They are available in both shielded and unshielded models.
– Separate Amplifier : With these Proximity Sensors (highfrequency oscillation), the Amplifier and Sensor Head are separated to enable downsizing and facilitate adjustment.
– Capacitive : Capacitive Proximity Sensors can be used to detect non-metal objects, such as liquids and plastics.
– Others : Proximity Sensors are also available for specia applications in long-distance models, and slim models are available for use combined with Proximity Sensors.ultrasonic.
Features of Proximity Sensors
– No abrasion or damage to the object : The Proximity Sensors detect an object electrically without touching it, and so they do not cause abrasion or damage to the object.
– Longer service life : No contacts are used for output. They use semiconductor outputs, so the Sensors have a longer service life (excluding sensors that use magnets).
– Suitability for oil and water environments : Unlike optical detection methods, Proximity Sensors are suitable for use in locations where water or oil is used. Detection takes place with almost no effect from dirt, oil, or water on the object being detected.
– High-speed resonance : They provide high-speed response, compared with switches that require physical contact.
– Wide temperature range : They also find a great utility in a wide temperature range (from -40 to 200°C)
– Not affected by colors: They detect the physical changes of an object, so they are almost completely unaffected by the object’s surface color.
– Affected by ambient conditions : Unlike switches, which rely on physical contact, Proximity Sensors are affected by ambient temperatures, surrounding objects, and other Sensors.
Inductive and Capacitive Proximity Sensors are affected by interaction with other Sensors. Because of this, care must be taken when installing them to prevent mutual interference. Care must also be taken to prevent the effects of surrounding metallic objects on Inductive Proximity Sensors, and to prevent the effects of all surrounding objects on Capacitive Proximity Sensors.
Industry segments utilizing the Proximity Sensors
Packaging, Machine Tools and Molding industries are the notable industries utilizing Proximity Sensors.
– To detect the presence of cans during conveyance in order to prevent missing print with an ink-jet printer.
– To detect presence of a thin aluminum cap on water bottles
-To detect milk/juice inside a non-transparent white tetra pack.