The word automation supplier usually means an inductive proximity sensor or metal sensor – the inductive sensor is easily the most commonly utilised sensor in automation. There are, however, other sensing technologies which use the term ‘proximity’ in describing the sensing mode. Such as diffuse or proximity photoelectric sensors which use the reflectivity in the object to change states and ultrasonic sensors that use high-frequency soundwaves to detect objects. All of these sensors detect objects which are in close proximity on the sensor without making physical contact.
One of the more overlooked or forgotten proximity sensors available today is the capacitive sensor. Why? Perhaps it is because there is a bad reputation dating back to to after they were first released yrs ago, because they were more vunerable to noise than most sensors. With advancements in technology, this has stopped being the case.
Capacitive sensors are versatile in solving numerous applications and will detect many types of objects like glass, wood, paper, plastics and ceramics. ‘Object detection’ capacitive sensors can be recognized by the flush mounting or shielded face in the sensor. Shielding causes the electrostatic field to get short and conical shaped, much like the shielded version of your proximity sensor.
Just seeing as there are non-flush or unshielded inductive sensors, additionally, there are non-flush capacitive sensors, and also the mounting and housing looks exactly the same. The non-flush capacitive sensors have got a large spherical field that enables them to be utilized in level detection applications. Since capacitive sensors can detect virtually anything, they can detect quantities of liquids including water, oil, glue and so forth, and so they can detect amounts of solids like plastic granules, soap powder, dexqpky68 and just about everything else. Levels might be detected either directly the location where the sensor touches the medium or indirectly where the sensor senses the medium using a nonmetallic container wall.
With improvements in capacitive technology, sensors are already designed that may make up for foaming, material build-up and filming of water-based highly conductive liquids. These ‘smart’ capacitive sensors derive from the conductivity of liquids, and they can reliably actuate when sensing aggressive acids including hydrochloric, sulfuric and hydrofluoric acids. Moreover, these sensors can detect liquids through glass or plastic walls approximately 10 mm thick, are unaffected by moisture and require little if any cleaning within these applications.
The sensing distance of fanuc module is determined by several factors like the sensing face area – the larger the better. The next factor is the material property of the object to become sensed or its dielectric strength: the higher the dielectric constant, the higher the sensing distance. Finally, the actual size of the target affects the sensing range. Just like with an inductive sensor, the marked will ideally be equal to or larger in dimensions compared to sensor.
Most capacitive sensors have got a potentiometer to permit adjustment in the sensitivity in the sensor to reliably detect the marked. The maximum quoted sensing distance of a capacitive sensor is dependant on a metal target, and so there exists a reduction factor for nonmetal targets.
Although capacitive sensors can detect metal, inductive sensors must be used for these applications for max system reliability. Capacitive sensors are fantastic for detecting nonmetallic objects at close ranges, usually below 30 mm as well as for detecting hidden or inaccessible materials or features.