The term automation supplier usually identifies an inductive proximity sensor or metal sensor – the inductive sensor is the most commonly utilised sensor in automation. There are actually, however, other sensing technologies that use the phrase ‘proximity’ in describing the sensing mode. Included in this are diffuse or proximity photoelectric sensors that utilize the reflectivity in the object to change states and ultrasonic sensors which use high-frequency soundwaves to detect objects. Every one of these sensors detect objects that happen to be in close proximity towards the sensor without making physical contact.
One of the most overlooked or forgotten proximity sensors that you can buy may be the capacitive sensor. Why? Perhaps it is because they have a bad reputation going back to when they were first released years back, since they were more vunerable to noise than most sensors. With advancements in technology, this is no longer the case.
Capacitive sensors are versatile in solving numerous applications and may detect various types of objects for example glass, wood, paper, plastics and ceramics. ‘Object detection’ capacitive sensors can be identified by the flush mounting or shielded face of your sensor. Shielding causes the electrostatic field to be short and conical shaped, similar to the shielded version of your proximity sensor.
Just as there are non-flush or unshielded inductive sensors, there are also non-flush capacitive sensors, and the mounting and housing looks the same. The non-flush capacitive sensors use a large spherical field that allows them to be applied in level detection applications. Since capacitive sensors can detect virtually anything, they are able to detect quantities of liquids including water, oil, glue or anything else, and so they can detect quantities of solids like plastic granules, soap powder, dexqpky68 and all sorts of things else. Levels can be detected either directly the location where the sensor touches the medium or indirectly in which the sensor senses the medium through a nonmetallic container wall.
With improvements in capacitive technology, sensors have already been designed that could make amends for foaming, material build-up and filming water-based highly conductive liquids. These ‘smart’ capacitive sensors are based on the conductivity of liquids, plus they can reliably actuate when sensing aggressive acids like hydrochloric, sulfuric and hydrofluoric acids. Moreover, these sensors can detect liquids through glass or plastic walls around 10 mm thick, are unaffected by moisture and require a minimum of cleaning over these applications.
The sensing distance of fanuc parts depends upon several factors such as the sensing face area – the greater the better. The subsequent factor is definitely the material property in the object to be sensed or its dielectric strength: the higher the dielectric constant, the higher the sensing distance. Finally, how big the objective affects the sensing range. Just like having an inductive sensor, the prospective will ideally be similar to or larger in size compared to the sensor.
Most capacitive sensors possess a potentiometer to enable adjustment in the sensitivity of your sensor to reliably detect the prospective. The highest quoted sensing distance of the capacitive sensor is dependant on metallic target, and so there exists a reduction factor for nonmetal targets.
Although capacitive sensors can detect metal, inductive sensors needs to be employed for these applications for optimum system reliability. Capacitive sensors are perfect for detecting nonmetallic objects at close ranges, usually below 30 mm and also for detecting hidden or inaccessible materials or features.