§ 188.8.131.52 of IEC 60947-1 defines 4 pollution degrees:
TURCK proximity sensors belong to category 3 acc. to IEC 60947-1 conductive or dry, non-conductive dirt that becomes conductive due to condensation.
Diffuse mode sensors with background suppression operate with an emitter an several receivers. The position of the object as well as the optical structure of the sensor determine on which receiver the largest quantity of light falls. The sensor electronics then determines whether the reflecting target is in or outside the measuring range. They are available either with fixed or adjustable field.
Like retroreflective sensors, diffuse mode sensors host emitter and receiver circuitry in the same housing. In this sensing mode, an object is not detected through the interruption of a light beam but through the reflectivity of an object. An object is detected when sufficient light is reflected back to the emitter. The switching distance of diffuse mode sensors depends largely on the reflectivity of the object.
Square metal plate to determine the measuring range sn:
Thickness: 1 mm
Edge lenth 3 x sn, if 3 x sn is greater than the diameter of the active face, otherwise just the diameter of the active face.
Sensors with dynamic output respond highly sensitive and create a short pulse upon attenuation.