Proximity switch

摘要

In a proximity switch (1) having a transmitter (3) for outputting waves (5) and a receiver (4) for receiving these waves, the transmitter (3) and/or the receiver (4) are provided with a cover (11) of a material transparent to the waves (5) to be radiated or to be received and, behind the cover (11), at least one further second transmitter (13) and at least one further second receiver (14) are in each case arranged at such a lateral distance from one another that in the case of a contamination of the cover (11) causing a reflection, the waves (15') of the second transmitter (13) reflected from this cover can be picked up by the second receiver (4). This embodiment of the proximity switch (1) makes it possible immediately to trigger a contamination signal in the case of a complete contamination (12) of the cover (11) which has suddenly occurred or has continuously risen to a particular value. This signal can be evaluated so that subsequent damage is avoided and reliable monitoring of the degree of contamination of the proximity switch (1) is achieved. <IMAGE>