Abstract: A sensor for monitoring a monitoring area having a transmitter for transmitting radiation into the monitoring area for reflection at an object in the monitoring area, a test transmitter for transmitting a test signal comprising radiation, a receiver for receiving the radiation of the transmitter that is reflected at the object or the radiation of the test transmitter, and an evaluation device for ascertaining a distance value on the basis of the delay in the transit time or the phase of a modulation between the transmitted and received radiation of the sensor. The sensor further comprises a memory for storing an expectation value for the expected distance value of the received test signal, and a comparison device for comparing a distance value on the basis of the received test signal with the expectation value and for outputting a safety signal on the basis of the comparison.

Abstract: A sensor for monitoring a monitoring area having a transmitter for transmitting radiation into the monitoring area for reflection at an object in the monitoring area, a test transmitter for transmitting a test signal comprising radiation, a receiver for receiving the radiation of the transmitter that is reflected at the object or the radiation of the test transmitter, and an evaluation device for ascertaining a distance value on the basis of the delay in the transit time or the phase of a modulation between the transmitted and received radiation of the sensor. The sensor further comprises a memory for storing an expectation value for the expected distance value of the received test signal, and a comparison device for comparing a distance value on the basis of the received test signal with the expectation value and for outputting a safety signal on the basis of the comparison.