Method and device for monitoring an oil level in a machine

A method for monitoring an oil level in a machine by means of an optical sensor, wherein a transmitter transmits a light beam into an optical system, and the light beam is reflected or refracted by the optical system, as a function of the oil level to be monitored, to a receiver, where a reception signal is generated, the light beam being emitted at a set transmission power during the monitoring operation, and an oil deficiency being recognized when the reception signal exceeds a predefined level value,

• characterized in that the transmission power of the light beam is settable between a minimum and a maximum transmission power, and a check of a degree of contamination of the optical system is carried out according to the following test operation as soon as an oil deficiency is recognized, the test operation having the steps of:
• a. transmitting a first light beam with the transmitter at the maximum transmission power to generate a first reception signal at the receiver,
• b. transmitting a second light beam with the transmitter at a pre-set transmission power that is less than the maximum transmission power to generate a second reception signal at the receiver,
• c. determining the difference between the first reception signal and the second reception signal
• d. comparing the difference between the first reception signal and the second reception signal with reference values indicating the degree of contamination of the optical system.