A sensor device detects an object, in particular for optically detecting smoke particles. The sensor device contains a transmitting device for emitting transmit radiation, a receiving device for receiving receive radiation having scattering radiation that is generated by an at least partial scattering of the transmit radiation by the object, and for outputting a measurement signal indicative of the receive radiation, a signal modification device for modifying the measurement signal and for outputting a modified measurement signal, a level of the modified measurement signal increasing after the transmitting device has been switched on, and a calibration device for monitoring the modified measurement signal. The calibration device is embodied such that a reaching of a predefined signal level for the modified measurement signal can be detected and that a time interval between the switching on of the transmitting device and the reaching of the predefined signal level can be determined.