A sensor device which is suitable for receiving and transmitting signals and can be placed on a test persons head, includes a sensor device housing having a signal pin on its distal side for receiving a signal and a connection on its proximal side for the signal transmission of a signal received by the signal pin. A sensor device holder has an axial through opening in which the sensor device housing is disposed so as to be steplessly axially displaceable. When the sensor device housing is axially displaced relative to the sensor device holder, the sensor device housing does not change its radial orientation. A cap having a plurality of sensor devices is also provided.
