The analogue rotational speed sensor Sensor-PPC-04/12-SDS-CAB allows contactless speed measurements on rotating parts. This is based on an opto-electrical measuring principle which determines the rotational speed using a reflective marking strip on the shaft with a high level of precision. The touch-based rotational speed measurement is achieved by using a contact adaptor which is attached to the sensor and touches the rotating component during the measurement. This process also provides highly accurate measuring results. For particularly small surfaces, the focusing adaptor makes it easier to measure the values.