Disclosed is an arrangement for the intrinsically safe detection of movements of a body, such as a wheel. The arrangement includes a magnetic encoder (5, 25) and a sensor (26), the magnetic encoder (5, 25) moving with the body and is magnetically coupled to at least two sensor elements (S1, S2) of the sensor (26) via a magnetic air gap. The sensor (26) has at least two mutually separate signal paths (S1, fl; S2, f2) which have at least one of the sensor elements (S1, S2) and a signal conditioning stage (28, 29). A primary measuring signal path (S1, f1) is constructed so that during normal operation represents an output signal the basic frequency of the encoder movement or the temporal profile of the output signal have patterns. The temporal occurrence of the patterns correspond to the basic relative speed between the sensor (26) and the pole pairs of the encoder (5, 25) which are detected by the sensor.