Speed sensors measure rotational movements on involute or rectangular geared sensor wheels in 1 and 2 channel versions. They are available for cog wheel modules from 1.0 to 3.0. They have a max. switching frequency of 20,000 Hz, or 25,000 Hz in special implementations. The speed sensor is also suitable for zero speed. The DWG 04 works based on the eddy current principle, in which different voltages are transmitted from the primary to the secondary inductor, depending on the position of the tooth tip and tooth base. The geometric arrangement of multiple inductors results in two output signals with a phase offset of 90°. This measuring method makes it possible for the sensor wheel to be made from non-magnetic, electrically conductive materials such as aluminium. However, ferromagnetic materials like steel cogs can also be detected. The flange housing of the sensor is made from brass; the electronics are completely sealed.