A device for injecting preparations is controlled by a sealed circuit block (10) containing integrated sensors (17, 21, 22, 23 24) which monitors selected parameters. Two pairs of integrated Hall elements (21, 23 and 22, 24) monitors movements relative to a sine formed magnetic field presented along the perimeter of a multipoled magnetized ring (7). The Hall elements in each pair are displaced 180° magnetically relative to each other and the two pairs of Hall elements are displaced 90° magnetically from each other. Each pair is coupled to a differential amplifier (25, 26) to provide a cosine and a sine signal, respectively. The sine signal is divided by the cosine signal to create a tangent signal as an entrance to a table showing the angle of the movement.