displaced 10 u00b0 apart along the gray code sequence track it will be readily acknowledged that the contact arms of the gray code sensor assembly may be arranged with other spacings while still obtaining the same sensor output as the gray code sensor assembly rotates with respect to the gray code cylinder for example in a situation where the contact arms sw 1 and sw 2 are arranged as shown on the figure the contact arm sw 3 may be moved a distance corresponding to one or more complete periods to either side fig1 is a schematic representation of the three contact arms 294 a 294 b and 294 c as they wipe over six consecutive distinct code positions position 0 to 5 each of the three contact arms will generate a code change when entering and leaving an isolated area this configuration provides a total of 72 gray code changes pr revolution in the depicted device which is a half incremental injection device the number of distinct rotational positions p pr revolution is 36 and therefore each position that the dosage selector can be adjusted to correspond to two different adjacent gray code states another embodiment may include a full incremental injection device which may comprise 24 distinct rotational positions p pr revolution of dosage selector 260 in accordance with the above by selecting the present described gray code sensor system which has 72 gray code states oversampling by a factor of either 2 or 3.