By using a two-part assembly of a rotary member (10) bearing one or more wipers (14) clipped on to a substrate member (1) bearing one or more tracks (3), subassemblies may be supplied which can be used by manufacturers of articles (20,21,22) in which it is desired to sense the angular position of one member (20) relative to another (22), but which are easy to install and reliable in use. The assembly provides substantial savings in terms of the number of individual components used, thus reducing manufacturing and assembly costs. Manufacturing costs may also be reduced by using track material as a bearing material, as both track and bearing may be applied simultaneously, e.g. by screen printing.