Probe head

A probe head (10) for orientating a probe relative to a head of a coordinate measuring machine, has a support (12), a rotor (14) rotatable relative to the support (12), and a swivel (18) rotatable relative to the rotor (14). The rotor (14) and swivel (18) are mounted for rotation through a series of discrete, and repeatable rest positions. The relative orientation of support (12), rotor (14) and swivel (18) is detected by an indicating mechanism comprising a printed circuit board (34) having a series of electrical conductive elements (36) and (38) and a contact arm (40) mounted for rotation over the conductive elements on the circuit board (34). When the electrical contacts (42) to (46) come into register with the conductive elements (36) on the circuit board (34) a pulse is transmitted to a micro-processor (50) which determines the relative orientation of e.g. the support (12) and rotor (14); this is shown on an LCD (52). The micro-processor may also provide instructions (on the LCD (52)) indicating in which direction the rotor (14) should be moved in order to attain a predetermined position stored in a memory of the micro-processor; an indication is provided on the LCD (52) that such a predetermined position has been attained.