Abstract: A probe head for orientating a probe relative to a head of a coordinate measuring machine, has a support a rotor rotatable relative to the support, and a swivel rotatable relative to the rotor. The rotor and swivel are mounted for rotation through a series of discrete, and repeatable rest positions. The relative orientation of support, rotor and swivel is detected by an indicating mechanism comprising a printed circuit board having a series of electrical conductive elements and a contact arm mounted for rotation over the conductive elements on the circuit board. When the electrical contacts of the contact arm come into register with the conductive elements on the circuit board a pulse is transmitted to a micro-processor which determines the relative orientation of e.g. the support and rotor which is shown on the LCD.

Abstract: An optical analogue probe (9) is used on a co-ordinate measuring machine (1). Prior to use, it is datumed to compensate for any misalignment of the angle (.theta.) of its measurement axis (12A) from each of the machine's axes (X,Y,Z). Trigger points (D2,D3) are defined near opposite ends of the probe's measurement range (MR). A first set of machine X,Y,Z co-ordinates of at least four points (40) on a test sphere (38) are taken at one probe trigger point (D2). A corresponding set of co-ordinates for another four points (44) are taken at the other trigger point (D3). For each set of co-ordinates, a calculation is made of the center of the sphere, giving respective center points (42,46). The vector between these center points (42,46) is parallel to the measurement axis (12A) of the probe (9). From this vector, direction cosines are calculated for correcting the probe output to give X,Y and Z values.