Co-ordinate measuring

A method of inspecting an article using co-ordinate positioning apparatus comprising a fixed part, a movable part, co-ordinate measuring means for providing outputs indicative of the relative positions of the fixed and movable parts, and probe means mounted on one of said fixed and movable parts for sensing points on a said article mounted on the other of said fixed and movable parts, the method comprising:

• moving the probe means relative to the other of said fixed and movable parts towards at least one point on a datum surface provided on said other of said fixed and movable parts;
• determining co-ordinates of said at least one point in response to the probe means and outputs of the co-ordinate measuring means;
• making a decision, on the basis of the position of said at least one point as indicated by said determined co-ordinates, that said at least one point lies on the datum surface;
• and
• in response to said decision, calculating and storing a stylus qualification offset for correcting measurements made on a said article.

A method of inspecting an article using co-ordinate positioning apparatus comprising a fixed part, a movable part, co-ordinate measuring means for providing outputs indicative of the relative positions of the fixed and movable parts, and probe means mounted on one of said fixed and movable parts and having a plurality of styli for sensing points on a said article mounted on the other of said fixed and movable parts, the method comprising:

• moving the probe means relative to said other of said fixed and movable parts towards at least one point on a datum surface provided on said other of said fixed and movable parts;
• determining co-ordinates of said at least one point in response to the probe means and outputs of the co-ordinate measuring means;
• making a decision, on the basis of the position of said at least one point as indicated by said determined co-ordinates, that said at least one point lies on the datum surface and as to which of said plurality of styli has touched the datum surface;
• and
• in response to said decision, selecting a stored stylus qualification offset corresponding to the stylus which has touched the datum surface for use in correcting measurements made on a said article.

Apparatus for use in inspecting an article, the apparatus comprising a co-ordinate positioning apparatus having a fixed part, a movable part and co-ordinate measuring means providing outputs indicative of the amount of relative movement between the two parts;

• probe means mounted on one of said fixed and movable parts of the co-ordinate positioning apparatus for relative movement towards points on an article on the other of said fixed and movable parts to sense such points;
• said probe means providing a signal indicative of such sensing;
• and computing means arranged to use outputs of the measuring means to
• (a) detect the direction of relative movement of the probe means towards each of said points,
• (b) determine co-ordinates of each of said points in response to the probe means and outputs of the co-ordinate measuring means, and
• (c) on the basis of said directions, make a decision concerning the geometrical shape of at least a portion of said article.