I'm trying to come up with a (relatively) inexpensive method of measuring the top and bottom position on a workpiece. What I'm thinking is two spring retracting, pneumatic extending(so varying air pressure could create a lighter touch on the material) measurement probes. I'm just having problems finding something small enough for the work area. The two probes need to touch tips for zero positioning and then extend out at least 40mm out of the way(20mm for each probe). They should also have accuracy and repeatability in the 1 μm range.

I've found the Solatron model 9771165-1's. But, lordy, 174.9 mm total length for 20 mm of probe travel. That'd put the total height of my probe contraption to 350mm to scan a 0.8-35mm thick object.. Each one is $708 too. The price is doable, the size would be a huge inconvience. I could put them side-by-side and rig up all sorts of extension bars and so forth to get them back around to touch tips and cut the height in half, but I'd prefer not to do that as it seems itching for more problems.

Anyone have any other suggestions? Less expensive and smaller would be great.