Harold and Susan Vordos wrote:

which is, a long travel
indicator is able to measure. Â* Â*A DTI is distinctly different from a long
travel indicator in that it is specifically made for comparison readings,
due in part to the adjustable tip, which includes parallax error, a
function of the angle of the tip.

Math often helps: :-)
Length of feeler: 19mm
Travel: 0.2mm
Resolution: 0.002mm

Swing in degrees: 0.6°
cos(0.6°) = 0.999945
The error is in the 5th place, two magnitudes less than the resolution

An other one:
Length: 19mm
travel: 1mm
resol.: 0,01mm

- swing 3° - error 0.9986, almost two magnitudes less than the resolution

None of that is an issue with a long
travel indicator, assuming it is set up in the proper attitude in
relationship to the work in question.

Certainly, for long travels you are absolutely right. But that's the reason
why the other type has only such short travels.


Nick
--
The lowcost-DRO:
http://www.yadro.de