Browse Prior Art Database

Noncontacting Surface Height Gage

IP.com Disclosure Number: IPCOM000075066D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Hoekstra, J: AUTHOR

Abstract

This device is a height gage which does not contact the surface to be measured, has a measuring range of 0.1 inch, and maintains a resolution of a few microinches.

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Noncontacting Surface Height Gage

This device is a height gage which does not contact the surface to be measured, has a measuring range of 0.1 inch, and maintains a resolution of a few microinches.

Referring to the figure, there is shown partly in cross-section, a linear variable differential transformer 2 having a 0.1 inch measuring range and a repeatability of 4 microinches with a resolution of 0.3 microinches. The structure designated by the numeral 4 is the core of the transformer. A probe tip 6 is provided which is attached to the core 4. The bottom of tip 6 is designed as an air thrust bearing, the whole assembly sliding in a journal type air bearing, not shown, to minimize friction. The assembly is contained in a housing, not shown, which contains transformer 2 and an air inlet 8 to provide the air bearing.

In the operation of the gage the air escaping from the probe tip 6 creates a gap between tip 6 and the substrate surface 10. Such gap is typically 0.002 inch, the gap being determined by the diameter and the weight of the probe and the air pressure applied via air inlet 8. The air bearing resulting from the compressed air produced through air inlet 8 maintains the gap between probe 6 and surface 10. Consequently, any surface-height change will result in a displacement of the probe tip 6 and, consequently, core 4 of linear variable differential transformer 2.

This gage presents several advantages in its operation over known devices. Thus, it does not con...