from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun An instrument for measuring the curvature of a surface, as of a sphere or cylinder.
from The Century Dictionary.
- noun An instrument for measuring the radii of spheres; a sphere-measurer.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Physics) An instrument for measuring the curvature of spherical surface, as of lenses for telescope, etc.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun A device used to measure the
curvatureof a surface, such as a lens.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun a measuring instrument for measuring the curvature of a surface
Sorry, no etymologies found.
The curvature is tested from time to time by a spherometer, and the tool is increased or decreased in curvature by turning it on a lathe so as to cause it to grind the glass more at the edges or in the middle according to the indications of the spherometer.
The process of fine grinding is continually checked by the spherometer, and the art consists in knowing how to move the grinding tool so as to make the lens surface more or less curved.
It will be recognized that in working with the spherometer, only the points in actual contact can be measured at one time, for you may see by Fig. 6 that the four points, _a a
It is well to control this process by means of a spherometer, so that the desired radius may be approximately reached.
Here is a very fine spherometer that Dr. Hastings works with from time to time, and which he calls his standard spherometer.
Many devices have been added to the spherometer to make it as sensitive as possible, such as the contact level, the electric contact, and the compound lever contact.
Science in Philadelphia, there was quite a discussion as to the relative merits of the spherometer test and another form which I shall presently mention, Prof. Harkness claiming that he could, by the use of the spherometer, detect errors bordering closely on one five-hundred-thousandth of an inch.
I may add that if this spherometer is placed on a plate of glass and exact contact obtained, and then removed, and the hand held over the plate without touching it, the difference in the temperature of the glass and that of the hand would be sufficient to distort the surface enough to be readily recognized by the spherometer when replaced.
We come now to an instrument that does not depend upon optical means for detecting errors of surface, namely, the spherometer, which as the name would indicate means sphere measure, but it is about as well adapted for plane as it is for spherical work, and Prof. Harkness has been, using one for some time past in determining the errors of the plane mirrors used in the transit of Venus photographic instruments.
Taking for granted that we have this standard plate, the spherometer is placed upon it, and the readings of the divided head and indicator, _d_, noted when the point of the screw,