noun
definition
An SI/MKS unit of measure, the length of one millionth of a meter. Symbols: µm, um, rm.
noun
definition
A device used to measure distance very precisely but within a limited range, especially depth, thickness, and diameter.
Examples of micrometers in a Sentence
Material in the rings ranges in size from a few micrometers to several tens of meters.
Quekett in his Treatise on the Microscope ascribes to Ramsden the practical introduction of the spider web in micrometers.
Therefore, we have developed so-called ' scanning stressy probes ' which allow for a tip height of a few hundreds of micrometers.
To obviate this difficulty Felice Fontana of Florence (Saggio del real gabinetto di fisica e di storia naturale, 1 755) first proposed the use of spider webs in micrometers,' but it was not till the attention of Troughton had been directed to the subject by Rittenhouse that the idea was carried into practice.'
The great improvement now introduced into all the best micrometers is to provide a screw s, which, not as in the Fraunhofer micrometer, moves only one of the wires, but which moves the whole micrometer box, i.e.
Repsolds in more recent micrometers under construction give a second motion to the eyepiece at right angles to the axis of the micrometer screw; this enables the observer to determine the zero of position-angle for his movable webs with the same accuracy as he formerly could only do for the so-called position-angle webs.
Micrometers used for subdividing the spaces on graduated circles and scales have, in general, only a single pair of cross-webs or parallel webs moved by a single screw.
Double Image Micrometers are described in the article HELIO METER (q.v.).
Struve (Description de l'Observatoire ' Central de Pulkowa, pp. 196, 197) adds a few remarks to Steinheil's description, in which he states that the images have not all desirable precision - a fault perhaps inevitable in all micrometers with divided lenses, and which is probably in this case aggravated by the fact that the rays falling upon the divided lens have considerable convergence.
Treponeme-A term used to refer to any member of the genus Treponema, which is an anaerobic bacteria consisting of cells, 3-8 micrometers in length, with acute, regular, or irregular spirals and no obvious protoplasmic structure.
For reference, a micrometer is one millionth of a meter, and a human hair is 100 micrometers in diameter.
This type of filter consists of fiberglass fibers that range in size from .5 to 2.0 micrometers.
According to Department of Energy standards, HEPA filters should remove at least 99.97 percent of the air particles that are 0.3 micrometers in size.
They provided a splendid, rigidly mounted, equatorial stand, fitted with every luxury in the way of slow motion, and scales for measuring the displacement of the segments were read by powerful micrometers from the eye-end.
In both eyepieces micrometers or cross-wires are used for measuring in the plane of the real FIG.
We have not had an opportunity of testing this, nor Grubb's more recent models; but, should it be found possible to produce such images satisfactorily, without distortion and with an apparatus convenient and rigid in form, such micrometers may possibly supersede the filar micrometer.
Yet the beautiful images which these micrometers give permit the measurement of very difficult objects as a check on measures with the parallel-wire micrometer.
Repsolds employ for the micrometers of their reading microscopes the form of construction shown in fig.
The excellent manner in which the scales and micrometers are mounted, the employment of a compound microscope for viewing the scales, with its ingeniously arranged and admirably efficient reversing prism, and the perfection of its slow motions for focusing and reading, combine to render this a most accurate and convenient instrument for very refined measures, although too slow for work in which the measures must depend on single pointings in each of two reversed positions of the plate, and where speed of working is essential.
The reading micrometers e, f also serve to measure, independently, the separation of the segments, by scales attached to the slides; such measurements can be employed as a check on those made by the screws.