Dictionary > Micrometer

Micrometer

micrometer
An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given directly is that of the image of the object formed at the focus of the object glass. Circular, or ring, micrometer, a metallic ring fixed in the focus of the object glass of a telescope, and used to determine differences of right ascension and declination between stars by observations of the times at which the stars cross the inner or outer periphery of the ring. Double image micrometer, a micrometer in which two images of an object are formed in the field, usually by the two halves of a bisected lens which are movable along their line of section by a screw, and distances are determined by the number of screw revolutions necessary to bring the points to be measured into optical coincidence. When the two images are formed by a bisected objects glass, it is called a divided-object-glass micrometer, and when the instrument is large and equatorially mounted, it is known as a heliometer. Double refraction micrometer, a species of double image micrometer, in which the two images are formed by the double refraction of rock crystal. Filar, or bifilar, micrometer. See Bifilar.
(Science: mechanics) Micrometer caliper or gauge, a caliper or gauge with a micrometer screw
92c
, for measuring dimensions with great accuracy. Micrometer head, the head of a micrometer screw. Micrometer microscope, a compound microscope combined with a filar micrometer, used chiefly for reading and subdividing the divisions of large astronomical and geodetical instruments. Micrometer screw, a screw with a graduated head used in some forms of micrometers. Position micrometer. See Position. Scale, or linear, micrometer, a minute and very delicately graduated scale of equal parts used in the field of a telescope or microscope, for measuring distances by direct comparison.
Origin: Micro-: cf. F. Micrometre.
A metric unit of length equal to one millionth of a meter.


You will also like...

squirrel
Animal Water Regulation

Animals adapt to their environment in aspects of anatomy, physiology, and behavior. This tutorial will help you understa..

Plant Water Regulation
Plant Water Regulation

Plants need to regulate water in order to stay upright and structurally stable. Find out the different evolutionary adap..

Water Cycle
The Water Cycle

The water cycle (also referred to as the hydrological cycle) is a system of continuous transfer of water from the air, s..

Adaptation Tutorial
Adaptation Tutorial

Adaptation, in biology and ecology, refers to the process or trait through which organisms or the populations in a habit..

Plant biology
Plant Biology

Plantlife can be studied at a variety of levels, from the molecular, genetic and biochemical level through organelles, c..

Early Earth
The Origins of Life

This tutorial digs into the past to investigate the origins of life. The section is split into geological periods in the..

Related Articles...

No related articles found

See all Related Topics