Accession No
4232
Brief Description
micrometer, by Cambridge Scientific Instrument Company Ltd., English, 1914 (c)
Origin
England; Cambridge
Maker
Cambridge Scientific Instrument Company Ltd.
Class
weights & measures; metrology
Earliest Date
1914
Latest Date
1914
Inscription Date
Material
wood; plastic; metal (brass)
Dimensions
box length 146mm; breadth 125mm; height 133mm
Special Collection
Cambridge Instrument Company Collection
Provenance
Donated by the Cambridge Instrument Company.
Inscription
Description Notes
Micrometer for sheet metal 0 – 0.4 ins, in wooden case. Micrometer mounted on black-painted metal support. Plastic vertical scale calibrated in 0.1 inch. White plastic circular scale on micrometer head calibrated in 0.001 inch. Brass fine control.
References
Events
Description
Micrometer
Micrometers were used mainly by astronomers and microscopists to measure objects. They were first devised in about 1609 and used the exact number of turns of a screw to measure small distances. Micrometers were inserted into the path of a telescopes and microscopes, and were also used to accurately measure quadrant scales.
Early examples of the micrometers used in telescopes were calibrated geometrically using a piece of card at a distance of about 200m with lines of known separation on it. However, this introduced inaccuracies of a few seconds of arc due to the closeness of the card compared with the distance of real observations. It was not until 1672 that this problem was overcome and accurate calibration was possible.
18/10/2002
Created by: Saffron Clackson on 18/10/2002
FM:44066
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