Metrology-3-Length Flashcards
What year was the metric system established in France?
1795
What year was the yard bar adopted as the British standard of length?
1824
What year was the British Yard standard destroyed by fire?
1834
What year was the New Imperial Standard Yard legalised by Act of Parliament?
1855
What year was the metric system legalised in Britain?
1864
What year was the international prototype Metre established?
1889
What year did Michelson/Benoit use wavelengths for metre measurements?
1892
In 1791 what did the French Academy of sciences decide to do?
Redefine the metre: 1m= 1/10,000,000
What year was the first inter-comparison between the yard and metre?
1896
What year was the Yard/Metre ratio frozen at the 1922 value for science and technology?
1932
What year was work started on defining the metre as a wavelength standard?
1933
What year was the Krypton-86 wavelength standard of length adopted?
1960
What year was the Krypton-86 metre/yard standards legalised in Britain?
1963
What year was the metre defined as the pathlength travelled in 1/299,792,458 seconds?
1983
What year was the length standards related to iodine stabilise HeNe lasers
1998
What were the first metre/yard end standards manufactured from?
Brass and platinum/iridium
What was the accuracy of the end standards limited by?
The deformation of the bar and bar supports
What was the original definition of the metre?
One ten-millionth (1/10,000,000) of the quadrant of the North Pole to the Equator.
What were the length standard designs improved to use?
The line standard approach
Gold plugs inserted into the standard with rulled lines. Metre measured between lines on plugs using microscopes.
What was the latest version of the prototype metre designed to have?
X-shaped cross section
The centre of the bar is calculated to lie in the neutral plane of the cross section, providing a stable dimensional artefact.
What can light be described in terms of?
Wavelength and Frequency, both which can be accurately measured.
Who worked with cadmium red wavelengths in 1892-93, allowing lengths up to 100mm to be measured by fringe counting?
Michelson and Benoit
Definitions of 1 metre in terms of different wavelengths of light?
- 1 metre= 1,553,164.1 wavelengths of cadmium red.
- 1 metre= 1,650,763.7 wavelengths of krypton-86 (orange in colour).
- 1 metre= 1,579,778.8 wavelengths of iodine-HeNe at 633nm
1 wavelength= 0.000000633
Ranges of calibrated length bars and gauge blocks?
range from 1.0005mm up to 100mm in length.
Gauges and bars can combine to produce?
Any length in the range 1.0005mm to 100mm with 1.0005mm steps if necessary.
What sets do Gauges come in?
Sets of 47 or 88 gauges
How are gauge blocks manufactured and what out of ?
Manufactured accurately from steel alloys and ceramics
What can be gauges be used for ?
*Calibrate micrometres, verniers and other measuring instruments
* Gauges may also be used with comparators
What are used to calibrate length bars and gauges?
Calibration equipment using iodine-HeNe laser interferometres.
Where would length bars and gauges be sent for calibration against secondary standards?
A specialist UKAS laboratory or NPL
What are Length bars and Gauges on the traceability cahin?
Transfer standards, they come in differenet standards
