Metrology-3-Length

Question 1

What year was the metric system established in France?

Answer 1

1795

Question 2

What year was the yard bar adopted as the British standard of length?

Answer 2

1824

Question 3

What year was the British Yard standard destroyed by fire?

Answer 3

1834

Question 4

What year was the New Imperial Standard Yard legalised by Act of Parliament?

Answer 4

1855

Question 5

What year was the metric system legalised in Britain?

Answer 5

1864

Question 6

What year was the international prototype Metre established?

Answer 6

1889

Question 7

What year did Michelson/Benoit use wavelengths for metre measurements?

Answer 7

1892

Question 8

In 1791 what did the French Academy of sciences decide to do?

Answer 8

Redefine the metre: 1m= 1/10,000,000

Question 9

What year was the first inter-comparison between the yard and metre?

Answer 9

1896

Question 10

What year was the Yard/Metre ratio frozen at the 1922 value for science and technology?

Answer 10

1932

Question 11

What year was work started on defining the metre as a wavelength standard?

Answer 11

1933

Question 12

What year was the Krypton-86 wavelength standard of length adopted?

Answer 12

1960

Question 13

What year was the Krypton-86 metre/yard standards legalised in Britain?

Answer 13

1963

Question 14

What year was the metre defined as the pathlength travelled in 1/299,792,458 seconds?

Answer 14

1983

Question 15

What year was the length standards related to iodine stabilise HeNe lasers

Answer 15

1998

Question 16

What were the first metre/yard end standards manufactured from?

Answer 16

Brass and platinum/iridium

Question 17

What was the accuracy of the end standards limited by?

Answer 17

The deformation of the bar and bar supports

Question 18

What was the original definition of the metre?

Answer 18

One ten-millionth (1/10,000,000) of the quadrant of the North Pole to the Equator.

Question 19

What were the length standard designs improved to use?

Answer 19

The line standard approach
Gold plugs inserted into the standard with rulled lines. Metre measured between lines on plugs using microscopes.

Question 20

What was the latest version of the prototype metre designed to have?

Answer 20

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.

Question 21

What can light be described in terms of?

Answer 21

Wavelength and Frequency, both which can be accurately measured.

Question 22

Who worked with cadmium red wavelengths in 1892-93, allowing lengths up to 100mm to be measured by fringe counting?

Answer 22

Michelson and Benoit

Question 23

Definitions of 1 metre in terms of different wavelengths of light?

Answer 23

• 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

Question 24

Ranges of calibrated length bars and gauge blocks?

Answer 24

range from 1.0005mm up to 100mm in length.

Question 25

Gauges and bars can combine to produce?

Answer 25

Any length in the range 1.0005mm to 100mm with 1.0005mm steps if necessary.

Question 26

What sets do Gauges come in?

Answer 26

Sets of 47 or 88 gauges

Question 27

How are gauge blocks manufactured and what out of ?

Answer 27

Manufactured accurately from steel alloys and ceramics

Question 28

What can be gauges be used for ?

Answer 28

*Calibrate micrometres, verniers and other measuring instruments
* Gauges may also be used with comparators

Question 29

What are used to calibrate length bars and gauges?

Answer 29

Calibration equipment using iodine-HeNe laser interferometres.

Question 30

Where would length bars and gauges be sent for calibration against secondary standards?

Answer 30

A specialist UKAS laboratory or NPL

Question 31

What are Length bars and Gauges on the traceability cahin?

Answer 31

Transfer standards, they come in differenet standards