NORAMET comparison of gauge block measurement by optical interferometry

Gauge blocks (GBs) are very important material standards that provide industry with reliable and traceable standards of length. At the highest accuracy level, the measurement of GBs must be performed by interferometry. The double ended interferometer (DEI) offers an alternative to obtain traceable measurements of the absolute length of GB shaped objects without the need for a platen to be wrung to one of the faces. In spite of this general advantage, there is no reliable DEI system being used at any National Metrology Institute (NMI). PTB, as the NMI of Germany, is developing a dedicated DEI which will be situated in a temperature-stabilized vacuum chamber. This paper describes a preliminary prototype DEI that was built firstly to study the measurement principle, and secondly to learn about the challenges and limitations to be taken into consideration for the final design. A comparison of results from the DEI measurements and those from PTB's existing single ended GB interferometers (SEI) indicates that the present prototype is a basis for the final version.

Section: Comparison Measurementssupporting

confidence: 92%

Challenges on double ended gauge block interferometry unveiled by the study of a prototype at PTB

Abdelaty¹,

Walkov²,

Franke³

et al. 2012

“…The CCDM comparison should link comparisons conducted by the regional metrology organizations EUROMET (Western Europe), COOMET (Eastern Europe), NORAMET (North and Central America) and APMP (Asia/Pacific Metrology Programme), involving one national metrology institute per region. The results of three regional comparisons have been reported so far [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

CCDM comparison of gauge block measurements

Vaucher¹,

Thalmann²

1998

A world-wide comparison of gauge block measurement by interferometry, decided on by the Comité Consultatif pour la Définition du Mètre (CCDM), has been carried out. Four national metrology institutes, each representing one of the regional metrology organizations EUROMET, NORAMET, COOMET and APMP, measured a set of seven rectangular gauge blocks of steel with nominal lengths between 1 mm and 100 mm. This paper reports on the results of the comparison and draws conclusions with respect to the execution of future CCDM (now CCL) key comparisons.

“…Length calibrations for reporting began on 8 May 2000. The combined standard uncertainty attributed to the absolute length calibration of this 900 mm gauge block on the NRC gauge-block interferometer [7] is 119 nm [8].…”

Section: Length Variations As a Results Of Environmental Disturbances...mentioning

confidence: 99%

Some important characteristics of gauge-block artefacts for international comparison

Decker¹

2001

This letter takes a brief look at gauge-block length as it is influenced to a subtle degree by the surface quality of the measuring face and the recent history of the gauge block environment. Change in length of short gauge blocks following wringing, and of long gauge blocks following air travel between laboratories, is demonstrated. These effects could have important implications for international comparison testing under time-limited conditions, particularly with the large number of comparisons related to the Mutual Recognition Arrangement (MRA).