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 Dimension And Angle Laboratory

​The Dimension laboratory provides traceability to the international definition of the metre through a gauge block interferometer. This instrument which uses two lasers calibrated by iodine-stabilized He-Ne laser, provides EMI with capability of measuring various artifacts either directly or indirectly as listed below.

End Standards
According to ISO 3650, the reference grade gauge block (grade K) are calibrated by interferometry. With frequency stabilized lasers coupled to a Twyman-Green interferometer designed by the National Physical Laboratory, United Kingdom, the laboratory is able to provide the following services:

Gauge Length Material Parameter CMC


             0.5 mm to 300 mm​



                 Central length



The same interferometer is also used for measuring other end standards artifacts such as length bars and square gauge blocks (Hoke gauges). Gauge blocks of lower grades (grade 0, 1 and 2) are calibrated by comparison with EMI reference gauge blocks. Using this method, the following service is available:

Gauge Length Material Parameter CMC
0.5 mm to 100 mm Steel Central length deviation  ​[0.07 +1.2∙L] μm
where L is in

Diameter Standards
Diameter standards such as plug and ring gauges (including GO and NO-GO) are calibrated by comparative measurement using reference gauge blocks or reference ring gauges as standards. In this category, the following services are provided by the laboratory:

Artifacts Range Parameter CMC
Internal diameter gauges

15 mm to 50 mm


1.0 μm
External diameter gauges

 Up to 80 mm


1.0 μm


The following form parameters can be measured by the laboratory:

Artifacts Range CMC

Optical flats and parallels

(maximum diameter 50 mm)

Flatness 0.05 μm​