National Physical Laboratory

NPL gauge block services reduce uncertainty

NPL reduced the measurement uncertainties and turnaround time of its gauge block services by combining better temperature control with improved operational procedures.

Gauge block
Gauge blocks are one of the most
flexible, cheap and popular length
standards used in industry

NPL gauge block measurement services are capable of such low uncertainties that the equipment is often purchased for use by other national measurement institutes around the world, via a licence with Hexagon Metrology. However, the achievable measurement uncertainty at NPL has been limited by the laboratory environment and, more specifically, by a lack of precise temperature control - until now.

Gauge blocks are length artefacts ranging in size from 0.5 mm to 1000 mm. Lengths within this range can be obtained in 1 µm (0.001 mm) increments, which makes gauge block sets one of the most flexible, cheap and popular length standards used in industry. Without them, engineers would have to calibrate a much larger selection of standards, which would be costly and time-consuming.

With the move to a purpose built laboratory, an opportunity arose to improve the achievable measurement uncertainty and decrease the turnaround time of NPL's measurement services.

NPL scientists in the Engineering Measurement Group worked closely with air conditioning engineers to establish a system to cope with the day/night variations in room temperature and the faster rate changes caused by the presence of engineers and machines in the laboratory. This can control the room temperature to well within the original 0.1 °C specification and control temperature within the instruments to around 0.05 °C.

This extra control, coupled with improved operational procedures developed by calibration staff, has allowed a faster throughput of gauge blocks to be maintained and reduced NPL's measurement uncertainty claim to better than half for longer gauge blocks.

NPL's service is now one of the top three in the world, but NPL's combination of short turnaround times and low uncertainty is unique. The faster turnaround will reduce downtime for customers who send their gauges to NPL and the smaller uncertainty of the service will allow customers to pass on this uncertainty reduction to their clients.

Find out more

Find out more about NPL's Dimensional Measurements

Find out more about NPL's gauge block, length bar and step gauge calibration services

For more information, please contact Andrew Lewis

Last Updated: 3 May 2012
Created: 26 Oct 2011

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