The exact knowledge of the coefficient of thermal expansion is crucial for highly accurate dimensional measurements. Is has got additional actuality by the discussions concerning an eventual change of the reference temperature for length measurements. Within the EUROMET intercomparison #229 for short gauge blocks, only two laboratories contributed results for the coefficient of thermal expansion. Several NMI's (NPL, PTB, OFM) are actually developping dedicated instrumentation for the measurement of the expansion coefficient. An intercomparison in this field is therefore very helpful to ascertain the measurement capabilities of the new instruments.
Three 100 mm gauge blocks of different material (steel, tungsten carbide, ceramic) are circulated. The expansion coefficient has to be measured around 20 °C. Otherwise, no detailed instructions should limit the variety of measurement methods.