Interferometric dimensional measurements at VTT MIKES are performed at a state-of-the-art laboratory; the measurement tables are vibration-dampened, the humidity stabilised and the laboratory temperature accurately set to 20 °C (see figure below). In different length laboratories, the direction of airflow is selected according to the requirements of the measurements carried out there. In laboratories where the best possible temperature uniformity, stability and minimum deviation from temperature 20 °C are required, an upward airflow is chosen. This is the best way to remove the heat generated by the equipment and to smooth out the temperature gradients in the laboratory. In addition, calibrations of long length transfer standards are performed automatically without people in the measurement room during the measurements. With these actions, the precision interferometer laboratory reaches the temperature uniformity (20 ± 0.05) °C and, if necessary, the temperature can be adjusted with a resolution of 0.01 °C. These laboratory conditions enable internationally accurate interferometric length measurements. The fully automated measuring programs of the interferometers, in turn, allow inexpensive calibrations. The design and implementation of the VTT MIKES building is described in more detail in Ref. 1.
On left hand side is a graph of the active vibration damping. The feet of the measurement tables (F) are fixed to steel space frames (E) filled with concrete to prevent ringing. Walk-on floors (G) are separated from the tables.The steel space frames are fixed to a pneumatically suspended heavy (70 ton) concrete platform (J), which is suspended by six pneumatic vibration isolators (K). The lowest part of the vibration isolation structure is a concrete raft foundation (I), which is cast directly on rock (A). On right hand side is agraph of the laboratory temperature control system. More details can be found in Ref. 1.
- A. Lassila, M. Kari, H. Koivula, U. Koivula, J. Kortström, E. Leinonen, J. Manninen, J. Manssila, T. Mansten, T. Meriläinen, J. Muttilainen, J. Nissilä, R. Nyblom, K. Riski, J. Sarilo and H. Isotalo, Design and performance of an advanced metrology building for MIKES, Measurement 44, 399–425 (2011). https://doi.org/10.1016/j.measurement.2010.10.013.
- Antti Lassila, Research Team Leader, tel. +358 40 767 8584, email antti.lassila(at)vtt.fi.
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