NEW TECHNIQUES FOR THE NONCONTACT MEASUREMENT OF DISPLACER MOTION OF A MINIATURE SPLIT-STIRLING CRYOCOOLER

This paper proposes optional methods to calibrate the static sensitivi ty of the measurement of displacer motion inside the cold finger of a split-Stirling cryocooler. The relative displacement measurement metho d, as previously proposed, required that the regenerator matrix materi al should have such a high magnetic permeability that the linear varia ble-differential transformer (LVDT) could measure the displacer motion without large signal amplification. This would be impossible for low- permeability materials, e.g. stainless steel 316L and 304L, contained in the displacer. Therefore, three options are proposed for the calibr ation of static sensitivity: contact, purge or dynamic calibration met hods. Temperature compensation is also found to be necessary to transf er the LVDT voltage to the true displacer displacement when performing the non-contact measurement of the displacer motion. (C) 1996 Elsevie r Science Limited