CALIBRATION OF A COMPACTION SIMULATOR FOR THE MEASUREMENT OF TABLET THICKNESS DURING COMPRESSION

For the calibration of a compaction simulator for punch displacement measurements, the displacement of the punch must be related to the voltage output of.a linear variable displacement transducer (LVDT) which is attached to the punch via its movable core, with correction for any deformation of the machine parts which are inherently incorporated in the LVDT readings. Contrary to common assumptions the relationship between the displacement of the movable core and the voltage output of the LVDTs used is not linear. Similarly, the deformation of the machine parts did not follow Hooke's law of linear elasticity but exhibited characteristics of non-linear elasticity. The data demonstrate the need for careful validation of the calibration of a compaction simulator when accurate punch displacements are required.