05.07.2007
The stability of the 1 kg vacuum mass comparator Sartorius CCL 1007 could be improved considerably for mass determinations in air by an additional thermal insulation. Mass determinations in air are now possible with standard deviations of less than 0.1 µg. Comparable results were achieved up to now only under vacuum conditions.
The aim of the scientific cooperation between Sartorius AG and PTB is the investigation and improvement of the characteristics of a novel No matching tab handler could be found for link handler key record:tt_news:1532. with respect to applications with highest requirements in the field of realisation and dissemination of the unit of mass, taking different influence quantities in air and vacuum into account. Investigations performed within the scope of this research cooperation showed for mass determinations in air a sensitivity of the comparator with respect to short-time variations of the temperature in the measuring room. To reduce this sensitivity, the system was provided with an additional thermal insulation of polymethyl methacrylate (acrylic glass, Figure 1). The improved insulation led to a higher stability of the weighing results in air. For mass comparisons of 1 kg mass standards of stainless steel in air, standard deviations of less than 0.1 µg could be determined. A comparable stability has so far only been achievable under vacuum conditions (5 · 10-6 mbar). Possible improvements to reduce the interchanging error between weights on different positions of the turntable and the influence of the geometry of mass standards on the mass determination will, among others, be the subject of further investigations.
Figure 1: 1 kg vacuum mass comparator Sartorius CCL1007 with additional thermal insulation
Contact person:
Michael Borys, FB 1.1, AG 1.11, michael.borys@ptb.de