Improved measurement accuracy and uncertainty budget of the BIPM primary standard manobarometer

The uncertainty budget of the BIPM primary standard manobarometer of the BIPM-Jaeger type, which has been replicated commercially for use in other national metrology laboratories, has been re-assessed. The effect of different media on the paths of the two white-light beams sensing the mercury column height has been studied using the actual spectrum of the light. The dominating contributions to the overall uncertainty have been reduced substantially.