Preliminary Study on the OMOP Joule Balance

The revised International System of Units has been implemented on May 20, 2019, and now, the Kibble/joule balance can be used to achieve the traceability of mass to the Planck constant. In principle, the Kibble/joule balance can be operated in three measurement schemes, in which the one-mode one-measurement phase (OMOP) scheme has obvious advantages over the other two schemes. The OMOP scheme was first proposed and tried in the Kibble balance, but due to the mutual interference between weighing and velocity measurements, the achieved mass/Planck constant measurement uncertainty did not match the goal of 5 × 10
^-8
. However, the mentioned interference can be well suppressed in the joule balance based on its quasi-static measurement characteristic. Therefore, the feasibility of the OMOP joule balance is analyzed in this article, and the measurement sequence is introduced in detail. Three factors involved in the OMOP joule balance that may affect the final mass measurement uncertainty are analyzed and demonstrated, i.e., the consistency of the two independent coils of the bifilar coil, the current effect of the special coil system, and the performance of the improved flux linkage difference measurement system. Besides, it is found that the stability of excitation current decreases significantly due to the movement of the magnet system, but the theoretical analysis shows that this does not affect the measurement result of the OMOP joule balance.