Micro-force measurements: a new instrument at METAS

We designed and developed a new instrument for calibrating micro-force sensors. The calibration is traceable to the SI unit of mass and is realized from 1 µN-60 mN by means of electromagnetic force compensation of a balance. The expanded measurement uncertainty of our instrument comprises two contributions, an absolute contribution of 0.13 µN and a relative contribution of 2700 ppm. We verified our instrument in a bilateral comparison between METAS and PTB's instruments for forces from 40 µN up to 20 mN. The degrees of equivalence found by the two institutes are in excellent agreement.