On an IC electronic balance control system and its impact on the calibration

The contribution deals with an “1974 integrated circuit” version of an electronic damping and nulling system, adapted to a torsion balance which now is more than twenty years old. The discussion of calibration results reveal that masses of about 0.5 mg, in certain cases, can be intercompared with a relative precision of 3 × 10^?5, indicating that the balance sensibility is better than 2 × 10^?8 g. As the deflection sensitivity of the balance is 1.3 × 10^?4 deg/μg the position sensor on the balance can detect, over a few minutes, average displacements of about 4 × 10^?7 cm (i.e. ～ 40 Å).