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Torsion balance-based system for high-precision force measurement in horizontal plane: part II. Static and dynamic improvement

In this paper, improved static and dynamic capabilities of the torsion force measurement system (TFMS) are reported based on an earlier development presented in part I (Yan et al 2018 Meas. Sci. Technol. 29 084001) of this work. The force measurements through a closed-loop operation mode are set up, by which the cut-off frequency is improved from 0.002 Hz to 0.1 Hz. Two different actuation and compensation mechanisms are introduced; in the first case the small forces are produced electromagnetically by a commercial voice coil actuator, in the second case electrostatically using a customized capacitive actuator. We apply Newton’s polynomial interpolation to evaluate the measurement results, which reveals that the TFMS is able to resolve forces with approximately 2 nN resolution in the measuring range of  ±3 µN.