The Design of an Instrument to Realize Small Torque at NIST

Abstract

After the recent redefinition of the International System of Units (SI), torque no longer needs to be traceable to a calibrated mass in a gravitational field suspended from a known lever arm and disseminated through a chain of torque transducers. An SI-traceable torque can be directly realized using the Kibble principle where a torque is generated by a calibrated electromagnetic transducer. Here, a set of theoretical designs for a new instrument aimed at direct realization of torque to 0.1% accuracy is analyzed and examined for feasibility. With careful attention to magnet design, a robust and easily implemented torque calibrator can be built.