Angle encoder (AE) errors in rotary tables are a dominant source of systematic uncertainty in precision gravitational experiments employing rotating torsion balances. Here, we present and validate an in situ calibration method that leverages the torsion balance itself as a high-sensitivity angular reference. The technique is demonstrated on an apparatus designed to search for exotic spin-dependent interactions. This proof-of-principle demonstration achieves a calibration accuracy at the nanoradian level. This accuracy is limited by statistical fluctuations and uncertainty in the pendulum’s moment of inertia. As a direct result, the systematic torque arising from AE errors is suppressed to a residual level of ${10}^{-17}\mathrm{N}\mathrm{m}$. Finally, we discuss pathways to reduce the calibration uncertainty by an additional order of magnitude, which would establish this technique as a stand-alone method for high-precision AE calibration.

Close

PrevNext

View figure in article

• Experimental studies of gravity
• Metrology
• Rotation sensing
• Bend & torsion tests
• Precision measurements
• Weak measurements