An Integrated Noncontact Torque Sensor Based on Diamond NV Centers

High-precision quantum sensing techniques based on diamond nitrogen vacancy (NV) centers have been widely used in many industries. The quantum precision measurement schemes based on NV centers have been continuously reported in recent years. However, there is still a gap in research on noncontact torque measurement applied to common steel shaft materials. Therefore, in this article, an integrated noncontact torque sensor based on diamond NV centers is proposed. The magnetic flux gathering module, microwave (MW) antenna, light path system, fluorescence acquisition module, amplifying and filtering circuit (AAFC), copper coil, and power conversion circuitry were integrated into the torque sensor, with a volume of approximately 33.18 cm3. In our work, infinite gain multiple feedback amplification filter circuits had been used to improve the signal quality and magnetic flux aggregation modules to improve the detection sensitivity of the system. The ellipsoidal light gathering cavity was used to enhance the fluorescence utilization. The magnetoelastic effect of ferromagnetic materials had been combined to realize the noncontact trial measurement of ordinary steel shafts (with low magnetostriction coefficient). Subsequently, the noise sensitivity of the torque sensor of about 36.218 nNm/Hz1/2 was verified. This new torque sensor has a high magnetic spatial sensitivity and can, therefore, be used for torque detection of bearings in a wide range of ferromagnetic materials with low magnetostrictive coefficients.