A robust inexpensive torque magnetometer with on-line data analysis

Abstract

A simple and robust torque magnetometer which has a wide sensitivity range, from 10^-6 to 0.2 N m, is described. The design is based on that of Aldenkamp et al. (1960) but uses a modified mutual inductance method for measurement of angular displacement which in conjunction with a lock-in amplifier provides a direct reading of torque. This output is fed, together with a voltage proportional to magnet angle, to an on-line microcomputer, Fourier analysis of the torque curve, including a shearing correction takes approximately one minute following the complete input of data. The instrument is suitable for work down to liquid helium temperatures and up to about 450K.