A computerhyphen;controlled allhyphen;pass phase shift filter for a variable frequency twohyphen;phase ac magnetic susceptometer

摘要

A wellhyphen;established method for the accurate measurement of small changes in ac magnetic susceptibility is to initially null and then monitor the output of the susceptometer as various parameters are modified. Use of a computerhyphen;controlled phase shift filter has allowed us to build a system that will introduce virtually orthogonal signals to compensate for the inhyphen;phase and outhyphen;ofhyphen;phase components of the output. The system described is designed for use over the frequency range 50 Hzndash;4 kHz. Extended frequency ranges are possible with only slight modifications. thinsp;