Screened chamber with active screening for medical measuring appts. - measures magnetic field using induction coil around room and applies appropriate compensation current to coils to cancel LF interference field

摘要

The screened chamber (2) includes an induction coil (4) for measuring interference fields. A field coil (6) is arranged around the chamber, and a controller (10,12,14) applies a compensation current to it in accordance with the measured field. The induction coil is arranged parallel to the field coil around the outside of the chamber. The induction coil is pref. fixed at a distance from the outer walls of the chamber, the axes of the coils being vertical. The controller includes an AGC amplifier (10), and an equaliser for the frequency characteristics of the induction coil and the field coil. USE/ADVANTAGE - For measurement of magnetic fields generated by human body. Compensates only for homogeneous magnetic interference fields.