1 Introduction to MagnetoHydroDynamic Gyros
When a a charged particle moves through a magnetic field it will produce a current in a conductor within the field. A MagnetoHydroDynamic (MHD) gyroscope is based on this idea. An MHD uses a charged particle within a fluid. The sensor housing moves with the platform. The fluid inside the sensor remains still as do the particles. So in this case the field moves and the particles stay still. The relative motion generates a current which is measured.
The physics of any sensor limits its performance. In the case of MHDs the fluid moves with slow rate platform motion. The slower the rate of platform motion the closer the rate of fluid to the platform rate. As a result the differential rate between the sensor housing and sensor fluid becomes smaller and smaller. This becomes a gain or scale factor change lowering the closed loop bandwidth (eventually to zero).