  Integrators are fundamental instruments to recover differential signals from
magnetic probes in Experimental Advanced Superconducting Tokamak (EAST)
experiments. A kind of difference integrator is introduced which has the same
structure as the standard difference amplifier. The linear fitting method is
used for determining the effective drift slope, then the plasma control system
(PCS) use the drift slope to rectify the integration signal in real time. A new
integrator controller was developed, which uses an ARM micro-controller and the
lightweight IP protocol stack to realize the network control. The tests show
that the upgraded integrator works well, its CMRR is high up to 125 dB when the
common voltage is 1.5 V, and the processed integration drift is about 200 uVs
/1000 s.
