The RFAII-S is a portable instrument specifically designed to perform on-line rotor flux measurement in Hydro-Generators. The RFAII-S can be connected to IRIS TFProbe or other types of flux probes installed in the air gap. The instrument determines condition of pole insulation based on multiple algorithms and can be used for a spot measurement or automatic data acquisition over several days without intervention from an operator. The instrument comes equipped with user selectable USB or Ethernet communication ports and can store over 150 flux measurements in internal memory.