Control.com - Nerds in Control

In order to review the operation of a GE Frame 6 Gas Turbine we were provided a host of data which we are very familiar with. The one proces value missing was the FSR. Although we found a tag CPD/FSR refdif. The property is given in Degree C. How to interpret this value?

Someone might have programmed the control system to calculate the difference between the CPD-biased exhaust temperature control reference and the FSR-biased exhaust temperature control reference and called it "refdif." The two references are expressed in terms of temperature; the difference would also be expressed in units of temperature.

Apologies for a late reply. This could be the case, but than I still do not know the background of this setting.

can you tell me what the CPD represent?
and what is its effect on the FSR ?