AD7745 VT SETUP

When I set up Register ,VT SETUP =F1h,result of measurement depends on Δ (REFIN(+)ーREFIN(-))?

Other Register Set up

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CAP SETUP 80h

VT SETUP  :F1h  

EXC SETUP 0Ah

CONFIG  : F9h

CAP A    :E9h

CAP B    :70h

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(A condenser is connected between CIN and EXCA.)