How to Read Wheatstone Bridge negative voltage with Arduino?
INA126 is an  InAmp of the two-OpAmp variety.  The REF pin, which can be used to provide an ofset for the output.  

\$ V_O = G (V_{(+)}-V_{(-)}) + V_{REF} \$



This is similar the output offset trimming circuit in fig.2 in the INA126 datasheet.