Emman, Thank you so much for testing it out. The resistors are thin film resistors on silicon die. They are part of a thermal sensor. I spent quite a good amount of time. today, and found that it had to do with the nulling of the bridge. Unlike the individual PCBs that I had tested before, this new connection seems to be very sensitive to nulling. A small imbalance and away it goes in one direction, more so than a single PCB setup. I also tried some other changes.
1)I tried removing the buffer on PCB2 and it doesnt seem to make a difference. Appears like the buffer on PCB1 is good enough.
2) Avoiding the buffer on PCB1 however, seems to affect PCB1 output. Maybe due to the shielded cable's capacitance?
Can you please confirm this for me.
Finally, would you recommend another 8221 in place of the buffer on PCB2 to remove the noise on the transfer line by using a shielded twisted pair? Will that improve the noise on V_bc?
Sorry for bombarding you with so many questions but your support is always appreciated.