I think we can handle both reservoirs with same code (no need for else). Probably just need to add a macro somewhere that converts a reservoir ID and primary/backup selection into a loadcell ID.
General comment: Should floating point values be of the format N.NF? What is the coding standard? My experience has been that it's best to always specify the "F".
Check NEARLY_ZERO #define. Value should be 0.00000001F. I believe previous review commented indicated that all floating point #defines should have "F" at the end.
Call checkDialysateConductivity() once at top of function. Then use return value for the two if conditions. Also, this second if should be an else if to ensure you don't do both.
I think we should add the new THd temperature sensor now. I know it's currently using TRo connection (and so we don't have a TRo), but we should handle that with build switch (THd reads from TRo channel and TRo can just be a copy of TDi for now if THD_USING_TRO_CONNECTOR build switch enabled, actual future code where both sensors exist on their own connectors if build switch is disabled).
