50 kpa / 1024 = 0.0488 kpa

28 inch WC = 6.9 kpa

6.9 kpa = 141 posibilities

If i use a 200 cfm calibration orifice that gives me a resolution of 1.42 cfm. Hmmm not sure that is enough.

One solution would be use their + / - 7kpa sensor rather than + / - 25kpa but 28 cfm would be nearly at the endo of its range.

That would give a resolution of:

14 kpa / 1024 = 0.01367

6.9 kpa = 504 posibilities

200 cfm orifice plate gives resolution of 0.4 cfm which would be fine.

Does that sound about right Simon?