How to determine scale range (KG/h)and set range (mbar)for Differential Pressure Transmitter (foxboro) while using Differential pressure transmitter for flow measurement?

Is there any sizing tool for FOXBORO DPT production?

 

The transmitter's flow range/scale is determined by the flow (at design conditions) through the primary flow element, like an orifice plate or an averaging pitot tube.

The primary flow element's vendor calculates the pressure drop at maximum flow rate and that's the value that used to range the transmitter.