Control.com - Nerds in Control

Use this website www.clabberhead.com you will need to know the bore of the orifice plate you are measuring the DP across. The internal diameter of the pipe, you will find this from ppipe table by comparing it to the pipe specification, normally marked on the PID's. Basically the DP is equal to the (square of the mass flow)/((square of (pipe CSA X square of beta ratio))x density).

now we assume density, internal area and beta ratio are all constants then flow squared is proportional to DP.
so to get linear flow reading we must sqare root DP either at the transmitter or ar the PLC but not at both.
use table below for quick calibration of a transmitter with square root extraction.

%flow  percentage 0f DP rage applied mA signal 
 0     0                           4
10     1                           4.16
20     4                           4.64
30     9                           5.44
40     16                          6.56
50     25                          8
60     36                          9.76
70     49                         11.84
80     64                         14.24
90     81                         16.96
100    100                        20