flow transmitter

There are several variables, here is a link that should be helpful.

http://www.clabberhead.com/sob.php

Your question is not very clear,so I am going to assume what you meant.

You have an orifice plate sized to have a differential pressure of 2000.00 mm H2o when 47 tonnes/hr of steam is flowing through it,but somebody calibrated the flow transmitter to -38.9 to 4284 mm H2O.How to intrepret the actual flow with the wrong calibration.

The signal output from a transmitter is directly proportional to the differential pressure across it.

The differential pressure across the transmitter however is proportional to the square of flow.

Suppose you read a 30% signal(I am assuming no square root extraction is done in transmitter) then this represents (4284+38.9)* 0.3= 1296.87 mmH2O.

2000 mmH2O=47 tonnes/hr.Therefore 1296.87 mmH2O is equal to square root of

1296.87/2000 * 47=37.846967 tonnes/hr.