Msf Function Block - Honeywell UMC800 Reference Manual

Function Blocks

2.38 MSF Function Block

Description
The MSF label stands for Mass Flow Calculation. This block is part of the Calculations category. It looks
like this graphically on the Control Builder.
Function
Calculates gas mass flow (OUT) from differential pressure input value (X) that represents a pressure drop
across an orifice plate (for example). It accepts two other inputs to include pressure (Y) and/or
temperature(Z) compensation in the calculation. The calculation includes square root extraction.
• OUT = Kq
•
106
sqrt [(dP
* *
Kq = Orifice Constant
dP = Differential pressure which
= (Kx X) + Bx; where:
*
Kx = Delta pressure scaled for desired engineering
units
X = Analog input value
Bx = Delta pressure bias in desired engineering
units
P = Absolute gas pressure which
= (Ky Y) + By where:
*
Ky = Pressure scaler for desired engineering units
Y = Gas pressure analog input value
By = Pressure bias in desired engineering units
T = Absolute gas temperature which
= (Kz Z) + Bz where:
*
Kz = Temperature scaler for desired engineering units
Z = Gas temperature analog input value
Bz = Temperature bias in desired engineering units
! If (Kz
Z) + Bz = 0, then: OUT = O
*
If calculation is <= Dropoff, OUT=0, else OUT=Calculation
Function Block Reference Guide
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