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This is an optional feature and will only be available if it has been licensed in the key file.
Acquire must be in Config mode to perform these steps.
The formula editor allows a simple single-line formula to be added to a calculation field or flow computer field. Formulas can also be used to aggregate fields from multiple flow computers.
The Fomula window will be displayed:
Two types of formulas can be defined: read formulas and write formulas.
Read formulas take values from the flow computers and perform the calculation for display purposes.
Read formulas have the syntax value:=expression where expression is a mathematical formula e.g. value:=value*1000.
Write formulas take values from the flow computers, perform the calculation and then write the result back to the field in the flow computer. Write formulas can only be applied to flow computer and RTU fields.
Write formulas have the syntax writevalue:=expression where expression is a mathematical formula e.g. writevalue:=writevalue/1000.
Any field from any of the flowcomputers can be selected and can be included in the calculation.
eg value:=field(“[Omni]STR01 Pressure”)
Multiple fields can also be included in the calculation:
eg value:=field(“[Omni]STR01 Gross Flowrate”)+field([Omni]STR02 Gross Flowrate”)
These fields can also come from multiple flowcomputers:
eg value:=field(“[Omni 1]STN01 Gross Total”)+field([Omni 2]STN01 Gross Total”)
Variables can be declared and used as part of the calculation:
If statements can also be written to display a value based on a Boolean expression being satisfied. The following formula returns the difference between the limit:
var temperature := field("[Omni 6000]Temperature"); var high_temperature := field("[Omni 6000]Temp Hi-Lim"); if (temperature > high_temperature) value := temperature - high_temperature; else var low_temperature := field("[Omni 6000]Temp Lo-Lim"); if (temperature < low_temperature) value := temperature - low_temperature; else value := 0; end if end if
The calculation can include any of the following operators. A full list is available in the operator popup menu.
|#||not equal to|
|>=||greater than or equal to|
|<=||less than or equal to|
|<<||Bit Rotate Left|
|>>||Bit Rotate Right|
|abs||absolute value, i.e. always positive|
The Field List window for the selected flow computer will be displayed:
The selected field will be added to the formula:
This will test that the formula’s syntax and the returned value are correct:
The Formula window will be displayed again:
The formula will be saved.