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SMV 3000 Transmitter User’s Manual 1/9956
6.6 DPConf Configuration - PV1, Continued
Output Conformity
Select the output form for differential pressure (PV1) variable to represent
one of these selections. Note that calculated flow rate process variable
(PV4) includes a square root operation and it is not affected by this
selection.
• LINEAR
d
• SQUARE ROOT
d
Factory setting.
Background
The PV1 output is normally set for a straight linear calculation since
square root is performed for PV4. However, you can select the
transmitter’s PV1 output to represent a square root calculation for flow
measurement. Thus, we refer to the linear or the square root selection as
the output conformity or the output form for PV1.
About Square Root
Output
For SMV 3000 transmitters measuring the pressure drop across a primary
element, the flow rate is directly proportional to the square root of the
differential pressure (PV1) input. The PV1output value is automatically
converted to equal percent of root DP when PV1 output conformity is
configured as square root.
You can use these formulas to manually calculate the percent of flow for
comparison purposes.
• 100 = %P
Where, ∆P = Differential pressure input in engineering units
Span = Transmitter’s measurement span (URV – LRV)
%P = Pressure input in percent of span
Therefore,
%P
100
• 100 = % Flow
And, you can use this formula to determine the corresponding current
output in milliamperes direct current.
(% Flow • 16) + 4 = mA dc Output
Continued on next page