Honeywell SMV800 SmartLine User Manual page 52

Note: Scaling only affects the value shown on the display, it does not affect the Loop Output
1. Linear scaling of the displayed PV value
When "Linear" is selected for PV Scaling, the Display will scale the selected PV input according
to the following formula:
((PV value – input low limit) / input span) x (Scaling High – Scaling Low) + Scaling Low
If the PV Selection is Pressure, the input low and high limits are the LRV and URV respectively.
If the PV Selection is Percent Output, the input low and high limits are 0 and 100%. If the PV
Selection is Square Root, the input low and high limits are 0 and 100 %Flow.
2. Square Root scaling of the displayed PV value (Not Applicable For Modbus)
When "Square Root" is selected for PV Scaling, the Display computes %Flow from the
Differential Pressure. This calculation is independent of the Transfer Function setting in the
transmitter. This allows the user to output Differential Pressure via the 4-20 mA loop output while
displaying the equivalent flow value on the Display. In addition, the Display value can be scaled
to show the flow in flow units (gal/min, gal/h, etc.) by entering the correct scaling limits via the
Scaling Low and Scaling High parameters.
For example:
PV Selection:
PV Scaling:
Scaling Low:
Scaling High:
Display Units:
LRV:
URV:
The Display will calculate 0-100 %Flow from the Differential Pressure and then scale this
to 0 to 2500 gal/h.
Note: The Square Root calculation is referenced to the LRV and URV settings of the transmitter
and its uses the LRV and URV to calculate the %DP input into the Square Root flow algorithm.
For normal flow applications, it is assumed that the LRV is set to zero and that zero pressure
equals zero flow. If the LRV is less than zero, the Square Root calculation will calculate the flow
as bi-directional flow.
Page 44
Differential Pressure
Square Root
0.0
2500.0
gal/h
0.0
set as required by the process
SMV800 Transmitter User's Manual
Revision 10