Pressure Transfer Function- Selecting Output Conformity; Table 23 Selecting Output Conformity - Honeywell ST 3000 User Manual

6— Configuration - Pressure transfer function— Selecting Output Conformity
Pressure transfer function— Selecting Output Conformity
Output form options
You can select the transmitter's output to represent either a straight linear calculation, or a square root
calculation for flow measurement applications using a differential pressure type transmitter. Thus, we refer
to the linear or the square root selection as the output conformity or the output form.
The procedure in Table 23 shows how to select the desired Output conformity.
Step
1 From "Online" menu, select "Device setup" and press right arrow key.
2 Scroll down to "Basic setup" and press the right arrow key.
3 Scroll down to "PV xfer fnctn" and press the right arrow key.
4 Using the [ ⇑ ] and [ ⇓ ] keys, choose either Linear or Square root, then press ENTER.
5 Either:
• press SEND to download change to transmitter, or
go to another procedure and continue making changes.
•
About square root output
For differential pressure transmitters measuring the pressure drop across a primary element, the flow rate is
directly proportional to the square root of the differential or pressure drop. The ST 3000 transmitter's
output is automatically converted to equal percent of flow when its output conformity is configured as
square root.
You can use these formulas to manually calculate the percent of flow for comparison purposes.
(Note: This formula assumes that LRV = 0.)
Where,
Therefore,
And, you can use this formula to determine the corresponding current output in milliamperes direct current.
60

Table 23 Selecting Output Conformity

∆P
Span • 100 = %P
∆P = Differential pressure input in engineering units
Span = Transmitter's measurement span (URV – LRV)
%P = Pressure input in percent of span
%P
100 • 100 = % Flow
(% Flow • 16 mA) + 4 mA = mA dc Output
ST 3000 HART Transmitter Release 300 User Manual
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10/05