Emerson Rosemount 3490 Series Reference Manual page 77

Reference Manual
00809-0100-4841
Select a standard non-linear open channel profile
Use P113 (or P123) to select V Notch (5/2), Flume (3/2) or Manning from the option list.
The control unit then automatically populates P115 (or P125) with data from the built-in
library.
The flow calculations for these non-linear profiles require an input value over the range 0.0
to 1.0. Parameter P114 (or P124) is therefore used to convert (scale) the input signal to be
a value within the range 0.0 to 1.0 for the flow calculation.
Note
Rosemount 3491/3493:
P113, P114, and P115 are in the menus SETUP → [CONTROLLER] → INPUT CHANNEL →
Ch1 Profile, → Ch1 Pre scale, and Ch1 NLP Data (respectively).
Note
Rosemount 3492:
P113, P114, and P115 are in these menus: SETUP → [CONTROLLER] → PV CALCULATION
→ CHANNEL 1 → Ch1 Profile, → Ch1 Pre scale, and Ch1 NLP Data (respectively).
P123, P124, and P125 are in these menus: SETUP → [CONTROLLER] → PV CALCULATION
→ CHANNEL 2 → Ch2 Profile, → Ch2 Pre scale, and Ch2 NLP Data (respectively).
When using the App Wizard, select V-Notch Weir (5/2), Flume/Weir (3/2), or Manning at
the prompt for a profile. This populates parameter P113 (or P123).
Setting P114 (or P124) when a 4–20 mA level transmitter is connected
The 4–20 mA level transmitter should ideally provide a mA signal that is already scaled for
the full level range expected in the flow channel. P114 (or P124) can then be kept set at
the default value of 1.0.
If the mA signal is not scaled for the full level range of the channel, P114 (or P124) must be
programmed with a value to convert (scale) the mA signal to be a value in the range 0.0 to
1.0. For example, if the maximum current is below 20 mA for a full channel, say 12 mA, set
P114 = 16 × (12 – 4) = 2.
Setting P114 (or P124) when a HART level transmitter is connected
The maximum level measurement from the HART transmitter must be equal to the height
of the liquid when the channel is full.
The level measurement, after any input offset has been applied, must be re-scaled to the
range 0.0 to 1.0 ready for input to the NLP calculation.
For example, if the level measurement range is 0.0 to 1.5 m, set P114 = (1.0/1.5) = 0.667
Setting P116 (or P126) to the maximum flow expected in the channel
Finally, parameter P116 (or P126) must be programmed with the maximum flow expected
in the channel, which will occur at the maximum liquid level in the channel.
The control unit Primary/Process Value (D800) for the flow rate is derived by applying the
normalized transmitter input (range 0.0 to 1.0) to the profile, and then converting
(scaling) by parameters P114 and P116 (or P124 and P126).
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January 2021
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