ProSoft Technology MVI56-AFC - Manual (Page 183)

MVI56-AFC ♦ ControlLogix Platform MVI56-AFC Backplane Communication
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 183 of 316
February 25, 2011
Special Notes
The Meter Process Variable Block must provide all process variables in the
format you configured through the AFC Manager for each meter run that is
implemented.
This OFB can handle process variables in the following formats:

Floating Point - Recommended format, used by sample ladder logic

Scaled Integer

4 to 20 mA (raw A/D count)
Note 1: For water % (liquids only) floating point is not available. As a Scaled Integer it must be
copied to element 1 as an INT with two decimal places implied. For example, water % value of 7.23
must be entered as 723. The AFC divides this value by 100.
Note 2: The floating point format takes up two elements (32 bits) for each process variable. For
example, the Temperature must be copied from a floating point tag in the controller to elements 2
and 3 of the OFB.
Note 3a: Temperature as a scaled integer must be copied to elements 2 and 3 as a DINT with 2
decimal places implied (1/100th of a degree). For example, a temperature of 24.97°F must be
copied as 2497.
Note 3b: Flowing pressure as a scaled integer must be copied to elements 4 and 5 as a DINT with
no decimal places implied for the SI units (kPa) and one decimal place implied for the U.S. units
(psi). For example, a pressure of 5000 kPag must be copied as 5000 and a pressure of 259.7 psi
must be copied as 2597.
Note 3c: Differential Pressure as a scaled integer must be copied to elements 6 and 7 as a DINT
with 2 decimal places implied for inches of H
2
O (hw) and 3 places for kPa (1/100th & 1/1000th of
the selected unit). For example, a DP of 37.52 in H2O must be copied as 3752.
Note 3d: Flow Rate as a scaled integer must be copied as a DINT to elements 4 and 5 with zero
decimal places implied. To obtain a desired precision, choose an appropriate Flow Input Unit
(Meter Configuration window, Primary Input Characteristics panel)
Note 3e: Pulse Frequency may be supplied in scaled integer or 4 to 20 mA formats only in version
2.05 or later; in version 2.04 or earlier only floating point format is available. As a scaled integer it
must be copied to elements 10 and 11 as a DINT in units of Hz with no decimal places implied. For
example, a frequency of 2574 Hz must be copied as 2574.
Note 4: Note that three options for the product density for liquid meters are available, and if the
Scaled Integer option is selected then density must be copied as a DINT to elements 8 and 9 as
follows:

Kg/m3 - One implied decimal place (513.7 kg/m3 must be entered as 5137)

Relative Density - Four implied decimal places (1.0023 60F/60F must be entered as 10023)

API - Two implied decimal places (80.45 API must be entered as 8045)
Note 5: For the 4 to 20 mA format, the raw A/D count from the analog input module must be copied
as a DINT to the proper pair of elements of the OFB (or for Water %, as an INT to element 1).
Note 6: Refer to Function Block Structure (page 168) for information on Bit 8 and 9 settings.