ProSoft Technology PTQ-AFC - Manual (Page 90)

Quick Start PTQ-AFC ♦ Modicon Quantum Platform
User Manual Liquid and Gas Flow Computer for Hydrocarbon Products
Page 90 of 259 ProSoft Technology, Inc.
June 23, 2011
6.10 Accumulators
The accumulators store the current amount of measured quantity for a meter
channel. This section provides detailed information about the accumulators.
6.10.1 Accumulator Totalizer and Residue
The accumulators are expressed as the totalizer and residue parts. This
implementation allows the accumulation of a wide range of increments, while
keeping a high precision of fractional part with an approximately constant and
small round off error.
The totalizer stores the integral part of an accumulator as a 32-bit (or split)
integer. The residue is the fractional part (always less than 1.0) expressed as a
32-bit IEEE floating point.
The Total Accumulator is given by the formula:
ACCUMULATOR = TOTALIZER + RESIDUE
Example
If the meter monitor window shows the following values for the accumulators:
The total resettable accumulator 1 value (net) is 12.8031153.
The accumulator totalizer values can be configured to "split" with the low-order
word rolling over from 9999 to 0000 at which time the high-order word is
incremented. Refer to the AFC Manager (AFC Manager / Meter Configuration /
Split Double Accumulators) to select this feature.
A 32-bit value is more suited to computation and has a greater range than a split
value, whereas a split value is easier to read when it is represented as a pair of
16-bit numbers, as in a processor data file.