ProSoft Technology PTQ-AFC - Manual (Page 75)

PTQ-AFC ♦ Modicon Quantum Platform Quick Start
Liquid and Gas Flow Computer for Hydrocarbon Products User Manual
ProSoft Technology, Inc. Page 75 of 259
June 23, 2011
6.7.6 General Features
Process Variable Interface
Process variables for each of the meter runs must be produced by the controller
for consumption by the AFC module. A versatile architecture for backplane
transfer of process variables and other data and signals allow you to easily
implement the data transfer. The sample ladder logic automatically transfers the
process variables to the module and reads the calculation results to the
processor.
Meter Scan Time
For good measurement, the process I/O must be sampled, and the flow
calculations completed quickly in order to avoid losing process information and
measurement accuracy. The process I/O scan time for the module is under one
second for all meter runs.
Note: This is time-dependent on design of the ladder logic implemented to support the two-way
data transfer between the AFC module and the controller. The meter calculation scan independent
of the process I/O scan may take longer.
Multiple Meter Accumulators
Each meter channel supports the following set of full 32-bit accumulators that
may be configured in binary or split decimal format with user-defined rollover
values:

Gross Volume
 Gross Standard Volume (liquid only)
 Net Volume
 Mass
 Water (liquid only)
 Energy (gas only)
Access to the above accumulators is available directly from the two Modbus
Slave communications ports.
Product Batching
Any or all of the available meter runs may be configured for field installation that
requires shipping and/or receiving product batches of predetermined size. The
configuration utility option of selecting resettable accumulators provides a simple
way to use the power of ladder logic to design product batching, monitoring, and
control tailored to suit specific field requirements.
The Meter Signals feature can be used to create an archive or reset an
accumulator after the batch is concluded. Refer to the Ladder Logic section for
your platform for more information on using this feature.