OMNI 4000/7000 Operations and Maintenance Guide
– Rev F
3-45
OMNICONNECT® Operations
3.6.6 Product Interface Detection
The flow computer can automatically detect product interfaces by monitoring the user-configured
sustained rate of change in the specific gravity/density of a new product in the line (Figure 3-2
and Table 3-3). For example, a custom Boolean statement can be programmed to be active
whenever the specific gravity rate of change and the Batch Preset Reached flags are set. These
flags can cause a 'batch end' command to be issued with custom Boolean statements or remotely
through Modbus writes from external devices.
Figure 3-2: Interface Detection Screen
Table 3-3: Product Interface Detection Flags
Interface Detection
Flags
Description
Gravity/Density Rate of
Change and Sample
Time
The specific gravity/density rate of change alarm flag is a flag within
the database that is triggered whenever the rate of change of the
gravity/density with respect to flow exceeds the preset limit for a
sustained amount of time. It is used to detect a change in flowing
product and is available for use in programmable Boolean
equations and digital I/O channel functions.
Line Pack Delay
In many cases, the densitometer or gravitometer used to detect the
product interface is mounted well in advance of the flow meter
measuring the product or at the valve manifold. A Line Pack Delay
flag, which is delayed by the amount of line pack Bbl (m
3
or liter),
provides an accurate indication of when the interface reaches the
flow meter and it is time to execute a batch end command.
3.7
PID Configuration
Operators may use proportional-integral-derivative (PID) control to position valves and adjust
pump motor speeds through the front panel, as explained in Section 6.6.6 PID Control. However,
before output and setpoint adjustments can be made to the PID loops, the configuration and
setup entries must be programmed into the flow computer through OMNICONNECT.
