User guide

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NT® INTEGRATED FLOW CONTROLLER WITH DEVICENET™ COMMUNICATION USER GUIDE
Maintenance
Normal Operation
During normal operation, the stan-
dard NT
®
Integrated Flow Controller
with DeviceNet
TM
communication re-
quires no maintenance, other than a
periodic re-zero of the unit.
Re-zero Function
The no flow calibration of the flow
controller can be re-zeroed, meaning
that the flow output that corresponds
to zero flow may be reset.
NOTE: When executing the re-zero
function, there must be at least
1 PSIG (7 kPa) of static pressure.
Optimum pressure for re-zero is the
operation pressure, typically greater
than 10 PSIG (69 kPa).
NOTE: The following procedure
must be followed precisely to
ensure proper flow controller
re-zero.
The no flow calibration of the
flow controller can be re-zeroed,
meaning that the flow output that
corresponds to zero flow may be in-
ternally reset. This is done with
DeviceNet
TM
service requests. The
‘Zero_Adjust’ service command in
the Analog Sensor Object is sent
to begin a re-zero process. The
‘Stop_Zero_Adjust’ service command
in the Analog Sensor Object is sent
to stop the re-zero process.
When the re-zero function is activat-
ed, the flow controller valve module
will close fully to ensure that fluid is
not flowing. The unit will verify the
no-flow condition, and then re-zero
the flow module. The entire re-zero
function is completed in 10 seconds.
In order to obtain best performance,
the re-zero function should be per-
formed, at minimum if possible, every
30 days of service when operating at
ambient temperature conditions.
The re-zero function should be per-
formed more often if operating at
higher temperature. It is also recom-
mended to perform a re-zero after
start-up and after fluid temperature
changes of greater than 9°F (5°C).
Best performance will be achieved
by re-zeroing between each dispense
cycle.
Autozero Function
The no flow calibration of the
flow controller can be autozeroed,
meaning that the flow output that
corresponds to zero flow may be
automatically, internally reset when-
ever the set point is zero. Selecting
the ‘enabled’ setting of the ‘Autozero
Enable’ attribute in the Analog
Sensor Object does this. This is the
default setting.
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