Rosemount 3491, Reference Manual, Page: 71 / 152

Reference Manual
00809-0100-4841, Rev. AA
May 2007
4-39
Rosemount 3490 Series
P404 mA Mode (Factory default is “Instantaneous”)
On model 3493, this optional parameter is for assigning the Current Output to
follow a rolling average of the calculated MCU PV (typically flow). To do this,
select the
Rolling
option.
The time period for the rolling averaging is defined using P590, which is also
for defining the logging interval (see “Logging (3493 Only)“ on page 4-35).
P210 MCU PV Damping (Factory default is 0)
The 3490’s current output is proportional to the calculated MCU PV. It is
possible to apply damping to the MCU PV using P210, which will have the
effect of damping the current output.
Relays
NOTE:
Relay states are frozen when 3490 Series Control Unit is in "off-line" mode.
Menu Navigation List: (for locating relay parameters)
1. MAIN MENU / SETUP / [CONTROL UNIT /] OUTPUT / RELAY
2. MAIN MENU / SETUP / [CONTROL UNIT /] DUTY(Mode) / OVERRIDES
3. MAIN MENU / SETUP / [CONTROL UNIT /] DUTY(Mode) / CUSTOM
Overview of Relay Functions
Relay outputs 1 to 4 are normally On Point / Off Point control relays which
may be used to start/stop pumps or open/close valves at different levels. They
normally energise at one level and de-energise at a different level. For further
details, see Section “On/Off Point Control“ on page 4-42.
Alternatively, they can be programmed as out-of-limit alarms; they energise
between defined points and will de-energise outside those points. They may
also be programmed to perform a variety of auto-sequences and auxiliary
functions, such as pump-down operations, pump rotations to equalise wear,
and de-sludge/cleaning. For further details, see Section “Alternative Duties“
on page 4-43.
Relay output 5 is normally a fail safe fault relay but may be re-allocated to
another duty.
NOTE:
Relays are frozen while the 3490 Series Control Unit is off-line, preventing all
relay operations apart from Totaliser and Sampler relays.
Relay Wizard
Relay outputs can be set-up easily using the "Relay" Wizard, accessible by
navigating to the RELAYS menu screen. The Wizard also forms a part of the
"Duty" Wizard.