Emerson Rosemount 3490 Series Reference Manual page 11

Reference Manual
00809-0100-4841
Calculation and display of the control unit PV
The control unit PV is typically a live transmitter reading, which can be any measured value
e.g. level, temperature, or Pressure.
Alternatively, the control unit PV is a volume or flow value calculated using the live
transmitter level reading. The control unit is pre-programmed with standard tank shapes
and flow algorithms to simplify the configuration for calculating volume or flow from the
live transmitter level reading. A 20-point programmable look-up table is provided for non-
standard applications.
Output of measured variable as an isolated 4–20 mA signal
The output signal is driven by the control unit PV.
Relay control functions
There are five freely assignable relay outputs. By default, Relay 5 is a fault relay but can be
assigned to a control duty. The other relays are available to operate at user-entered PV
values.
The control unit is pre-programmed with popular pump control routines for wet well and
sump control, along with energy saving overrides.
Voltage-free (digital) contact closure inputs
There are two digital input ports for accepting contact closure signals to override control
unit functions.
HART transmitter interrogation and programming
Any HART transmitter can be connected. The control unit recognizes the transmitter as an
"unknown instrument" but supports the Universal and Common Practice HART
commands.
When a Rosemount 3100 Series Transmitter is connected, the control unit recognizes the
transmitter and allows full access to the transmitter's configuration parameters. Refer to
the Rosemount 3101/3102/3105
Manual
transmitter bottom reference) using the control unit and other HART-based devices.
Related information
Support for HART Transmitters
2.2.2 Difference, sum, and product functions
The Rosemount 3492 Differential Control Unit has all the functions of the standard control
unit, plus extra functions for calculating the difference, sum, or product of two separate
inputs from HART transmitters.
2.2.3 Data logging functions
The Rosemount 3493 Logging control unit has all the functions of the standard control
unit, plus a 7000 event logging function.
Emerson.com/Rosemount
for full information about programming the transmitter parameters (e.g.
Reference Manual or Rosemount 3107/3108
Control unit overview
January 2021
Reference
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