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Reference Manual
IP2030/RM, Rev AA
Section 2: Control Unit Overview
June 2014
Section 2: Control Unit Overview
2.3 Control unit functions
2.3.1 Standard functions
The Mobrey MCU900 Series control unit provides these standard functions:
Calculation and display of the control unit Primary / Process Value (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 4–20mA signal
The output signal is driven by the control unit Primary / Process Value (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 (see Appendix E: Support for HART® Transmitters).
When a Mobrey MSP Series HART transmitter is connected, the control unit recognizes
the transmitter and allows full access to the transmitter’s configuration parameters.
Refer to the reference manual of the transmitter for full information about
programming the transmitter parameters (e.g. Transmitter Bottom Reference) using
the MCU900 Series control unit or other HART-based devices.
2.3.2 Difference, sum, and product functions (on MCU902 only)
The Mobrey MCU902 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.
2.3.3 Data logging functions (on MCU90F only)
The Mobrey MCU90F Logging control unit has all the functions of the standard control unit, plus
a 7000 event logging function.