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Reference Manual
IP2030/RM, Rev AA
Appendix E: Support for HART
®
Transmitters
June 2014
139
Appendix E: Support for HART Transmitters
Appendix E Support for HART
®
Transmitters
E.1 Overview
The Mobrey MCU900 Series control unit is able to accept digital data from any HART 5/6/7
compatible transmitter. However, the control unit is not Device Descriptor (DD) based and only
fully supports transmitters that have been factory programmed into the on-board library.
E.2 Fully supported HART transmitters
Fully supported HART transmitters, where all parameters of the transmitter are accessible for
reading and writing by the MCU900 Series control unit:
Mobrey MSP400RH level transmitter (HART 5)
Mobrey MSP900GH level transmitter (HART 5)
Mobrey MSP900SH level transmitter (HART 5)
Mobrey MSP900FH flow transmitter (HART 5)
Note
If a Mobrey MSP Series transmitter is connected, refer to the reference manual on the
Mobrey brand pages at www.emersonprocess.com for full information about
programming the transmitter parameters (e.g. Transmitter Bottom Reference) using
the MCU900 Series control unit or other HART-based devices.
E.3 Generic support for HART transmitters
E.3.1 Compatibility between transmitter and control unit
The MCU900 Series control unit is designed to provide an intrinsically safe power supply to
power a I.S approved transmitter that is field-mounted in a hazardous area. The control unit
provides a nominal 24 Vdc supply.
Communication with the transmitter is HART, provided the transmitter current output is
configured in a passive mode to enable the control unit to power the current loop.
The addition of components (both resistive and semiconductor) as part of the I.S certification
and HART communication result in the terminal voltage varying with load current. Increasing
the load current in the loop results in a decrease in the terminal output voltage of the control
unit. Most HART transmitters require a minimum input voltage to work correctly, and for HART
communication to function. For example, a Mobrey MSP900GH Ultrasonic Level Transmitter can
operate over a voltage range of 12 to 40 Vdc (12 to 30 Vdc for intrinsically safe installations).
Consideration must be given to the loop resistance of the cable connecting the transmitter to
the controller to ensure sufficient input voltage is available at the transmitter.
Care must be taken in checking compatibility of the control unit when selecting the required
HART transmitter. Ensure that the input voltage requirements of the transmitter and the loop
resistance are below the limits given in Table E-1 on page 140.