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Reference Manual
IP2030/RM, Rev AA
Section 3: Installation
June 2014
Section 3: Installation18
3.4.6 Connecting HART transmitters to the Mobrey MCU902
The Mobrey MCU902 control unit takes the input from two HART transmitters and calculates
the sum, difference, or product of the two inputs.
Note
The transmitters must be HART compatible for the MCU902 to operate correctly.
Connection of the two transmitters to the MCU902 can be done by:
cabling both transmitter cables wired directly into Current Input terminals on the
MCU902 (Figure 3-6), or
using a single cable wired directly into Current Input terminals with the two
transmitters connected to this single cable via a suitable junction box (Figure 3-6).
Figure 3-6. Connecting two HART transmitters to the Mobrey MCU902
A. HART Transmitter Tx1
B. HART Transmitter Tx2
C. Junction box
For correct operation, each HART transmitter must be changed to “multi-drop” mode to allow
them to communicate with the Mobrey MCU902 control unit through a common connection.
Each HART transmitter must therefore have their poll address changed from the factory default
address of “0” to a unique address.
The MCU902 control unit is used to achieve this address change, but requires the transmitters
to be connected in a specific sequence as detailed here:
1. With the power supply turned off, connect the first HART transmitter to the Current
Input terminals on the MCU902 control unit (see Figure 3-6).
2. Check the voltage-selector-switch is set for the correct voltage on the
mains-powered control unit (115 or 230 Vac), and then turn the power on.
3. After applying power, the control unit searches for a HART transmitter.
A HART transmitter with the factory default polling address of 0 is found after 15
seconds. The control unit automatically changes the Transmitter Poll Address from “0”
to “1” and it is designated “Tx1” (Transmitter 1) and assigned to Channel 1.
The control unit reads parameters from the HART transmitter and makes them
available for local interrogation and programming within the menu system.
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