Emerson Rosemount 3144P, Reference Manual

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43
Reference Manual
00809-0100-4021, Rev JA
HART Commissioning
April 2017
HART Commissioning
Note
The transmitter determines the differential temperature by subtracting the reading of Sensor 2 from
Sensor 1 (S1– S2). Ensure this order of subtraction is consistent with the desired reading for the
application. Refer to
Figure 2-4 on page 13 , or inside the transmitter terminal-side cover for sensor
wiring diagrams.
If using an LCD display for local indication, configure the meter to read the appropriate variables by using
“LCD display options” on page 92 .
Average temperature
Field Communicator
The transmitter configured for dual-sensors can output and display the average temperature of any two
inputs. Use the following procedure with Traditional Fast Keys to configure the transmitter to measure
the average temperature:
Configure sensor 1 and sensor 2 appropriately. Select 1 Device Setup, 3 Configuration, 2 Sensor
Configuration, 1 Change Type and Conn. to set the sensor type and number of wires for sensor 1. Repeat for
Sensor 2.
Note
This procedure configures the average temperature as the primary variable analog signal. If this is not
needed, assign the average temperature to the secondary, tertiary, or quaternary variable.
If using an LCD display, configure it to read the appropriate variables using “LCD display options” on
page 92 .
Note
If Sensor 1 and/or sensor 2 should fail while PV is configured for average temperature and the Hot
Backup feature is not enabled, the transmitter will go into alarm. For this reason, it is recommended
when PV is sensor average, that the Hot Backup feature be enabled when dual-element sensors are used,
or when two temperature measurements are taken from the same point in the process. If a sensor failure
occurs when the Hot Backup feature is enabled, while PV is sensor average, three scenarios could result:

If sensor 1 fails, the average will only be reading from sensor 2, the working sensor.

If sensor 2 fails, the average will only be reading from sensor 1, the working sensor.

If both sensors fail simultaneously, the transmitter will go into alarm and the status available (via
HART) states that both sensor 1 and sensor 2 have failed.
In the first two scenarios, the 4–20 mA signal is not disrupted and the status available to the control
system (via HART Protocol) specifies which sensor has failed.
HART 5 Fast Keys
2, 2, 3, 3
HART 7 Fast Keys
2, 2, 3, 3