100
Reference Manual
00809-0100-4021, Rev GC
Section 3: HART commissioning
April 2014
HART® commissioning
Special considerations
To initiate operation between a 3144P transmitter with dual-sensor option and the HART
Tri-Loop, consider the configuration of both the differential, average, first good temperatures,
Sensor Drift Alert, and the Hot Backup feature (if applicable).
Differential temperature measurement
To enable the differential temperature measurement feature of a dual-sensor 3144P operating
in conjunction with the HART Tri-Loop, adjust the range end points of the corresponding
channel on the HART Tri-Loop to include zero. For example, if the secondary variable is to report
the differential temperature, configure the transmitter accordingly (see “Set process variable
output order” on page 99) and adjust the corresponding channel of the HART Tri-Loop so one
range end point is negative and the other is positive.
Hot Backup feature
To enable the Hot Backup feature of a 3144P transmitter with dual-sensor option operating in
conjunction with the HART Tri-Loop, ensure that the output units of the sensors are the same as
the units of the HART Tri-Loop. Use any combination of RTDs or thermocouples as long as the
units of both match the units of the HART Tri-Loop.
Using the Tri-Loop to detect sensor drift alert
The dual-sensor 3144P transmitter sets a failure flag (through HART) whenever a sensor failure
occurs. If an analog warning is required, the HART Tri-Loop can be configured to produce an
analog signal that can be interpreted by the control system as a sensor failure.
Use these steps to set up the HART Tri-Loop to transmit sensor failure alerts.
1. Configure the dual-sensor 3144P variable map as shown.
2. Configure Channel 1 of the HART Tri-Loop as TV (differential temperature). If either
sensor should fail, the differential temperature output will be +9999 or –9999 (high or
low saturation), depending on the position of the Failure Mode Switch (see “Alarm
switch (HART)” on page 13).
3. Select temperature units for Channel 1 that match the differential temperature units of
the transmitter.
4. Specify a range for the TV such as –100 to 100 °C. If the range is large, then a sensor
drift of a few degrees will represent only a small percent of range. If Sensor 1 or Sensor 2
fails, the TV will be +9999 (high saturation) or –9999 (low saturation). In this example,
zero is the midpoint of the TV range. If a T of zero is set as the lower range limit (4 mA),
then the output could saturate low if the reading from Sensor 2 exceeds the reading
from Sensor 1. By placing a zero in the middle of the range, the output will normally
stay near 12 mA, and the problem will be avoided.
Variable Mapping
PV Sensor 1 or Sensor Average
SV Sensor 2
TV Differential Temperature
QV As Desired
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