Emerson Rosemount, Reference Manual

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97
Reference Manual
00809-0100-4021, Rev GC
Section 3: HART commissioning
April 2014
HART® commissioning
Intermittent Sensor Detect (advanced feature)
The Intermittent Sensor Detect feature is designed to guard against process temperature
readings caused by intermittent open sensor conditions. An intermittent sensor condition is an
open sensor condition that lasts less than one update. By default, the transmitter is shipped with
the Intermittent Sensor Detect feature switched
ON and the threshold value set at 0.2% of
sensor limits. The Intermittent Sensor Detect feature can be switched ON or OFF and the
threshold value can be changed to any value between 0 and 100% of the sensor limits with a
Field Communicator.
Transmitter behavior with Intermittent Sensor Detect ON
When the Intermittent Sensor Detect feature is switched ON , the transmitter can eliminate the
output pulse caused by intermittent open sensor conditions. Process temperature changes (

T)
within the threshold value will be tracked normally by the transmitter’s output. A

T greater
than the threshold value will activate the intermittent sensor algorithm. True open sensor
conditions will cause the transmitter to go into alarm.
The threshold value of the 3144P should be set at a level that allows the normal range of process
temperature fluctuations; too high and the algorithm will not be able to filter out intermittent
conditions; too low and the algorithm will be activated unnecessarily. The default threshold
value is 0.2% of the sensor limits.
Transmitter behavior with Intermittent Sensor Detect OFF
When the Intermittent Sensor Detect feature is switched OFF , the transmitter tracks all process
temperature changes, even from an intermittent sensor. (The transmitter in effect behaves as
though the threshold value had been set at 100%.) The output delay due to the intermittent
sensor algorithm will be eliminated.
3.10.5 Open sensor holdoff
The Open Sensor Holdoff option, at the normal setting, enables the 3144P to be more robust
under heavy EMI conditions. This is accomplished by the software having the transmitter
perform additional verification of the open sensor status prior to activating the transmitter
alarm. If the additional verification shows that the open sensor condition is not valid, the
transmitter will not go into alarm.
For users of the 3144P that desire a more vigorous open sensor detection, the Open Sensor
Holdoff option can be changed to a fast setting where the transmitter will report an open sensor
condition without additional verification of the open condition.
3.11 Diagnostics and service
Diagnostics and service functions listed below are primarily for use after field installation. The
Transmitter Test feature is designed to verify that the transmitter is operating properly, and can
be performed either on the bench or in the field. The Loop Test feature is designed to verify
proper loop wiring and transmitter output, and should only be performed after you install the
transmitter.
HART 5 Fast Keys
2, 2, 7, 4
HART 7 Fast Keys
2, 2, 7, 4