Honeywell STT25D Operator's Manual page 26

SYMPTOM
Communicator
MESSAGE/
High input "INPUT OPEN"
(with upscale
fail-safe)
"I/P OUT OF
SPEC"
(indicates that
the input is
above URL or
below LRL)
Unstable None
onscale input
Since any
identified
problem would
give upscale or
downscale fail-
safe.
Fail-safe "HARDWARE
output signal ERROR"
Smart Temperature Transmitter STT250 – Operator Manual
HART POSSIBLE CAUSE
DISPLAY
Bad sensor wire
connection.
Incorrect operating
voltage.
Bad sensor wire
connection.
Intermittent open circuit
of sensor.
Wiring disturbed by
strong electromagnetic
interference.
A fail-safe output signal
can be caused by
several reasons.
CURE
Check field wiring
and connections
for partial short
circuit.
Check STT250
connections are correct
polarity.
Check that the
transmitter is in its
voltage operating area
and line resistance is
not excessive.
Check connection and
wiring for intermittent
connections.
Check that sensor fault
detection is "ON", this
allows detection of a
bad sensor.
Protect wiring by using
appropriate grounding,
shielding etc.
The HART
communicator will
indicate the source of
the problem by
displaying the
appropriate error
message.
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