Honeywell STT25D, Operator'S Manual

Page: 26 / 40

Smart Temperature Transmitter STT250 – Operator Manual 23
SYMPTOM HART
Communicator
MESSAGE/
DISPLAY
POSSIBLE CAUSE CURE
High input " INPUT OPEN "
(with upscale
fail-safe)
" I/P OUT OF
SPEC "
(indicates that
the input is
above URL or
below LRL)
Bad sensor wire
connection.
Incorrect operating
voltage.
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.
Unstable
onscale input None
Since any
identified
problem would
give upscale or
downscale fail-
safe.
Bad sensor wire
connection.
Intermittent open circuit
of sensor.
Wiring disturbed by
strong electromagnetic
interference.
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.
Fail-safe
output signal " HARDWARE
ERROR "
A fail-safe output signal
can be caused by
several reasons. The HART
communicator will
indicate the source of
the problem by
displaying the
appropriate error
message.