Honeywell STT25D, Operator'S Manual

Page: 23 / 40

20 Smart Temperature Transmitter STT250 – Operator Manual
SYMPTOM SFC 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 "STATUS CHECK =
O.K."
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 " CRITICAL STATUS " A fail-safe
output signal
(critical status)
can be caused
by several
reasons.
The SFC will indicate
the source of the
problem by displaying
the appropriate error
message.