Honeywell STT25D Operator's Manual page 23

SYMPTOM
High input
Unstable
onscale input
Fail-safe
output signal
20 Smart Temperature Transmitter STT250 – Operator Manual
SFC MESSAGE/
DISPLAY
"INPUT OPEN" (with
upscale fail-safe)
"I/P OUT OF SPEC"
(indicates that the
input is above URL or
below LRL)
"STATUS CHECK =
O.K." since any
identified problem
would give upscale or
downscale fail-safe.
"CRITICAL STATUS" A fail-safe
POSSIBLE
CAUSE
Bad sensor wire Check field wiring and
connection. connections for partial
short circuit.
Check STT250
connections are correct
polarity.
Incorrect
Check that the
operating
transmitter is in its
voltage.
voltage operating area
and line resistance is
not excessive.
Bad sensor wire Check connection and
connection. wiring for intermittent
connections.
Check that sensor fault
detection is "ON", this
Intermittent
allows detection of a
open circuit of
bad sensor.
sensor.
Protect wiring by using
appropriate grounding,
Wiring disturbed
shielding etc.
by strong
electromagnetic
interference.
The SFC will indicate
output signal the source of the
(critical status) problem by displaying
can be caused the appropriate error
by several message.
reasons.
CURE