GDS-68XP Operation & Maintenance Manual, Revision 3.5
Page 50
11
TROUBLESHOOTING
GUIDELINES
FAULT
INDICATION
ON
OUTPUT
CHANNEL
(CH2)
Value
shows
+105%
of
scale
–
indicates
an
OVERRANGE
condition,
where
the
sample
gas
caused
the
sensor
to
read
more
than
100%
of
scale.
Value
shows
‐
15%
of
scale
–
indicates
a
NON
‐
RETURN
‐
TO
‐
ZERO
FAULT
during
recovery
mode.
Indicates
sensor
may
be
saturated
with
target
gas.
Increase
the
purge
interval
to
allow
more
time
for
the
sensor
to
recover.
Value
shows
‐
17.5%
of
scale
–
indicates
a
SAMPLE
PEAK
IDENTIFICATION
ALGORITHM
FAULT
;
peak
was
not
found
in
maximum
allotted
time.
Check
sample
flow
rates
and
sensor
life.
Values
shows
‐
20%
of
scale
–
indicates
a
LOSS
OF
FLOW
for
more
than
10
seconds
during
sample
pre
‐
charge
or
sample
recovery.
Check
sample
flow
or
pump
performance.
Value
shows
‐
22.5%
of
scale
–
indicates
a
CALIBRATION
fault
–
either
the
resting
input
value
at
the
start
of
the
last
cycle
was
higher
than
10%
of
scale
OR
a
GASMAX
calibration
occurred
during
the
cycle.
Value
shows
‐
25%
of
scale
–
indicates
SENSOR
FAULT
from
GASMAX
monitor.
FAULT
INDICATION
ON
RAW
SENSOR
CHANNEL
(CH1)
Fault
or
Overrange
on
power
‐
up.
Certain
toxic
sensors
indicate
off
‐
scale
low
or
high
at
power
up
and
quickly
drift
towards
zero.
This
is
normal
behavior.
Continuous
Fault
indication.
Remove
sensor
and
examine
for
moisture
or
discoloration.
Replace
sensor
if
wet
or
discolored.
Fault
indication
generally
indicates
sensor
useful
life
is
exhausted.
Sensors
left
unpowered
for
more
than
3
months
are
subject
to
accelerated
degradation
and
may
demonstrate
a
permanent
loss
of
sensitivity.
SENSOR
FAILS
CALIBRATION
Sensor
reading
during
zero
calibration
exceeds
upper
limit
of
zero
–
sensor
is
defective
and
should
be
replaced.
Sensor
reading
during
span
calibration
too
low
–
sensor
may
be
defective.
However,
it
may
be
possible
to
temporarily
continue
operation
by
increasing
PREAMP
GAIN.
GDS
‐
68XP
AND
RECEIVING
DEVICE
DISPLAYED
VALUES
DON’T
MATCH
Check
that
zero
and
full
scale
range
values
match
between
GDS
‐
68XP
and
receiving
device
(controller).
Use
DIAGNOSTICS
menu
to
force
the
OUTPUT
channel
(Ch2)
to
12mA
and
verify
half
‐
scale
reading
on
remote
controller.
Check
for
high
impedance
shorts
to
ground
on
4
‐
20mA
wiring.