LFE 2000 Series - Page 101

958-3I
REV.
B
The last
part of
this
section
rncludes
typical
waveforms
as
observed
on an
oscilloscope.
These
waveforms
are
intended
to
provide
an
aid
to
the
t-epair
personnel
with a
good
comprehension
of
rnodern
analog/digital
circuits
and
components
'
TroubleshootlnB
and
repair
at
the
circuit
level
should
not
be
attempted
by
unqual
j-f
ied
Personnel
.
r0.2
TYPES
OF
FAILURE
While
the
unit
the
proper tYPe
is
still
assembled,
determine/and
of
input
sensor
and
aPPIY
Power
or
verify
the
faj-lure
mode'
Connect
to
the
unit.
Observe
the
disPlaY:
l.
If
the
drsplay
is
stable
and
shows
a
f atlure
message
such
as
INPI'IT
(IPEN'
POWER
FAILURE,
RTC
FAILURE,
or
RAM
FAILURE
or
if
the
display
is f
lashing
the
DATA
LOST/PLEASECALmessage,refertotheSectionl0.3,ERRORMESSAGES.
2.
If
the
drsplay
looks
normal
(Shows
a nornal
OPERATOR
LOOP
or
TUNE
LO0P
Inessage)'
determrne
whether
or
not
the
display
will
respond
to
the
keypad'
If
keypad
response
appears
normal,
proceed
to
step
3 below.
If
the
dlsplay
wi
I
I not
respond
to
the
keypad,
troubleshoot
the
kr:ypad
crrcult'
sorne
features
such
as
Remote
setpornts
do
dlsable
portions
of
the
keypad'
some
models
also
have
an
arrow
itey
9N/9FF
feature.
check
the
TIrNE
LooP
trr
verify
that
arrow
keys
are
not
turned
off'
NOTE:
Advance
the
drsplay
so
that
the
process
variable
is
drsplayed
in the
OPF'RATOR
LOOP.
If
the
readrng
appears
to
be
accurate
and
reacts
to
Illput.
chatiges'
the
AiD
converslon
circuitry
is
working,
proceed
t.o
st.ep
4.
If
the
reading
does
ntlt
respond
to
-lnput
changes,
or
rf
the
reading
is
changjng
and
irraccttrate
'
ver-lf
y
that-
the tnput
circuitry
ancl
jurnpers,
the
input
sensor,
and
the
1l-lpllt
p;lt
t
number
{'rgits
drsplayable
f rom
the
CAL
L00P
are
consist'ent
'
If
rro
drscl
eparr('I
P5
are
f
ounfl,
a
problern
exists
in
the
A/D
conversion
ci
rcui
try
clrr
the
T
/O
brl;ri
rl
'
If
the
readrnt
rs
changrnB
and
inaccurate,
Lhe
unit
rnay
have
been
stepped
through
the
rnput
calibratjon
sub-loop
without
appl
yrrrg t-he
cal
rbrat
iotr
vttl
t ar-rl '
Recalibration
with
proper equipment
should
be
attempted
bef
rr
r-e
asstlnri
IrE'
l
hardware
fai
lure.
Check
the
outputs
and
alarrns
present in
the
unit
(
ref
er
to
part rrttnrber
irt
CAL
L00P)
for
proper
operation.
Outputs
can
be checked
by
varying,
the
process or
alarnr
setpolnts
wi-th
respect
to
the
process variabl
e.
i)bserve
d ispl;ly
indicators,
check
continuity
through
relay
contact,
check
voltage
and
currerlt
values
of arralog
outputs,
check
solid
st at.e
olltprlts
ttslnS
arr
AC load '
(
see
Section
7.
)
t,FE
Instrurnents
Drvtsron
-94-