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E9ALZERS
The OMS 421
has
64 measurement channels which
can
CAUTION: Group together the measurement jobs
be
programmed with different parameters
and for
diffe"
with the
same range
of
measurement
rent types
of
operation
as
required.
In
multichannel
ope
and
program them
in
sequential
measu-
ration,
all
those channels between
<cycle>
«BEGIN»
rement channels. This
will
increase the
and
«END»
are
worked through sequentially.
lifetime
of
your electrometer preampli-
It is
a
good
idea
to check
each
measurement channel in.
fler,
tended
for
multichannel operation
in
single channel
ope-
ration before beginning cycle measurements. After this
6.8.3.1 Settling
has been done,
all that
is
left
is
to optimize the measu-
rement
cycle
speed
(cycle
time).
When the detector type
is
not defined
as
either
«PIRANI», «PENNING»
or
«A-lNPUT»,
<cycle>
The measurement cycle time comprises
the
measure-
«FUNCT»
:
«SETTL»
can be used to
call the auxiliary
ment
and
transient times
(pause) for all
the measurement
.
function
for
investigating the transient behavior
for
a
channels mcluded
in the
cycle.
channel switchover
in
multichannel operation. This
car-
ries the
transient
process
from the previous channel
over
Working out the pause time
irtto the selected channel
so
it influences the transient
.
behavior
of
that
channel. This visualization allows
you
to
The
pause
time
is
calculated
by
the control unit takmg
.
,
optimize
the pause
time
I
calibration
factor <amplif>
the following critena mto consideration:
«PAUSE» «P-CAL».
-
Electrometer
range of
measurement
-
Filter time constant
-
Transient time
for
the
RF
generator
--
previous
---++---selected
channel
channel
-
Voltage changes
for
the SEM
-
Detector
switchover
(Faraday
-
SEM, Chopper Lock-in
on
-off,
changing
<mon>
a,
the QMU channelL
and
<AO>
connectors
The calculated
pause
time
is
displayed under
<amplif>
«PAUSE».
It
can be
adjusted individually
by
the
user
from the same
menu
under the «P-CAL» parameter.
IElP NOTE:
The minimum
pause
time
is
1
ms.
It
cannot
be
set
lower
than
that
with calibration
fac,
<sync>
A
tor
0.0.
connector
Pause
When the measurement channel
is
changed,
the
unpro-
cessed
signal
for
that channel not set to »SKIP«
that
immediately preceeded
the
current selected channel
is
output
as the
measured value. During the
pause
time,
the measurement signal
is
sampled periodically (ma×.
every
0.1 ms)
and output. This allows the transient
be-
havior to
be
observed
on an
oscilloscope via the monitor
An
auxiliary function
is
available under
<cycle>
output
or
recorded
via
the analog
output.
«FUNCT»
:
«SETTL» to optimize the
pause
time
(refer
to
The
<sync>
output signal
for
the quadrupole controller
the following section).
(OC
421) triggers the oscilloscope
each
time the
selec-
ted channel
is
started. Trigger the negative flank to
ana-
The time
for
the entire measurement cycle
is
also calcu-
lyze
the transient behavior at
a
channel change.
lated
by
the control unit
and
indicated under
<cycle>.
The pause
time
can
be
adapted to the transient behavior
----
by
modifying the value
for the
«P-CAL» parameter
(optimization).
When the
pause
time
has
elapsed,
further
measurements
are
made and the results filtered
by
the moving average
function
before
the values
are
output.
It is
best to trigger
the
positive flank
to show
the DWELL values
on
the
--------
oscilloscope. The measurement results
are
presented
in
this
way
during the measurement, allowing the time
ET
NOTE:
To keep the measurement cycle time
as
entered
for
«DWELL»
to be
analyzed
and
optimized.
short
as
possible, program those channels
with
the same
type
of
detector, the
same
SEM voltage
and
identical measurernent
range sequentially
in
groups,
OMS421gg.opm
Measuring with the
QMS
421
83
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