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OPERATION
MODELS 6108,
610BR ELECTROMETERS
Using
the Model
6LOLA Probe
is
a simple
way to insure.good
input
connections.
NOTE
Clean
and dry
connections
and cables
are very
important
to maintain
the value
of all
insulation
materials.
d.
Any change
in
the
capacitance
of the measuring
circuit
to ground
will
cause
extraneous
disturbances.
Make the measuring
setup
as rigid
as possible,
and tie
down connecting
cables
to prevent
their
movement.
If
a continuous
vibration
is
present,
it
may appear
at
the output
as a sinusoidal
signal
and
other
precautions
may be necessary
t"
isolate
the
instrument
and the
connecting
cable
from
the vibration.
e.
For
Low impedance
measurements,
unshielded
Leads and a binding
post
adapter
may be used.
However,
keep the
leads
short.
f.
When measuring
currents
LO-l4
ampere
or less
with
the FEEDBACK switch
at FAST, some insulators
-
such as Teflon
-
may produce
random
signals
which
show up as erratic
meter
deflections.
Insulation
used
in
the Model
6108 is
carefully
selected
to minimize
these
signals.
.s.
Connect
the M"deL 610B to the
circuit
only
when a reading
is being
made.
I"
some cases,
the
grid
current
can charge
the
external
test
circuitry
when
it
is
connected
to the
Electrometer
input.
One example
is measuring
a
capacitor's
Leakage
resistance
by observing
the
decay
of its
terminal
voltage.
If
the
Leakage
currant
is
less
than
the grid
current,
there
is
no
decay
of
the
terminal
voltage
when the
electrometer
is
Left
connected
across
the
capacitor's
terminals.
Instead,
there
is a build-up
which
seems to indicate
that
the
capacitor
dielectric
has a negative
resistance.
NOTE
Techniques
and applications
are
thoroughly
discussed
in thebrochure,
Electrometer
Measurements,
by Joseph
F. Keithley.
It
is
available
by writing
to Keithley
I"stnlae"ts,
1°C.
2-4. Preliminary
Procedures.
a.
Check
the
117-234
Switch
and the Fuse
for
the
proper
ac Line
voltage.
NOTE
Make sure
MRTRR Switch
is
sst
to POWER OFF before
connecting
or disconnecting
the
power
cord.
b.
Set the
controls
as follows:
METER Switch
POWER OFF
Range Switch
VOLTS
Multiplier
Switch
1
FEEDBACK Switch
NORMAL
ZERO CHECK Button
LOCK
a
0667R
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