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MODELS 610B,
610BR ELECTROMETERS
MAINTENANCE
Control
Circuit
Designation
Ohms Calibration
Rll5
18
4-10
Meter
Center
Zero
Calibration
R167
18
4-11
Meter
Calibration
R175
18
4-11
DC Amplifier
Balance
RL77
19
4-8
TABLE 4.
Model
610B Internal
Controls.
The Table
Lists
all
internal
controls,
the
figure
picturing
the
location
and the paragraph
describing
the adjustment.
2.
The dc amplifier
balance
adjustment
(paragraph
4-8)
is necessary
about
every
six
months
or when amplifier
components
are replaced.
3.
Verify
the value
of the high-megohm
resistors
(paragraph
4-9)
about
every
six
months
to check
on drifting.
4.
Calibrate
the ohms ranges
(paragraph
4-10)
about
once a year
or when
range
resistor
or power
supply
components
are
replaced.
5.
Calibrate
the meter
zero
(paragraph
4-11)
about
once a year
or when
components
are
replaced.
6.
Check the Model
610B (paragraph
4-12)
once a year,
after
the
other
adjustments,
or if
improper
operation
is
suspected.
c.
If
the tide1
610B is not
within
specifications
after
the calibrations
and adjustments,
follow
the
troubleshooting
procedures
or contact
Keithley
Instruments,
Inc.,
or its
nearest
representative.
4-7.
GRID CURRENT
CHECK.
Check grid
current
whenever
excessive
noise
or drift
is
suspected.
To read
the grid
current
of
the Model
610B,
set
the
front
panel
controls
to:
METER Switch
+
tiltiplier
Switch
.Ol
Range Switch
10-11
AMPERES
ZERO CHECK Button
Unlocked
FEEDBACK Switch
FAST
Cap the INPUT Rece
less
than
2 x 10-L e
tacle.
The grid
current
indicated
on the meter
should
be
ampere.
If
this
is
exceeded,
check
the
+Zl volt
supply
and the electrometer
Tube,
VlOl.
4-8.
DC AMPLIFIER
BALANCE ADJUSTMENT.
Gradual
aging
of components
may require
an occasional
adjustment
of the amplifier
balance.
Also
adjust
if
amplifier
components
are
replaced.
This
adjustment
sets
the
gain
to allow
the meter
to
receive
the
correct
signal
on all
ranges.
1064R
33
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