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OPERATION
MODEL 630 POTmTIOMETRIC ELECTROMETER
b.
Power Cord.
The Model 630 is designed
for
a 105-125 volt,
60-cps
line
source,
un-
less
otherwise
specified
on the rear
panel.
The 3-wire
power cord with
the NEMA approved
3-prong
plug
provides
a ground
connection
for
the cabinet.
A 3:2 prong adapter
is provi-
ded.
C.
NULL DETECTOR OUTPUT. Two terminals,
marked + and -,
supply
a dc signal
from the
null
detector.
d.
COARSE ZERO Switch.
A screwdriver
adjustment
is provided
for bucking
out the con-
tact
potential
of the vibrating-reed
capacitor.
The Switch
has a i-100 millivolt
span in
ten ZO-millivolt
steps.
e.
117-234
Switch.
The screwdriver-operated
slide
switch
sets
the Model 630 for
117
or 234volt
ac power lines.
2-3.
PRELIMINARY PROCEDURES.
a.
Check the 117-234
Switch
and the Fuse for
the proper
ac line
voltage.
Connect
the
power cord.
b.
Set the Model 630 front
panel
controls
as follows:
DETECTOR INPUT Switch
ZERO CK
RANGE Switch
500
NULL Switch
VTVM
POLARITY Switch
-I.
Reference
Voltage
Dials
ZWXJ
The decimal
light
between
the third
and fourth
Dials
will
light.
Allow
the instrument
to'warm
up 30 minutes
to meet the specified
accuracy
on all
ranges.
c.
Set the NULL Switch
to 1.0 MV.
Zero the meter with
the METER ZERO Control.
Nor-
mally,
using
the COARSE ZERO Control
on the rear
panel
is not necessary.
Return
the
NULL Switch
to VTVM.
Check meter
zero periodically.
Null
detector
drift
can be up to 2 millivolts
per day, which
will
cause inaccuracies
in continuous
readings.
Setting
the
DETECTOR INPUT Switch
to ZERO CK disconnects
the input
signal
source
from the
instrument,
avoiding
polarization.
It
is not necessary
to disconnect
the input.
2-4.
OPERATING PROCEDURES,
a.
The Model 630 is used first
as a voltmeter
to determine
the approximate
value
of
the unknown voltage.
It
is then used in the potentiometric
mode to determine
the voltage
to 10.01%.
6
Vibrating
capacitors
are extremely
sensitive
to shock and vibration.
when
making
a measurement,place
the Model
630 on a vibration
free,
rigid
structure
or on some material
which
will
minimize
vibration.
Also,
tightly
tie
down
the input
cable
and any attached
circuitry;
any cable
flexure
will
generate
electrostatic
charges
which
the Model 630 will
detect.
L265R
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