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MODEL 615 ELECTROMETER
OPERATION
NOTE
In some cases,
the offset
current
can charge
the external
test
circuitry.
One example
of
this
occurs
when measuring
a capacitor's
leakage
resistance
by observing
the decay of
the Germinal
voltage.
If
the leakage
current
is less
than the offset
c"rrent
(less
than 5
x lo-l5
ampere),
there
may be no decay of the
terminal
voltage
when the Electrometer
is
left
connected
across
the capacitor's
termi-
nals.
k.
The Model 6012 Triaxial-to-Coaxial
Adapter
en-
ables
using
coaxial
cables
and accessories
with
the
Model 615 by adapting
the triaxial
INPUT connector
to
the UHF coaxial
type,
CAUTION
The Adapter
connect?
circuit
law to case
ground.
The Model 615 cannot
be used off-
ground when using
the Adapter.
The instru-
ment cabinet
will
be at the same potential
as the input
law.
NOTE
Keep the shield
cap (provided)
on the INPUT
Receptacle
when the Electrometer
is not
in
use co prevent
overloads
due to external
noise
pickup.
2-2.
PKECMINARY
OPERATING
PROCEDURES.
a.
Check the 117-234V Switch
for
the proper
AC line
voltage.
b.
Check for proper
rated
fuse.
C.
See the front
panel controls
as follows:
ZERO CHECK Button
RANGE Switch
SF.NSItI"ITY
Switch
wise- Position
FEEDBACK Switch
NORMAL
POWER Switch
OFF
d.
Connect
the power cord.
Place POWER Switch
to
ON position.
After
one-half
hour warm-up,
adjust
the
ZERO Conerol
if necessary.
Zero is indicated
by con-
tinuously
flashing
* polaricy
lights.
NOTK
The rear
panel COARSE ZERO Control
may be
adjusted
if
a large
zero offset
is indicated.
e.
After
a few moments increase
the voltage
sensi-
tivity
by advancing
the Switch
to one position
CLIUIIC-
erclockwiae.
Continua
zeroing
with
the FINE ZERO
Control.
f.
The Model 615 may have excessive
drift
or zero
offset
after
long periods
of storage
or after
an over-
load.
This my be corrected
with
the zero controls
although
drifting
may continue
for
several
hours.
NOTE
If
the Model 615 has been stared
for a long
time,
the offset
current
may exceed the
specification
when first
used,
but should
decrease
to below the specified
amo"nt
after
one or two hours
of "se.
This
is an
inherent
characteristic
of the input
tran-
sistors;
the instrument
is not faulty.
g.
Although
the offset
current
of the Electrometer
is much below that
found in conventional
voltmeters,
it
cm be observed
on the readout
since
the offset
currene
charges
the input
capacitance,
the Electrome-
ter appears
to drift
when the input
is open.
Use the
ZERO CHECK Button
to discharge
the charge
build-up,
h.
Follow
the particular
procedures
in paragraphs
2-3 co 2-7 for measuring
voltage,
current,
resistance,
and charge.
2-3.
DIGITAL READOUT OPERATION.
a.
Valtmecer
Digital
Readout.
1.
When the RANGE Switch
is placed
in the VOLTS
position,
ehe Electrometer
digital
readout
desig-
nates
the actual
voltage
measured using
four numer-
ical
digit
readouts.
2.
The SENSITIVITY
Switch
has four
positions
which control
the lighted
decimal
point
location
and therefore
the full
scale
voltage
range.
The
full
scale
voltage
range far each
SENSITIVITY
Switch
position
is shown in Table
5.
TABLE 5.
SENSITIVITY
Switch
Decimal
Point
Position
msi.cion
I
-~-
I I
0.1
Positicm
1 (full"
counterclockwise)
counterclockwise)
.xXxX
1 1
Position
Position
2 2
x.xXx
x.xXx
10 10
Position
Position
3 3
xX.xX
xX.xX
100
100
PosFtFon
PosFtFon 4 4 (fully
(fully
xXx.x
xXx.x
clockwise)
clockwise)
3.
The fourth
(left
most digit)
readout
permits
a.* averrange
display.
The largest
reading
that
can
be displayed
"sing
all
four
digit
readouts
is 1999.
If
there
is'an
overload
condition,
then all
read-
outs will
blank
(none of the digital
readout
tubes
will
be lighted).
The polarity
(*)
display
indica-
0570
5
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