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MODEL 615 ELECTROMETER
OPERATION
3.
Set the front
panel
controis
as fallows:
ZERO CHECK SULLO"
LOCK
RANGE Switch
1011 OHMS
SENSITI"ITY
Switch
Fully
Counterclock-
wxse
FEEDBACK switch
NORMAL
4.
Connect
the unknown resistance
between
the
electrometer
input
high and low as for normal Mode
Voltage
Measurements.
5.
Unlock
the ZERO CHECK Hutton
to make a mea-
S"Tellle"t.
NOTE
Do nae open circuir
the Electromeeer
on the
OHMS ranges;
the input
will
de"elop
a large
voltage
due to its
constant
currene
charac-
teristic.
Keep the input
shorted
or the
ZERO CHECK Button
locked.
6.
the unknown resistance
is determined
by multi-
plying
the digital
display
times
the RANGE twitch
setting.
"se the smallest
RANGE Swiech setting
for
beBe possible
accuracy.
7.
The applied
test
voltage
is indicated
directly
on the digital
display
in volts.
8.
The test
current
is the reciprocal
of the OHMS
Range setting.
NOTE
Shield
the input
if
the resistance
sample
exceeds
108 ohms.
Fast COnSLant current
Resistance
Measurement.
(&ommended
for
10"
to 1ol4 ohms measurements).
1.
The Fast Mode permits
faster
response
speed
when measuring
very
high
resistances.
2.
set
the
front
panel
controls
as follows:
ZERO CHECK Button
LOCK
RANGE Switch
1011 OHMS
SENSITI"ICY
SWFtch
Fully
Counterclock-
wise
FEEDBACK Switch
FAST
3.
connect
the unknown resistance
between
the
Electrometer
input
high and GUARD Terminal
as for
Fast Mode Voltage
Measurements.
4.
""Lock
the ZERO CHECK Button
to make a mea-
SuremenL.
5.
the unknown rcsisrance
is determined
by multi-
plying
the digital
display
times
the RANGE switch
setting.
6.
The low terminal
of the INPUT Receptacle
is
now a driven
guard.
It may be used t" minimize
the
effects
of capacity
berween hi&h end low and errors
due to leakage
reSiSta"ce
between big,,
and low.
7.
The Model 6oLl Input
Cable.
supplied
with
the
Model 615, provides
a convenient
means of making
guarded
reeistance
meesurements.
connect
the shart-
in&t link
between
the CASE GRO"ND and GUARD Terminals
"n the rear
panel.
This
allows
the CASE GROUND ur
blue
test
lead terminal
to be connected
CO the Luw
impedance
side of the unknown resistance.
me inner
shield
or the black
test
clip
is the GUARD Terminal.
d.
Volt-Ammeter
Resistance
Measurement
(to
10'6
ohms).
1.
In the Volt-Ammeter
method the voltage
applied
to the sample is arbitrarily
set at any cO""enir"t
uoltage.
The current
through
the resistance
sa,"ple
is measured by the Electrometer.
'rhe resistance
of
the unknown is calculated
in terms of the known
voltage
impressed
and the resultant
measured current
2.
This method requires
the use of the folluwing
FIGURE 6.
Volt-Ameter
Resistance
,.,easuremenc.
0470
11
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