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OPEP.ATION
MODEL 615 ELECTROMETER
instr"me"ts
and *cc***0ri**.
1 - Voltage
Source,
such as Keithley
Models
240A or 241.
1 - Shielded
switch,
such as Keithley
Models
6104,
3011 or
4194.
1 - Test Cable,
such as Model 6108
1 - Model 6012, "XF to Triax
Adapter.
3.
Connect
the voltage
source,
switch,
and uo-
known resistance
as shown in Figure
6.
since
the
~lecrrometer
is used for
the measuremene of current,
refer
to Paragraph
2-5 for complete
instructions.
NOTE
Refer
to Paragraph
2-6 for complete
instruc-
tions
for meking off
ground measurements.
4.
To make a eesistame
measurement,
place
Switch
s in the "OFF" position
8s shown in Figure
6.
Ad-
,,st
the voltage
source
for a predetermined
voltage.
Place Switch
S in the "ON" position
to
apply
the
voltage
ecross
the unknown resistance.
Allow
a
per-
iod of time for
the current
through
the unknown re-
sistance
to stabilize.
Unlock
the ZERO CHECK Sutton
to take a current
reading.
Adjust
the RANGE Switch
and SENSITIVITY
Switch
to obtain
a satisfactory
reading.
5.
After
a reading
is made. place
the ZERO CHECK
Sutton
to LOCK poeition
and place
Switch
s to
"OFF"
pOSiti"".
Rem""*
the unknown resista"Ce
and replace
with
a second sample if
necessary.
NOTE
If
the voltage
applied
to the sample is not
100 times
the Electrometer
input
drop,
the"
the unknown resistance
ia calculated
es
follows:
R
x
= Vsource
-
"Input
oroe
lMeeasured
Eq. 1
where Rx = ""known
resistance,
VSource - Applied
voltage,
"Input
Drop = Electrometer
input
voltage
drop
and l"easured
= Current
measured by Electrom-
eter.
2-8.
CHARGE mASuP.EMmTS.
a.
Charge measurement
or current
integration
can be
accomplished
using
the Model 615 in the coulombmeter
mode,
The electrometer
indicates
the voltage
across
a
very
accurate
self-contained
capacitor.
The Electrom-
eter
output
is
therefore
a voltage
which
is
propor-
tional
to the integral
of the applied
curreot.
NOTE
For a more complete
discussion
of current
integration,
request
the Keithley
Product
Note entitled
"Using
the Electrometer
Volt-
meter
es a Current
Integrating
or Charge
Meas"ring
I"sCr"ment."
12
b.
Set the front
panel
controls
as
follows:
ZERO CHECK Button
KANCE Switch
SENSITIVITY
Switch
LOCK
10-7 COULOMBS
Fully
Counterclock.
wise
FEEDS.4CK switch
FAST
c.
Connect
the Electrometer
to the current
eource
to be measured
as described
in Paragraph
2-5.
d.
Unlock
the ZERO CHECK Sutton
to make B measure-
ment.
Adjust
the SENSITIVITY
Switch
to obtain
a see-
isfactory
reading.
changing
the SENSITIVITY
Switch
setting
doea not affect
the transfer
of charge
from
the source
to Electrometer.
e.
The coulombmeter
reading
is determined
by mulci-
plying
the digital
display
times
the RANGE Switch
CO"LOMBS setting.
If
the RANGE Switch
must be changed
to obtain
a satisfactory
reading,
repeat
steps
b, c.
and d above.
NOTE
The input
offset
current
of the Electrometer
contributes
a charge
of 5 x IO-l5
coulomb
per second and should
be subtracted
from the
actual
reading.
f.
After
a coulombmeter
reading
is made, discharge
the integrating
capacitor
in the Electrometer
by
placing
tile ZERO CHECK BUteon to I.OCK position.
Dis-
charge
capacitor
for
at lease
20 seconds on the IO-'
COULOMB range before
making another
measurement.
2-9,
RECORDER OUTPUTS.
The Modal 615 provides
several
outputs
for
~~.
1toring
an a"al"g
or dIgital
signal.
me "ario"
outputs
are
summarized
as follows.
NOTE
For informeti""
concerning
Static
Charge
measurements,
request
the Product
Note
entitled
"Electrometer
Stetic
Charge
Measurements".
The Model 615 should
be
used with
Keithley
Models
2501 end 2503
Static
detector
Probes
for
Static
Charge
Meas"rements.
0" not sttempe
to use the
Model 615 in the COULDMBS mode for
Static
Charge meesuremeots
since
the Electrometer
is very
sensitive
to charge
trensients.
1.
1MA OUTPUT. This
""tpot
provides
a 1 milli-
ampere analog
outpoe
corresponding
to a full
range
itlP"C .
NOTE
The Keithley
Model.370
may be conveniently
used to obtain
a chart
record
with
1% Ii"-
earity.
The Model 370 haa 10 speeds,
re-
quires
no preamp,
and permits
operation
up
to *lOO volts
off
ground when used with
the Model 615.
A special
phone plug
such
as Switchcraft
S-290 must be used with
the
Model 615.
0470
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