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OPERATION
MODEL 615 ELECTROMETER
2.
Model 6103A Divider
Probe for measurements
up
to 30
kilovolts.
This
probe permits
meas"rements
with
overall
accuracy
of Cg%.
1012
Input
r**i*t**c*
is
ohms maximum.
The actual
voltage
is obtained
by multiplying
the Electrometer
digital
display
times
the divider
ratio.
NOTE
The Model 6012 Triaxial-to-Coaxial
Adapter
must be
used
with
Models 6102A and 6103A
sF"ce tile probes
are termFnated
with
a LW
connector.
When using
the Model 6012,
the
case ground is connected
to inp"t
law so
that
the Electrometer
may not be used for
off
ground measurements.
-
2-5.
CURRENT
MEASUREMENTS.
a.
The Model 615 can measure an unknown current
when the low impedance
terminal
is up to 100 volts
off
case ground.
Safe operation
of the Electrometer
is
insured
by grounding
the case.
To "se the Model 615
far
off
ground current
measurements,
disconnect
the
shorting
link
between
LO and CASE GND Terminals
on the
rear
panel.
(Refer
co Figure
2).
CAUTION
Operating
the Model 615 at more than 100
volts
off
ground may permanently
damage
the instrument.
The isolation
between
circuit
low and ground could
break
down
making the instrument
unusable
for safe
off
ground meawrements.
Refer
to Paragraph
2-6 for complete
instructions
for
making off
ground meas"eements.
b.
The Model 615 can meas"re
currents
in two modes:
Normal Mode and Fat
Mode.
1.
Normal Mode.
In the Normal Mode -
used on
eny renge -
the cwrent
is determined
by measuring
the voltage
drop across
a self-contained
reeistor
shunting
the electrometer
amplifier
input.
This
method permits
a minimum noise
m~as"rement
when re-
sponse speed is not.critical.
2.
Fwt
Mode.
I"
the F.ast Mode -
for "se only
below
10-S ampere range -
a self
contained
resistor
is connected
between
the electrometer
amplifier
in-
put and output
(in
the feedback
loop).
This method
permits
faster
response
speed since
the effect
of
input
capacitance
is minimized.
The input
volcsge
drop is reduced
to less
than 100 microvolts
on any
range.
Refer
to Table
7 for
typical
Response and
Noise
performance
for various
values
of input
capac-
itance.
C.
Normal Mode Current
Measurements.
1.
Set the front
panel
controls
as follows:
ZERO CHECK nutron
LOCK
RANGE Switch
10-l
AMPERES
SENSITIVITY
Switch
Fully
Counterclock-
wise
FEEDBACK Switch
NORMAL
NOTE
To
make off
ground measurements,
refer
to
Paragraph
2-6.
2.
Connect
the
Model 6011 Triaxial
Input
Cable
for meeauring
s,, unknown current
as follows.
a)
The heavy wire
with
red clip
cover
should
be connected
to the source
high
potential.
b)
The thin
wire with
black
clip
cover
should
be connected
so as to place
the Electrometer
in
series
with
the c"rrent
to be measured.
c)
The thin
wire
with
green
clip
cover
should
not be connected
when the shorting
link
between
LO and CASE GND Terminals
an the rear
panel
is
connected.
3.
Unlock
the ZERO CHECK Button
to make B mea-
surement.
4.
Adjust
the RANGE Switch
to increase
the Slec-
emmeter
sa"siti"ity
for
CUrrent
measurements.
5.
The full
range c"rrent
for
the Electrometer
is determined
by multiplying
the digital
display
times
the RANGE Switch
setting.
The best
accuracy
for current
meas"rements
is obtained
by "sing
a
TABLE 7.
Typical
Effects
of External
Inp"t
Capacitance
on Response Speed and Noise Performance
in C"rre,,t
Measurements
with
the Model 615.
i-l****
Rise Time (seconds)
Output
Noise
(Peak-Co-Peak)
No C
$;to
-
2eE
5000pF
No C
-
x
5000pF
2.0
2.0
2.0
6 x lo-l5
1.5
x 10-14
7 x 10-13
$"
.07
.45
.45
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8.5
x 10-14
10-S
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.07
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,015
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$5;
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10-7
,003
.003
,003
10-6
s'x
10-11
2
x 10-10
.003
,003
,003
3.3
x 10-10
s
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