Fluke 415B Instruction Manual page 31

415B
d.
Set
the
Model 750A
COARSE
and
FINE
controls to
mid-position.
e.
Set the
Model 4I5B
POLARITY
switch
to the
desired
polarity and the
OUTPUT VOLTAGE
controls
to
same
voltage value as
the
Model 750A INPUT
con-
trol.
f.
Set the
Model 845B
controls as follows:
POWER
ON
OPR/ZERO OPR
RANGE
To
reduced
sensitivity
(1
volt for
example)
g.
Set the
Model 415B
HIGH
VOLTAGE
switch
to
ON.
Throw
the
STANDARD CELL
switch on the
Model
750A
to
MOMENTARY
and
note the deflection on
the
Model 845AB. Then
adjust the
Model
415B
OUTPUT
CONTROLS,
including the vernier,
to
achieve zero indication on
the
Model 845AB.
In-
crease
sensitivity of the
Model 845AB
as
null is
approached.
h.
Using
the
COARSE
and
FINE
controls on the
Model
750A,
adjust for
a final null on the 10 microvolt
range
of the
Model 845AB.
i.
Calibrated
output voltages are
now
available at the
Model 750A
OUTPUT VOLTAGE
terminals.
The
desired voltage value
is
selected with the
Model
750A
OUTPUT VOLTAGE
control.
2-19. Leakage Current Measurements
2-20. The Model
41 5B, in
conjunction with
any John
Fluke differential voltmeter,
may
be
used
to
determine
leakage
current at high voltage
in
insulators, capacitors
and
test
instruments.
Proceed
as
follows:
a. Connect the equipment as shown
in Figure
2-4.
The
protection
circuit
shown
in
Figure
2-4 provides
pro-
tection
to
the voltmeter by
limiting
the input to
less
than one
volt in
the event
of
a short
in the
component
under
test.
The
resistors
must
be non-inductive
(composition, Allen Bradley
type).
b. Set the differential
voltmeter
to
measure
100 milli-
volts.
c.
Set the
HIGH
VOLTAGE
switch
to
ON.
When
the
HIGH
VOLTAGE
lamp
illuminates gradually
in-
crease
the output
of
the Model
41
5B
until the desired
test
voltage or
limit
of
leakage current
is
obtained.
d.
An
indication
of
100
millivolts
on
the
voltmeter
in-
dicates
a
leakage current
of
0. 1
microamperes and
corresponds
to a
measured
resistance
of
3
x 1010
ohms when
3000
volts
is
applied from
the
Model
415B.
2-21.
Circuit Protection
2-22.
The
overcurrent
protection
circuit
of
the
Model
415B
is
adjusted
at the
factory
to
operate 32
milli-
amperes
load current. This adjustment
is
accessible
through
the top cover and
may
be set to operate
at
other
load currents up
to
35
milliamperes.
To
re-adjust the
overcurrent
circuit
to
operate
at
a load
current other
frhan
39.
mill
isi
mnorno
fofor
t-rv
4 3
3
2-6
Figure
2-4.
LEAKAGE CURRENT
TESTING
Rev.
1