Fluke 8506A Instruction Manual page 143

8506A
3.
Connect
a
test
DVM
between
TP4
(HI)
and
TP1
(LO).
4.
Adjust
R34
for a
test
DVM
reading of
2.5
±0.03V
dc.
4-124.
Variable
resistor
R61
in.
the
Sensor
Protect
circuit
controls the
maximum
voltage applied
to the
rms
sensor.
It is
set at
the factory
and should not
require
any
additional adjustment.
If
any components
in
the
circuit
are replaced during troubleshooting
the
circuit
can
be
adjusted or
verified
using the following procedure:
1.
Adjust
R61
fully clockwise
(CW).
2.
Manually
select
the
AC +
DC
function
and
the
IV
range.
3.
Apply
a
2V
dc input
to
the
UUT
input
terminals.
4.
Connect
a
test
DVM
between
TP6
(HI) and
TP1
(LO).
5.
Adjust
R61
for a
test
DVM
reading of
2.2
±0.0 IV
dc.
4-125. Variable
resistor
R78
in
the
Ranging
Amplifier
is
the coarse adjustment
for the zero
adjustment R15.
It is
set
at the factory
and
does not
require calibration
adjustment.
However,
if
any components
in
the
circuit are
replaced during troubleshooting, or
if
R15
is
at
one
extreme without
bringing the
circuit into tolerance,
R78
can be adjusted using
the
following procedure:
1.
Adjust
R15
to
the center of
its
adjustment
range.
2.
Connect
a
test
DVM
between
TP3
(HI)
through
a 10 kilohm
resistor
and
TP1
(LO).
3.
Adjust
R78
for a
test
DVM
reading of 0
±2 uV
dc.
4.
Perform
the
Thermal True
Converter
Adjustments
to verify
the calibration of the
UUT.
4-126.
Variable
capacitor
C8
compensates
the ranging
amplifier
in
the
X20
setting
and
requires adjustment
only
if
repair
or replacement of components
takes place
in the
ranging
amplifier.
Use
the following procedure
to adjust
C8
if
required.
1
.
Short
the center wire of
P2
to
ground.
The
shell
of the
P2
connector
is
not
at
ground.
2.
Select the 100
mV
range
on
the
UUT.
3.
Connect
an
oscilloscope probe
to
TP3
with
the
ground
clip in
TP1.
Select oscilloscope
settings
of
50
mV/div
and
0.5
ms/div.
4.
Adjust
C8
for
minimum
noise
on
the
scope
display.
5.
Select
an
oscilloscope sweep speed of
0.01
us/div.
6.
Verify that the amplifier
is
stable,
i.e.,
not
oscillating.
7.
If
the amplifier
is
unstable, readjust
C8
until the
minimum
noise
is
obtained without causing
the
amplifier to oscillate.
4-127.
Variable capacitor
C9
compensates
the ranging
amplifier
in
the
X6.25
setting
and
requires adjustment
only
if
repair
or replacement of
components
takes place
in
the
ranging
amplifier.
Use
the following procedure
to
adjust
C9
if
required.
1
.
Short the center wire of
P2
to
ground.
The
shell
of the
P2
connector
is
not
at
ground.
2.
Select the 300
mV
range
on
the
UUT.
3.
Connect an
oscilloscope
probe
to
TP
3
with
the
ground
clip in
TP1. Nominal
scope
settings are 50
mV/div
and
0.01 us/div.
4.
Adjust
C9
for
minimum
capacitance,
i.e.,
with
the center
adjustment screw
all
the
way
out.
5.
Adjust
C9
in
toward
maximum
capacitance
until the oscillations stop.
Adjust
C9
in at
least
two
full
turns (720°).
4-128.
Thermal
True-RMS
Attenuator
Assembly
4-129. Variable capacitor C13
in
the
X.08 Attenuator
circuit
is
the coarse
adjustment
for the
10V
range
adjustment
Cl
5. It
is
set at the factory
and
does not
require calibration adjustment. However,
if
any
components
in
the
circuit are replaced during
troubleshooting, or
if
C15
is
at
one extreme without
bringing the
circuit
into tolerance,
Cl
3
can be
adjusted
using the following procedure:
1.
Adjust
C15
to
the center of
its
adjustment
range.
2.
Manually
select
the
AC
HI
ACCUR
function
and
the
10V
range.
3.
Apply an
input of 10V
at
50
kHz
to the
UUT
input terminals.
4.
Adjust
C13
for
a
UUT
reading between
9.9850
and 10.0150V
ac.
5.
Perform
the
Thermal
True-RMS
Converter
Adjustments
to verify the calibration of
the
UUT.
4-29