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540B
THERMAL TRANSFER
STANDARD
A54
B
SHUNT
•o
CABLE
6002-212860
CURRENT
TRANSFER
SWITCH
o. A40 CURRENT SHUNT
AND
CONNECTIONS
THERMAL
TRANSFER
STANDARD
A54
SHUNT
A40A SHUNT
CABLE 6002-212852
b.
A40
A CURRENT
SHUNT
AND
CON
NECTIONS
Figure 2-8. CABLES AND CONNECTIONS FOR CURRENT
SHUNTS
2
-32.
HI
GH
FREQU
ENCY VOLTAGE
MEA SUREMENT
AND
CALIBRATI
O
N
2-33.
GENERAL
2-34.
A special cable, supplied with the
Model
540B,
provides
a means
of
connecting
the
output
of an external
thermal converter to the HIGH FREQ CONVERTER jack
on
the front panel of
the
Model
540B for high
frequency
ac voltage
measurements.
The Fluke Model A55 Ther-
mal Converter series
of
nine
high frequency
thermal
converters are supplied in ranges
identical with
the
Model 540B
ranges
up
to and including
50
volts. These
converters
make accurate measurements up
to
50
MHz
possible.
When
using external thermal converters
the
internal thermocouple, range
switch,
transfer switch,
search and
protection
circuits are not used. Since no
protection is provided for
the
external
thermal converter
it
will
be necessary to use all normal cautions to avoid
overloads. The instruction manual
for
the A55 Thermal
Converters should be used
to
obtain
the
correction factor
due
to
transmission line effects.
CAUTION!
Always
use a
thermal
converter whose
r
ated
value is
equal
to or greater
t
han the rms
value
of
the ac voltage
to be measured.
If
the
approximate
value of the ac voltage is
unknown,
measure
with
a
high frequency
voltmeter
before
connecting
to
the
thermal
converter.
2-35.
MEASURING
AN
UNKNOWN
HIGH FREQUENCY
VOLTAGE
2-36.
Complete
the
Battery Check of
Figure
2-4. Re-
move
the plug from
the HIGH FREQ CONVERTER jack
on the
Model
540B.
Connect
the
selected
Model A55
Thermal Converter output to
the
HIGH FREQ
CON-
VERTER jack
using the
interconnecting cable,
supplied
2-
10
with
the Model
540B.
This cable
allows
the external
converter
to be connected
close
to the
ac
being
meas-
ured, thus
reducing
transmission line effects.
Connect
the thermal converter
to
the
ac
source to
be measured.
The voltage may
be 1/2
to
1 times the rated value
of
the
converter.
Use
the procedure in Figure
2-11.
Note!
Depending on how the Model A55
Thermal
Convert
er
is
connected
to the
source
of the
unknown
voltage, it
may be
necessary to
make
corrections
for
standing waves at
frequencies
above
5
MHz.
See the
Model
A55 Thermal
Converter manual
for
further
information.
2-37.
CALIBRATING A HIGH
FREQUENCY
VOLTAGE
SOURCE
2-38.
Complete
the Battery Check of
Figure 2-4.
Re-
move
the plug
from the
HIGH
FREQ CONVERTER jack
on the
Model 540B front
panel. Connect
the
selected
Model
A55
Thermal
Converter output to the
HIG.
H FREQ
CONVERTER
jack
using
the interconnecting cable, sup-
plied with
t he
Model
540B.
This
cable
allows
the
ex-
t
ernal converter to
be
connected close
to
the ac being
calibrat
ed,
thus
reducing
transmission
line
effects.
Connect the
thermal
converter to the ac
source
to
be
calibrated. The
voltage may be 1/2
to
1 times the
rated
value
of
the
converter.
Use
the
procedure in Figure
2-12.
Note!
If
the input
impedance
of the instrument
being calibrated
is not 50 ohms
,
it
may be
necessary to
correct
for the
standing
wave
between
the
center
of
the tee and the instru-
ment
being
calibrated
at frequencies above
5
MHz.
See the Model
A55
Thermal Con-
vert
er
m
anual
for
further information.
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