I
I
I
SECTION
VI
ACCESSORIES
6-1. MODEL
A55
THER
MAL CO
NV
ERTERS
6-2. lliTRODUCTION
6-3.
Nine
Fluke
Model
A55
Thermal
Converters
(Figure 6- 3)
are
available with
ratings
of
0. 5, 1, 2,
3,
5, 10, 20, 30, and 50 volts,
each
of which
may
be
used
fr
om
1/2
to 1
times
the rating.
These
converters
make
possible extremely accurate
thermal-transfer
ac
meas-
urements from sub-audio frequencies to the
VHF
region.
AC/DC
difference
of
the
Model A55
series
is
compa-
rable
to
that
of
theoretical
standards
maintained by the
National
Bureau
of
Standards.
6-4.
CONSTRUCTION
540B
6-5.
A specially
constructed
thermocouple,
selected
for
frequency
characteristics
and
low DC
reversal
error,
is
the thermally responsive element of the Model
A55
series.
AC
and
de input
voltages
are
applied
di
-
rectly
across
the
thermocouple
heater
on the 0. 5 volt
model.
For
higher
voltages,
low
temperature
coef-
ficient
metal
- film
resistors
provide
the
proper
range
multipliers
.
Figure
6·1
. M
ODEL
A55
THERMAL
CONVERTERS
AND
ACCESSORIES
6- 1
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