Fluke 6060B - User Interface; Amplitude Control; Attenuators; Level DAC

THEORY
OF OPERATION
•
Configures the
Generator functional
blocks to
produce
the required
output and
then applies
linearization
and
compensation
data to
optimize
the instrument
performance and
resolution.
•
Implements a set of self
test
and diagnostic
functions,
3-12.
User Interface
The Generator
software
is implemented
with a simple
operating
system that allows
several tasks
to
operate in a
round-robin
fashion
on
a equal priority
basis. Input and
output to the front
panel and to the
IEEE-488
Interface
option*
however,
execute at a
higher priority and
are handled as interrupt
routines.
At power-on,
the software performs
an instrument
self test and
initializes
both the RAM
and the Generator
hardware.
Three tasks
are continuously
in operation:
Service task
Key task
lEEE^SS
task
The
service task checks the
status signals.
The
key task
and
IEEE-488 task
process user
input. A fourth task
is activated
only when
needed
to process certain
UNCAL
(uncalibrated)
or REJ ENTRY
(rejected entry)
conditions that
cause the instrument
STATUS display to flash.
3-4
3*13.
Amplitude
Control
Amplitude
is
programmed using
a 23-step
(6.02 dB per step)
attenuator assembly
and a
I2“bit vernier
level DAC. The
level DAC
settings depend
on a combination
of the
programmed
output level
and amplitude
correction
data.
The amplitude
correction
data compensates
for level
inaccuracies
and is a
function
of the
Generator frequency.
Correction
factors
are stored
in the Output
and the Attenuator
Calibration
EPROMs.
Each
Output and
Attenuator
assembly
comes with a
matched
calibration
EPROM. The
assemblies
may
be replaced
under
the Module
Exchange
Program with
only minor
adjustments
needed
after installing
the replacements.
3-14.
Attenuators
One 6-dB, one
12-dB, and five
24-dB sections
of the Attenuator
are programmed in
combination
to provide
course level
control.
The
indicated
voltages at which the
Attenuator
changes ranges
are
2"'^
volts,
where
m
=
I,
2, 3,
...23
for
non-AM,
or
m
=
2, 3,
,4,
.,,24
for AM
operation
Table
4D-I5 lists
the Attenuator
sections
programmed
for various
displayed
levels.
3-15.
Level
DAC
The level DAC setting (LEV
0 through
9)
is calculated
from
the
Generator
output
level. If
level
correction
is enabled, the level
DAC setting
is further
modified
by the data stored
in
the Output and
Attenuator
calibration
EPROMs.
To minimize level
transients
that could
damage external
circuitry,
the following
sequence
is used in programming
the Attenuators
and the level DAC
when the
Attenuator
setting is
changed:
I
I
t