Functional Block - Fluke 93 Service Manual

3-2
CIRCUIT
DESCRIPTIONS
3.2
FUNCTIONAL
BLOCK
DESCRIPTION
3.2.1
Introduction
This section contains
an
overall
block
diagram
of the
ScopeMeter. Refer
to figure 3.1
The
block
diagram can be
divided
in
two
parts.
The
upper
part of
the
diagram shows
components
that
are
situated
on
the Printed Circuit
Board
(In
the following
text:
PCB),
that
Is
connected
to
the
ScopeMeter^s bottom
cover.
Because
this
PCB
contains mainly analog
circuits,
it
is
called the
analog
A2PCB.
The
lower
part of
the
diagram
contains the
digital circuitry of the
ScopeMeter. This
circuitry
Is
located
on
the digKal
A1 PCB,
the
PCB
connected
to
the ScopeMeter's
lop
cover
The
general
layout of the
block diagram
is
the
same
as
the
layout of the
circuit
diagrams
In
chapter
10.
The
circuits
that
can be found on
the
same
circuit
diagram
(chapter
1
0)
are placed
in
a dashed
box
in
the block diagram.
Analog
A2
PCB
The
signals
at
the red and
gray
6NC
input
connectors
are attenuated
Oy
the
CHANNEL
A
ATTENUATOR
section
and
the
CHANNEL
B ATTENUATOR.
These
attenuators are set
by
the
Microprocessor
(on the
digital
A1
PCB)
via
the
ANALOG CONTROL
CIRCUIT. Also
input protection
circuits
are provided here.
The
output signals of the attenuator blocks are fed
to
the
ANALOG
ASIC
(ASIC
» Application
Specihe
Integrated
Circuit).
TNs
component
is
controlled
by the
ScopeMeter's microprocessor
(on
the
digital
A1 PCB).
The
Analog
ASIC
incorporates
signal amplification
and
channel
selection.
It
also
prepares
the signal
for
sampling
by
the
Analog
to Digital
Converter (ADC).
The
red
and
black
banana
connectors are connected
to
the
EXTERNAL (BANANA)
IN
PUT/0
UTPUT
CIRCUIT.
When
the
ScopeMeter
Is
set
to
mV. DIODE
or
OHM
METER
mode,
the External (banana)
input/output
circuit
outputs
its
signal
Into
the
Channel
A
Attenuator
section.
In
SCOPE
mode,
the
circuit
can
act
as a
trigger
input.
The
trigger signal
Is
fed to the
Analog ASIC.
In
the Analog
ASIC
"channel
A",
"channel B"
or "External thggeh'
can be
selected as
trigger source.
The
trigger
signal
is
used
to
generate the
DELTA-
T
voltage (time
relation
between
trigger
moment
and sampling
momer^t).
The
built-in
GENERATOR
uses the
External (banana)
input/output
circuitry
as output.
It
is
possible
to
generate
a
DC
voltage
and a square wave
voltage.
ScopeMeter model 97
also
can
generate
sine
wave
voltages,
a
ramp
voltage,
and a ramp
current.