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HP 437B Service Manual

HP 437B
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HP
437B
Service
Sheet
BD1
The
analog
timer
measures
the
width
of
the
pulse
at
the
output
of
the
analog-to-digital
converter
(in
the
Analog
Section)
and
converts
it
to
data
that
can
be
interpreted
by
the
microprocessor
as
a
measurement.
The
analog
timer
also
generates
a
microprocessor
interrupt
signal.
This
interrupt
signal
occurs
every
5
milliseconds.
The
keyboard
and
display
PIA
provides
the
interface
between
the
microprocessor
and
the
display/keyboard
controller.
Data
from
the
data
bus
is
read
by
the
PIA
and
sent
to
the
display/keyboard
controller.
Keystroke
information
from
the
display/keyboard
controller
is
read
by
the
PIA.
The
PIA
places
the
data
on
the
data
bus
where
it
is
read
by
the
microprocessor.
The
display/keyboard
controller
is
an
8-bit
microprocessor.
The
controller
detects
keystroke
information
from
the
keyboard,
converts
it
to
parallel
data
and
transmits
it
to
the
microprocessor
through
the
PIA.
The
microprocessor
sends
display
data
through
the
PIA
to
the
controller.
The
controller
then
sends
the
data
to
the
display.
The
service
function
switch
consists
of
seven
single-pole
single-throw
switches.
These
switches
allow
the
user
to
set
seven
of
the
eight
data
lines
on
the
data
bus
to
ground.
Certain
settings
of
these
switches
cause
the
microprocessor
to
invoke
certain
self
tests.
The
service
function
switch
is
also
used
to
set
a
default
HP-IB
address.
The
LED
data
latch
is
used
to
convey
operating
information
of
the
Power
Meter.
Data
from
the
data
bus
causes
the
LEDs
to
illuminate
or
blink
in
certain
patterns.
These
patterns
convey
information
about
errors
and
operating
states.
More
information
about
the
LED
data
latch
and
service
function
switch
can
be
found
in
the
troubleshooting
information
in
this
section.
The
HP-IB
interface
is
a
bi-directional
device
that
allows
the
Power
Meter
to
interface
with
external
instruments
and
controllers.
Control
signals
and
data
from
the
data
bus
are
received
by
the
HP-IB
interface
and
transmitted
onto
the
external
HP-IB
bus
through
two
devices:
the
HP-IB
transmit/receive
buffer
and
the
HP-IB
data
control.
Similarly,
control
signals
and
data
from
external
instruments
and
controllers
are
received
by
the
HP-IB
interface
and
transmitted
onto
the
data
bus.
Analog
Section
The
Analog
Section
measures
the
input
signal
from
the
power
sensor.
The
signal
is
amplified,
filtered,
and
then
measured.
The
Analog
Section
then
produces
a
pulse
with
a
width
that
is
proportional
to
the
power
level
of
the
measured
signal.
This
pulse
width
is
counted
by
the
Digital
Section.
The
microprocessor
converts
this
count
to
a
power
measurement.
Power
levels
(from
an
external
source)
are
converted
to
a
DC
voltage.
A
220
Hz
square
wave
signal
from
the
power
meter
amplitude
modulates
the
DC
voltage.
This
creates
a
220
Hz
signal
whose
amplitude
is
proportional
to
the
sensed
power
level.
The
220
Hz
amplitude
modulated
signal
from
the
power
sensor
is
fed
into
the
input
amplifier.
The
input
amplifier
contains
a
shaping
network
to
compensate
for
non-linearities
in
ranges
4
and
5
of
the
power
sensor,
SERVICE
8-17

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HP 437B Specifications

General IconGeneral
BrandHP
Model437B
CategoryMeasuring Instruments
LanguageEnglish

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