HP 5245L Service Manual

Model
5245L
Figure
z-tl.
Scaler Operation
2-47.
SAMPLE
RATE.
The
sample-rate multivib-
rator is
triggered
at the leading
edge of the transfer
pulse;
it
produces
a
pulse
which may
be varied from
55 milliseconds
to
5
seconds
with the
front
panel
SAMPLE
RATE
control.
The
trailing
edge
of
the
sample rate
pulse
isdifferentiated
tooperatethe reset
amplifier.
The
reset
pulse
resets
the decimal
coun-
ters
and Iov-frequency
decade
dividers.
2-48.
HOLDOFF. The holdoff
multivibrator
pro-
duces
an
output
pulse
which
starts at
the
leading
edge
of
the sample
rate
pulse
and lasts
until 55
milliseconds
after the
end of
the
sample-rate
pulse.
The holdoff
pulse
disables
the
gate
flip-flop
to
prevent
retrigger-
ing
until
the sample
rate multivibrator
timing
capac-
itor has
completed
recharging.
A
sync
pulse
from
the
gate
control
circuit
(collector
of
Q1
through C10 or
when
in
TIME INTERVAL
from
the
start
line
through
CR?
and C11)
gives
the holdoff
pulse
a
precise
length
Figure
2-12.
Time
Sequence
02349-1
o5245- B
-3
o621r-A-20
and
prevents
the
gate
flip-flop from
being
triggered
prematurely.
During
the slight
delay
between the end
of
the
gating pulse
and
the
start of
the
holdoff
pulse,
the
gate
flip-flop is
disabled
by
an inhibit
signal
from
the transfer
multivibrator.
2.49.
ovERAtt
COUNTER
OPERATION.
2-50. The
entire
counter
is
shorvn in
a
logic
block
diagram
in Figure
2-73.
The front-panel
FUNCTION
switch
applies
a controlvoltage to
selectedAND
gates
in
the
function
control assembly
(A21)
to arrange
circuits
for
each
counter function
(see
tabulation in
Figure 7-2).
The front-panel TIME
BASE
switch
arranges the decade
dividers
(A28-A34)
into
two
groups
using
gate
circuits in
the time-base control
assembly
(A35);
the first
group
produces
decade
division of
the oscillator
(A26)
output,
and the
second
group produces
decade
division of
the counter
input
during multiplied
period
measurements.
For details
of
inter-connections
between circuit
modules
(assem-
blies) refer
to the overall
diagram
Figure
7-2.
2-5T,
INPUT
SWITCH ASSEMBLY
A1.
2-52.
The input
switch assembly, designated SENSI-
TIVITY
(VOLTS
RMS) on frontpanel,
is
a
five-position
switch
(CHECK,
10, 1,
.1,
and
PLUG-IN).
Refer
to
the schematic diagram, Figure
?-3,
for
circuit de-
tails. Switch
functions
are
listed
below.
a.
Provides
three
attenuation
steps
(X1,
X10, X100)
for
signal
applied
to the SIGNAL
INPIIT
connector.
The attenuator
output is connected
to
the
input
ampli-
fier
A19.
b. Connects
output of
plug-in
unit
to
input
ampli-
fier
A19
when switched to
PLUG-IN
position.
c.
Produces
gate
controls 1,
2, 3,
5,
6,
and
27
by
combining
switched -15
volts
from
A3
(FUNCTION
switch)
;
distinguishe
s between
C HE CK
and
not
-C
HE CK
positions.
d.
Combines
switched
-15
volts
from
A3
to contri-
bute to
generation
of
gate
controls
4,
21,
22, 23, 24,
25, 26, 27, 28, and 29; distinguishes
between
CHECK
and
not-CHECK
positions.
Srvitching
for these
gate
controls
is finished
in
A2
(TIME
BASE switch).
Section II
Paragraphs 2-41
to
2-52
GATE
FF
TRANSFER
MV
SAMPLE RATE MV
HOLDOFF
MV
RESET
GATE LIGHT
I SEC
DDA
OUTPUT
q
35MS
I
I
I
-.{
l+
I
I
I
vARtABLE
I
l+55MS
TO
5SEC
55MS
lr
20us
SET COUNTER
CONTROLS
TO.
FREQUENCY,
I SEC
GATE,
MAX.
SAMPLE
RATE
2-t7

HP 5245L Specifications

General

Brand	HP
Model	5245L
Category	Cash Counter
Language	English