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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
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