HP 5245L Service Manual

r
:
I
Model
5245L
pulse.
Consequently,
when a frequency
is
applied
to
the input
of the decade
divider,
the
first
binarydivides
it
by
two
(since
the
first
pulse
switches
the binary to
the opposite
state and
a
second
pulse
is required
to
return
it
to its
original
state)
and again
by two
in
the
second
binary
(making
a
total division
by
four) and
so on,
with an
expected
total
division
of
sixteen
at
the
output
of
the fourth
binary.
The
desired division
by
ten is
obtained
bya feed-ahead
pulse
to the fourth
bi-
nary
and feedback
pulses
to the
second and third bi-
naries.
Therefore,
after
the
eighth
input
pulse
is
received
the binaries
wiII be in
a
state
as if
they
had
counted fourteen
pulses.
Then,
when the
ninth and
tenthpulses
are received
the
desired final output
pulse
is
produced.
Operation is
similar
to that described
for
the decimal
counters
discussedin
Paragraphs 2
-76
and
2-??
except
that
there
is
no display array con-
nected
to the
binaries. Note
that A31
throughA34
are
suppliedwith
a reset input
sothat
only a
certain
num-
ber of input
pulses
to the decade
dividers
are necessary
after
reset
before an
output is
produced.
Refer
tothe
schematic diagram
Figure
7-24,
for
circuit details.
2.IT7" TIME-BASE
CONTROL ASSEMBLY
A35.
2-118.
GENERAL.
The
purpose
of
the time-base
control
is
to
a) Iower
the output
impedance
of the
10
MHz signal
from
multiplier
A21;
b)
select
a f requency
between 0.1 Hz
and
10
MHz
as
controlled
by
the TIME
BASE
switch, and
c)
provide
a multiplied
period
sig-
nal
when
the
FIINCTION
switch
selection is between
10
and 100K
PERIOD
A\IERAGE.
Inhibit
gates
? thru
11
(CRB,
CR11,
CR14,
CR1?, and
CR20)
are normally
open;
a control
voltage
to turn
one of
these
gates
off
is
applied
only for
multiplied
period
measurement.
Multi-period
gates
7
thru 11(CRg,
CR12,
CR15, CR18,
and CR21)
are
normally
closed;
one
onlyis opened for
multiplied
period
measurements.
Selected frequency
gates
21
thru 28 are
controlled
by
the
TIME-BASE
switch.
2-Lt9.
SELECTED
FREQUENCY
CONTROL. For atl
ope
rating functions
except PE
RI
OD AVE
RAGE
C Im C K,
gates
21
thru
29
are onfor
the TIME
BASE
selections
listed
in
Table
2-4.
For
example, if
the TIME
BASE
switch
is
set to
1
ms,
the control
voltage
is applied
to
gate
25,
turning it
on and
permitting
the
l
kHz
signal
from
A30 to be amplified
byQ11
and
Q12;
the
ampli-
fied
l
kHz
is supplied as
the
selected frequencytoA2l.
Section
II
Paragraphs
2-117
to 2-122
(For
PERIOD
AVERAGE
CIIECK,
gate
21
is
on, re-
gardless
of
TIME
BASE
seleetionrandl00kHz
is
sup-
plied
as
the
selected frequency.
)
2-120. MULTIPLIED
PERIOD
CONTROL.
Control
voltages for
gates
? through 11
are
supplied
only for
multiplied
period
measurements,
as listed in
Table
2-5.
These
control
voltages
select
one to
give
steps
of decade
division
for
the
period
signal
supplied by
A21.
Example
1: The FUNCTION
switch
is
set
to
IO-PERIOD
AVERAGE;
gate
control
11
is
on, turning
off inhibit
gate
11
(to
prevent
further
division of the
signal
from
4.26)and turning on multi-period
gate
11;
the amplified
period
signal
from
Q1
is
passed
thru
CR21,
divided
by ten
in
A34, and
supplied thru
Q10
as
the multiplied
period
signal.
Example 2: The
FUNCTION
switch is
set to IK-PERIOD AVERAGE;
gate
control
9 is on,
turning
off
inhibit
gate
9 and
turning
on multi-period
gate
9;
the amplified
period
signal from
Q1
is
passed
through CR15,
divided by
ten in 432,
passed
by
CR1?,
divided in A33,
passed
by
CR20,
divided
in A34,
and
supplied through
Q10
as
the multiplied
period
signal.
Table
2-5.
Multiplied
Period
Control
Gate Control On
Function
Switch
7
B
I
10
11
lOOK PERIOD
A\TE
lOK PERIOD
A\TE
lK
PERIOD
AVE
1OO
PERIOD
AVE
10 PERIOD
AVE
2-12t.
GATING
CONFLICT. A
few
combinations
of
TIME
BASE
and FUNCTION
switch
selections
produce
overlapping
decade-divider
requirements.
For
ex-
ample,
a TIME
BASE
selection
of
0.
1s and
a
FUNC-
TION
selection
of 10K-PERIOD
AVERAGE
turns
on
gate
control
23
and
gate
control 8;
the
expected
selected
frequency
of 10
Hz
is
not
supplied through CR16-Q7
since
the
frequency-dividing
chain is
blockedatCRll;
the counter
display is
therefore
meaningless.
An
alarm
for unallowed
switch combinations of
this sort
is
given
by the lighting
of an asterisk
(*)
at
the
right
end
of
the front
panel
display.
The asterisk is also
used
to indicate
two other non-useful
control
combin-
ations:
1)TIME
BASE of 0.1
psand
frequencyFUNC-
TION,
and
2) TIME
BASE
of 10
SEC and
PERIOD
function.
The
asterisk lamp
(in
A9)
is
controlled
by
switching
contacts
on
both
the
TIME
BASE
and
FUNC-
TION
switches.
2-L22.
CIRCUITS.
Refer
to
the schematic diagram,
Figure
7-25, for
circuit
details. Most
of
the
gates
in
A35
are
of
the type
described in Paragraph
2-6,
but
gates
28
and 29
are
two-diode AND
gates,
described
in Paragraph
2-94.
The inhibit
gates
(CR8,
CRl1,
CR14, CR1?,
and CR20) are
similar
to conventional
AND
gates
except that they are always
on
(forward-
biased
diode) in
the absence
of the control
voltage and
off
(reverse-biased
diode)when
the control
voltage
is
applied.
Table
2-4.
Normal
Time
Base Control
Gate
Control On
Time
Base
Switch
2l
22
23
24
25
26
27
28
29
10s
1s
0. 1s
10 ms
1ms
0. 1ms
10
ps
1
trts
0. 1ps
02349-1
2-23

HP 5245L Specifications

General

Brand	HP
Model	5245L
Category	Cash Counter
Language	English