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Model
3484A
+SV
DELAYED
TRIGGER
INITIATE
AUTO RANGE
OELAY
COMMAND
fL
IP HOP
AUTO ENABLE
DELAY
ENABLE
3
4
84
A
B
30 381
VARIABLE
DELAY
fUNCllON
ANO
FILTER
SELECTION
RELAXATION
OSCILLATOR
HOLD
CIRCUIT
To 3'BOA/B
MANUAL ANO
DELAYED
TRIGGER
CIRCUIT
-
TOJ480Ail
Section
IV
TO
3'tOA/8
TO
EXTER
N
AL
TRIGGER
GATI
Figure
4-6. Delay Generator
Block
Diagram.
Delay
Generator
causes
anolher
sample
to be initiated.
This
HOLD
conrution prevenls
the
3480A/B
from sampling
during
an
autorange
cycle.
4-36.
Print Command
Circuit.
An
output
from the
Delay
Flip-Flip
goes
to
the
Print
Command Circuit.
During
an
autorange
cycle,
the
output
of
the
Print Command
Circuit
output goes
HIGH
al
the
beginning
of the sample
period
and
remains
HIGH
until
after a measurement has
been
taken
at the
end
of the delay
period.
Thjs prevents
a
recorder
from printing an
erroneous
reading
during an
autorange cycle. During an
External
Trigger.
delay,
the
Print
Command signal goes
HIGH
at
the
beginning of
the
delay
period
and remains
HIGH
until
after
the
measurement
has
been
taken.
4-37.
Manual and Delayed Trigger Circuit.
4-38.
When
the
TRIG
pushbutton
is pressed
,
the
output
of
the
Manual Trigger Flip-Flop
goes LOW. When
the
push-
button
is
released, the
flip-Jlop
output
returns
to
HIGH
,
resulting
in
a pulse
through
a coupling capacitor.
Trus
pulse
turns
on the
output
transistor
for approximately 120
microseconds.
The resultant negative-going
output
pulse
is
the trigger
command
to
the
3480A/
B
Sample Generator
Circuit.
4-39.
During
a
delayed
trigger
cycle,
initiated either by an
autorange
command
or a
delayed External
Trigger com-
mand,
an
output
from
the
Delay
Flip-Flop performs
the
same
electrical
function
as pressing the
TRIG
pushbutton.
While the
Delay Flip-Flop output
is
LOW, the capacitor
in
the
Trigger
circuit
is
grounded.
Then
when the
Delay
Flip-Flop
is
reset,
a trigger
command
is
applied to the
3480A/
B.
4-40.
Delay and External Trigger G ating.
441
. The
Delay
and External Trigger
Gating
circuits are
shown in
Figure 4-7. When
the
EXT TRJG
DELAY
jumper
on Range
and
Function
Assembly
A3
is
connected
in
the
OUT
position
,
the
output
of
Inverter
Dis
LOW,
holding
the
output
of
the
Delayed Trigger Gate
HIGH
.
In
addition
,
the
Delay Enable signal
is
HIGH,
disabling the
Delay Generator
Flip-Flop.
Also,
one
input to the
Trigger
Command
Gate
is
HIGH, aJJowing this
gate
to
be
controlJed
by
the
External
Trigger input.
442.
Assume
that
the
instrument is
between samples
(Print
Command
signal
is
LOW)
when
a
negative-going
External Trigger
Command is applied.
The
LOW
External
Trigger
command immeruately
causes Inverter
C
output
to
go HIGH, and
the
Trigger
Command Gate
output
goes
LOW.
At
the
same time,
the
External
Trigger
Command
applied
to
the
Print
Command
Gate causes
its
output
to
begin
to
go HIGH, charging the capacitor at its
output. As
soon
as the
capacitor has
charged
to the
threshold
voltage
of
Inverter
B,
this output goes
LOW,
returning
the
Trigger
Command
Gate
output
to HIGH. The
delay caused
by the
capacitor
is
approximately
55 microseconds. The
resulting
55
microsecond
negative-going
pulse
output of
the
Trigger
Command
Gate constitutes
a trigger
command to the
3480A/B
Sample
Generator.
443. During
a
sample
period,
The
Print
Command
signal
is
HIGH.
Inverter
A output
is then
LOW, holding
the Print
Command
Gate
output
HIGH.
Inverter
B
output
is
then
LOW
and
the
Trigger
Command
output
remains
HIGH
.
Consequently,
an
External Trigger
Command
applied dur-
ing a sample period is
prevented from
triggering
the
3480A/B.
444. When the EXT TRJG
DELAY
jumper
is connected
in
the IN posi tion, the Delay Enable signal is
LOW,
enabling
4-7
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