Advanced Features
Example: select B delay by time with a delay
of
96.Sms
ATrig BTrig
OOOOOOOns
0096.SOOOms
A Sweep
BSweep
1
A + N Disabled 2
In Independent
Gate 3
CountNxB
4
Independent 5
ADelay
6
BDelay
7
8
The A sweep
is
unaffected, and a capture
is
initiated by a
valid A trigger after arm. The B sweep begins its capture
96.Sms after the receipt
of
a valid B trigger after arm. Nega-
tive time delays allow capture
of
events
prior,,,
the trigger
point.See Section 1.4 for more details.
Combining Trigger Functions
The above trigger functions can be freely combined with the
following exception:
'A
divide by N' and
'B
delay by N' cannot be used
simultaneously;
The
trigger menu shows the two trigger channels A and B at
the top, with two paths downwards to the two timebase
sweeps A and B. A Trig and B Trig are the valid triggers as
determined by the source and coupling etc. selections.
These pass into the trigger system and are acted upon by the
functions outlined above. Eventually, after processing,
they emerge to begin the sweeps.
To
understand how the sweep
is
started it
is
merely neces-
sary to follow the path up to its source. There follow two
examples to clarify this.
ATrig
BT rig
1
000625
A+N
2
Gate 3
CountNxB
4
:------~:
Independent 5
OOOOOOOns
ADelay
6
0005000ns
BDelay 7
A
Sweep
BSweep
8
The input signal for this example could be a
PAL
A TV sig-
nal.
50
Section 2
The A Sweep
The A sweep can only be captured on every 625th trigger.
If the coupling selection
of
the A trigger channel were
TVL
(TV line) then the same
TV
line would be captured on each
acquisition. The line that
is
captured could be controlled by
the phase advance and retard buttons.
TheBSweep
This captures on the same
TV
line as the A sweep but there
is
a delay
of
5µ.s
before the B sweep begins. This could be
showing the rear porch
in
more detail.
Example no.2
A Trig BTrig 1
A+N
2
=-·
enable -
~
Gate
Gate 3
000313
CountNxB
4
:
---
- -
--:
Independent 5
OOOOOOOns
A Delay
6
OOOOOOOns
BDelay
7
A Sweep BSweep
8
If
the trigger coupling
is
set to
TVF
(TV frame) and the B
trigger to TYL (TV line) then this trigger set-up could be
used to display a complete
PAL
TV
field and a selected line.
The A timebase should be set to display
TV
frames and the
B timebase
to
display
TV
lines. Both sweeps are enabled by
the same event.
The A Sweep
The A trigger enables the gate and then 313 B Triggers later
the A sweep
is
triggered. (the 313th line
is
line 1
of
the sec-
ond interlaced frame).
TheBSweep
The next A trigger enables the gate and then
313
B Triggers
later the B sweep
is
triggered. The next trigger sequence
will again trigger an A sweep.
Trigger Output
The 4070
is
fitted with a rear panel trigger output at
TTL
levels via a BNC connector. This provides a pulse at the
trigger point
of
each new acquisition.
If
a trigger delay facil-
ity
is
used, this event occurs
at
the end of the delay period.
This output can be used to synchronize other equipment
such as additional oscilloscopes
or
logic analyzers to the
4070.
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