37
Subject to change without notice
mode is automatically set to the value used during “sea”
(search) operation.
Photo 3
MODE: “del” (DELAY)
TIME/DIV: 5ms/div
Trigger coupling: TvF
Trigger slope: falling (-)
Delay time:
4div x 5ms/div = 20ms
Reducing the time coefficient (increasing the time base speed)
now expands the signal. If the signal start position is not set to
the optimum, it can still be shifted in the
X
direction by
changing the delay time.
Photo 4 shows a 50 fold X magnification caused by setting the
time coefficient to 0.1ms/div (5ms/div : 0.1ms/div = 50). The
reading accuracy also increases with higher X magnification.
Photo 4
MODE: “del” (DELAY)
TIME/DIV: 0.1ms/div
Trigger coupling: TvF
Trigger slope: falling (-)
Delay time: 20ms
The delayed and expanded signal display can be triggered again if
a signal slope suitable for triggering appears after the delay time.
For this, one must switch to
“dTr”
(2nd triggering after the expiry
of the delay time - after Delay Triggering). The settings selected
before switching, automatic Peak value triggering / Normal
triggering, trigger coupling, the trigger
LEVEL
setting and slope
setting, remain valid and trigger the start of the delay time.
The
”After Delay”
Triggering automatically switches to normal
triggering (indicated by the
NM LED
) and DC trigger coupling. These
default conditions cannot be changed. But the trigger level (
LEVEL
)
and the trigger slope direction can be altered in order to enable the
triggering at the desired signal section. The trace does not start and
the screen remains blank if the signal amplitude is not sufficient for
triggering or if the setting of the trigger
LEVEL
is unsuitable.
The expanded display can also be displaced in the X direction by
changing the delay time (
DEL/TR. POS.
) under suitable settings.
However, the displacement is not continuous as in the untriggered
“del” (DELAY)
operation but jumps from one trigger slope to another
- with most signals this is not evident. This means, in the case of TV
Triggering, that it is possible to trigger not only with line synchronizing
pulses but also on suitable slopes occurring within the line.
Of course, the magnification is not restricted to a factor 50 as
mentioned in the example. The limit is given by the increasing
loss of trace intensity as the magnification is increased.
The manipulation of time delay requires a certain experience,
especially with complicated signal combinations which are
difficult to display. The display of sections of simple signals is,
in contrast, fairly easy. The time delayed display is also possible
in the dual channel, addition and difference modes.
In chopped DUAL mode, if after switching over to “del” or “dTr”,
the time deflection coefficient is reduced (TIME/DIV.), the channel
switching mode doesn`t change automatically to alternate.
Photo 1
(composite video signal)
MODE: “DEL. MODE” OFF
TIME/DIV: 5ms/div
Trigger coupling: TvF
Trigger slope: falling (-
)
Switching over from undelayed to delayed time base automatically
sets the hold off time to minimum so that the HO LED extinguishes,
the DEL/TR. POS. knob function changes from hold off time to
delay time control and the READOUT indicates “sea”.
In search (“sea”) mode a part of the previously complete visible
trace becomes blank. The length of the blanked sector depends on
the delay time
(DEL/TR. POS.)
setting and can be set between
approx. two and seven divisions after the normal trace start position.
Consequently the trace is displayed with reduced length.
If the maximum delay time is not sufficient, the time coefficient
must be increased (
TIME/DIV
knob) and the
DEL/TR. POS.
knob set to the later starting point.
Note:
Actually the trace start is not really delayed in “sea” (search)
condition, as the blank sector serves only as an adjusting
indicator making visible the delay time which will be active
after selecting “del” (delay time base) or “dTr” (delay time
base in triggered condition).
Photo 2
MODE: “sea” (SEARCH)
TIME/DIV: 5ms/div
Trigger coupling: TvF
Trigger slope: falling (-)
Delay time:
4div x 5ms = 20ms
Figure 2 shows that the delay time can be measured. It is
identical with the displacement of the start of the trace. One
can calculate this by multiplying the blanked out section
(horizontal) by the time deflection coefficient setting.
The full length trace will be visible when switched from “sea”
(SEARCH) to “del” (DELAY), starting with the section previously
selected, providing the (stored) current time deflection
coefficient is not too small.
If the trace is invisible or hardly visible because of too much expansion
(too small deflection coefficient), the time deflection coefficient must
be increased with
TIME / DIV
knob. A larger deflection coefficient
than in the
“sea” (SEARCH)
mode cannot be set.
Example:
The SEARCH setting selected in figure 2 is 5ms/cm.
The display in “del” (DELAY) mode, also with 5ms/div
is delayed but unexpanded (1:1). A further increase in
the deflection coefficient, e.g. 10ms/div would be
meaningless and therefore automatically blocked.
Please note that the previous time coefficient chosen in
“del”
“del”
“del”
“del”
“del” and
“dTr”
mode is stored and automatically set after
activating one of those modes. If the stored time coefficient
in “del” /
“del” /
“del” /
“del” /
“del” /
”dTr”
mode was higher than the actual value in
“sea”
“sea”
“sea”
“sea”
“sea” (search) mode, the time coefficient in
“del” / ”dTr”
Triggering and time base
