28
Subject to change without notice
the heading ”Triggering and time bases“ and the instrument
specifi cations. The following settings are available:
17.1.1
Trig. Filter
–
AC:
The trigger signal is AC coupled via a large capacitor in
order to reach a low cut-off frequency.
Readout:
”Tr:Source, Slope, AC“
–
DC:
The trigger signal is DC coupled. No peak triggering is
possible.
Readout:
”Tr: Source, Slope, DC“
–
HF:
AC coupling with a small capacitor suppressing low
frequency signals. Hence the signal display and the trigger
signal derived are not any more identical. The trigger point
symbol is switched off. As a combination of HF coupling and
LF or Noise Reject is not meaningful both menu options will
not be shown.
Readout:
”Tr:Source, Slope, HF“.
–
LF:
The trigger signal is sent through a low pass in order to
suppress high frequency components. As this will already
suppress hf the noise rejection mode will be set to OFF
automatically.
Readout:
”Tr:Source, Slope, AC or DC, LF“.
–
Noise Reject:
Noise rejection (reduction) means a reduced
trigger amplifi er bandwidth and consequently less trigger
signal noise.
Readout:
”Tr:Source, Slope, AC or DC, NR“.
17.1.2
Slope
SLOPE determines whether the rising or falling portion of
a signal shall trigger, the level is set with the LEVEL A/B
15
control.
In BOTH MODE both slopes will trigger. This allows e.g. the
display of eye diagrams.
17.2 Menu: Video
In order to reach the menu ”Video“ proceed as follows:
Press MODE
16
to open the ”Trigger“ menu, select ”Video“, then
press the FILTER pushbutton
17
. Further information can be
found under ”Video“ (TV signal triggering) in the chapter ”Trig-
gering and time bases“ and in the instrument specifi cations.
The following settings are available:
17.2.1
Frame, Line.
Depending on the setting chosen triggering will be on frame
or line sync pulses. The selection will also affect other menu
items.
Readout:
”Tr:Source, TV“.
17.2.1.1
Frame
–
ALL:
In this mode the sync pulses of each half frame can
trigger.
–
Even:
In this mode only the sync pulses of even half frames
can trigger.
–
Odd:
In this mode only the sync pulses of odd half frames
can trigger.
17.2.1.2
Line.
-
All:
In this mode all line sync pulses can trigger.
-
Line No:
The line number with its line pulse that is used for
triggering can be selected with the INTENS knob
2
.
-
Line min:
One pushbutton operation will be suffi cient to
switch back to the lowest possible line number.
The movement of the trigger symbol is vertical only. The range
of this symbol is limited in order to prevent that this symbol will
overwrite other readout information. As soon as the trigger sym-
bol leaves the graticule its form will change, this change signals
in which direction the trigger symbol left the graticule.
Depending on the time base mode the LEVEL control will affect
the time base A or B triggering. Press the HOR VAR pushbutton
26
in order to select the time base mode in the ”Time base“ menu. In
”Search“ mode (alternate time base mode) the last trigger level
setting for time base A will remain valid (graticule left) if time
base B is switched to triggered mode. (Menu ”Time base“: set
B trigger to positive or negative slope). Thereafter the LEVEL
A/B control will control the time base B trigger, a second trigger
point symbol will be shown and marked with ”B“.
16
MODE
(pushbutton)
Pressing this pushbutton will open the ”Trigger“ menu, where
AUTO and NORMAL can be selected. Choosing ”Slope“ will allow
to trigger on any signal shape. For video signals select ”Video“
and press the FILTER pushbutton
17
in order to fi nd a choice
of special trigger modes for composite video signals.
In XY mode the pushbuttons MODE
16
, FILTER
17
and SOURCE
18
are disabled as there is no triggering in XY mode.
16.1 Auto (trigger)
Automatic triggering (Auto) is active if the NORM display
20
is not illuminated. In ”Auto“ the time base will be periodically
started even if there is no signal or when no triggers are ge-
nerated because the settings are incorrect. Signals of
<
20 Hz
can not be triggered as the automatic start will have occurred
before the signal arrived. Automatic triggering is possible with
or without peak detection. The LEVEL A/B
15
control will be
active in both modes.
In peak detection mode the range of the level control is limited
to the peak-to-peak voltage of the signal. Without peak detection
any level can be set. If the trigger level is set such that no trig-
gers are generated the automatic triggering will nevertheless
start the time base. The signal will thus remain visible but will
be untriggered.
Whether peak detection is active or not depends on the mode
and the settings in ”FILTER“ (trigger coupling). The mode active
will be shown by the behaviour of the trigger point symbol when
turning the LEVEL knob.
16.2. Normal (trigger)
If the NORM-LED
20
lights up normal triggering was selected. In
normal trigger mode both the peak detection and the automatic
time base start will be disabled. Hence if there is no suffi cient
trigger signal the screen will remain dark in analog mode. In
this mode there is no lower frequency limit for signals.
17
FILTER
(pushbutton)
After this pushbutton is depressed it will depend on the settings
chosen in MODE
16
(Edge, Video) which menu will be offered. In
XY mode the pushbuttons: MODE
16
, FILTER
17
and SOURCE
18
are disabled as XY displays can not be triggered.
17.1 Menu: Slope
The menu ”Edge“ will appear if ”Edge“ was selected in the
”Trigger“ menu to be called with MODE
16
pushbutton and
after the FILTER
17
pushbutton was depressed. For further
information see ”Trigger coupling“ (Menu ”FILTER“) under
C o n t r o l s a n d R e a d o u t
