35
Subject to change without notice
–
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“.
21.1.2
Slope
”SLOPE“ determines whether the rising or falling portion of
a signal shall trigger, the level is set with the LEVEL A/B
control.
In BOTH MODE both slopes will trigger, this is also true in single
sweep mode. This allows e.g. the display of eye diagrams.
21.2 Menu: Video
In order to reach the menu VIDEO proceed as follows:
Press MODE
to open the TRIGGER menu, select VIDEO, then
press the FILTER
pushbutton. Further information can be
found under VIDEO (tv signal triggering) in the chapter Trigge-
ring and time bases“ and in the instrument specifi ca-tions. The
following settings are available:
21.2.1
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“.
21.2.1.1
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.
21.2.1.2
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
.
–
Line min:
One pushbutton operation will be suffi cient to
switch back to the lowest possible line number.
21.2.2
Norm
The pushbutton allows the selection of the US standard of 525
lines and 60 Hz or the European standard with 625 lines and
50 Hz. With any change of standard the line number will be
automatically changed, too.
21.2.3
Polarity
Composite video signals may have both polarities. Selection of
the right polarity is vital as the scope should be triggered by the
sync pulses and not the video content.
Positive polarity is defi ned by the video content being more
positive than the sync signals and vice versa.
If the polarity was wrongly selected there will be no triggering
at all, an untriggered display or no signal capture.
SOURCE pushbutton
Depressing this pushbutton will call various menus depen-
ding on the previously selected mode (MODE
pushbutton):
EDGE, VIDEO, LOGIC. In XY mode the pushbuttons: MODE
,
FILTER
, SOURCE
are disabled as XY displays can not be
triggered.
In the TRIGGER SOURCE menu the source is selected from
which the trigger signal is to be taken. The options depend on
the actual mode of the scope.
C o n t r o l s a n d R e a d o u t
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.
20.2. Normal (trigger)
If the NORM-LED
lights up normal triggering was selec-
ted.
In normal trigger mode both the peak detection and the au-
tomatic time base start will be disabled. Hence if there is no
suffi cient trigger signal the screen will remain dark in analog
mode. In DSO mode signal capturing will also stop unless the
roll mode was selected.
In this mode there is no lower frequency limit for signals.
20.3 Single (sweep/capture)
In single sweep/capture mode the time base selected will accept
only one trigger for one sweep/capture after it was armed. The
NORM-LED will light up, Auto triggering is disabled.
For further information about the precise operation see RUN/
STOP pushbutton
description.
FILTER pushbutton
After this pushbutton is depressed it will depend on the settings
chosen in MODE
(Edge or Video) which menu will be offered.
In XY mode the pushbuttons: MODE
, FILTER
and SOURCE
are disabled as XY displays can not be triggered.
21.1 Menu: Slope
The menu ”Edge“ will appear if ”Edge“ was selected in the
TRIGGER menu to be called with MODE
pushbutton and after
the FILTER
pushbutton was depressed. For further informa-
tion see ”Trigger coupling“ (Menu FILTER) under the heading
”Triggering and time bases“ and the instrument specifi cations.
The following settings are available:
21.1.1
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 will be ”parked“ in DSO mode and will not react to
the LEVEL A/B
control. In analog mode 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“.
