37
Subject to change without notice
In normal trigger mode there is no lower frequency limit for
signals. Without trigger, the last signal capture will be displayed
as long as the oscilloscope settings are not changed, to transmit
the recorded signal via the interface.
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 and the
RUN/STOP lit periodically.
For further information about the precise operation see RUN/
STOP pushbutton
6
description.
21
FILTER
(pushbutton)
Preliminary note!
The pushbuttons MODE
20
, FILTER
21
and SOURCE
22
refer
to the trigger unit. In XY mode these pushbuttons are without
effect as XY displays are untriggered.
After this pushbutton is depressed it will depend on the set-
tings chosen in MODE
20
(Edge, Video, Logic) which menu will
be offered.
21.1 Menu: Slope
The menu EDGE will appear if EDGE was selected in the TRIG-
GER menu to be called with MODE
20
pushbutton and after the
FILTER
21
pushbutton was depressed. For further information
see ”Trigger coupling“ (Menu FILTER) under the heading ”Trig-
gering and time bases“ and the instrument specifications. 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. If on condition AC
coupling automatic triggering (MODE: AUTO) is selected,
automatic peak triggering is active.
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 no longer identical, the trigger point symbol
will be ”parked“ in digital mode and will not react to the LE-
VEL A/B
19
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. No peak triggering is possible.
Readout: ”Tr:Source, Slope, HF“.
– LF:
The trigger signal is sent through a low pass fi lter to
suppress high frequency components. As this will suppress
hf, the noise rejection mode will be set to OFF automatically.
No peak triggering is possible.
Readout: ”Tr:Source, Slope, AC or DC, LF“.
– Noise Reject:
Noise rejection (reduction) means a reduced
trigger amplifier 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
19
.
In ”Both mode“ both slopes will trigger, this is also true in single
sweep mode. This allows e.g. the display of eye patterns.
21.2 Menu: Video
In order to reach the menu ”Video“ proceed as follows: Press
MODE
20
to open the ”Trigger“ menu, select ”Video“, then press
the FILTER
21
pushbutton. Further information can be found
under ”Video“ (tv signal triggering) in the chapter ”Triggering
and time bases“ and in the instrument specifications. The fol-
lowing 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
2
.
– Line
min:
One pushbutton operation will be sufficient 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 change of standard, the line number will be auto-
matically changed, too.
21.2.3
Polarity
Composite video signals may have both polarities. Selection of
the correct polarity is vital, as the scope should be triggered by
the sync pulses and not the video content. Positive polarity is
defined 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.
21.3 Menu: Logic
(digital mode only)
The following description refers to the selection of the trigger
source and the logic levels available in the TRIG. SOURCE menu
called with the pushbutton
22
.
The following settings may be combined if these conditions
are met:
– Digital mode.
– The trigger menu was called with MODE
20
.
– LOGIC was then selected. (Readout: ”Tr:Logic“.)
– The FILTER pushbutton
21
was depressed and the LOGIC
menu reached.
21.3.1
AND, OR:
Logic AND or OR.
21.3.2
True, False
This refers to not inverting or inverting the output of the above
AND or OR function.
Readout: ”Tr:Logic“.
C o n t r o l s a n d R e a d o u t
