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Subject to change without notice
T r i g g e r S y s t e m
6 Trigger System
The trigger system of the HMO is
easy to handle by just observing the
concept of instrument operation.
Fig. 6.1: Front panel control area of the
trigger system
There are 4 keys destined for frequently used functions:
–
TYPE
– selection of trigger type EDGE (EDGE A/B)
,
PULSE
,
LOGIC and VIDEO
–
SLOPE
– type of slope
–
SOURCE
– determines the triggers source
–
FILTER
– determines the exact trigger conditions
Additional keys are provided for the selection of the trigger
modes: (AUTO. NORMAL, SINGLE).
6.1 Trigger modes Auto, Normal, Single
The basic trigger modes are directly selectable with the key
AUTO NORM. In AUTO mode the key will not be lit. If the key is
pushed it will light up red indicating NORMAL mode.
The oscilloscope always presents a signal in AUTO mode and
a signal will automatically yield a stable display if it fulfills the
trigger conditions.
In NORMAL mode the signal will be displayed if it fulfills the
trigger conditions, if it fails to do so the last stable triggered
display will remain on the screen.
If it is desired to record a signal which fulfills the
trigger
conditions only once, the key SINGLE must be pushed, it will
light up white. This indicates that the single trigger mode
is active, the RUN/STOP key will blink. The next return of
28
C
29
30
33
31
34
35
36
32
Fig. 6.2: Coupling modes with slope trigger
the signal will cause a single capture, the oscilloscope then
goes into the STOP mode, indicated by the RUN/STOP key
lighting up in red.
6.2 Trigger sources
Trigger sources are the 2 or 4 analog channels and the ex
-
ternal trigger input. If the optional logic probe HO3508 with 8
or 16 logic channels is connected, also those up to 16 digital
channels can serve as trigger sources. The soft menu key
AC LINE
enables you to trigger the trigger at system frequency.
The trigger signal is extracted internally from the power supply.
6.3 Slope trigger
The easiest and by far the most frequently used trigger is the
slope trigger. The oscilloscope triggers if slopes that were
set with the SLOPE key occur within the signal selected in the
SOURCE menu. The signal slope has to pass through the set
trigger level.
The trigger type Slope Trigger is selected in the Autosetup mode
(
AUTOSET key). If, for instance, you select the
pulse trigger and
press the AUTOSET key the setting will switch to Slope Trigger.
The TYPE
31
key in the trigger control panel allows you to set the
trigger type. This opens a menu with corresponding options. If
the SLOPE
type is not active (highlighted in blue), you can press
the respective soft menu key to select this type. The slope type
(rising, falling or both) can be set directly with the SLOPE
35
key. This will shift the setting forward by one, i.e. from rising to
falling slope, to both slopes, and pressing the key yet one more
time will trigger another rising slope. The center of the status
line on the top of the display and the display above the SLOPE
key
35
show which slope type has been selected.
The FILTER
36
key allows you to select how to couple the signal
for the trigger circuit:
AUTO LEVEL: Automatic filter setting (default setting).
AC:
The
trigger signal is coupled via high pass filter with a
minimum cut-off
frequency of 5 Hz which suppresses the
DC portion of the triggering signal. With a changing DC
portion, the
trigger level remains at the set point in the AC
signal. The trigger type AUTO (AUTO/NORM key) includes
the Peak-Peak mode which sets limits for the trigger in
the AC signal. This setting means that the trigger condition
will be met for any applied signal without having to set the
level. For the
trigger type NORM (AUTO/NORM key), the
Peak-Peak mode is deactivated, allowing the
trigger level
to be moved past the peak values of the signal.
DC:
The
trigger signal is coupled to the trigger circuit with all
signal portions (AC and DC voltage). This has no impact
on the triggering signal.
HF:
The
trigger signal is routed via a 30 kHz (-3dB) high pass
filter. The
trigger level is no longer adjustable. This mode
should only be used with very high frequency signals.
LP (low pass):
The
trigger signal is coupled via low pass with a maxi
-
mum cut-off frequency of 5 kHz. This filter removes high
frequencies and is available with AC and DC coupling.
NR (noise reduction):
A low pass filter with a maximum cut-off
frequency of
