Dataman 520 Series - Manual (Page 20)

DATAMAN oscilloscope
User’s Guide
events. Figure 2.1.2.2 shows several valid and invalid trigger events (all inputs are
enabled).
A B E
valid
invalid
invalid
valid
valid
selected
trigger event
Fig. 2.2.2.2. – Examples of trigger events (all inputs are enabled)
The digital pulse filters (DF) are implemented in both primary and secondary trigger
levels. If activated, they filter out pulses shorter then the value 4*N*Ts, where Ts is
the actual real time sampling period and N is the value set by the user (1 <= N <=
32767). If we want to use this option it is necessary to set the valid trigger event to the
end of the pulse. For example, if the pulse we want to filter off is positive (0 to 1 to 0)
the trigger event should be set to the trailing edge (1 to 0). If the pulse is inverse (1 to
0 to 1), the trigger event should be set to the leading edge (1 to 0). The outputs of the
digital pulse filters are connected to event counters (EC). It counts the unfiltered
pulses. If the MS switch is set to the primary level, the output of the primary event
counter will change from 0 (FALSE) to 1 (TRUE) to indicate the valid trigger event
after reaching the terminal count, which is user selectable in the range of 1 to 32767.
If the MS switch is set to the secondary level, the output of the primary event counter
activates the secondary trigger level. The input selector, digital filter and event
counter can be set for secondary level independently to define the valid trigger event.
The trigger circuits of the DATAMAN 520 series DSOs are equipped with an Hold
Off timer (TDL). It blocks the triggering event for a time period T=4*H*Ts from the
start of data acquisition, where Ts is the actual real time sampling period and H is the
user selectable value from 0 to 32767. It is important to set the proper value H to
ensure that the hardware of the oscilloscope acquires the proper amount of data before
the trigger event. For example, if we want to display the waveform for a time period
of Tz before the trigger it is necessary to set T >= Tz to ensure that all of the data will
be displayed. The DATAMAN 520 series oscilloscopes have four triggering modes
implemented:
AUTO – Data acquisition is triggered by a valid trigger event. However, when after
certain time the trigger event does not occur, measurement starts.
NORMAL – Data acquisition is triggered by a valid trigger event.
SINGLE – Data acquisition starts after activation from the control panel and it is
synchronized by the valid trigger event. Just one measuring cycle is executed.
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