5.2 Trigger modes and time-stamps
Acqiris SA240P User's Manual 57
at the first card initialization,
at the last initialization with reset flag = 1,
or when using Set Time function (IVI-C) or writing Time (IVI.NET).
The time-stamp counter is reset each time the time reference is configured.
User can control the reset of the time-stamp counter thanks to the TimeResetMode property:
Immediate: The time-stamp counter is reset upon software, using Set Time function (IVI-
C) or writting Time (IVI.NET), then it continues counting freely.
OnFirstTrigger: The time-stamp counter is reset by the first trigger of a (multi-record)
acquisition.
Parameters
IVI-C
InitialXTimeSeconds: Specifies the seconds portion of the absolute time at which the first data
point was acquired.
InitialXTimeFraction: Specifies the fractional portion of the absolute time at which the first
data point was acquired.
The actual time is the sum of InitialXTimeSeconds and InitialXTimeFraction.
Adding these values in a variable of type double implies a loss of precision.
IVI.NET
StartTime: StartTime is the time between the first valid data point (that is the data point at index
FirstValidPoint) in the waveform and the trigger. Positive values indicate that the StartTime occurred
after the trigger. If StartTime is zero, the waveform is not relative to anything, or the relative measure
is zero, or the waveform is empty.
EndTime: EndTime is the time between the last valid data point in the waveform and the
TriggerTime. Positive values of EndTime indicate that it occurred after the trigger. If EndTime is
zero, there is exactly one data point and the StartTime is zero, or the waveform is empty.
TotalTime: TotalTime is the timespan represented by the valid points in the waveform.
Numerically, it is equivalent to the IntervalPerPoint * (ValidPointCount - 1). It is also numerically the
EndTime – StartTime. TotalTime is zero if there is exactly one data point in the waveform, or the
waveform is empty.
TriggerTime: TriggerTime is the absolute time at which this measurement was triggered. Note
that this differs from Start Time in that the trigger may have occurred at some time other than when
the first data point was captured, as in pre-trigger or post-trigger applications. TriggerTime is an
absolute time and cannot be set to zero. If it is set to NotATime, the waveform is empty or there is no
absolute reference for the waveform.
Self-Trigger
Apart from the trigger sources described in the section Trigger (page 15) (internal and external
triggering), another trigger mode called Self-Trigger is proposed.
In this mode, a periodic trigger signal from the ADC Card is automatically generated and can be
used to synchronize the user system. It also allows to minimize the synchronous noise.
It can be used with digitizer and averager acquisition mode.
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