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How Can I Acquire Pretrigger Samples with NI-SCOPE?



Primary Software:
Primary Software Version: 3.0
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I am using the NI-SCOPE driver and I would like to acquire pretrigger samples, how can this be done?

Solution:
With NI-SCOPE, you can specify how many pretrigger samples you want to acquire using the reference position input of the niScope Configure Horizontal Timing.vi in LabVIEW, or the refPosition argument of the niScope_ConfigureHorizontalTiming function in a text-based programming language.

The reference position (refPosition) input specifies the position of the Reference Event in the waveform record as a percentage of the record. This percentage can range from 0-100%, and will represent the number of pretrigger versus posttrigger points that are stored.

For example, a 0% reference position means that all of the points stored in the record will have arrived immediately after the trigger, while the 100% reference position means that the record will consist entirely of points that occurred immediately prior to the trigger. Similarly, a 50% reference position means that half of the record will be pretrigger samples and half will be posttrigger samples.

ni_Scope Configure Horizontal Timing VI, reference position highlighted
NI-SCOPE Configure Horizontal Timing with a reference position of 50%

Related Links:
NI High-Speed Digitizers Help: Horizontal:Reference Position Property
NI High-Speed Digitizers Help: Coercions of Horizontal Parameters

Attachments:





Report Date: 03/27/2007
Last Updated: 06/08/2012
Document ID: 47QC624G

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