Edge detection in analog waveform

[MEP007]

Hi,

 I have an analog waveform (4x channel), one channel contains digital pulses (rising/falling edges). I need to find all falling edges - their time stamps. I can't find any suitable functions to do this 😕

 For ex. Transition Measurement.vi is fine, but it finds only one edge and there is no offset option, to move "cursor" behind already known edge. My data are quit big, so I don't want subset the waveform into another waveform and find edge by edge. So my wish is detect all falling edges and obtain 1D-array with time indexes. 

 Thanks for any help. Cheers

[PrimaryKey]

Hello MEP007,

there are many ways to accomplish that. Here are few ideas:

1. Calculate first derivative of the signal and use that to locate min. of the waveform.

2. Point-by-point check when the point Y value is in range 4 to 1 V while at the same time being close together on the X-axis. (this option is valid when your sampling rate allows to measure the transition between high and low)

Here is a quite nice and very simple example that, I think, will help you.

http://decibel.ni.com/content/docs/DOC-11651

Unfortunately, when doing it with high-level function you often have to prepare the data.  

Those are just ideas and there are many other ways of answering this question.

Hope that helps, RavenBlack

[MEP007]

Thanks,

 the 1st derivative is working very well, then I am using Peak detect.vi - it works fast and reliable ! Thank you.