LabVIEW/SignalExpress: How can I automate measuring the time between two pulses?

[wdavis8]

Hi everyone, bit of a newbie here so please bear with me.  

I'm a student at a university conducting a muon decay experiment with an oscilloscope connected to some photomultipliers.  To summarize, if a muon enters the detector it will create a very small width pulse (a few ns).  Within a period of 10µs it may decay, creating a second pulse.  The oscilloscope triggers on the main pulse 5-15 times per second, and a decay event happens roughly 1-2 times per minute.  I am trying to collect 10 hours of data (roughly 1500-2000 decay events) and measure the time it takes for each decay.

I've been able to set recording conditions in SignalExpress that starts recording on the first pulse and stops recording on the last.  The Tektronix TDS 1012 oscilloscope however feeds 2500 points of data from this snapshot into a text file (for use in excel or other software).  Even if I perfectly collected the data, I would have 100,000+ data points and it would be too much to handle.  I don't know how (or if it's possible) to reduce the sample size.

To conclude, using Labview or SignalExpress, I would like to be able to have the software

1.  Differentiate between the single pulse detections and double pulse decay events

2.  Record only when two pulses appear on the oscilloscope

3.  Measure the time between these two pulses and ONLY that to minimize the amount of data recorded.

Any help would be GREATLY appreciated, thanks!

[wdavis8]

Quick bump, thanks!

[K_Joy]

Hi wdavis8,

I am not that familiar with Tektronix, but there should be a place in the dialog that you go through when you create the action step to acquire date to specify a sampling rate. That would allow you to reduce the number of data points you are seeing, but may reduce the quality of the data.

If it’s just a matter of that much data being hard to dig through when you have that many points, you could do some analysis on the data after the fact, and then create a new file with only the data you want to look at. For example, you could identify the peaks in the data, and based on the distance between them or the difference in magnitude, selectively write data to a new file.  

Here is some information about peak detection in LabVIEW:

http://www.ni.com/white-paper/3770/en/

You could also do some downsampling on the data to get fewer data points:

https://decibel.ni.com/content/docs/DOC-23952

https://decibel.ni.com/content/docs/DOC-28976

Those are just a few quick ideas. 

Kelsey J

Applications Engineer

[wdavis8]

Thanks Kelsey, I'll look into that.  I was thinking of creating 5 minute sample files, running a python script to delete anything with only one pulse, then measuring the time values between pulses.  Looks like that will be the most viable option.

[Dennis_Knutson]

This is really the wrong place to be asking about SignalExpress. The LabVIEW board is for programming. If you want to use LabVIEW, this should be a relatively straight forward task. Can you post a capture of the initial and second pulse? Real data and not just an image, please.