Triggering a spectrum

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jcclq
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Joined: Thu Jul 22, 2021 1:05 pm

Triggering a spectrum

Post by jcclq »

Hi all

I am trying to record a batch of many spectra. My system exhibits sometimes some bursts of noise, and this is what I am interested in.

To do so, I would like to set a threshold on the Y-axis, so I will store only the spectra whose one frequency is above this threshold. Is there a way to do so? I found a chapter about the oscilloscope function, like a standard oscilloscope, but I could not find the equivalent for spectra.

If that is not possible, I could manage with a threshold condition on AC RMS, because if my system gets suddenly noisier, it would not be only 1 single frequency to exhibit a high peak but a range of frequency, then increasing the AC RMS value.

Thanks for your help!

JC

Gerry
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Posts: 1009
Joined: Mon Aug 11, 2014 11:14 am

Re: Triggering a spectrum

Post by Gerry »

Hi jcclq,

Unfortunately, there is no way to Trigger a Spectrum capture using Spectrum Mode, because the Trigger only operates on live data in the hardware, while a spectrum is calculated in the software, once the data has been captured and sent to the computer.

You need to use a secondary view for a Spectrum plot, and then Trigger in Scope Mode in the Primary view, as shown below:
Triggering on burst noise for sepctrum capture.png
You also can't Trigger on AC RMS for the same reason that you can't Trigger from a Spectrum plot (RMS can only be calculated using PicoScope 6 Measurements, or plotted using PicoScope 6 Math Channels). However you don't need the RMS values to trigger, you can just set a Trigger Threshold in between the highest AC/DC pk-pk level of noise when you are getting the bursts (that you want to analyze) and the highest AC/DC pk-pk level when everything is quieter (no bursts).

Regards,

Gerry
Gerry
Technical Specialist

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