PicoScope 7 Software
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Spectrum dropping
Spectrum dropping
Hi
I am acquiring a batch of spectra to calculate the RIN spectra, and I noticed that sometimes, this goes very low. I checked in oscilloscope mode, and I did not notice any drop to 0. I only noticed that sometimes I have a drop of 1%, but not sure it can explain.
I used AC coupling, but of course I still have a peak at 0-frequency. I noticed that a drop on the spectrum is also associated to an increase of the 0-frequency signal. I thought that this 0-frequency increase could be due to the 1% drops, but I don't see how it could explain the drop of the other frequencies in the spectrum?
I am attaching 2 typical spectra: a common one, and one with a drop.
Thanks in advance for any help
JC
I am acquiring a batch of spectra to calculate the RIN spectra, and I noticed that sometimes, this goes very low. I checked in oscilloscope mode, and I did not notice any drop to 0. I only noticed that sometimes I have a drop of 1%, but not sure it can explain.
I used AC coupling, but of course I still have a peak at 0-frequency. I noticed that a drop on the spectrum is also associated to an increase of the 0-frequency signal. I thought that this 0-frequency increase could be due to the 1% drops, but I don't see how it could explain the drop of the other frequencies in the spectrum?
I am attaching 2 typical spectra: a common one, and one with a drop.
Thanks in advance for any help
JC
- Attachments
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- Common spectrum.PNG (10.99 KiB) Viewed 8527 times
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- Spectrum with a drop.PNG (9.72 KiB) Viewed 8527 times
Re: Spectrum dropping
can you post a .psdata of both examples.
Benno
Benno
Re: Spectrum dropping
Hi bennog
Thanks for your reply. I don't have some .psdata files right now but I'll try to record some.
Best regards
JC
Thanks for your reply. I don't have some .psdata files right now but I'll try to record some.
Best regards
JC
Re: Spectrum dropping
Hi
I recorded a batch of spectra in .psdata format. I attached 3 successives spectra. The middle one (#565) is the strange one, and I also attached some 'usual' spectra, the one jsut before (#564), and the one just after (#566).
Thanks for your help!
JC
I recorded a batch of spectra in .psdata format. I attached 3 successives spectra. The middle one (#565) is the strange one, and I also attached some 'usual' spectra, the one jsut before (#564), and the one just after (#566).
Thanks for your help!
JC
- Attachments
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- Usual-#564.psdata
- (58.13 KiB) Downloaded 390 times
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- Low-#565.psdata
- (15.81 KiB) Downloaded 388 times
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- Usual-#566.psdata
- (65.42 KiB) Downloaded 395 times
Re: Spectrum dropping
If you had added the scope view you could have seen the measured values are out of range.
So the low spectrum is because you have almost no signal because all signal is clipping to the top or bottom of the range.
Probably because you had 50/60 Hz (looks like 60) hum on the signal.
So the low spectrum is because you have almost no signal because all signal is clipping to the top or bottom of the range.
Probably because you had 50/60 Hz (looks like 60) hum on the signal.
- Attachments
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Re: Spectrum dropping
Thanks a lot. Yes it is clear now. In my case it is 50Hz (I am based in UK). I probably have a bad contact on my BNC line. I will also make sure it is all well grounded.
This is really helpful. I didn't know I could look at the scope view as well, now I will check this!
Best regards, thanks again
JC
This is really helpful. I didn't know I could look at the scope view as well, now I will check this!
Best regards, thanks again
JC