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5203 Scope creates spur

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5203 Scope creates spur

Postby jom » Tue Aug 14, 2007 3:42 pm

Hello

I've been giving my new 5203 a good workout lately and have noticed a spurious tone at 8 kHz that seemingly is coming from the scope. I'm working on an HF radio so when I see spurs I certainly don't immediately think it's the test equipment. But I actually turned off the supplies and the other equipment (except the spectrum analyzer) and the tone is still there. I had originally seen it with the Scope's spectrum output mode but I used my "real" spectrum analyzer" and found the spur at 8 kHz. Then I turned of Pico Scope software and the spur disappeared. Anyone seen having a similar problem?

jom
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Postby ziko » Thu Aug 16, 2007 8:27 am

Hi Jom,

In order to be able to identify this we need to know the following:

1) What settings you have in the software, could you send a settings file so we can try and do the same set-up

2)How are you connecting the inputs to the scope (are they terminated), what kind of cables are you using?

3) What equipment are you using and how are you varying it.

The more information you can provide the easier it will be to help you.

Kind regards
Ziko

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Postby jom » Sat Aug 18, 2007 12:58 am

ziko wrote:Hi Jom,

In order to be able to identify this we need to know the following:

1) What settings you have in the software, could you send a settings file so we can try and do the same set-up

2)How are you connecting the inputs to the scope (are they terminated), what kind of cables are you using?

3) What equipment are you using and how are you varying it.


1) I'll try to send a settings file once I figure out how. :D

2) I'm using your 250 MHz probes. The probes are grounded to the board I'm testing.

3) I have some signal generators, power supplies and a spectrum analyzer. I turned off all of the devices with only the scope ON and I get the spur. I'll retest this to verify.

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Postby ziko » Tue Aug 21, 2007 12:20 pm

Hi Jom,

If you choose File->Save Current Waveform As-> then choose a file name and from the drop down selection you can save it as "Settings files (*.psettings)" , you can either email it to us on support@picotech.com, send it as a private message or make an attachment in the forum post.

Kind regards
Ziko

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Postby jom » Sun Aug 26, 2007 1:18 am

Thanks. I had sent some data for another problem that was Ticket #TS00003967. There's a pretty good chance that the spur will show up in that data. If you could use that data it would save me a lot of trouble. If you can't, let me know.

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Postby jom » Wed Aug 29, 2007 3:28 am

Were you able to use the earlier file I sent?

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Postby ziko » Thu Aug 30, 2007 1:07 pm

Hi Jom sorry was just dealing with a backlog of emails over the bank holiday weekend.

The only file I have was called Measurement Problem Data2.psdata it didnt get through the help desk email but the website administrator forwarded it to me, I cannot see any spikes or spurious information in that waveform at 8kHz.

By the way R6.0.11 is out today. If you could send me another psdata file with what you can see it would be appreciated.

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Postby jom » Mon Sep 03, 2007 12:08 am

We have a holiday weekend here (Labor Day) too. I should be back in the lab Tuesday (or possibly tomorrow if I "feel" like it...lol). I try to get some data then with the new release.

I am a bit surprised the data I sent earlier didn't have the spur. Odd. Anyway, I'll try it again...

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Same proble 8kHz

Postby cis » Tue Dec 11, 2007 5:21 pm

We have exactly the same problem but at 130kHz. We have a 3424 with software version 5.16.2.

One channel is connected to nothing (floating) and one channel with 50ohms.

The one with with 50 ohms (blue curve) shows a small 130kHz peak, the floating one (white curve) shows big 130kHz peak (and 260kHz, ...). See picture

We have disconnected everything and the computer is on battery (laptop) to avoid ground issues. We tried with the DC power supply of the laptop and we see the same behaviour.

We thing that this is related to a DC-DC convertion either in the computer to generate the 5V of USB, either inside the picoscope to supply amplifiers or ADC.

Is their any DC-DC converter inside the picoscope?

The other post suggest that is could come from the software but there is no answer since september, did you found a solution?

regards

Leon
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Postby ziko » Wed Dec 12, 2007 4:56 pm

Hi Leon, best thing to send us the unit so we can see if there is a problem with the unit.

Email me at support@picotech.com put in the subject heading "FAO Ziko"

Include your return address and a brief summary of the problem.

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Postby Lego » Tue Jan 29, 2008 5:01 pm

Hey guys,

I work together with Leon.
We bought a second picoscope since we couldn't spare the first in our tests. The same problem occurs with this one too, though less strongly.
We actually made our own program to handle the data and we do a bit of oversampling on the FFT (average over several acquisitions) to lower the noise floor due to quantification.
Still, if we use your program, we notice the spur now that we know there might be one at 150kHz, but it almost disapear in the quantification noise.
Is there any way we could fix this by ourselves? It looks pretty sensitive to the supply, the spur magnitude changes if we change of computer, but not if we use our own home-made supply-usb cable, it sometimes disapear if we move the plug a bit as well.

Best regards,

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