Too much noise during the data acquisition

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Michele
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Too much noise during the data acquisition

Post by Michele » Sun Aug 19, 2018 9:50 am

Hi,

I own a picoscope 2205, (Resolution: 8bit Bandwidth: 25 Mhz, sampling: 200MS/s Memory: 16 kS) for a few years, but I've never used it a lot. Now I'm using it and when I try to measure a normal sine, generated from the AWG of picoscope, I get a very noisy signal. I tried many things, including using other function generator but the problem still remains. I attach a photo of the problem... I think it isn't normal. I'll appreciate every type of help!

Michele
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Schermata 2018-08-19 alle 11.34.31.png
Photo of the problem

Gerry
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Re: Too much noise during the data acquisition

Post by Gerry » Mon Aug 20, 2018 12:04 pm

Hi Michele,

That is very specific interference on your Signal Generated waveform rather than just noise.

Could you take photographs of your setup (one from a distance, so that we can see what is in the immediate surround area, and one showing how the Sig Gen is connected up) and post the image, and could you also post another Scope plot with the Sig Gen disconnected, and a Spectrum plot of the signal with the Sig Gen reconnected.

Regards,

Gerry
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Michele
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Re: Too much noise during the data acquisition

Post by Michele » Tue Aug 28, 2018 4:21 pm

Here is the material, I apologize for the delay. But I do not think the problem is in the AWG, because it also behaves the same with the sine generated by the arduino function generator. (If I measure the signal with arduino I see that the wave is correct).

Thanks in advance,

Michele

Gerry
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Re: Too much noise during the data acquisition

Post by Gerry » Wed Aug 29, 2018 5:57 pm

Hi Michele,

I don't believe it's the AWG/Sig Gen either, which is why I asked for the images and the psdata files.

I can't find any files. Can you use the editing tools to upload them directly into your post.

Regards,

Gerry
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Michele
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Re: Too much noise during the data acquisition

Post by Michele » Thu Aug 30, 2018 11:14 pm

oh sorry!
Attachments
DSCF2650.JPG
setup
DSCF2649.JPG
setup
Schermata 2018-08-28 alle 18.07.55.png
Schermata 2018-08-28 alle 18.10.57.png
spectrum
Schermata 2018-08-28 alle 18.10.57.png (71.99 KiB) Viewed 2098 times
Schermata 2018-08-28 alle 18.08.17.png
no signal

bennog
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Re: Too much noise during the data acquisition

Post by bennog » Fri Aug 31, 2018 5:45 am

can you also post a .psdata file ?

Save the trace somewhere and post it here ?

Benno
Last edited by bennog on Fri Aug 31, 2018 3:18 pm, edited 1 time in total.

Gerry
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Re: Too much noise during the data acquisition

Post by Gerry » Fri Aug 31, 2018 11:45 am

Hi Michele,

The way that you have the Sig Gen connected up to the input of the scope is prone to picking up Electromagnetic Interference from anything that is radiating it, such as fluorescent lights, switching power supplies in appliances, etc. Looking at the time domain waveform, for example, we can get something similar by amplitude modulating a 10kHz sine wave with a 60kHz square wave.

To get to the bottom of this, first of all, could you try this in another room where there would be minimal sources of interference, and nothing switched on (or better still, it looks like you're running the scope from a battery powered Mac, so if you're near a park or field or similar open space, try it there). When you try it could you pull the spring clip off of the probe and just poke the probe tip inside the inner receptacle of the Sig Gen's BNC connector, and attach the ground clip to the outer ring of the connector.
Alternatively, you could buy a short inexpensive BNC to BNC lead (50cm length would do) and use that to directly connect the Sig Gen to the input channel with much less cable that is completely shielded (we have a 1m BNC to BNC cable for £9 here: https://www.picotech.com/accessories/bn ... cable-1.1m that would be also do the job).

Could you let us know how you get on.

Regards,

Gerry
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Michele
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Re: Too much noise during the data acquisition

Post by Michele » Tue Sep 04, 2018 9:57 am

Hi,

unfortunately the problem still remains. I have tried both outside and with a shorter cable and at all the frequencies generated the measured waveform is the same.
I'm afraid the problem is right in the instrument.

Thanks for everything,
Michele

bennog
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Re: Too much noise during the data acquisition

Post by bennog » Tue Sep 04, 2018 3:07 pm

can you post some .psdata files from different frequencies
e.g 1 kHz sine and 100 kHz sine
Also if possible a sawtooth signal of same frequencies.

Benno

Gerry
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Re: Too much noise during the data acquisition

Post by Gerry » Wed Sep 05, 2018 4:16 pm

Hi Michelle,

OK, as we can't reproduce what you're seeing on a Mac, I have just 2 more questions that I need to ask to avoid you sending us a perfectly working device.

Have you seen this at all when you used the PicoScope a while ago?
What is the version number of the Picoscope 6 software you're using? (you can find this in the 'Help' Menu under 'About PicoScope 6')

Just to be sure that you don't have some obscure error to do with the setup or data files, could you save the data file of the problem waveform image that you sent to us, in psdata format, and post it here.

Regards,

Gerry
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Michele
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Re: Too much noise during the data acquisition

Post by Michele » Sat Sep 08, 2018 8:50 am

The tool has never worked properly and also for this reason I have always used it little.
I enclose the indicated material if you need anything else, let me know.

Thank you very much,

Michele
Attachments
Schermata 2018-09-08 alle 10.43.12.png
About PICOscope
Schermata 2018-09-08 alle 10.43.12.png (60.08 KiB) Viewed 1914 times
saw_tooth.psdata
Saw_tooth_1khz.psdata
(131.38 KiB) Downloaded 68 times
sine.psdata
sine.psdata_10khz
(112.46 KiB) Downloaded 71 times

bennog
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Re: Too much noise during the data acquisition

Post by bennog » Sat Sep 08, 2018 9:41 am

Ok looking at the data there can be 2 things mis with the scope.
Only from logic interpretation of the psdata files.
I don't know the inner workings of the PS 2205 so this is all a guess

- Calibration data corrupted in the scope. This is the most likely cause of the problem.

- Missing bits in ADC conversion.
this is less likely because if this was the case the signal would have jumped half the size in negative direction before doing the big step in positive direction.

It is definitely a internal problem in the picoscope. See below sine and sawtooth waves next side by side.
The jumps appear in both waveforms at exactly the same voltage positions.
side by sied.png

Gerry
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Re: Too much noise during the data acquisition

Post by Gerry » Mon Sep 10, 2018 9:28 am

Hi Michele,

Thanks for for your answers.

Could you send us an email at support@picotech.com with your full postal address and we will give you a returns number to send the Scope back to us, so that our test and repair team can look at it for you.

Regards,

Gerry
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