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| Oscilloscope probe ground leads act as FM attennea |
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| Martin72:
I just tried this out here as well. At first glance it looks good, but if you dissolve it further, you can see a ripple on the "roof". If you take advantage of the good properties of the rigol and resolve more vertically, you can clearly see a ripple of about 30khz. In my case, the ripple remains, regardless of whether groundspring or alligator clip or not connected to ground at all (the probe already has ground). This is a disturbance that probably comes from the power supply. But this is really nothing bad... ;) |
| ebastler:
--- Quote from: Martin72 on October 25, 2023, 07:22:46 pm ---If you take advantage of the good properties of the rigol and resolve more vertically, you can clearly see a ripple of about 30khz. This is a disturbance that probably comes from the power supply. But this is really nothing bad... ;) --- End quote --- Thanks for giving the "zoom in to look for characteristic frequencies" suggestion a try! While your cursor positioning for the frequency measurement is debatable ;) (I would estimate ~40 kHz), the switching supply clearly seems to be the source here. |
| dmulligan:
--- Quote from: Fungus on October 25, 2023, 01:44:30 am ---Mine looks like this: --- End quote --- So that was an interesting exercise. In order to match your conditions I had to upgrade to firmware 00.01.01 as pressing Auto gave me a different memory depth and sample rate. I also saw a couple more differences in your screenshot pointing to you using new firmware. Sadly I get no change in behaviour with new firmware. Do you have BW Limit enabled for that channel? Does it change if you set your probe attenuation to 10x since you are running your probe at 10x? |
| Martin72:
--- Quote ---While your cursor positioning for the frequency measurement is debatable --- End quote --- Argh, new glasses please... |O OK, but I don“t repeat this today, also the following not... ;) Following an idea, I went back to the study and did the following... Siglent HD and the rigol switched on, first measured the siglent ref. generator with the siglent, then with the rigol. Then measured the rigol ref. generator with the siglent. The case is clear, the disturbance comes from the generator, which catches something... But as I said, this is nothing bad as small as it is, just do not think that would now be a flaw. |
| ebastler:
--- Quote from: dmulligan on October 25, 2023, 07:57:32 pm ---Sadly I get no change in behaviour with new firmware. --- End quote --- Do you have the switching power supply right next to the scope? If so, does anything change if you move it as far away as the cable allows? (Not too likely because the noise is probably largely wire-bound, not radiated. But worth a try, I think.) Also, which brand of power supply was shipped with your scope? It seems that Rigol shipped a no-name, fixed 12V supply with early units, but had problems with it. They transistioned to LiteOn or Lenovo supplies -- proper USB-C supplies capable of negotiating the voltage, which must cost them more, and probably are better quality and less noisy too. |
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