Hantek dso2d15 Noise from internal power supply

[iw2evk]

Hi,

somone have tried to modify internal circuit of dso2d15 for reduce the radiofrequency noise irradiated from scope?
I've placed a ferrite sleve on main cord but it's not sufficent for reduce noise.
All around the scope for about 1mt i've strong radio noise on wide spectrum frequencies.

need help , please

Roberto iw2evk

[Aldo22]

I think it's the screen, not the power supply.

[iw2evk]

Nothing to do ?
use a shieded cable for carring out the signal far away to oscilloscope ?

[Aldo22]

Nothing to do ?
use a shieded cable for carring out the signal far away to oscilloscope ?

If you want to shield it for the other devices, a Faraday cage may help. 

If you simply want to see less noise, you can try the following:
- Use a direct, short BNC connection to the DUT whenever possible.
- If you use the probes, use the 1x mode (for the smallest signals anyway).
  The less stuff hanging on the probe (sprung hook, alligator clip) the less “antenna” you have.
- Turn on the bandwidth limiter (BW 20M).
- If it does not trigger cleanly, a trigger holdoff can help (perhaps via PC).
- For repetitive signals, the "Average" acq. mode can help (or a little less the HR mode, for any signal type).

Noise is everywhere. Maybe it's not just coming from the scope?

I don't think the noise is that bad if you help a little.
In the attached image you can see a measurement with
- Probe (1x), sprung hook and alligator clip (i.e. completely normal).
- BW limitation on
- Average Acq. (8x).

This is a very small signal for a measurement with the probes (6.5mVpp) and it still looks reasonable to me.

[Aldo22]

And before you curse the DSO2000:
It has pretty good sensitivity for such a cheap scope.
With a FNIRSI 1014D or 1013D you would see as much as in the attached picture of the signal above (50mV/div).
In this case the noise is not an issue. 

[iw2evk]

Hi,

i've order a double shelded 50 ohm bnc to bnc 1mt cable.

So i suppose can take awey the DUT from scope and reduce noise.

P.s. my test are on radio device, so i suppose i due buy a 50 ohm attenuator for reduce the signal from internal scope generator to input of radio..
Or i can make the attenuator with a kit ?

[Aldo22]

i've order a double shelded 50 ohm bnc to bnc 1mt cable.

So i suppose can take awey the DUT from scope and reduce noise.

I'm not sure if that's a good idea. Maybe you pick up even more noise this way, because the cable is longer?

Can you show a picture/screenshot of what it looks like in your case?

When I place the probe directly on the scope/screen (picture 1), I see a lot of noise.
But in normal operation (picture 2) I don't think the noise is excessive.

The setting in the pictures is: probe 10x, without BW limitation, with HR mode and persistence 1s (100us, 20mV/div).

https://youtu.be/sWPRAKayC3g

[Maximplus]

Many people note that this oscilloscope has a primitive and noisy power supply. Its replacement or additional screening with filtration should help significantly. Unfortunately, the source is 2-channel, there are 5 and 12 V, inconvenient to replace. There is a lot of information on the redesign on youtube, including a video where a classic power supply with linear stabilization was used. Without pulse conversion.

[iw2evk]

Mhh..

can i add some ferrite bead on internal cable and/or ceramic capacitors on pcb  of voltage regolator output ?

I don't have  found imeges on web..