Products > Test Equipment

Spikes and noise on Rigol DHO814

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shapirus:
Definitely not the cleanest PSU. I tried a car cigarette lighter plug with USB-C outputs, and it was actually better than this. So it makes sense to look for a less noisy power supply, but the question is how do we tell them apart from each other without buying and returning a dozen or two before finding a better one.

Fungus:

--- Quote from: shapirus on March 14, 2024, 11:00:14 pm ---Definitely not the cleanest PSU.

--- End quote ---

Mine is perfectly clean and so is just about every other person on here.

So unless yours is defective then the spikes are coming from the environment.

Spikes like these can definitely come from the mains. Dave's done videos on tracking these problems down, I posted one above.


--- Quote from: shapirus on March 14, 2024, 11:00:14 pm ---I tried a car cigarette lighter plug with USB-C outputs, and it was actually better than this.

--- End quote ---

In your car?

jim_griff:

--- Quote from: Fungus on March 15, 2024, 07:02:56 am ---
--- Quote from: shapirus on March 14, 2024, 11:00:14 pm ---Definitely not the cleanest PSU.

--- End quote ---

Mine is perfectly clean and so is just about every other person on here.

So unless yours is defective then the spikes are coming from the environment.

Spikes like these can definitely come from the mains. Dave's done videos on tracking these problems down, I posted one above.


--- Quote from: shapirus on March 14, 2024, 11:00:14 pm ---I tried a car cigarette lighter plug with USB-C outputs, and it was actually better than this.

--- End quote ---

In your car?

--- End quote ---

The evidence all points towards the PSU bricks of some people's devices. Occam's Razor:

1. Some people who own this scope are measuring the exact same signal, and in totally different parts of the world.
2. These signals are all being tracked down to the Rigol PSU brick (inductive coupling tests).
3. These signals are not able to be measured through the mains 120V/230V supply (unless Rigol PSU switched on).
4. Other devices and power bricks do not exhibit this exact signal and have their own switching signature, but much lower amplitude.
5. The signal disappears when using other power supplies to power the scope.

It's 100% noisy Rigol power bricks, albeit not all of them. Some have obviously been engineered better than others - different revisions, perhaps.

csuhi17:
We have known this problem for a long time.
The early sales gave a noisy power supply, then if I remember correctly they switched to LiteOn and Lenovo.
I didn't see in the above posts which one was added for those of you who find it noisy.

I use it with a sound technician's 12V power supply, but the LiteOn that comes with it doesn't make more noise for me either.

I tested the LiteOn, I charged a solar powerbank with it, it said 20V and 66W.
I couldn't test it at 15V.

In the OP's first post, I don't see what the channels are set to. 1x 10x
I also don't know if there is something connected to CH1, CH2.

If you have the opportunity to try it with another power supply, perhaps with a car battery, you can find out that everything is fine with the oscilloscope.
If you can't solve it any other way, then return it.
Maybe write to the seller about what can be done in this case.

There are two pictures of the power supply, with 20V 66W.
And the third is just for interest, the ground wire of the probe was oxidized or dirty at the part where it connects to the probe. With a handheld scope, I only measured ~40Vpp with the same probe.
After I cleaned everything was fine.

shapirus:

--- Quote from: Fungus on March 15, 2024, 07:02:56 am ---Mine is perfectly clean and so is just about every other person on here.

--- End quote ---
No switching supply is perfectly clean. Did you actually try to capture its EMI by shorting the probe's ground strap to the tip and using it as an antenna to sense noise close to the PSU?

I'll tell you more, the scope itself is also emitting like crazy. Easily sensed in the vicinity of the input power connector, where the several switching converters are located. But at least it doesn't seem to couple into the analog input lines.


--- Quote from: Fungus on March 15, 2024, 07:02:56 am ---So unless yours is defective then the spikes are coming from the environment.

Spikes like these can definitely come from the mains. Dave's done videos on tracking these problems down, I posted one above.

--- End quote ---
Are you kidding me? Two people thousands of kilometers apart show an identical switching noise waveform, (which in my case raises in amplitude dramatically as the ground loop antenna gets closer to the PSU brick), and you still tell that this may be coming from the environment?


--- Quote from: Fungus on March 15, 2024, 07:02:56 am ---
--- Quote from: shapirus on March 14, 2024, 11:00:14 pm ---I tried a car cigarette lighter plug with USB-C outputs, and it was actually better than this.

--- End quote ---
In your car?

--- End quote ---
No, on my bench. Cars aren't the only source of 12V DC power in the world.

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