Products > Test Equipment
Spikes and noise on Rigol DHO814
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eTobey:
Hi there,

i bought a Rigol DHO814, which is my first > 250 bucks Oscilloscope. While trying it out on my prototype, i discovered spikes (and noise?) coming from the power supply. It has a frequency of 54-70 Khz. Connecting earth does help, if its not to far away.

I connected a coil on the leads and held it to the cable. Interestingly, the amplitude changed with position on the cable.

I found out, that i have to connect all GND, in order for the spikes to be lower than with the yellow and blue curve on the picture. But it was still about 22mV. With a little bit of aluminium and ferrite, i could lower this to just under 10mV. One turn in the ferrite does a little, two turns does better, but three turns makes it worse.
Now i wonder if i have a bad power supply?

Is there also something i can do / could try, to clean up the signal?
ebastler:
What probes were connected to the scope inputs when you captured those screenshots, and what were the probes connected to on the other end? (Including ground connections of rhe probes, if any?)
eTobey:
I had 2 probes connected, but only one GND of them. Another probe was laying unconnected.
ebastler:
Does the noise go away when you disconnect the probes from the scope , i.e. is it picked up by them rather than within the scope? Does it help if you move the power supply far away from the probes and your prototype under test?
eTobey:
The noise goes away from the probe that is beeing disconnected, but it then adds up on the other channel!

The noise does not change, if i put the powersupply with the foil near the probe, but if the blue probe has a disconnected GND, then the noise gets from about 25mv to about 20mV, when the powersupply is near... wtf?
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