Author Topic: How to reduce noise on digital oscilloscope?  (Read 2161 times)

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Offline sonielkrafTopic starter

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How to reduce noise on digital oscilloscope?
« on: October 22, 2024, 12:00:51 am »
Hello everyone, I have problem with my digital oscilloscope, the signal on testing like noise, how to reduce them?
 

Offline KungFuJosh

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Re: How to reduce noise on digital oscilloscope?
« Reply #1 on: October 22, 2024, 12:06:48 am »
Which scope do you have? What is the max frequency you need to see?

If you need less than 20MHz, then set the 20M filter on your scope channel(s).

If your scope supports it, use averaging in your acquisition menu.
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Offline sonielkrafTopic starter

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Re: How to reduce noise on digital oscilloscope?
« Reply #2 on: October 22, 2024, 12:16:34 am »
My scope is siglent sds1102dl, bandwidth 100mhz, may be I need 20mhz, how to set bandwidth?
I attachment image noise
 

Offline tggzzz

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Re: How to reduce noise on digital oscilloscope?
« Reply #3 on: October 22, 2024, 12:20:00 am »
Hello everyone, I have problem with my digital oscilloscope, the signal on testing like noise, how to reduce them?

The general solution to all signal processing problems is to integrate for longer.

If you want a more specific solution, you have to be specific in terms of signal/noise voltage/bandwidth, probing technique, construction technique.

At the very least show a screenshot of the noise and a photo of how probes are connected to your circuit.
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Offline KungFuJosh

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Re: How to reduce noise on digital oscilloscope?
« Reply #4 on: October 22, 2024, 12:30:34 am »
My scope is siglent sds1102dl, bandwidth 100mhz, may be I need 20mhz, how to set bandwidth?
I attachment image noise

It says "BW Limit" in your screenshot. Try that.
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Offline sonielkrafTopic starter

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Re: How to reduce noise on digital oscilloscope?
« Reply #5 on: October 22, 2024, 12:34:09 am »
This is image of probe testing on 8mhz, the sinus signal is not smoothly, an in other image is zooming signal
 

Offline sonielkrafTopic starter

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Re: How to reduce noise on digital oscilloscope?
« Reply #6 on: October 22, 2024, 12:36:31 am »
 Like this?
 
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Offline lugaw

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Re: How to reduce noise on digital oscilloscope?
« Reply #7 on: October 22, 2024, 12:43:53 am »
There's a lot of reason why you are seeing what you are seeing.

Why would you want to see a perfect sinewave?  Does the circuit output a perfect sinewave or you are just assuming it outputs a perfect sinewave?
 
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Offline sonielkrafTopic starter

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Re: How to reduce noise on digital oscilloscope?
« Reply #8 on: October 22, 2024, 01:08:41 am »
I try measure all sinewave is same result,
The scope condition if testing signal calibration on 1khz is same, the signal is not smooth,

I zoom it's, like any noise, why, my scope is not normally?
 

Offline indman

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Re: How to reduce noise on digital oscilloscope?
« Reply #9 on: October 22, 2024, 05:34:50 am »
Hello everyone, I have problem with my digital oscilloscope, the signal on testing like noise, how to reduce them?
 
In my opinion you have no problem with the oscilloscope, the noise of signal digitization is in every device, in some it is more, in some it is less.
There is no such thing as a silent digital oscilloscope. ;)
The fact that you see a distorted sinusoid does not refer to noise, but probably a strong interference with the signal either from the circuitry of the board or from a long wire on the ground contact probe, which you as an antenna catch this interference.
« Last Edit: October 22, 2024, 05:40:42 am by indman »
 

Online smaultre

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Re: How to reduce noise on digital oscilloscope?
« Reply #10 on: October 22, 2024, 06:05:24 am »
When you tested DUT, does you apply any galvanic isolation (powering scope by standalone UPS/Battary) techniques preventing ground loops ?
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Online tautech

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Re: How to reduce noise on digital oscilloscope?
« Reply #11 on: October 22, 2024, 06:14:57 am »
I try measure all sinewave is same result,
The scope condition if testing signal calibration on 1khz is same, the signal is not smooth,


I see some error.
Have you run the Self Cal ?

When a channel is AC coupled the Probe Compensation signal should be 50% above and below the 0V position.
Also the Trigger level is outside the waveform amplitude so press the Level encoder to set to 50% of the waveform amplitude.
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Offline sonielkrafTopic starter

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Re: How to reduce noise on digital oscilloscope?
« Reply #12 on: October 22, 2024, 06:38:40 am »
I was self calibration sir, but this result, any problem with powersupply,? I test voltage as service manual is normally to...
 

Online pcprogrammer

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Re: How to reduce noise on digital oscilloscope?
« Reply #13 on: October 22, 2024, 08:34:57 am »
The fact that you see a distorted sinusoid does not refer to noise, but probably a strong interference with the signal either from the circuitry of the board or from a long wire on the ground contact probe, which you as an antenna catch this interference.

This is a very good observation. Looking at the photo showing the probe connection on the board, there are three coils besides the probe tip, and with the ground lead "miles" away from the scoping point, it easily picks up the signals the coils may emit. Looking at the signal on the scope it shows switching spikes. So are these coils part of a switching supply?

Try winding a lead around the probe tip and connected it to ground at a point near to where you are probing and make it your probe ground connection too.

The small noise on the calibration signal looks like just a couple of bits in the digitization and is fairly normal. A electrically noisy environment can make it a bit worse, but does not invalidate the signal you see.

Online Fungus

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Re: How to reduce noise on digital oscilloscope?
« Reply #14 on: October 22, 2024, 08:40:42 am »
I try measure all sinewave is same result,
The scope condition if testing signal calibration on 1khz is same, the signal is not smooth,

I zoom it's, like any noise, why, my scope is not normally?

It's normal

 

Offline indman

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Re: How to reduce noise on digital oscilloscope?
« Reply #15 on: October 22, 2024, 08:48:15 am »
Looking at the photo showing the probe connection on the board, there are three coils besides the probe tip, and with the ground lead "miles" away from the scoping point, it easily picks up the signals the coils may emit. Looking at the signal on the scope it shows switching spikes. So are these coils part of a switching supply?
You are right, and if you look even more closely, you can see to the right of the probe a large row of relays, which also have windings with wire and can be sources of interference. ;)

It's normal
This video is a must watch for anyone who owns a digital oscilloscope. Then there will be fewer questions about noise. ;)
« Last Edit: October 22, 2024, 08:51:50 am by indman »
 

Offline Kean

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Re: How to reduce noise on digital oscilloscope?
« Reply #16 on: October 22, 2024, 12:50:32 pm »
I agree regarding the probing of the PCB being a potential problem.  The probe is close to potentially radiating components, and has a very long ground lead that will pick up noise.

The PCB that the OP is probing appears to be this Indonesian transceiver kit: https://products.ajetronic.com/2024/06/kit-radio-bitx-allband-tanpa-power.html
Quote
Allband Bitx Radio Kit without Power Amplifier (Just Exciter, need additional linear amplifiers to be able to transmit)

A video showing it (Indonesian):

Found via text labels of "ye3cif.com" and "AJE-101".  I didn't find a schematic for this, but there are schematics of other PCBs on an Indonesian amateur radio site ye3cif.com
 

Online Aldo22

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Re: How to reduce noise on digital oscilloscope?
« Reply #17 on: October 22, 2024, 04:06:43 pm »
Nevertheless, I still wonder how an intact scope in AC coupling mode can produce such an offset, as tautech mentioned.

 

Offline Kean

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Re: How to reduce noise on digital oscilloscope?
« Reply #18 on: October 22, 2024, 04:14:30 pm »
Nevertheless, I still wonder how an intact scope in AC coupling mode can produce such an offset, as tautech mentioned.

The fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?
 

Offline indman

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Re: How to reduce noise on digital oscilloscope?
« Reply #19 on: October 22, 2024, 04:17:10 pm »
The fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?
Is it also likely that the user himself shifted the signal higher or lower after the capture? ;)
 

Online Aldo22

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Re: How to reduce noise on digital oscilloscope?
« Reply #20 on: October 22, 2024, 04:29:09 pm »
The fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?
Is it also likely that the user himself shifted the signal higher or lower after the capture? ;)
But relative to the “1” arrow (not the vertical center of the screen)?
My Hantek keeps the arrow in the center of the wave form, even if I move it vertically after the capture.
 

Offline indman

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Re: How to reduce noise on digital oscilloscope?
« Reply #21 on: October 22, 2024, 04:37:02 pm »
But relative to the “1” arrow (not the vertical center of the screen)?
My Hantek keeps the arrow in the center of the wave form, even if I move it vertically after the capture.
The picture of the screen was taken at an angle to the display, so the proportions and size may be visually distorted. The photo shows that the test signal magnitude is approximately 3Vpp. The level of the arrow is labeled CH1/1.44V, which corresponds roughly to the middle of the signal.
 

Online Aldo22

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Re: How to reduce noise on digital oscilloscope?
« Reply #22 on: October 22, 2024, 04:45:59 pm »
The picture of the screen was taken at an angle to the display, so the proportions and size may be visually distorted. The photo shows that the test signal magnitude is approximately 3Vpp. The level of the arrow is labeled CH1/1.44V, which corresponds roughly to the middle of the signal.

No, it's all on one level. This is not an optical illusion, you have the graticule to compare.
You can clearly see that there is about 1V above the arrow and about 2V below the arrow.
I have never seen that in AC coupling.
 

Offline IC_Toaster

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Re: How to reduce noise on digital oscilloscope?
« Reply #23 on: October 22, 2024, 09:07:31 pm »
The picture of the screen was taken at an angle to the display, so the proportions and size may be visually distorted. The photo shows that the test signal magnitude is approximately 3Vpp. The level of the arrow is labeled CH1/1.44V, which corresponds roughly to the middle of the signal.

No, it's all on one level. This is not an optical illusion, you have the graticule to compare.
You can clearly see that there is about 1V above the arrow and about 2V below the arrow.
I have never seen that in AC coupling.

I agree with you and tautech. I find it strange.
 

Offline hpw

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Re: How to reduce noise on digital oscilloscope?
« Reply #24 on: October 23, 2024, 09:34:12 am »
Hello everyone, I have problem with my digital oscilloscope, the signal on testing like noise, how to reduce them?

Using averaging... as a normal setting as on old 8bit LeCroy 20Gs WM & SDA
 


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