How to reduce noise on digital oscilloscope?  - Page 1
Forum section: electronics / testgear

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 12:00:51 am
content: Hello everyone, I have problem with my digital oscilloscope, the signal on testing like noise, how to reduce them?

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 22, 2024, 12:06:48 am
content: 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.

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 12:16:34 am
content: My scope is siglent sds1102dl, bandwidth 100mhz, may be I need 20mhz, how to set bandwidth?I attachment image noise

author: tggzzz
author_rank: Super Contributor
timestamp: October 22, 2024, 12:20:00 am
content: Quote from: sonielkraf on October 22, 2024, 12:00:51 amThe 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.

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 22, 2024, 12:30:34 am
content: Quote from: sonielkraf on October 22, 2024, 12:16:34 amIt says "BW Limit" in your screenshot. Try that.

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 12:34:09 am
content: This is image of probe testing on 8mhz, the sinus signal is not smoothly, an in other image is zooming signal

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 12:36:31 am
content: Like this?

author: lugaw
author_rank: Regular Contributor
timestamp: October 22, 2024, 12:43:53 am
content: 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?

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 01:08:41 am
content: 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?

author: indman
author_rank: Super Contributor
timestamp: October 22, 2024, 05:34:50 am
content: Quote from: sonielkraf on October 22, 2024, 12:00:51 amIn 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.

author: smaultre
author_rank: Regular Contributor
timestamp: October 22, 2024, 06:05:24 am
content: When you tested DUT, does you apply any galvanic isolation (powering scope by standalone UPS/Battary) techniques preventing ground loops ?

author: tautech
author_rank: Super Contributor
timestamp: October 22, 2024, 06:14:57 am
content: Quote from: sonielkraf on October 22, 2024, 01:08:41 amI 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.

author: sonielkraf
author_rank: Contributor
timestamp: October 22, 2024, 06:38:40 am
content: I was self calibration sir, but this result, any problem with powersupply,? I test voltage as service manual is normally to...

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 22, 2024, 08:34:57 am
content: Quote from: indman on October 22, 2024, 05:34:50 amThis 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.

author: Fungus
author_rank: Super Contributor
timestamp: October 22, 2024, 08:40:42 am
content: Quote from: sonielkraf on October 22, 2024, 01:08:41 amIt's normal

author: indman
author_rank: Super Contributor
timestamp: October 22, 2024, 08:48:15 am
content: Quote from: pcprogrammer on October 22, 2024, 08:34:57 amYou 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.Quote from: Fungus on October 22, 2024, 08:40:42 amThis video is a must watch for anyone who owns a digital oscilloscope. Then there will be fewer questions about noise.

author: Kean
author_rank: Unknown
timestamp: October 22, 2024, 12:50:32 pm
content: 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.htmlQuoteA 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 siteye3cif.com

author: Aldo22
author_rank: Super Contributor
timestamp: October 22, 2024, 04:06:43 pm
content: Nevertheless, I still wonder how an intact scope in AC coupling mode can produce such an offset, astautechmentioned.

author: Kean
author_rank: Unknown
timestamp: October 22, 2024, 04:14:30 pm
content: Quote from: Aldo22 on October 22, 2024, 04:06:43 pmThe fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?

author: indman
author_rank: Super Contributor
timestamp: October 22, 2024, 04:17:10 pm
content: Quote from: Kean on October 22, 2024, 04:14:30 pmIs it also likely that the user himself shifted the signal higher or lower after the capture?

author: Aldo22
author_rank: Super Contributor
timestamp: October 22, 2024, 04:29:09 pm
content: Quote from: indman on October 22, 2024, 04:17:10 pmBut 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.

author: indman
author_rank: Super Contributor
timestamp: October 22, 2024, 04:37:02 pm
content: Quote from: Aldo22 on October 22, 2024, 04:29:09 pmThe 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.

author: Aldo22
author_rank: Super Contributor
timestamp: October 22, 2024, 04:45:59 pm
content: Quote from: indman on October 22, 2024, 04:37:02 pmNo, 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.

author: IC_Toaster
author_rank: Regular Contributor
timestamp: October 22, 2024, 09:07:31 pm
content: Quote from: Aldo22 on October 22, 2024, 04:45:59 pmI agree with you and tautech. I find it strange.

author: hpw
author_rank: Frequent Contributor
timestamp: October 23, 2024, 09:34:12 am
content: Quote from: sonielkraf on October 22, 2024, 12:00:51 amUsing averaging... as a normal setting as on old 8bit LeCroy 20Gs WM & SDA

author: sonielkraf
author_rank: Contributor
timestamp: October 23, 2024, 05:00:39 pm
content: Quote from: Kean on October 22, 2024, 12:50:32 pmyeah, its hf transceiver, owwh maybe noise is produce by interference on circuit?or the ground probe is very near?

author: Kean
author_rank: Unknown
timestamp: October 24, 2024, 03:10:13 pm
content: Quote from: sonielkraf on October 23, 2024, 05:00:39 pmClip the probe tip to the probes ground lead to make a loop and place that near (but not connected to) the transceiver circuitry.Look at what you see on the scope, and maybe post a screenshot or photo.