Author Topic: Rigol DS 2072 noise problem (Read 42452 times)

madworm · « **Reply #25 on:** July 27, 2012, 07:50:37 am »

I had a similar problem when toying with a current shunt amplifier (mV signal). Something was injecting spikes (different frequency and rep-rate). After eliminating everything else, it turned out to be my PC's power supply - of course it was running all the time, as I was consulting google.

JimmySte · « **Reply #26 on:** July 27, 2012, 08:16:32 am »

Hi playfsx
Last week I also purchased a DS2072 scope... I love it...
I've been playing with it all week and in Dave's latest video he mentioned that someone on the forums was saving issues with their scope,
so I powered mine up and ran the same tests as you did in your original post...
long story short no issues in the signals on mine...

here with the channel B lead floating... at my desk, in front of my pc

here with the lead shorted out

playfsx · « **Reply #27 on:** July 27, 2012, 06:30:01 pm »

thanks very much JimmySte your fist post and you try to help me

, im all most sure the is not the scope any more

Quote from: notsob on July 27, 2012, 06:33:40 am

This is probably a dumb question - "do you have fluorescent lighting ?", if answer is yes, have you tried turning it off. (I'm looking for a source of power spikes within your house)

yep and here is your answer:

Quote from: playfsx on July 25, 2012, 06:10:34 pm

Quote from: sotos on July 25, 2012, 05:57:34 pm
Maybe you have a Dimmer for your lights or electronic transformer for them.

They produce a lot of noise.

I’m thinking, because you said only in the night you have the problem.

im not have dimmer , i don't thing to be any from my device that causing that , i have unplug every single device from all my house include light bulbs and try it, and accusal the spices become some mV more intensive

Quote from: madworm on July 27, 2012, 07:50:37 am

I had a similar problem when toying with a current shunt amplifier (mV signal). Something was injecting spikes (different frequency and rep-rate). After eliminating everything else, it turned out to be my PC's power supply - of course it was running all the time, as I was consulting google.

i have test i is one of my devices that doing that so it's no the case, maybe some else in the building doing something .. if this is the case i can not doing anything, only to filter this spikes.

i search in google for filtering my mains and i found a device called Power conditioner ( http://en.wikipedia.org/wiki/Power_conditioner) is this device going to help ? is anyone have try one of this ?

TerminalJack505 · « **Reply #28 on:** July 27, 2012, 07:28:12 pm »

You might try an appropriately rated (voltage/amps) line filter. A line filter is just a common-mode choke and a couple of capacitors so they're not terribly expensive. You might also clamp a ferrite core onto the power cable just for grins since they're even cheaper.

playfsx · « **Reply #29 on:** July 28, 2012, 02:11:35 am »

Quote from: TerminalJack505 on July 27, 2012, 07:28:12 pm

You might try an appropriately rated (voltage/amps) line filter. A line filter is just a common-mode choke and a couple of capacitors so they're not terribly expensive. You might also clamp a ferrite core onto the power cable just for grins since they're even cheaper.

I have one nice big ferrite and i try it , the is seems to be not any difference, i gone find more details for the line filter and maybe try one,

meanwhile i get the ups in my home for more testing, i make a video so you can see more details and i recommend to see it, maybe you can pick up something who i miss.

but in short , if i power the scope from the ups (with out earth connection) and the probes is away from the mains i get only the noise from the ups. with ground connection i still getting spikes.

If the probes is close to the mains and even is not power in the cable the probes can pick up the spikes, i tried to going the probes close only to the earth (ground cable) and i can still pick up noise.

So i tried to measure the transformer while the scope is power from the ups as the A Hellene suggested , and i get the spikes , but this is not mean that this spikes existing on the ac line because the probes are probably pick up directly from the mains cable ( maybe can get it from the earth cable or maybe not ) , so my measurements probably are incorrect .

so now im in dead end $:-\$ , if i must filter my mains i must do it for all the room , and maybe this is not going to work at all , maybe the noise coming from the gound( earth) cable and how i can filter that ?

zaoka · « **Reply #30 on:** July 28, 2012, 04:01:29 am »

I think that you have problem with home grounding. Scope have filters built in for sure so there is no need to make new one.

I would try to get isolation transformer and power scope with it, with ground lead disconnected, than measure your AC line and see what is going on. (just be carefull not to tuch metal parts during this measurement). try to measure between all combinations (neutral - ground, neutral -hot and hot - neutral)

Also measure voltage between ground and neutral with AC multimeter when there is no problem as well as when problem appears.

T4P · « **Reply #31 on:** July 28, 2012, 04:16:09 am »

I think you have an issue with a floating ground somewhere

tom66 · « **Reply #32 on:** July 28, 2012, 11:13:15 am »

Something I notice, the noise isn't at the peak of the waveforms, but slightly offset to the right: it is leading the voltage waveform. This makes me think the thing producing the noise is some kind of system with a PFC capacitor, perhaps a large motor installation? Maybe some kind of commutator arcing?

A Hellene · « **Reply #33 on:** July 28, 2012, 01:25:27 pm »

playfsx, from your second video demonstration of the noise problem, and from the walking spikes parts of it in particular, it seems that the mains line trigger circuitry of your scope is not responsible for the depicted interference, as I initially suspected.

Now, here is an interesting waveform I captured, using my 100 MHz DS1052E:

Ch1 to the mains line; Ch2 floating

Channel 1 was reading the mains voltage directly¹, using a 100x probe, and
Channel 2 was reading whatever it could pick up while unconnected, using the standard 10x probe, floating.

Please note that it made no difference at all turning ON or OFF the 75W monitor (a DELL U2410) right in front of me, or the 250W halogen roof lamp (driven by a traditional and noisy phase-control TRIAC dimmer), or the 1.3KW room air-conditioning unit (the thermometer outside my window now reads 37 deg.C!). The captured waveforms were exactly the same, either the noisy units above were powered on or off.

For those who will notice it, the mains voltage was externally measured to be 228.7 VAC RMS, while the DS1052E measured it to be 218 VAC RMS (DS1052E error: -4.7% or -3bit); in defence of the DS1052E, I will have to state that I did not warm it properly up before taking these readings, neither have I recently run auto-calibration².

The interesting parts in the captured waveform above are the time points -1.7div (-3.4 ms) and +3.3div (+6.6 ms), where Ch1 captures a couple of seemingly innocuous mains disturbances, which are absolutely synchronised to the Ch2 obvious spikes. The problem is that, though the Ch1 and Ch2 waveforms are out of synch by ~1.4div (~2.8 ms), the Ch1 and Ch2 spikes are in perfect synchronisation. Channel crosstalk, do I hear some of you murmuring? Well, maybe. But, by disconnecting the Ch2 probe, the second trace became a nice and clean flat line while the spikes at the first trace remained as they were exactly, and of the same shape and amplitude. So, I suppose that my scope is not really lying to me...

This means that:
1. The depicted spikes are probably generated erroneously within the oscilloscope front-end amplifiers.
2. Our mains lines are actually that dirty.
3. We are both being bombarded by who-knows-what kind of electromagnetic weapons

(I am kidding!).

What I can only say is that, in order to trust what my DS1052E tells me about my mains line spikes, I would have to repeat those readings with a higher class oscilloscope and not with another entry-level one.

-George

EDIT:
1. DO NEVER TRY doing that if you are not absolutely sure of what you are doing, because the probe ground clip is the instrument's ground, which is hardwired to the mains power supply ground! Be very careful when messing with the mains line.

2. More than half an hour later, the mains line was reported by the DS1052E to be 221 VAC RMS, while it was measured to be 223.2 VAC RMS.

Wim_L · « **Reply #34 on:** August 03, 2012, 02:44:47 pm »

I had a similar problem a while ago, with a bad Volcraft DSO-8104 (though probably a relabeled Instek GDS-2104). Lots of junk visible with a 100Hz period. I'll attach some old screenshots. The big dirty band was really a lot of tiny spikes, with some ringing.

Confirmation came when I tested with another scope nearby. It measured a flat line on the same system (just a voltage source connected over a 100 or 180 ohm resistor, not an open probe!) but when the DSO-8104 was nearby and turned on or merely in standby (not connected to the same device being measured, just sitting on the same table plugged in), the analog scope also saw the same spikes! The power supply in that scope must have been causing some rather impressive EMI. Sent the thing back and got a different model of scope.

And yes, grounding quality definitely can affect how heavily a power supply radiates. But some supplies are inherently better than others. An old Philips PM3206 or a newer (well, also discontinued now) Hameg 1508-2 never did it on those same power outlets.

I'd definitely try getting another scope, perhaps some oldie analog, and seeing if you can measure the same spikes (for seeing short low repetition rate spikes on an analog, keep in mind Turning the trace brightness up and darkening the room may be required).

Teneyes · « **Reply #35 on:** August 25, 2012, 06:56:05 pm »

Quote

so i decide to make a "self calibration", i wait to finish and when it start up, not only there is no have fix it the problem but the expire all the trial version module who i have !! the scope come fully unlock (56Mpts i2c spi ....) for limited time (about 30 hours) ... all gone without even taste it ..

Hi All , Yes the DS2072 : Self-Cal has a bug that expires Options(Rigol confirms), BUT Rigol has sent me the options codes to restart the Trial Options,...I haven't try it yet.

Dread · « **Reply #36 on:** September 07, 2012, 11:40:43 pm »

Stop wasting time and send it back. From what I see in your videos there is something wrong with the switching power supply or some filter component has failed.

playfsx · « **Reply #37 on:** September 14, 2012, 10:33:47 am »

Quote from: Dread on September 07, 2012, 11:40:43 pm

Stop wasting time and send it back. From what I see in your videos there is something wrong with the switching power supply or some filter component has failed.

This is not the case, my mains is the problem i have confirm that look the second video, i only hoping now that the device that cause that they stop working now that the summer is over , one night accusal i don't get any spikes

Overall im very happy with the scope, it have some software bugs but it's fixable .

btw i upload a video to show the X Y capability's of the scope

hgjdwx · « **Reply #38 on:** November 06, 2012, 05:35:42 am »

Your Rigol DS2072 noise problem solved?

WLUWLU · « **Reply #39 on:** December 15, 2012, 10:26:44 pm »

To my believe you don't have to fault the Rigol DS2000 series for the spikes you see. Don't forget the higher the sensitivity in the fronend the more the likelyhood of picking up unwanted signals. I have these for instance too but to verify ran a crosscheck with a Tektronix TDS1000 & TDS2000 series and exactly the same thing. Just a bit less visible since the TDS series don't have the fasted wfm update rate. This I think is more related to incoming via your probes and I would not make a snap judgement like "this is coming from within your DSO". I just e.g. plugged in the laptop charger into my HP Compaq 2510p (fairly old machine but used as my beater). As soon that switched mode PSU has to charge the laptop (thus being loaded) I see a big jump of "dirt" on my Rigol DS2102. That charger for my HP I bought last year from some chinese company as an OEM part but I doubt the quality. Once the HP has a fully depleted battery and I do switch it on (charging & running the same time) for the first 30mins or so that charger makes some really funny chirping noise which then disappears as soon a certain charge has been performed and it has to work a bit less. Me running about at least 2 laptops and some other goofy equipment (2 phonechargers & 1 DECT phone station) plugged in my noise floor in general is pretty high. Going higher in the mV input stage of the Rigol gets rid of it. If I run my other testkist along, like a Tek DSO, 2 bench lab DMM's, 1 Omnicron CMC net simulator, 1 Agilent 33120A, soem Grundig Digimess stuff nothing really happens because more decent testequipment usually employ better quality internal PSU circuitry vs some real cheapo consumer stuff.
You could maybe try getting your lab EMI safe and improve general earth grounding and so forth but than you could as well spend thousands of $$ just trying to get it right.

marmad · « **Reply #40 on:** December 15, 2012, 10:39:26 pm »

I believe he solved the problem with his mains supply months ago already. Perhaps he should mention it here - or else lock the thread.

Oh, he did actually kind of mention it a couple of posts back.

tigerwillow1 · « **Reply #41 on:** February 23, 2013, 11:27:46 pm »

I see what looks like an unreasonable noise problem with the DS2072. I'm also new to DSOs so maybe there's something I don't understand. No matter what vertical sensitivity I'm on, I always have 3 or 4 bits of noise. I know to expect LSB error, but I thought that would only introduce one bit's worth of noise. For example, if I'm set to 1 volt per division with no input signal, the scope says and shows a 120 or 160 millivolt gap between the min and max level. It's not analog noise because it's proportional to the vertical sensitivity setting, always 3 or 4 bits. The result is the same if I leave the BNC input unconnected, shorted to ground, or terminated. The attached picture is a sweep captured at 1 volt/div with 75 ohm terminators connected, then expanded to 50 mV/div. Each A-D step at 1 volt/per div is 40 millivolts, which is what the picture shows. I expect the trace to "flop around" one bit, but not the 3 or 4 bits that I consistently see.

Just to rule out electrical interference, I hauled the scope a hundred feet from the house and powered it from an inverter generator with identical results.

Hydrawerk · « **Reply #42 on:** February 23, 2013, 11:35:09 pm »

This is weird. Write a message to Drieg, he sells those scopes and knows them well. He can give you an advice. There is something wrong with your DS2072, I think... But IMHO this fault is very rare.
https://www.eevblog.com/forum/blog/the-dark-side-of-the-rigol-hack-bricked-scope-how-to-fix-it/

marmad · « **Reply #43 on:** February 24, 2013, 12:09:41 am »

Quote from: tigerwillow1 on February 23, 2013, 11:27:46 pm

I see what looks like an unreasonable noise problem with the DS2072. I'm also new to DSOs so maybe there's something I don't understand. No matter what vertical sensitivity I'm on, I always have 3 or 4 bits of noise. I know to expect LSB error, but I thought that would only introduce one bit's worth of noise.

My DS2072 has the same noise characteristics as yours - and people seem to feel it's good for it's class. I'm no expert about these things, but from what I understand, many things contribute to the noise floor of an oscilloscope - the LSB error of the ADC being just one contributing factor. The front end of an oscilloscope is comprised of an attenuator, pre-amplifier and all of the path routing before the ADC - any one of which can introduce noise. And one other thing to consider - the DC gain accuracy for the DS2000 series is listed at ±2% full scale - which means, in essence, that signals smaller than 8 vertical divisions (in this case, noise) will have proportionally larger possible errors.

marmad · « **Reply #44 on:** February 24, 2013, 12:26:47 am »

BTW, if you use the 'High Res' acquire mode, the pk to pk noise level will drop - sometimes significantly depending on the timescale.

drieg · « **Reply #45 on:** February 26, 2013, 05:08:44 pm »

Quote from: tigerwillow1 on February 23, 2013, 11:27:46 pm

I see what looks like an unreasonable noise problem with the DS2072. I'm also new to DSOs so maybe there's something I don't understand. No matter what vertical sensitivity I'm on, I always have 3 or 4 bits of noise. I know to expect LSB error, but I thought that would only introduce one bit's worth of noise. For example, if I'm set to 1 volt per division with no input signal, the scope says and shows a 120 or 160 millivolt gap between the min and max level. It's not analog noise because it's proportional to the vertical sensitivity setting, always 3 or 4 bits. The result is the same if I leave the BNC input unconnected, shorted to ground, or terminated. The attached picture is a sweep captured at 1 volt/div with 75 ohm terminators connected, then expanded to 50 mV/div. Each A-D step at 1 volt/per div is 40 millivolts, which is what the picture shows. I expect the trace to "flop around" one bit, but not the 3 or 4 bits that I consistently see.

Just to rule out electrical interference, I hauled the scope a hundred feet from the house and powered it from an inverter generator with identical results.

What you experience is normal on digital oscilloscopes, it is like digital zoom on your camera. What you see is a noise fluctuation betwen 3-4 quantization levels which is 1-2 bits, not 3 or 4 bits. You can see how the number of levels changes (usualy from 2 to 4) as you move signal up and down (with fine vertical offset), so the noise looks sometimes bigger (4 levels) and sometimes lower (2 levels). 1-2 bits are normal and usual on these units, so nothing wrong with your scope

tigerwillow1 · « **Reply #46 on:** February 27, 2013, 02:36:20 am »

Thanks all for the feedback about the A-D noise (not sure if that's the proper term here, but whatever is behind it, it has the appearance of noise). I'll say I'm disappointed, having assumed I'd be seeing the +/- 1/2LSB inherent in A-D converters. I also have to realize that even though paying for the DS2072 hurt, it's still at the low end of the DSO world. Its capabilities for what it costs are nothing short of mind-boggling, however that doesn't stop me from hoping for perfection. If anybody here has a different brand DSO and is curious enough to take the time, I'm very interested in finding out how the competition stacks up, i.e. how many different A-D steps it resolves a steady zero input to.

Teneyes · « **Reply #47 on:** February 27, 2013, 05:57:32 am »

Quote from: tigerwillow1 on February 27, 2013, 02:36:20 am

. how many different A-D steps it resolves a steady zero input to.

Does anyone Know how the DS2000 is configured when the the input is set to GND with AC-DC-GND switch, as this quantisation level jumps does not show in this Stopped Frame digital Zooming?

BTW Analog zooming works better than most DSO down to 500uV

drieg · « **Reply #48 on:** February 27, 2013, 08:38:00 pm »

@tigerwillow1: Here is my LeCroy DDA-120 / LC584AXL (8GSa/s, 1GHz, 16Mpts)

tigerwillow1 · « **Reply #49 on:** February 28, 2013, 06:24:20 pm »

Drieg - Thanks for that picture. It's looking more and more like I have an unrealistic expectation about the A-D resolution. This all started when I was looking at a rock-solid 13.5 volt input and the peak voltage readout said 15.1 . With the features come added responsibility in learning how to interpret them.

Teneyes - I've concluded, rightly or wrongly, that the GND setting is a software feature. In the context of the live inputs, it's too perfect.


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Author Topic: Rigol DS 2072 noise problem (Read 42452 times)

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