How Thick is Your Baselne on Your Digital Oscilloscope? - Page 1
Forum section: electronics / testgear

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 10:35:23 am
content: How thick is your baseline?One of the tings I've always liked about my old analog oscilloscopes is the low noise baseline display. I see a nicethinflat line. By positioning the free running trace at the bottom baseline and just using the graticule and subdivisions for readoutI can make DC voltages measurements quickly and quite accurately.It was so convenient to use my scope as a voltmeter, with it's tiny 1 or 10x probe tip, to see all the important voltages at a glance, and not upset the circuit as what happens when using the unshielded probes on my trusty Fluke DVM.I have a RIGOL DS4024and viewing the baseline, without any probe connected or with a 10x probe connected, always has athick baseline, at 200mHz bandwidth, a fairly thick one(.2 major div), with 100mHz bandwidth(>1 minor div.) and with 20 MHz bandwith setting still about 1 minor div.And there is no noise nearby.The noise source is within the scope itself. My 20MHz analog scope sitting directly below it has a nice flat baseline under the same conditions. My Tek 60-MHz 465 has also a beautiful flat baseline.Butat any bandwidth, and with the input set to GroundI finally see the beautiful flatline display that I am so used to seeing with my analog scope.I am wondering if I bought the wrong scope. I really miss my baseline!Does anyone have a Tek DS403x series baseline picture with no averaging and just a probe connected. I've heard that 9-bit vert. digitization give a better baseline.If anyone has an approx. equiv. model of an Agilent or a Tektronix DSO or DPO,how thick is your (Non-averaged) baseline? Please post a picture!?

author: jpb
author_rank: Super Contributor
timestamp: June 14, 2013, 10:47:10 am
content: My scope is at home (a LeCroy WaveJet) and I'm at work but my measurements of the noise level were in line with those reported in Agilent's app note:http://cp.literature.agilent.com/litweb/pdf/5989-3020EN.pdfThe main issue with a digital scope is it is only 8 bit (though more in high res mode). If you limit the bandwidth and turn on averaging the line is a lot smoother of course.If the scale is set up properly, and you're not trying to measure small voltages below a few mV, then I would say the noise is around one or two bits so you should be able to measure to between a tenth and a fifth of a division by eye.The advantage of a digital scope is it can also give you a mean value as a number which is probably more accurate.What you need to ask is for people to post pictures of zero input on a scale that you're interested in, then we could do some sort of comparison.To be fair the bandwidth needs to be limited to the same amount otherwise wider bandwidth scopes would be penalised. Also I presume this needs to be with probe attached?

author: SLJ
author_rank: Frequent Contributor
timestamp: June 14, 2013, 11:02:54 am
content: Are you using the same prob on both scopes to compare the two?

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 11:16:09 am
content: Yep. Same probe.

author: nctnico
author_rank: Super Contributor
timestamp: June 14, 2013, 11:27:57 am
content: You probably have peak-detect active. The analog scope doesn't show the noise. The digital does.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 14, 2013, 11:30:39 am
content: It's not really a fair comparison, because the noise bandwidth is completely different between the old 20 MHz scope and your newer 200 MHz scope. What do you get if you engage the 20 MHz bandwidth filter on the Rigol?If the two scopes have a similar noise figure in terms of V/sqrt(Hz), then a scope with 10x the bandwidth would be expected to show a line more than 3x thicker with no input signal for this reason alone. It's one reason scopes include bandwidth limiting filters that you can turn on. At a guess, when you select GND coupling on your Rigol, it's either a software feature that ignores the ADC output entirely, or it couples the ADC input directly to a fixed voltage and completely bypasses the front-end amplifiers.Also, one of the major advantages of a digital scope over an analogue one works against it here. On the analogue scope, you see a line whose cross-section accurately reflects the temporal distribution in voltage, ie. it's brightest in the middle and rapidly decays to an invisibly low level as you look above and below. In other words, it has very high dynamic range in the 'Z axis'.The digital scope's display system, however, tends to exaggerate the brightness of infrequent captures, and though this is normally a benefit as it makes infrequent events more clearly visible, it does make the baseline appear thicker than arguably it should be.

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 11:37:15 am
content: I don't have peak detect active making this test.No special features turned on at all, but I compare the effects of bandwidth limitation on the Rigol DS4024.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: June 14, 2013, 12:26:13 pm
content: You may want to put High Resolution on, not sure where it is located in the Rigol.

author: Harvs
author_rank: Super Contributor
timestamp: June 14, 2013, 12:46:04 pm
content: Quote from: KedasProbe on June 14, 2013, 12:26:13 pmDS2000 is the same (as is I imagine most DSOs with graded intensity displays). It's not something that I've really ever thought about, as I just turn on Avg voltage measurement function (it's been about 5yrs since I've used a CRO though.)Pretty much anything you turn on like Hi Res mode or averaging (which does significantly improve the line width) kills the update rate, so kind of a no win situation there.

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 12:49:19 pm
content: KedesProbe:Correction: Hi-Res setting can be tuned on, traces becomes very thin and dim,update rate of display about 1 sec/update at 1mS/div horiz. sweep. on the DS4000 series

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 14, 2013, 12:52:04 pm
content: Here's a trace from the 50 MHz Tek TDS310 I keep in my office. Not as nice as the trace on my 250 MHz Tek 475A, but you need storage for this, and it was $125 with 2 Tek P6109B probes. I get about the same amount of noise on my TDS380.

author: Harvs
author_rank: Super Contributor
timestamp: June 14, 2013, 01:06:58 pm
content: Quote from: Paul Price on June 14, 2013, 12:49:19 pmAccording to the manual it does. It's the same as the DS2000, under the Acquire menu.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: June 14, 2013, 01:54:43 pm
content: Quote from: Harvs on June 14, 2013, 01:06:58 pmYes, I just checked it the lab, it's there.

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 04:30:18 pm
content: Thanks dfmischler for the picture of the analog scope trace.KedasProbes and Harvs: Thanks for reminding me where the Hi-Res is located. Not too easy to setup if I suddenly decide to make some fast DC measurements.Yes, Hi-Res mode gives a sharp but dim display but it takes 1-Sec to update the display in Auto Sweep even at 1mS/div Horiz. Sweep.It is even worse at lower time/div settings. Too long for me to wait to jump about a circuit and having to wait a second for the trace to reset to the baseline.Turning on Averaging if even worse, take at least a second to display the result and two sweeps at say, 100mS/div that is way to long to wait for the purpose of fast voltage measurements. Doesn't change the noise level at the flat top of a sq. wave nor at the baseline of it.I would like to see what a trace looks like on an Agilent (8-bit) or Tek (9-bit) scope.

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 14, 2013, 04:53:03 pm
content: Quote from: Paul Price on June 14, 2013, 04:30:18 pmThat trace was from a Tektronix TDS310 50MHz 500MS/s 1Kpt/channel digital storage scope built around 1993.If anybody cares it is part of a Dallas 1-wire search sequence that I was having trouble with. The view is from about 110 meters cable distance from the DS2480B master. Note the nice slew rate controlled edges and the horrible glitch (I think this is when the DS2480B's active pullup tries to take over from the passive pullup).

author: Salas
author_rank: Frequent Contributor
timestamp: June 14, 2013, 05:05:42 pm
content: That Tektronix TDS line has nice waveform depiction due it uses the phosphor's natural persistence. Its bulky using a CRT but it was a good, reliable line. Still many of those at work out there.

author: jpb
author_rank: Super Contributor
timestamp: June 14, 2013, 05:30:54 pm
content: Here are screen grabs at 2mV division (the most sensitive) and 1V a division with 20MHz bandwidth. They are flat enough for me but perhaps too fat for your liking.(I've just used normal mode without averaging or other schemes to flatten them further.)Note 8V/256 = 31.25 mV and 16mV/256 = 62.5 microV so at 1V/div the peak-to-peak is only 1bit whilst at the most sensitive range (2mV/div) it is 3 bitswhich I think is as good as you might expect.

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 14, 2013, 05:34:30 pm
content: Quote from: jpb on June 14, 2013, 05:30:54 pmDo they look that nice when viewed on the screen? How about a photograph (or a bad cell phone picture like mine)?

author: jpb
author_rank: Super Contributor
timestamp: June 14, 2013, 05:38:40 pm
content: Quote from: dfmischler on June 14, 2013, 05:34:30 pmI'll try and get a photo but because these were screen saves and the screen is a VGA lcd there isn't much difference between the two.edit: here is the photo - unfortunately there is a bit of reflection but I think you can see it well enough.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 14, 2013, 06:59:55 pm
content: Quote from: Paul Price on June 14, 2013, 04:30:18 pmHere's a few captures from my Agilent MSO-X3054A and Tek TDS754DBoth scopes are 500 MHz bandwidth, all images are taken with no probe attached.

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 08:59:43 pm
content: Thanks for the pinup's JBP. This looks twice as flat as my Rigol which shoes about 1-minor div noise bar regardless of the volts/div setting when viewing a top or baseline bottom of a clean square wave.It is a little hard to see your picture result since you don't display a graticule, so I must visually guess.AndyC_772, thanks much for taking the time to send me these screenshots.The Agilent Normal Mode display,(top of your set of pictures displayed) looks close to what I see on my DS4024 in the Normal mode.The TDS754 scope noise floor looks no better then my DS4024.In the Hi-Res mode on the DS4024, the baseline is minimally thick and quite dim altogether just slow to respond to a voltage change.I must try to take some display shots myself to show what I am talking about with my cellphone camera and post them here.

author: ftransform
author_rank: Frequent Contributor
timestamp: June 14, 2013, 09:04:21 pm
content: if you are measuring DC voltages, did you consider turning on a low frequency low pass filter?they tend to clear stuff up on oscopes

author: Paul Price
author_rank: Super Contributor
timestamp: June 14, 2013, 09:07:25 pm
content: Ftransform: Thanks for the tip, but in general, I use a scope to see what the electrons are doing out there, not hide their play from my eyes.The noise I see is generated in the scope, not external to the scope, so no Lo-Pass Filter would work here.

author: ftransform
author_rank: Frequent Contributor
timestamp: June 14, 2013, 09:10:44 pm
content: Quote from: Paul Price on June 14, 2013, 09:07:25 pmit totally cleans up my 1052e display to a flat line

author: Unknown
author_rank: Unknown
timestamp: June 15, 2013, 02:41:03 am
content: Noise coming from the wall is tremendous,.get a PS Audio Power Plant Premier,use shielded power cables.eliminate all common noise. see Dave video:

author: rf-loop
author_rank: Super Contributor
timestamp: June 15, 2013, 11:15:12 am
content: It is very nice of someone do tests and show images about:Scope (DS2000: 70, 100 or 200MHz model) settings 1 or 2 channel in use.Full BWNo average, no any kind of filtering, no high res mode.Horizontal speed 1ms/divAcquire (sampling) mode peak (or how it is named in Rigol) and normal 8 bit mode (no high res)(or if not peac acquire mode, with 14M memory selected and then scope stopped and zoomed out so that more data is displayed)Inputs open. (or external 50 ohm terminators on channels BNC. specially if envinroment is noisy)(Just all settings so that pure maximum level of front end peak-peak noise is visible on the screen.)Probe factor 1xVertical:500uV/div1mV/div2mV/div5mV/div10mV/div

author: Paul Price
author_rank: Super Contributor
timestamp: June 15, 2013, 02:19:36 pm
content: I have discovered that if I select Hi-Res mode and AUTO trigger on my DS4024 and set the time/div to 100uS/div or faster, then the display is very quick to update and the line is a flat, but dim, as can be possibly be displayed. The only problem here is that if there is any repetitive signal in the D.C. waveform the scope goes nuts.Thanks again for everyone for taking the time to post pictures!From what you all have seen here, which scope do you think is best in having the best thin baseline display?Of course I must consider all the pros and cons of a scope besides this one behavior and there are many things I like about the DS4024 and I think overall, I like the cost v. performance of the DS4024.I am going to waste a fortune of inkjet ink and print some of these pictures out and compare them to my baseline.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 15, 2013, 05:21:51 pm
content: Generally if you want to accurately get the DC value you would just use the scope measure functionality either on the whole trace or with cursors. That isn't to say it isn't worth figuring out how to get a cleaner signal display on your DSO, but you should be able to quickly measure voltages without it.

author: Unknown
author_rank: Unknown
timestamp: June 15, 2013, 08:04:03 pm
content: Quote from: Paul Price on June 15, 2013, 02:19:36 pmunder $10kusd., the only scope that can go to 0.5mV/div is the Rigol DS2202,no scope can do all things,but then again, when i had Instek gds-1102A-U,the baseline when connected directly to the wall was higher & unstable vs. connected to Ps Audio Power Plant Premiere, small & stable, if i made a short on the tip of the probe with the ground, was even smaller, i could see a very thin base line way under <1mV/div.Better Power first.All DSO/MSO have a Switch Mode PSU, and those are noisy Meanwell are around +/-100mV ripple & noise, i´m surprised to see that a scope with a switch mode psu has a 1mV/div sensitivity.A switch mode psu is affected by external power coming from the wall, increasing noise.If you want better than Ps Audio Power Plant Premiere, the New P5 or P10, and/or the Accuphase PS- series.http://www.accuphase.com/model/ps-1220.htmlhttp://www.accuphase.com/cat/ps-1220_e.pdfi don´t know how stable is the regulation of the Accuphase, but the PPP is flawless 120.5v.the Accuphase noise is near -84.375dB.The Signal Generator in the Accuphase is Analog, in the PS Audio is DDS.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 16, 2013, 12:16:24 am
content: Quote from: Paul Price on June 14, 2013, 08:59:43 pmThat just sounds like ADC jitter to me. It's an 8-bit ADC and each value corresponds to one pixel, so a 2 pixel line is as good as you can get without some form of averaging.The DS2000 provides three forms of averaging: Average mode, which averages the results of multiple captures. As you noted, this is not what you want. Anti-Alias, which weights the intensity of each pixel based on neighboring pixels, and Hi-Res, which averages multiple sample points to generate each pixel. (I find it best not to mix these different averaging methods as having multiple active can produce some ugly results.) I use Anti-Alias most of the time, the main effect is just to enhance the trace. I've had Hi-Res severely distort the signal, so I don't use it any more. Both Anti-Alias and Hi-Res can slow down the capture rate depending on the other settings, as you noticed.Another tip is to go into Dots display instead of Vectors. The sin(x)/x interpolation can cause the trace to go above the measured values.Turning the intensity down can help minimize the appearance of noise. Since you're just looking to measure DC, you can turn down the memory depth, too.This is the thinnest trace I can get out of my DS2102, and I would guess you can achieve similar results:

author: Unknown
author_rank: Unknown
timestamp: June 16, 2013, 03:28:49 am
content: Quote from: Galaxyrise on June 16, 2013, 12:16:24 amPlease Make one with 0.5mV/div.one with 1mV/divother with 2mV/div.shorted probes.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 16, 2013, 04:08:54 am
content: Quote from: JuanPC on June 16, 2013, 03:28:49 amI'm not sure what you're after; there's so many settings to mess with! With just a 50R terminator attached and no BW limit, the trace is about a division tall and the scope reports 880uVpp at 100us/div. Turning on the 20MHz bandwidth limit cuts the noise in half, the trace is about half a division tall, and the scope reports 400uVpp. Turning on Anti-Alias while displaying vectors makes the center of the noise much brighter than the outside, making the apparent trace thinner. With dots, I didn't notice a difference (though it looks like 500uV/div is done in software, zooming in on 1mV/div.) Using High Res instead of Anti-Alias results in a one-pixel trace and a reported Vpp of 100uV.Not counting HighRes (which always shows a thin line), going to larger V/div makes the trace thinner until it's like in my screenshot.

author: Uup
author_rank: Regular Contributor
timestamp: June 16, 2013, 05:56:05 am
content: @ Paul, is the following what you see on your DS4024 at 10mV/d?10mV/d no bandwidth limit10mV/d 20MHz bandwidth limited10mV/d 100MHz bandwidth limited10mV/d Averaging on (2 ave)10mV/d Hires modeI also tried with a 50ohm terminator attached and it made no noticeable difference.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 16, 2013, 06:59:48 am
content: Quote from: rf-loop on June 15, 2013, 11:15:12 amAs I have a 2102, I implicitly some bandwidth limiting. Did you want dots or vectors?Dave did show what the noise floor looks like in his DS2202 playing around video (#369, around 10 minutes in.)

author: rf-loop
author_rank: Super Contributor
timestamp: June 16, 2013, 08:19:48 am
content: Quote from: Galaxyrise on June 16, 2013, 06:59:48 am2102 have of course some amount less noise as 2202.the purpose is to see the actual analog front-end peak to peak noise level (including ADC).Peak-to-peak instead of rms noise level is what we meet with the measurements if can not use any methods for hide this noise. Of course rms numbers, depends of method, give more nice values and manufacturers like show these, if they show any number about noise levels.Agilent:http://cp.literature.agilent.com/litweb/pdf/5989-3020EN.pdf"Peak-to-peak Noise: the peak-to-peak range of noise in an oscilloscope basedon a particular criterion such as time, number of acquisitions, and/or acquisitionmemory depth.RMS Noise random noise measured asone standard deviation"It is just the same as the pulse generators, for example, where the manufacturer like to tell us the rms jitter value, but the user will have to live, however, with peak to peak values. And more fun come when they do not tell us how they have measured and calculated rms. If now need sure know what is real peak to peak example so that 99.99% of samples are all inside some value (IF distribution is gaussian true random)... well... with what number you multiply this rms value. Is it ten or more...Sure, I know that the noise images are "ugly", but it is a reality.Of course, in practice, it is possible depending on the situation, "filter" produce noise out of sight. For example, using the BW limit, or waveform average (usual average) or High-Res (other kind of averaging with low speeds as long as true to the ADC sample rate is much higher than displayed sample rate)No average, no any kind of filtering, no high res mode.Horizontal speed: 1ms/divMemory: 14M (memory depth not auto but 14M selected. Becouse acquisition peak detect there can also use example 1.4M or even less, no markable difference?)Acquisition: Peak DetectSampling: Real timeAntialising: OffCoupling: DCBW limit: OffProbe 1x (Edit: in oscilloscope menu! Probe is not at all connected, open or terminated inputs)Display: Vectors.Sin(x)/x imitation or what ever it is and all other possible after ADC user adjustable filters off (if there is any).ScopeInput BNC: Just open, nothing connected (if have 50 ohm terminator and if it makes difference, then with terminator and without) (envinroment need be quite silent about EMI)Also 50ohm terminators can use so that center pin do not make connection but still terminator works as emi shielding cap.Vertical:500uV/div1mV/div2mV/div5mV/div10mV/div(scope internal TFT images)

author: Unknown
author_rank: Unknown
timestamp: June 16, 2013, 08:49:08 am
content: Quote from: rf-loop on June 16, 2013, 08:19:48 amX1 is debatable, better to include X10 too.Probe Shorted is better.

author: Paul Price
author_rank: Super Contributor
timestamp: June 16, 2013, 10:08:59 am
content: Thanks to UUp forclearly showing the problem, especially when trying to measure mV DC signals. What good is 10mV/div sensitivity if it is swamped out by noise.But a Big Thanks again to everyone who posted pictures and comments.Ejeffrey, the idea here is toquickly visuallymake DC measurements. Setting up cursors is not going in that direction.Well, things are drifting a little off topic into ways to make some unusual noise on a DPO/DSO oscilloscope. No thanks, I have enough!I like to think my scope as being the universal measurement tool and the idea here is to very quickly visually measure various power supply and other important bias points on a circuit using the scope as a DVMand relying on a thin baseline positioned on the bottom or top graticule line with DC coupling to get an accurate voltage reading just off the graticule.This was something easy to do with my analog scope and a very useful way to quickly check out every DC voltage quite accurately on whatever circuit I am working on in just a few seconds.Having a 1 minor division or so fuzzy baseline lowers the precision of measurement by an order of magnitude. Having one full division is unconscionable.

author: rf-loop
author_rank: Super Contributor
timestamp: June 16, 2013, 11:09:12 am
content: Quote from: JuanPC on June 16, 2013, 08:49:08 amNo. If we measure oscilloscope itself front end noise 10x selection in scope do not change anything in front end. If scope inputs are open or terminated there need use 1x setting in scope probe setting menu so that numbers what scope show are ok.For this measurement do NOT connect probe.If test with probe, it is other tests what I ask.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 16, 2013, 04:34:31 pm
content: Quote from: rf-loop on June 16, 2013, 08:19:48 amI can't have vectors on but six(x)/x off. Which would you rather have, sin(x)/x or dots?

author: rf-loop
author_rank: Super Contributor
timestamp: June 16, 2013, 04:39:03 pm
content: Quote from: Galaxyrise on June 16, 2013, 04:34:31 pmOk, then dots, least 5s persistence.

author: PA4TIM
author_rank: Super Contributor
timestamp: June 16, 2013, 10:57:19 pm
content: No filtering etc, 350 Mhz Hameg just standard setup. 1mV/div 10 MHz sinewave from a HP8640 generator

author: egonotto
author_rank: Super Contributor
timestamp: June 16, 2013, 11:41:09 pm
content: Hello,almost no noise at 1mV/DIV.I am impressed.Or is it a trick?Best Regardsegonotto

author: Hydrawerk
author_rank: Super Contributor
timestamp: June 17, 2013, 12:51:25 am
content: Remember that this Hameg has only 2500 waveforms per second update rate.

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 05:39:46 am
content: Quote from: Hydrawerk on June 17, 2013, 12:51:25 amHow it is related to analog front end noise, can you explain?-------------------But also, this was not this kind of noise test what I have asked about Rigol.Why it is so difficult to do these noise tests. These do not need any equipment. Just oscilloscope.

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 06:03:19 am
content: Quote from: PA4TIM on June 16, 2013, 10:57:19 pmCan you show withoiut signal, peak acquire mode, maximum memory, 1ms/div1Mohm and 50ohm inputs, 1mV, 5mV and 10mV/div (all possible filtering off)So we get some "reference" before someone show Rigol data.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2013, 06:17:44 am
content: Quote from: Paul Price on June 16, 2013, 10:08:59 amOnce you set up a measurement you can test many values and it will just show you the value. On most scopes it takes about four button presses to set up a simple DC measurement. This seems like a really weird thing to bitch about when you are willing to go fiddling with different BW limits, acquisition modes, and averaging to get your clean baseline.

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 06:17:58 am
content: Here is tested with very cheap Siglent SDS1102CMLOscilloscope inputs just open.Filters off. (user adjustable channel DSP filters off)Acquire normal.Note that also Agilent there normal acq but cursors peak.(agilent insert picture scale is adjusted for compatible with Siglent display)Acquire peak mode.Note that Agilent there normal acq but cursors peak.Here 2mV/div can not compare to other level settings because it have fixed 20M BW.And even as you see these fat traces, this result is good and acceptable in its class.Then here is old table for Owon (old version and more new version)And also same kind of test with new Owon.Peak mode.Note that Agilent have normal acquire mode and in image also low samplerate. So image is more nice for Agilent than if it have done with same settings.There have been lot of these tests available and long time for example Siglent and Owon.But example for Rigol what is more expensive and claimed with many words about special low noise front end. But real data is difficult to find.

author: PA4TIM
author_rank: Super Contributor
timestamp: June 17, 2013, 05:40:26 pm
content: Quote from: rf-loop on June 17, 2013, 06:03:19 amWhy ? That is a rather useless test, If I have much RFI here then it will show more noise as in a surroundig where no other gear is powered on. A better test is like my picture, a very small signal from a good generator in a 50 Ohm environment. That is what you want to know, how does it performe while measuring small signals. If there was a lot of noise in my trace it could only be the scope or the generator, nothing else ( I use good mil specs cables)With open inputs I can be everything. Like comparing the readings of multimeters while connected to nothing.And no this is no trick, look at my website, there are many screenshots from real meaurements made with this scope.What you want is something like comparing cars idling while waiting for a trafficlight.

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 06:51:10 pm
content: Quote from: PA4TIM on June 17, 2013, 05:40:26 pmPerhaps it is too difficult to enclose inputs example with connected or not connected terminator.Of course tests are good to do with good generator. I use in my tests HP8644B and or HP8642B.But on thois forum there is many many peoples who do not have equipments.This test with no signal is much more comparable as tests with what ever unknown signals.Perhaps also Agilent do something wrong? They do not test with signals here.Quote from: PA4TIM on June 17, 2013, 05:40:26 pmPerhaps it is too difficult to enclose inputs example with connected or not connected terminator.Of course tests are good to do with good generator. I use in my tests HP8644B and or HP8642B.But on thois forum there is many many peoples who do not have equipments.This test with no signal is much more comparable as tests with what ever unknown signals.Perhaps also Agilent do something wrong? They do not test with signals here.Quote from: PA4TIM on June 17, 2013, 05:40:26 pmPerhaps it is too difficult to enclose inputs example with connected or not connected terminator.If you afraid fat trace come from envinroment.I recommend this test becouse most of peoples example here in forum do not have enough good signal sources. I have not problem with signal for tests, normally I use HP8644B and or HP8642B.This test without signal is simple and very easy get image about noise what is comparable.So for comparison reasons I ask if you can do it with hameg for some kind of reference.Also I wonder why we can not see tests made with Rigol DS2000 what is claimed as very low noise front end.Also I can not keep thios document as bullshit. Why they use this method without signal.http://cp.literature.agilent.com/litweb/pdf/5989-3020EN.pdf

author: PA4TIM
author_rank: Super Contributor
timestamp: June 17, 2013, 07:16:51 pm
content: From that document: Each scope was terminated into 50 OhmSo no open input

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 07:40:32 pm
content: Quote from: PA4TIM on June 17, 2013, 07:16:51 pmYes, as also I have told: 1Mohm and 50ohm inputs.I have tested only some hundreds of oscilloscopes but I have sometimes find that in some cases 50ohm terminator rise visible noise level. Specially if something is wrong in front end design or if there is example internal some special "common mode" noise. In these some cases 50ohm termonator may rise noise. There is road for internal noise current what produce voltage mainly over this 1 Mohm. I have seen this.It can very fast check if terminator add noise or reduce noise. Also sometimes can use 1Mohm termination.Agilent: "Plus, we used a 1-M? input termination rather than the original 50-? termination"But this all is not so relevant here. Only what I hope see is some well known good oscilloscope as some kind of reference for this kind of noise images.

author: Orange
author_rank: Frequent Contributor
timestamp: June 17, 2013, 07:59:19 pm
content: The Hameg 3522 is 'only' 100 MHz BW at the 1 and 2 mV... non the less, the signal looks really clean even for a 100MHz BW.Tim, did you use averageSorry to be mean Tim, to be honest my Rigol has more noise in the 1mV range.The Rigol DS2072 with BW hack does 250MHz at 1mv- Orange

author: PA4TIM
author_rank: Super Contributor
timestamp: June 17, 2013, 08:08:43 pm
content: RF-loop:I think you do not understand what they write. They do not use the 50 Ohm open input, They terminate the the inputs with 50 Ohm.I do not care how many hunderd scopes you have tested. Quantity is not the same as quality. Just make the pictures you want if you do so much testing that must be no problem I guesOrange: I did not use avarage. The Hamegs have one of the lowest noise floors. They also have a real 1 mV range, most scopes only have a software <5mV range. They measure in the 5mV position but the software zooms in to 1mV

author: rf-loop
author_rank: Super Contributor
timestamp: June 17, 2013, 08:21:32 pm
content: Quote from: PA4TIM on June 17, 2013, 08:08:43 pmOf course I know what they did. But you do not now perhaps understand what I mean.But, why it is so difficult to show this test result. If Hameg is (and it is) good, why we can not use its test result as some kind of reference.Of course we all want look nice clean sinewaves but... I wonder why it is so difficult to show this tests result what even do not need any external equipment. But, also I wonder butterflies.

author: Orange
author_rank: Frequent Contributor
timestamp: June 17, 2013, 08:28:26 pm
content: Quote from: PA4TIM on June 17, 2013, 08:08:43 pmThe 1mV and 500uV range on the Rigol is also a 'real' full ADC range, no up-scaling used on this model. In fact I have not seen this anymore since decades. The last scope if seen that used up-scaling on low ranges was a Tek 468, one of the first digital scopes I used.... (1983 i think....)- Orange

author: PA4TIM
author_rank: Super Contributor
timestamp: June 17, 2013, 08:32:24 pm
content: But, why it is so difficult to show this test result. If Hameg is (and it is) good, why we can not use its test result as some kind of reference.I have good (medical) reasons, that is all I want to say about it.

author: Paul Price
author_rank: Super Contributor
timestamp: June 17, 2013, 09:34:30 pm
content: Galaxyrise,Thanks, I think the memory depth is not adj able on the DS4024 with most time base settings and if I could adj. it, it would take convenience out the back door.I don't want to press and twiddle and fudge around if I get an urge to quickly measure some DC voltages.

author: tinhead
author_rank: Super Contributor
timestamp: June 18, 2013, 02:21:07 am
content: Quote from: PA4TIM on June 17, 2013, 05:40:26 pmright, such test (assuming no signal connected to DSO, no external termination nor bnc shielding = open inputs ) is onlyusefull when comparing DSOs at same day/location/temp. and even operator. Therefore a compare like "my DSO is having this,so better than TEK but not such good as Agilent" is complettly useless, unless someone have of of these models fromAgilent app note and have exact same readings on such DSO - then, and only then, a compare to XYZ models make sense.Btw, your proposal to test with signal is exact that bad as with no signal, as there is no situation (except channel grounded)with no signal. And when using "defined" signal source you have still lot of differences due location/temp./operator etc.and of course model.So whatever you choose it's ok, as long you test more than one DSOs at time and compare results, a single measur ofsomething done somewhere by somebody at some time is useless, it is like "my dick is longer" (and everybody on earthknow that i have the longest).Quote from: PA4TIM on June 17, 2013, 08:08:43 pmfrom the Agilent document :"Each scope was terminated into 50-? and was set up to acquire waveforms with no input signal connected,using each scope’s maximum specified sample rate"hmm, terminated into can be as well "internal 50R termination enabled", but anyway, as said above this didn't reallymatter as we can't compare other DSOs to their in Agilent app note."using each scope maximum sample rate" is as well trap, however Agilent did it properly and (at least for peak-to-peak measurments)did it 10 times and used avg vales. But still, this is 2.5 to 10GS/s span and 8 to 32Mpoint of data, you can see here everythingbut not what really the noise is (the DSO with 10GS/s and 32M will pickup more peak-to-peak events than a 8M/ 2.5GS/s DSO).It is as ell important, when comparing this way, to check what is the memory depth at specific timebase when specific samplerate enabled.Quote from: PA4TIM on June 17, 2013, 08:08:43 pmoh well, Hameg is at least using this as sales argumentation. I give you example of cheap chinese DSO (Tekway/Hantek)set to not filter anything up to 500MHz (yes, the firmware can be forced to not use any filter), with 250MHz bw at 2mV/DIV.The signal didn't look bad (except the interleave distortion), not that far from what on Hameg.But there is small extra difference, you would have to zoom to see it, Hameg is using the same amount on vertical DIVas this chinese DSO, the resulting line looks thiner because Hameg is drawing half of the dots bit darker.I like it, it looks "analog" to me.Agilent/Rigol is using completly different way to draw waveform, their signal can be compared to Hamegwith persistency full on. But here again chinese DSO example, the baseline (not open input but external terminated with 50R)looks thin. With infinite persistency it looks however thick, with bit of persistency (0.2s) it looks still thicker as without any persistance, and that is what you can see on Rigol/Agilent (intensity grading / shading combination looks similar to otherDSOs with persistency on).So it's not (only-if any and not only marketing thing) lowest noise floor, but as well question how the UI designer decidedto draw waveform. Therefore it is better to compare Vrms of noise than line thickness.TO: The whole question "How Thick is Your Baseline on Your Digital Oscilloscope?" with combnation of "i wish to use it as DMM"is anyway crazy, who is using DSO as DMM? How can i casre about line thickness when the DSO inaccuracy is by 2-3% of full scale?

author: robrenz
author_rank: Super Contributor
timestamp: June 18, 2013, 02:48:49 am
content: Yeah its only 1MHz bandwidth but its pretty7A22 diff. amplifier both inputs grounded in a 7603 at 10µV/div.

author: Paul Price
author_rank: Super Contributor
timestamp: June 18, 2013, 10:20:56 am
content: Some people here are saying the problem is me, not the scope...I disagree!O: The whole question "How Thick is Your Baseline on Your Digital Oscilloscope?" with combnation of "i wish to use it as DMM"is anyway crazy, who is using DSO as DMM? How can i casre about line thickness when the DSO inaccuracy is by 2-3% of full scale?---------------------------or the quoted reply below:-------------------------------------------------------------------"Once you set up a measurement you can test many values and it will just show you the value. On most scopes it takes about four button presses to set up a simple DC measurement. This seems like a really weird thing to bitch about when you are willing to go fiddling with different BW limits, acquisition modes, and averaging to get your clean baseline."=========================================================================================I say again, for the nth time:What I often like or really need to do to analyze or troubleshoot a circuit is get a very quick overview of a circuit's operation, often DC voiltage at different critical points.This is especially importantin repairing equipment and with breadboarding complicated new designs.I don't need DVM accuracy so much asinstant feedback,I need an oscilloscopewith a 10x shielded probe to get a readout of DC levels to get an idea every expected voltage is showing the circuit is working as expected, and a quick idea if there is any signal or noise present that is unexpected, showing if everything is working as expected or is it that I have some defect in my wiring or some IC's operation.This is a very valuable, time-saving, efficient test strategy for me.

author: Paul Price
author_rank: Super Contributor
timestamp: June 18, 2013, 10:32:05 am
content: Thanks again to UUp for clearly showing the problem, especially when trying to measure mV DC signals. What good is 10mV/div sensitivity if it is swamped out by noise.Pa4tim:I would very much appreciate to see a flat line display of the Hameg. It looks too good to be true. Is there any chance of anyone making a short video showing use of the this Hameg low-noise scope measuring a few DC voltages around a simple circuit..without any special effects settings...just using this scope without averaging or hi-res mode?***************************************************************************************************O: The whole question "How Thick is Your Baseline on Your Digital Oscilloscope?" with combnation of "i wish to use it as DMM" is anyway crazy, who is using DSO as DMM? How can i casre about line thickness when the DSO inaccuracy is by 2-3% of full scale?---------------------------or the quoted reply below:-------------------------------------------------------------------"Once you set up a measurement you can test many values and it will just show you the value. On most scopes it takes about four button presses to set up a simple DC measurement. This seems like a really weird thing to bitch about when you are willing to go fiddling with different BW limits, acquisition modes, and averaging to get your clean baseline."===============Or this from the most quiet Hameg reply =============================================What you want is something like comparing cars idling while waiting for a trafficlight.=========================================================================================I say again, for the nth time: To work on a circuit I want to,as quickly as possible, jump around different test pointsand see what is going on.What I often like or really need to do to analyze or troubleshoot a circuit is get a very quick overview of a circuit's operation, often DC voiltage at different critical points.This is especially importantin repairing equipment and with breadboarding complicated new designs.I don't need DVM accuracy so much asinstant feedback,I need an oscilloscopewith a 10x shielded probe to get a readout of DC levels to get an idea every expected voltage is showing the circuit is working as expected.I want a quick view to get an idea if there is any signal or noise present that is unexpected, showing if everything is working as expected or is it that I have some defect in my wiring or some IC's operation.This is a very valuable, time-saving, efficient test strategy for me.

author: Paul Price
author_rank: Super Contributor
timestamp: June 18, 2013, 11:09:31 am
content: I wonder how much this costs.

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 11:13:42 am
content: Quote from: rf-loop on June 15, 2013, 11:15:12 amPlease could someone attach these images. Thanks.

author: SLJ
author_rank: Frequent Contributor
timestamp: June 18, 2013, 01:44:10 pm
content: Don't really care much about the baseline display for my use. I bought it for the waveform measurements at a glance. If I want to see a good waveform displayed I'll use my analog scope.What I would like to see is an option to choose to display maybe three or four measurements on the display at once in a large font like DC Volts, AC Volts, and Frequency at the same time along with a tiny waveform. More like a souped up DMM. Right now I have to sort through a table of around 16 measurements, most of which I don't care about.

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 02:08:54 pm
content: Quote from: Carrington on June 18, 2013, 11:13:42 amThis is the closest thing to this that I found in the eevblog. Please could someone attach more images.rf-loop: What are you trying to prove?

author: grenert
author_rank: Frequent Contributor
timestamp: June 18, 2013, 02:29:59 pm
content: To the OP:Clearly this is important to you, and it sounds like money is not a primary limitation here. Why not just demo a few of the instruments that seem most promising and see for yourself?

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 02:41:10 pm
content: Quote from: grenert on June 18, 2013, 02:29:59 pmWhat or who is OP?

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 18, 2013, 02:44:11 pm
content: Quote from: Carrington on June 18, 2013, 02:41:10 pmOriginal Poster. In this case Paul Price.

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 02:46:37 pm
content: Quote from: dfmischler on June 18, 2013, 02:44:11 pmOK thanks

author: rf-loop
author_rank: Super Contributor
timestamp: June 18, 2013, 02:55:17 pm
content: Quote from: Carrington on June 18, 2013, 02:08:54 pmProve something?No need prove anything.But many times we have seen measured risetimes, bandwidths, etc.Just for data. Of course I'm also interest about oscilloscopes, new and old, noise levels, as much as BW, risetimes, accuracy, sampling speeds, how they use memory, etc. All things. Noise is just one.Also, we have seen many many times when entry level and also experienced users are wondering digital scopes noise and if it is normal or not and if it is problem.If we can here really see reality of digital scopes normal things, and if also possible, measured or tested with some kind of comparable methods, it is just informative and may lead to better understanding.I do not wonder at all these Rigol images. They are just normal.But it is also nice if can see some low noise oscilloscope for some kind of reference.Just for better knowledge.Also we have seen lot of normal condition other oscilloscopes noise levels here and also oscilloscopes what have some real problem.Also, it is good for information.This is not some kind of agenda for proofing something.Knowledge is also good for beginners so they do not be so much disappointes if they have wrong dream before buy entry level new oscilloscope. It is just good to know what is normal and what is problem.Also some peoples have experience with analog scopes, then buy first digital oscilloscope and first day they are amazing why my digital scope trace is so noisy. This same noise is also in analog scopes (nearly). Just it can not see becouse phosphor do its work for hide it.This is one very common question: Why my digital scope is so noisy.

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 03:05:19 pm
content: Yep rfloop. Where does this noise come? What to do to mitigate it?And of course would be very interesting a comparison between oscilloscopes, under conditions as similar as possible.Between SDS7102V and DS2072. Which of the two you think is less noisy?

author: rf-loop
author_rank: Super Contributor
timestamp: June 18, 2013, 03:41:50 pm
content: Quote from: Carrington on June 18, 2013, 03:05:19 pmI do not have enough comparable data for this but my suspect is that DS2102 have some amount less noise. But not very big difference. (of course I talk Owon what do not have this special noise issue)

author: Carrington
author_rank: Super Contributor
timestamp: June 18, 2013, 04:07:20 pm
content: Quote from: rf-loop on June 18, 2013, 03:41:50 pmI hope someone adds more images to compare.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 19, 2013, 05:17:34 am
content: Quote from: rf-loop on June 16, 2013, 04:39:03 pmSorry for the delay. When I set up the suggested test, I got a result that I'd never seen before and I wanted to spend some more time playing with it. It seems I've finally found a case where Anti-Alias actually removes waveform aliasing! But without it, the display is really quite ugly. I used infinite persistence so it would use the two-tone persistence, and then waited 5-10s before pausing the scope and taking the screenshot. The persistence really makes the traces look heavy; it's probably not fair to compare these to any non-persistence captures.The trace gets to its thinnest at 20mV and then stays there as the V/div goes up. It's intriguing 10ms and 5ms have the same apparent noise. The only way to get a truly thin trace is with high res. I still feel like I must have messed something up; anyone else see that strange aliasing on theirs? Until this test, I'd only run into images that look like the DS2000 images previously posted in this thread.

author: Carrington
author_rank: Super Contributor
timestamp: June 19, 2013, 12:08:05 pm
content: Thank you very much "Galaxyrise". That is just ok.These signals do not have anything wrong.I know, it sounds absurd, but please: Can you do the same test but now connecting both terminals of the probe together (ie live/central and ground wire) to the ground lug of the Probe Comp. terminals.I want to compare the result with a similar test on the SDS7102V.Thanks.

author: Carrington
author_rank: Super Contributor
timestamp: June 20, 2013, 03:44:43 pm
content: Please can someone do the same test but now connecting both terminals of the probe together (ie live/central and ground wire) to the ground lug of the Probe Comp. terminals.Thanks.

author: Unknown
author_rank: Unknown
timestamp: June 20, 2013, 04:57:35 pm
content: That would make a decentmagnetic loop probe. Are you trying to detect stray fields or trying to measure front-end/ADC performance? In the latter cause you should use a proper low-inductance RF short (eg. BNC shorting cap, or tinfoil across the probe as Dave did in one of his early 'unusual oscilloscope phenomenon' videos). Preferably one without a few feet of coax with shielding of dubious quality. I find a 50 ohm terminator useful in a pinch, it's well shielded and fairly close to a short compared to the scope input at low to moderate frequencies.

author: marmad
author_rank: Super Contributor
timestamp: June 26, 2013, 09:12:51 am
content: Quote from: Paul Price on June 17, 2013, 09:34:30 pmNo offense, but if you believe this comment you wrote, you seriously need to figure out how to use a DSO properly. Not only does this affect the sample rate, but it will affect (usable) bandwidth and visible noise as well.

author: marmad
author_rank: Super Contributor
timestamp: June 26, 2013, 09:37:51 am
content: Quote from: Orange on June 17, 2013, 08:28:26 pmThe Agilent X-Series use scaling - their real resolution is to 4mv/div (1mv/div and 2mv/div are 'magnified').

author: Carrington
author_rank: Super Contributor
timestamp: June 27, 2013, 05:30:38 pm
content: Quote from: alm on June 20, 2013, 04:57:35 pmHi alm!I just want to make a comparison between the SDS7102 (unshielded case) and DS2072 (shielded case).And to do this under similar conditions:1) Take all probes and LAN or USB cables off of the scope and do a self calibration.2) Preferably the scope should be away from other noise sources such as fluorescent lights, computers, switching power supplies, etc.3) Connect a probe to the CH1 BNC and make sure it is properly compensated. Make sure the probe switch is set to x10.4) Connect both the probe and the 6.5" ground wire to the ground lug of the Probe Comp terminals.5) Set up the scope as follows:CH1:Coupling = ACProbe: Attenu = X10Limit = Full BandVolts/Div = 50.0mVVert Pos = 0.00divHorizontal:Horiz = MainHoriz Pos = 0.00nsSec/Div = 500µs or 1msTrigger:Type = SingleTrigMode= EdgeSource = CH1Coupling = ACSlope = /Mode&Hold = Auto, Holdoff = 100nsLevel = 0.00mVAcquire:Mode = Similar to Peak DetectMemory Length = MaxThank you very much.

author: rf-loop
author_rank: Super Contributor
timestamp: July 01, 2013, 08:17:46 pm
content: Here picture with Owon(inside pictures also Rigol (from Galaxyrise pictures) and level adjusted for same size div's)Owon input open. Capture mode peak. (so it use 1GSa/s data)(owon screen size is 800x600, image resized)

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: July 02, 2013, 06:21:48 am
content: Quote from: rf-loop on July 01, 2013, 08:17:46 pmVery similar! Did you have persistence enabled on the Owon? I'm guessing you did not, and that's why the Rigol line is more "blurry"

author: rf-loop
author_rank: Super Contributor
timestamp: July 02, 2013, 08:15:01 am
content: Quote from: Galaxyrise on July 02, 2013, 06:21:48 amVery similar? Nearly 50% more is very similar?No persistence on in Owon.But persistence do not add detected peak values. Rigol images did not have mesurement on display so it can not see with numbers but still brightest part of Rigol trace is more fat than Owon.It is not competition and difference is nearly marginal and I do not mean proof anything.... but I'm wondering Rigol advertisements where is"...to deliver an extremely low noise floor to help you capture smaller signals."Can we now advertise Owon that it have very extremely low noise floor.but Rigol advertised claims about special low noise is just ad without nothing more but just empty words. And this is "fun".(we also know that Rigol front end is nearly copy from Owon, but perhaps from earlier Owon.. )How can advertise low noiseif there is 500uV/div what have around 1000uV noise. But building of the imagination is advertising professionals work. And it looks like Rigol is very good in this.I have heard example total bullshits that Rigol DS1000E series signal capturing quality is better than Owon SDS. Of course these kind of opinions without facts are too easy to shoot down with raw data. Totally other question is who is listening becouse religions make it difficult. Very easy it happends that mind manipulating falses start live they own life. It is so easy to tell just like this cup is half of empty, but this cup is half of full, I take this last one.It just so simple case that Owon have some marginal amount less noise. It is natural also technically becouse SDS7102 have some amount less ADC noise. Rigol (DS2000) is with 2GSa/s (2x1G) ADC and Owon use 1GSa/s (2x500M) ADC but also it looks like Rigol use RuiFeng ADC (what also Owon have used previously). (not big difference but part of decibel here and part there etc.. it makes finally some amount less noise. But also it is good to note that Owon BW -3dB point is over 170MHz. Also Owon discrete fet front end (previously dropped out one noisy and hot amplifier) have less noise than old precessor.

author: marmad
author_rank: Super Contributor
timestamp: July 02, 2013, 11:35:04 am
content: Quote from: rf-loop on July 02, 2013, 08:15:01 amReally, rf-loop - this is all rather silly. There is no point in comparing these two scopes because the DS2000 is so vastly superior (and more expensive, of course). Whether the base line noise of one is slightly larger than the other - when you don't use any special features which have been added specifically to reduce noise - is like comparing a really fast car to a slow car and saying. 'Let's compare the speed if you don't press the accelerator of the fast car all the way down.'Instead, let's compare the noise level of the two scopes while using High-Res mode. Oh wait, the Owon doesn't do High-Res - or almost any of the dozens of features, speed, intensity grading, etc. of the Rigol. When it DOES do those things, then let's do a comparison.In the meanwhile, if you want to say that the Owon has slightly less base line noise while doing 35 wfrm/s and no other processing - fine. Unfortunately, I can't make my Rigol capture so few wfrm/s.And, of course, this doesn't even cover ALL of the bad posts/complaints here over problems with noise in certain versions of the SDS7102. Where are the similar complaints of design/manufacturing defects in the Rigol?Quote from: rf-loop on July 02, 2013, 08:15:01 amRigol BW -3dB point is over 175MHz in images posted by GalaxyRise.