Show us your noise floor - Page 1
Forum section: electronics / testgear

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 05, 2024, 08:13:17 pm
content: Hi group,The recent introduction of the Keysight HD3 series of oscilloscopes has prompted a discussion on noise floor.Please share your oscilloscope's noise floor here.To get this started:Tektronix MSO46 4-BW-500Sample mode, full bandwidth, 1mV/divHi-Res Mode 1mV/divHi-Res Mode 5mV/divRegards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 05, 2024, 08:40:39 pm
content: Hi, adding to the threadTektronix MSO24 2-BW-500This scope does not have an internal 50termination. This is with input open.And with the high-res mode turned on:Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 05, 2024, 08:44:53 pm
content: Hi,Tektronix MDO4104-3 1 GHz scopeAnd with the high-res mode on:Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 05, 2024, 09:04:52 pm
content: Hi,Agilent DSO-X 3034A (with BW50 500 MHz option)And with the high resolution turned on:I have run out of scopes. Please share yoursRegards,Jay_Diddy_B

author: sonpul
author_rank: Regular Contributor
timestamp: September 05, 2024, 09:26:46 pm
content: Siglent SDS1202X-E

author: Aldo22
author_rank: Super Contributor
timestamp: September 05, 2024, 10:00:46 pm
content: Quote from: Jay_Diddy_B on September 05, 2024, 09:04:52 pmThe $150 Hantek DSO2000 is probably not comparable, but here it is anyway.Normal Mode, 400kPtsHR Mode

author: Fungus
author_rank: Super Contributor
timestamp: September 05, 2024, 10:09:11 pm
content: Rigol DHO804: RMS ~66uV

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 05, 2024, 11:07:14 pm
content: Here's my SDS2504X HD.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 07, 2024, 12:29:36 am
content: SJL Gigawave 6400 prototype showing both normal and probability distribution modes.

author: hpw
author_rank: Frequent Contributor
timestamp: September 07, 2024, 08:18:20 am
content: Here some 8 / 12 / 14 bit simulations with 64K / 1M / 16M FFT & "von Hann FFT Window" and without any averaging.So be carefully to compare FFT noise floor with various FFT size settings. Even used detectors algorithm.

author: Furna
author_rank: Frequent Contributor
timestamp: September 15, 2024, 12:38:07 pm
content: Siglent SDS824X HDNoise 20M 5mV-1mV.pngBW 20MHzPP215 set 10X: CH1 1M andCH2 50Ωexternal terminator feed through. Vertical at 5.00 mV (limit when 10X)Elditest GE2501 set 1X: CH3 1M andCH4 50Ωexternal terminator feed through. Vertical at 1.00mVNoise 200M 5mV-1mV.pngBW 200MHzPP215 set 10X: CH1 1MΩ andCH2 50Ωexternal terminator feed through. Vertical at 5.00 mV (limit when 10X)Elditest GE2501 set 1X: CH3 1MΩ andCH4 50Ωexternal terminator feed through. Vertical at 1.00mV

author: Furna
author_rank: Frequent Contributor
timestamp: September 16, 2024, 07:01:57 pm
content: Siglent SDS824X HDNoise floor.png

author: trackersoft
author_rank: Contributor
timestamp: September 18, 2024, 07:08:24 pm
content: Tek 784A all inputs at 50 Ohm 1 mv

author: hpw
author_rank: Frequent Contributor
timestamp: February 27, 2025, 03:13:12 pm
content: My SDS2KX Plus FFT Noise on 10bits... not flat as an SA, means spurs seen...BTW: Hopefully a HD3 owner jumps in

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2025, 09:30:11 am
content: Quote from: hpw on February 27, 2025, 03:13:12 pmUnrealistic expectations maybe?It is a scope with 8 bit ADC.And then a try to compare it to a device that costs 20x more and has 14bit ADC..No need for pictures. I will tell you. HD3 is better. You should go and buy it.Just don't be disappointed that HD3 does not have 130dB dynamic range...Your expectations are a tad unrealistic. As you correctly say yourself, scope is NOT an SA.SA has different architecture and is made for different purpose.SA sucks at showing time domain data though..Tool for the job.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 06:00:43 pm
content: Not sure I am playing right. In the basement against 8 feet of dirt on 3 sides. All power to switching supplies of any sort are on a separate wall strip that is turned off. Only lites are ceiling LED (no diff between on and off) and an incandescent. All TE is on a second power strip and the switching psu (Riden) has its master switch off.No furnance or solar inverters clicking (but the main panel IS about 15 feet from me.Did a scope calibration and checked each probe for calibration.Note: There is a typo in the pic caption.Using LeCroy PP018s.Seems high compared to other Siglents shown, but what do I know.

author: tautech
author_rank: Super Contributor
timestamp: March 01, 2025, 07:20:16 pm
content: Quote from: watchmaker on March 01, 2025, 06:00:43 pmLooks like a SMPS wallwart nearby.....could be yards away.Even above in another room.Zero in on the noise frequency with a trigger setting for clues and expect to see something in the 20-30 kHz range....

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 07:45:30 pm
content: Quote from: watchmaker on March 01, 2025, 06:00:43 pmTurn on the 50 ohm input termination and measure in RMS.

author: awesomechapro
author_rank: Contributor
timestamp: March 01, 2025, 08:04:47 pm
content: Scope: Tektronix TDS3052B 500MHz, 5GS/s, 10K pts scopeSettings: 50Ω terminated, 1mV/Div, 1ms/Div, waveform intensity at maxMeasuring: 152μV RMS, 1.06mV Pk-Pk

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 09:21:21 pm
content: Quote from: tautech on March 01, 2025, 07:20:16 pmOh Hell. I will look in the AM, but yrs, I forgot about some not often used warts. Will get back. What is this about a 50option on the SDS 824??

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 09:53:36 pm
content: Sorry, I did not realize it was an SDS824, I saw the SDS5xx and made the assumption it was a high end unit.Never mind the 50ohm thing, but you are measuring peak to peak. For random noise Vpp is ~8*Vrms. Also, since you might have a DC offset, set up your measurement to Stdev. That will take out the DC offset.

author: egonotto
author_rank: Super Contributor
timestamp: March 02, 2025, 02:17:55 pm
content: Hello,Agilent DSO6104LBest regardsegonotto

author: watchmaker
author_rank: Unknown
timestamp: March 02, 2025, 02:20:14 pm
content: Quote from: tautech on March 01, 2025, 07:20:16 pmOK. I used the Siglent as a sniffer.All downstairs lights off.Both Power strips at the bench: OffMouse bluetooth removed and mouse: OffWiFi: OffSiglent plugged into outlet in another room (made no difference)LeCroy PP018 probe (only 10X).I still get a 60Hz signal carrying 1.25 KHz spikes. See pic.Checked NO probe: Still 500uV when input is set to 1:1.BUT, the hum disappears.The maddening thing is I am in a very rural area (12 acre lots) and the nearest neighbor is about 1 kilometer away (for you non imperials!)Amy thoughts/advice would be appreciated. I would hate to think I am stuck without building a Faraday cage! I AIN'T moving! (except maybe to seek asylum in Canada).THANKS!!!!

author: egonotto
author_rank: Super Contributor
timestamp: March 02, 2025, 02:45:44 pm
content: Hello,PicoScope 4262 with 50 Ohm terminating resistor, otherwise the results would be worse.Best regardsegonotto

author: BillyO
author_rank: Super Contributor
timestamp: March 02, 2025, 03:37:06 pm
content: Here are some of my scopes.SDS2504X+ in 10-bit modeSDS2504X+ in 8-bit modeSDS824X HDSDS1204X EHANMATEK DOS1104. This is an ultra cheap (<$200) 4ch. scope that is surprisingly good for the money. It does not have Stdev measurement so I did in Vpp to keep out any DC offset. 152uVpp is about 32uV Stdev for random noise!! Not too shabby.Adding in my FNIRSI 2C53T. Don't know how accurate the measurements are at these low levels, but that 840uVpp would be about 128uVrms assuming random noise.

author: watchmaker
author_rank: Unknown
timestamp: March 02, 2025, 04:36:15 pm
content: Oh Hell again!I am using Vp-p! and it looks like I should have been using STDEV.Will be back after a drink.Nope. Still way high. 2mV mean STDDEV.

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2025, 07:33:48 pm
content: Quote from: watchmaker on March 02, 2025, 02:20:14 pmGood, much as expected but something is still going on as there is still some PWM chirp on the waveform.When just a probe is fitted you have added a antenna and even though it's a 10x probe, a 10mV/div setting is actually at 1mV/div scope setting.What matters more is do you see this HF chirp when taking a measurement ?Try the probe comp output.We had a customer that was convinced his scope was faulty but after my insistence it wasn't (briefly checked before dispatch) a unknown of wallwart was discovered behind a curtain which solved the noise mystery.BTW, use the Save button on the top front panel for USB screenshots but in PNG format and Path Tips set to 3s Fade.

author: 2N3055
author_rank: Super Contributor
timestamp: March 02, 2025, 08:00:13 pm
content: Quote from: watchmaker on March 02, 2025, 04:36:15 pmI see there is a confusion. Or I think there is.Scope noise floor is with nothing connected to input and input set 1x probe...As soon as you connect probe you have giant antenna and 10x attenuation will make noise 10x larger....

author: watchmaker
author_rank: Unknown
timestamp: March 02, 2025, 08:20:48 pm
content: OOOHHHHH!I will get back. THANKS!

author: watchmaker
author_rank: Unknown
timestamp: March 02, 2025, 08:44:59 pm
content: Quote from: 2N3055 on March 02, 2025, 08:00:13 pmAs Dave likes to say "winner, winner, chicken dinner".50uV. I KNEW it had to be user error (loved the Fortran message "Possible bad operator".)

author: 2N3055
author_rank: Super Contributor
timestamp: March 02, 2025, 09:31:19 pm
content: Quote from: watchmaker on March 02, 2025, 08:44:59 pmforgot that one....

author: armandine2
author_rank: Frequent Contributor
timestamp: March 02, 2025, 09:47:57 pm
content: ... definitely no probe attached, and set to x1G W Instek MDO-2302Awill have to read manual regarding std.dev

author: awesomechapro
author_rank: Contributor
timestamp: March 03, 2025, 07:47:57 am
content: I've ran into a similar problem before, and it almost drove me nuts. Ultimately I ended up leaving my scope plugged in, and turned of my breakers one by one until I narrowed it down to one circuit. Then went around to all the plugs in that room, and turned them off one by one, until I found the culprit. Could be worth a try in your case?

author: Fungus
author_rank: Super Contributor
timestamp: March 03, 2025, 08:57:43 am
content: Quote from: awesomechapro on March 03, 2025, 07:47:57 amShould be thefirstthing you do, not something you "end up doing".

author: watchmaker
author_rank: Unknown
timestamp: March 03, 2025, 11:41:01 am
content: Since I opened this can of worms, I should provide some closure.My partner for the STEM project discussed in the Beginner sub is a top licensed Ham who is using 3 watt digital transmitters to "communicate" 13,000 miles.I sent him my original incorrect (for the purposes of this topic) screenshot showing 2-50mV traces with a 60Hz carrier and 1.25kHz spikes.He told me that is about what he gets in 60% of house that is not fortified against RF. At least at my bench it is around 2mV with the overhead LED light and the bench wallwart supply strip off.Also, I cannot receive FM in the lab area whereas I get very nice reception from collapsible antenna in all other parts of the house.So, as Tautec intimates, it likely does not interfere with my misuse of the Siglent scope.So not only was I applying the wrong statistic and method (thanks all), but I likely was chasing a red herring. AND, I should have realized the antenna thing about the probe given I made a Carlson probe that works to 24 MHz.Gotta start integrating instead of differentiating!

author: jonpaul
author_rank: Super Contributor
timestamp: March 03, 2025, 11:53:26 am
content: calssic TEK analog scopes far superior to the digital, especially the Chinese.Bewar of "marketing bits" that are claimed but unuseableJon

author: egonotto
author_rank: Super Contributor
timestamp: March 03, 2025, 01:04:40 pm
content: Quote from: jonpaul on March 03, 2025, 11:53:26 amHello,is that really the case, or is the noise just less visible?Best regardsegonotto

author: BillyO
author_rank: Super Contributor
timestamp: March 03, 2025, 02:47:14 pm
content: Quote from: jonpaul on March 03, 2025, 11:53:26 amGoing through what's been posted, the better Chinese scopes seem significantly better than most the "US" brands and as good as some costing in excess of 10x.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 03, 2025, 04:22:48 pm
content: The following timestamped video shows the Siglent 7000 series.https://youtu.be/zfPYjUXzVy0?t=614

author: 2N3055
author_rank: Super Contributor
timestamp: March 03, 2025, 05:22:20 pm
content: Quote from: joeqsmith on March 03, 2025, 04:22:48 pmIt does says experimental test data..And by mistake, Chris used RMS instead of StDev so DC offset was included.Noise is better than that:(SDS7404A scope, 1mV/div, 1ms/div)No ERES : 206,6 µV1 Bit ERES : 104,0 µV2 Bit ERES : 54,5 µV3 Bit ERES : 32,6 µV4 Bit ERES : 23,6 µV

author: egonotto
author_rank: Super Contributor
timestamp: March 03, 2025, 05:45:51 pm
content: Hello,With ERES 4, the SDS3000X HD is worse at 28 uV. With ERES 2 it has about 39 uV.Best regardsegonotto

author: KungFuJosh
author_rank: Super Contributor
timestamp: March 03, 2025, 06:24:28 pm
content: Quote from: 2N3055 on March 03, 2025, 05:22:20 pmHow is it at 1V/div? Does that have the 20M filter active? If not, how is it with the 20M filter?Thanks,Josh

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: March 08, 2025, 01:23:49 am
content: Here's my SDS824X HD, first with a 50-ohm terminator, then with the input open. Not sure what it all means but I tried to get the setup as close to an earlier post as possible.

author: coppercone2
author_rank: Super Contributor
timestamp: March 08, 2025, 01:32:53 am
content: its invite only

author: Smokey
author_rank: Super Contributor
timestamp: March 08, 2025, 03:02:31 am
content: what... no one has a tek camera "screen capture" to post from a 500 series?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: March 09, 2025, 01:11:16 pm
content: Though I recently got rid of my Tek boat anchors and I don't have any film for my Polaroid scope camera, this brings up something I've been thinking about. The wonderful high gain plug-in for the 500 series was the 1A7A. It went down to something like 10 uV/div. It, of necessity, also had adjustable high and low pass filters. It's maximum BW as only 1MHz. A noise measurement has to have a defined bandwidth. Without that it's meaningless. We're looking at the full BW noise of these scopes but we're usually measuring some DUT with far less BW. I'd think you'd want to set up a filter to define the measurement and to get a number that's more applicable to the majority of bench work. OTOH, I don't know enough about the architecture of digital scopes to know if they follow the same rules as analog.

author: cgroen
author_rank: Unknown
timestamp: March 09, 2025, 03:43:39 pm
content: SDS6204A (2 GHz)50 Ohm, 1mV/1mS/HighRes/stddev (can try other settings if needed)

author: ptluis
author_rank: Frequent Contributor
timestamp: March 10, 2025, 04:37:50 pm
content: I see different ways of measuring noise floor, some use 50ohm termination, others short the bnc, other remove all bnc connections, and so on.So I wonder what could be the proper way of measuring noise floor of a scope?For vertical range we should set the lowest possible, some goes to 500uv, others 1mv, 5mv, etcWhat about timebase? not everybody uses the same!Measurements Pk-pk, STdev, RMS?Well is there a consensus about a "universal" way of proper testing?I would like to read your thoughts about it.

author: colorado.rob
author_rank: Frequent Contributor
timestamp: March 10, 2025, 08:38:15 pm
content: Siglent SDS2204X (not plus, not HD). Measurements appear to be made before ERES, so there is no difference in measurement values with ERES on.

author: ptluis
author_rank: Frequent Contributor
timestamp: March 11, 2025, 01:10:05 am
content: The procedure to check the noise floor on the Siglent SDS1202X-E is explained in the attachment I posted here. This procedure is from the official Siglent service manual.

author: ptluis
author_rank: Frequent Contributor
timestamp: March 11, 2025, 02:26:45 am
content: And this is the procedure to measure noise floor for Siglent SDS1104X-E and SDS1204X-E, from official Siglent service manual

author: BillyO
author_rank: Super Contributor
timestamp: March 11, 2025, 10:04:45 pm
content: Quote from: ptluis on March 10, 2025, 04:37:50 pmStdev is the preferred way as it will not incorporate any small DC offset voltages. RMS does incorporate DC voltages. You can use Vpp and divide by 7 or 8 (I don't remember which). Depends on the nature of the noise. It needs to be truly random and not be picking up any LED noise or something else with a definite period.So Stdev is the only practical way to do it.

author: dzseki
author_rank: Frequent Contributor
timestamp: March 11, 2025, 10:49:44 pm
content: Quote from: Smokey on March 08, 2025, 03:02:31 amNot a Tek, but a trusty old HP 1720A50 Ohm, 10mV/div, full BW (275MHz), the best I can do...just for the record, it looks the same with the 20MHz BW limit on too