Low Noise (Sound) Oscilloscope - Page 1
Forum section: electronics / testgear

author: Morgan127
author_rank: Contributor
timestamp: May 14, 2018, 06:55:24 pm
content: Hi All,have anyone found a good oscilloscope that is silent. I really can't understand why all scope is so noisy (at least the one I got).It should be something like 200Mhz 4 Ch.TTI has some nice PSUs that is absolute silent.Cheers

author: glarsson
author_rank: Frequent Contributor
timestamp: May 14, 2018, 07:17:10 pm
content: Quote from: Morgan127 on May 14, 2018, 06:55:24 pmYes. It is amazing how much power can be had from a stack of two TSX3510P and two TSX1820P. In complete silence.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 14, 2018, 07:50:03 pm
content: I think they just aren't prioritizing it and end up with mediocre fans or an air path that's full of hard edged baffles. Since it doesn't seem to be well documented and people's opinions of how much is too much vary so much, I'm a fan of just replacing the fan in the scope you have. It's almost always possible to get a quieter fan for a given unit, though it's sort of a gamble again if you can find a fan rated powerful enough that's quiet enough to suit your taste.

author: David Hess
author_rank: Super Contributor
timestamp: May 14, 2018, 08:33:51 pm
content: Tektronix 7904 with two 200MHz 7A26 dual trace vertical plug-ins.It is a shame that modern test equipment is so noisy. Even my old oscilloscopes which have fans are practically silent.

author: Rich@RohdeScopesUSA
author_rank: Frequent Contributor
timestamp: May 14, 2018, 08:36:22 pm
content: Our RTB2000 (70MHz to 300MHz) is extremely quiet - so quiet we actually list it in the data sheet:Maximum of sound pressure level 28.3/30.2 dB (A) at 1.0/0.8 m distance (at +23 °C, 947 mbar (hPa), 20 % rel. humidity), in line with ISO EN 3744.https://www.rohde-schwarz.com/us/product/rtb2000-productstartpage_63493-266306.htmlOur 3000/4000 series are similar (and go up to 1GHz).-Rich

author: Bob Sava
author_rank: Regular Contributor
timestamp: May 14, 2018, 09:45:08 pm
content: I have Siglent SDS1104X-E, that originally sounded like a vacuum cleaner. If Siglent wanted to, for about the same price, they could have designed it with quiet 120mm fan blowing into the PSU and exhausting through PSU to outside just like ATX PSU, but they did not...I just modified this scope with with two 60mmx25mm 10dB fans. It's not silent but it'a what Sharp calls 'library quiet' with their air purifier line, which is about 29dB. It is probably as quiet as it can be w/o compromising airflow. For total silence I would have to 3d print a fan shroud as currently the case is amplifying the fan noise.

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 05:37:53 am
content: Quote from: Rich@RohdeScopesUSA on May 14, 2018, 08:36:22 pmYou used to make fanless 'scopes. What happened?Quote from: Bob Sava on May 14, 2018, 09:45:08 pmI had a Rigol, same thing.Now I usually feel the need to double-check the fan is working when I switch it on (it is!). All it took was a $7 fan and 15 minutes with a screwdriver.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 15, 2018, 08:12:42 am
content: The most noisy scope I had was a LECROY.It was so annoying, I returned it within one week and decided to never buy a Lecroy scope again.

author: JPortici
author_rank: Super Contributor
timestamp: May 15, 2018, 08:18:55 am
content: Quote from: HighVoltage on May 15, 2018, 08:12:42 amTrue datmy 1989 boat anchor lecroy is among the noisiest pieces of equipment i have used. It's only topped by workshop toolsNewer ones are way quieter though, you should give them another try

author: capt bullshot
author_rank: Super Contributor
timestamp: May 15, 2018, 09:12:24 am
content: A TDS2024 (200MHz, 4ch) It's rather old, pretty low on memory (yes, I know, this is a major critique point for these scopes), but fanless. An TDS224 (100MHz, 4ch) is even older and worse, but has quicker UI response.Many of the "new" scopes are really bad in terms of UI responsibility and ease to use in comparison with these old and primitive ones. Especially the TDS224 has an analog scope alike UI and responsiveness, most knobs are single function and simple menus for the basic functions, anyway there are no advanced functions that clutter the menus. That and there noiselessness is the main reason why I still use them as a daily first choice general purpose scope.If you know about the limitations, it still makes a good everyday usage scope.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 15, 2018, 09:15:07 am
content: Quote from: JPortici on May 15, 2018, 08:18:55 amWell, this one was not so old.... it was aLecroy WaveJet 354AA modern scope with modern interface and "good looking" too, kind of cute and lightweight.It sounded all the time more like an airplane jet engine.I thought the named it WaveJETfor the airplane sound.

author: Mr Nutts
author_rank: Regular Contributor
timestamp: May 15, 2018, 09:45:10 am
content: Wasn't this scope just a rebrand of an Iwatsu scope? The GUI doesn't look like it came from Lecroy.My old Wavepro is pretty loud but the little LT264 I got recently isn't too bad.And the Agilent and Tektronix scopes at work are about the same when it comes to noise.

author: julianhigginson
author_rank: Frequent Contributor
timestamp: May 15, 2018, 10:21:22 am
content: I have a dpo2024, it makes a bit of noise, but it's not that bad. I tend to tune it out when it's on for more than a few minutes.

author: exe
author_rank: Unknown
timestamp: May 15, 2018, 11:01:51 am
content: I totally agree, it's so annoying. Unfortunately, most people are used to use noisy equipment in noisy environment. This might be okay for work, but I have my lab at home and it's so annoying. Especially high-pitch sounds.

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 12:23:43 pm
content: You know you're in for a good fanning as soon as they start putting Windows operating systems in there.If R&S have stopped producing the HMO series then then I'm not sure there's any new fanless 'scopes out there. 28dBisvery quiet though, if you can afford R&S.Question: Do USB oscilloscopes have fans? If you have a PC on your desk then that might be an option.

author: exe
author_rank: Unknown
timestamp: May 15, 2018, 01:11:54 pm
content: BTW, is replacing the fan an option? I'd also check how how components get, may be a fan with less airflow would also do the job.

author: nctnico
author_rank: Super Contributor
timestamp: May 15, 2018, 03:04:53 pm
content: Quote from: exe on May 15, 2018, 01:11:54 pmI won't recommend using a fan with less airflow because that will reduce the expected lifetime of a piece of equipment. What does help is to use a higher quality fan and mounting it using rubber fan mounts. In my experience the rubber fan mounts alone will decrease the noise significantly.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 15, 2018, 03:46:52 pm
content: Yeah, generally my approach has been to look for the fan with the higher rated airflow and less noise, a lot of times the parts they're cooling already run warm and prolonged heat will eventually make them fail, so in the interest of having stuff stick around, I try to do at least as good of a job moving air as the OEM fans. You can run into issues with very obstructed air paths that need a higher static pressure fan to operate, but a lot of the quieter ones don't even specify that, so there are some applications where you just know you don't need too much and there are some where I pick a fan and just test it against the original with a power supply to try to get a feel for whether they push air similarly.Fan mounts can certainly help, but there is some equipment where the mounting is good and extra mounts do almost nothing. Sometimes you run into fan grilles or very close heatsinks that just obstruct the airflow, making a fairly quiet stock fan fairly loud... and while they can sometimes be improved with a replacement fan, there's usually a limit to how much of a difference that can make without changing fan positioning or grille cutouts - and especially when EMI sensitivity is an issue with an instrument, I'm hesitant to do much chassis metal work for noise concerns. Then with older equipment, sometimes the stock fan was actually pretty good at one point, but over time the dust/reduced lubrication/oxidation built up and made it noisy, sometimes just replacing it with an identical one can make a big improvement.

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 04:21:34 pm
content: Quote from: DaJMasta on May 15, 2018, 03:46:52 pmI don't know about Siglents, but ... as I pointed out in the "Rigol fan replacement" thread, a Rigol is designed to work in 50 degree Celsius ambient temperatures. I imagine Siglents aren't much different.That means there's quite a lot of wiggle room if you're using it in a 25 degree office.

author: nctnico
author_rank: Super Contributor
timestamp: May 15, 2018, 04:42:45 pm
content: Quote from: Fungus on May 15, 2018, 04:21:34 pmOMGNot that nonsense again! Please read up on reliability (MTBF) and how temperature influences that. Every 10 degrees more means half the expected lifetime. The maximum operating temperature means the internal components won't overheat but the lifetime will become a lot shorter. And knowing Rigol costs have already been cut so better have more airflow than less.

author: Bob Sava
author_rank: Regular Contributor
timestamp: May 15, 2018, 04:54:00 pm
content: Capacitor lifetime is hardly linear and seem long enough up to 60degC:@nctnico which components are you referring to?

author: Rich@RohdeScopesUSA
author_rank: Frequent Contributor
timestamp: May 15, 2018, 05:05:45 pm
content: Quote from: Fungus on May 15, 2018, 05:37:53 amThanks for the reminder - we actually still do! The RTH1000 is fanless and goes to 500MHzBut our benchtop scopes all have fans now (unlike the older HMO1002 you are probably referencing).-Rich

author: nctnico
author_rank: Super Contributor
timestamp: May 15, 2018, 05:19:47 pm
content: Quote from: Bob Sava on May 15, 2018, 04:54:00 pmAll components! It is a hard rule which is well known for reliability calculations.Look closely at the graph you posted and you'll see that between 50 and 60 degrees you loose half the lifetime and between 60 and 70 the life time halfs again. It is not a linear relation but exponential (square)!

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 05:34:35 pm
content: Quote from: nctnico on May 15, 2018, 04:42:45 pmOf course it will reduce the lifetimeon paperbut will it make a noticeable difference in real life if there's only 10% less airflow? I eagerly await your full analysis/explanation.Nobody's talking about using fans which have vastly different specs from the originals (assuming the originals are optimal, which they may not be - they're more likely to be over-specified if they have to give you a two year garantee in 50 degree heat).

author: nctnico
author_rank: Super Contributor
timestamp: May 15, 2018, 05:39:27 pm
content: Quote from: Fungus on May 15, 2018, 05:34:35 pmFirst explain from which dark hole the number '10% less' is coming from.

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 06:28:19 pm
content: Quote from: nctnico on May 15, 2018, 05:39:27 pmThe static pressure of the stock-vs-replacement fans is 25% different, the max airflow is exactly the same. There's not much blocking the fan, so... 10% ballpark, maybe 15%. Use 20% if you want, I don't really care, I don't believe it will be reduced by the full 25% though, not with the fan pressed right up against the output grille.Let's see what the numbers say.

author: Andreas
author_rank: Super Contributor
timestamp: May 15, 2018, 07:40:04 pm
content: Quote from: Morgan127 on May 14, 2018, 06:55:24 pmI have a PicoScope 5444A USB Scope -> fanless design (except the laptop where it is attached).with best regardsAndreas

author: DaJMasta
author_rank: Super Contributor
timestamp: May 15, 2018, 07:42:45 pm
content: Quote from: Fungus on May 15, 2018, 04:21:34 pmSure, but the wiggle room is a benefit for test equipment. Their overall lifetime is higher because of that sort of tolerance, and since I do occasionally upgrade my kit and sell them, I don't want to put in some dramatically quieter but just barely performing fan that will just be a timebomb in any space that isn't an air conditioned office. I also end up getting used equipment pretty commonly, so to try to get a nice long lifetime out of a piece of gear that may have already been heavily used, getting a closely rated fan is a precaution I have no issue taking. I've used my scope and counter outdoors, I'll occasionally carry stuff to somewhere else, and if it's possible (and it usually is), I'd like for them to perform well in any situation they normally would even if I modify them.Sure, it's gilding the lily, as Dave would say, but so is input protection and extra EMI filtering on the power cable..... it may not be required for normal operation, but it sure comes in handy sometimes!

author: Fungus
author_rank: Super Contributor
timestamp: May 15, 2018, 07:59:45 pm
content: Quote from: DaJMasta on May 15, 2018, 07:42:45 pmSure, but I was only talking maybe 10-15% worse. The fan I put in my Rigol (for example) was chosen for noise/performance ratio, not because it was the quietest possible.

author: GregDunn
author_rank: Frequent Contributor
timestamp: May 15, 2018, 08:05:45 pm
content: It surely is complex and not linear. Analog electronics and computer hard drives also have been shown to exhibit extended lifetimes with relatively small-looking decrease in operating temperatures. A significant amount of writing has been done on the subject:https://www.electronics-cooling.com/2017/08/10c-increase-temperature-really-reduce-life-electronics-half/https://ieeexplore.ieee.org/abstract/document/6740182/https://www.extron.com/company/article.aspx?id=thermalmgt1_ts

author: exe
author_rank: Unknown
timestamp: May 15, 2018, 09:00:24 pm
content: That's why I think it's better to measure temperature of critical components before doing any conclusions about fans (if this is feasible).I personally often trade cooling efficiency for silence. May be I'm accelerating ageing of my equipment, but that's deliberate choice (but my equipment is not too expensive). Having said that, I did kill a CPU and a video card, but they were severely abused and had many hours of work well above recommended temperature.There is another risk of getting the instrument out of spec. But I think it's more about precision bench DMMs.

author: Bob Sava
author_rank: Regular Contributor
timestamp: May 17, 2018, 06:53:08 pm
content: RTB2000 seems like a well designed scope (@20:58) that is supposedly very quiet:https://youtu.be/mcgJSKxj0i0?t=20m58s

author: Fungus
author_rank: Super Contributor
timestamp: May 17, 2018, 10:11:51 pm
content: Quote from: exe on May 15, 2018, 09:00:24 pmPrecision bench DMMs usually have internal heaters to run the voltage reference at a temperature well above 'normal' ambient just so they can stay in spec even on hot days.

author: exe
author_rank: Unknown
timestamp: May 21, 2018, 02:56:28 pm
content: Rumors say expensive DMMs can compensate temperature drift in software. So, they rely on fans to have certain known performance, otherwise software model will not work as expected. Don't know if this is true or not, that's what I read in a volt-nut thread.

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2018, 03:02:28 pm
content: Quote from: exe on May 21, 2018, 02:56:28 pmMaybe so but it's much easier to heat the reverence voltage to a known temperature.

author: glarsson
author_rank: Frequent Contributor
timestamp: May 21, 2018, 04:41:38 pm
content: Quote from: exe on May 21, 2018, 02:56:28 pmBut the cooling performance also depends on the room temperature and any object blocking air from entering or leaving. They have no external sensors for this and internal sensors will se the combined result of fan performance, room temperature and any blockage. That means that fan performance (within reason) can't be that important for the software.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 21, 2018, 05:26:56 pm
content: With a change in fan speed, there will be a change in temperature gradients, not just the overall temperature. A change in room temperature is more like changing the overall temperature if the fan's speed stays the same. It depends on the design on how important the air speed is - ideally it would not matter, but ideally temperature would not matter either.With modern DSOs things are usually way less sensitive than low DC voltage parts like a DMM. So in an DSO a spped controlled fan is usually not a problem, just like with an PC.