Siglent 1202X-E Fan Noise

[Roger Need]

I am a new subscriber to this forum.  I read many of the posts concerning the Siglent SDS1202X-E oscilloscope before ordering one 10 days ago from Amazon Canada (no local dealers in Western Canada).  There were a few comments about Siglent fan noise but mostly they were about other models like the 1104. .  So I hope those of you that own or sell these scopes can help me out.

The unit that I received is a BB model but it must have been in stock for awhile because the calibration letter was dated last February.  It was new because the power on screen showed that I was the first to power it up.  The firmware was 5.1.3.17 which is not the latest September 2018 release so I will have to update if I don't return the unit.  The scope works okay and seems quite accurate in terms of the frequency counter, voltage measurements and FFT operation.  Offsets are pretty good on the 500 uV scale.

The problem is the noise.  When I power it up in the morning it has some fan noise which is fairly noticeable and at a higher level than I expected.  I have a quiet lab without any other fans running most of the time.  What I thought I noticed was that the noise was getting louder after a few minutes and then about 10-15  minutes after start there is a whine which may be coming from the fan or the power supply.  In order to verify my observation I made a recording by placing a microphone near the fan exhaust grill on the right hand side.   I recorded the ambient noise with the 1202X-E turned off.   Then a 15 minute recording was made with the scope powered up and nothing connected. I then analyzed the recording with spectral analysis software and confirmed what I had been observing.   The plot below shows the difference from ambient noise after at 2, 9 and 13 minutes.  One can clearly see the noise slowly getting worse and several spectral peaks which are the "whine" I was referring to earlier.

As it stands it is not enjoyable to use this instrument.  I will either have to build a sound-proof enclosure around it (with quiet fans to provide airflow) or return it to Amazon for exchange or refund.  If this is the way this product normally operates there is no point in going through the hassle of return shipping just to get the same issue again. 

I hope I can get some feedback on these questions.

1. Is this typical for the 1202X-E or do I have a bad fan?
2. Why does it get worse as the unit warms up?  The fan is still pushing the same CFM of air - it is just warmer.
3. Could the spectral peaks be something to do with audio noise from the switching power supply?
4. It shipped without a CD in the Quick Start guide.  Anything of value on the CD that can't be downloaded?

Thanks for reading and any comments....

[Performa01]

First I have to say that most modern test instruments are pretty annoying for someone used to a quiet lab. Tiny fans can be found in just about any (semi-)modern test gear...

The Siglent DSOs are not very quiet, but also not particularly loud in my book and I've never experienced a noticable change in volume or tone over time. The fan is just blowing air, that produces some (pink?) noise, but there are no particularly annoying tones like hum or whine.

I'm currently not set up for sound recordings, but if you provide a short sample for me to listen, then I can tell you whether it's normal or not.

[tautech]

The Siglent DSOs are not very quiet, ......

Latest SDS1202X-E’s are quite quiet, somewhat more than early units.
They don’t have as much internal HW as 4ch units so can use a lower capacity quieter fan.

[TheSteve]

Welcome to the forum(I am also in BC).
I don't know how loud it should be, but if you find it irritating I would return it as it will forever annoy you. The fact that the noise changes is also a concern unless the fan is just breaking in.

[DaJMasta]

Are you sure the fan isn't speed controlled?  They certainly can be, and it would explain the warm up sound difference.  Also would be useful to look at the raw audio plots rather than difference plots, and it's worth making sure that your recording device doesn't have any auto-gain enabled or any noise gating, compression, or other features enabled.  Unlikely for a standalone mic and sound equipment, but quite likely with a device with an integrated mic and software.


When it comes down to it, though, if the sound bothers you, you really only have two options:  return it and either try another unit or try another kind of scope, or go in there and replace the fan with a quieter one.  As mentioned, it's atypical for fan noise to be a primary concern for test equipment, especially when you start moving towards higher end stuff, so while a small amount of noise on a scope may be noticeable in the quiet office a hobbyist works in, it's going to be well below ambient in most electronics lab settings.

[Rerouter]

At least for my 1104X-E, I can best describe the fan noise as noticeable, but not loud from a 1m distance,

[Roger Need]

I'm currently not set up for sound recordings, but if you provide a short sample for me to listen, then I can tell you whether it's normal or not.

I edited the recorded file to show what happens when turned on, after 2, 9 and 13 minutes and when the fan is blocked.  I annotated the waveform plot so you can see the events and the increasing noise.  Hoefully the recording attaches to this post.  If not it is on Google Drive here >> https://drive.google.com/open?id=14QU10jiJB_haCWSX3yFGMHBqU_aRLkhO

[tautech]

At least for my 1104X-E, I can best describe the fan noise as noticeable, but not loud from a 1m distance,

For factory ‘new’ 2 and 4ch units there is a noticeable difference in fan noise levels....for October ‘18 produced units.

[Rerouter]

So was a different model fan used? or something different, as mine was pre august.

[tautech]

So was a different model fan used? or something different, as mine was pre august.

Couldn’t say as I haven’t investigated it, I just know the 2ch models are now quieter.....I run every unit before dispatch.

[Roger Need]

For factory ‘new’ 2 and 4ch units there is a noticeable difference in fan noise levels....for October ‘18 produced units.

Thank you for this information.  How can one tell if the unit is October 2018 or later?  By certification letter or serial number?  Are the latest one still using BB in the serial number?

[tautech]

For factory ‘new’ 2 and 4ch units there is a noticeable difference in fan noise levels....for October ‘18 produced units.

Thank you for this information.  How can one tell if the unit is October 2018 or later?  By certification letter or serial number?  Are the latest one still using BB in the serial number?

The Cal cert is probably just a few days older than production date.
Recent SN# sold: SDS1ECDQ2R**** so CD is latest HW version in my stock.

[Performa01]

I edited the recorded file to show what happens when turned on, after 2, 9 and 13 minutes and when the fan is blocked.  I annotated the waveform plot so you can see the events and the increasing noise.  Hoefully the recording attaches to this post. 

Well, this doesn't sound abnormal to me, especially considering that the mic is close to the fan.

I think it might just be your first more modern unit with a fan - I felt the same annoyance when I got my first equipment with fan, introducing a lot of noise to the previously very quiet lab. And the smaller units are even worse - have you ever heard e.g. a Keithley 2001 DMM? That really has some whining tone to it...

Then there is the change of the tone on your unit. I remember that there have been complaints about fan noise in the past and this has subsequently been discussed in Siglent R&D. Back then I mentioned that a temperature controlled fan doesn't add significant cost and maybe this is what has been implemented by now (since Tautech mentions that recent SDS1202X-E are less noisy than the previous units).

The problem is, you will not find anything less noisy out of the box, except a faceless USB-scope, and the same problem will arise with pretty much any modern gear you're going to add to your lab, be it a signal/function generator, spectrum analyzer or even a DMM. Ironically, there are quite a few power supplies without fan, either with a big heatsink for the linear ones or SMPS designs with low power dissipation in the first place.

Anyway, fan noise is an ongoing topic here, for pretty much all devices. Fanless designs are really rare nowadays - and certainly not found in the class of an SDS1202X-E DSO. Users are sometimes "tuning" their gear, fitting less noisy fans, adding temp controllers and/or mechanic decoupling from the chassis.

[Roger Need]

Thank you to everyone that has taken the time to respond to my questions. I appreciate all the information and suggestions.  The features and performance in the 1202X-E are what I am looking for but at this point I think it best to send this unit back to Amazon for a refund as the noise level is too high to enjoy using this particular scope.   As Performa01 pointed out fan noise is a fact of life but hopefully the latest hardware version will be better.  The noise when it starts and runs for a few minutes is OK but not so great after 15 minutes

Tautech posted that the units from October 2018 are quieter and he should know because he tests each one leaving his shop.  I will try and find one of the CD or later versions from a supplier in Eastern Canada.  One wonders what else they might have changed besides the fans. 

Wishing you all a Merry Xmas and a Happy New Year....

[tautech]

As mentioned to Roger via PM’s, I’m reasonably sure another member has added a series resistor to the fan to slow it some and reduce fan noise.
This topic would benefit from other owners experience if they would care to share what they’ve done.
There’s also adding rubber mounts to reduce resonant coupled noise........also mentioned by Performa01.

[Roger Need]

Are you sure the fan isn't speed controlled?  They certainly can be, and it would explain the warm up sound difference. 

That is a good question.  From the screenshot of Dave's teardown they are only using two wires to the fan so it is not feedback speed controlled but maybe they just change the voltage to the fan as the temperature rises.  Maybe someone that has taken their unit apart has some info.

[CDaniel]

I looked some time ago ( maybe 1 year ) in my unit and has 2 wires . I didn't notice to be adjustable , it is just spinning all the time .
I think I mounted something rubbery underneath it , it's the metalic chassis that is vibrating from the fan . And this could be variable in time ...

[tek2232]

At least for my 1104X-E, I can best describe the fan noise as noticeable, but not loud from a 1m distance,

Mine 1104Xe fan is loud and always blowing at full speed can be heard in every  corner of
my "lab"   calibrated date = Jun-20-2018 hardware version 01-03 , maybe your 1104XE
is from a later date. ?

[Rerouter]

Away from my lab until boxing day, but It was a pre-august model, so If there was a change around then, then you missed out by less than a month

[tek2232]

Yes, that would be the case.

[Roger Need]

Are you sure the fan isn't speed controlled?  They certainly can be, and it would explain the warm up sound difference.  Also would be useful to look at the raw audio plots rather than difference plots, and it's worth making sure that your recording device doesn't have any auto-gain enabled or any noise gating, compression, or other features enabled.  Unlikely for a standalone mic and sound equipment, but quite likely with a device with an integrated mic and software.

The fan may be speed controlled but I do not have a device to measure CFM at the fan output port.  Here is the graph you requested comparing the ambient sound level with the sound after 9 minutes of operation.   Recorded in Windows 8.1 with an external microphone and no auto gain.  You can see that the difference varies from 10 to 15 db at the low to mid frequencies.  To the human ear a 10 dB increase in sound level will be perceived as twice as loud which is what I observe with my unit.  The spike in levels from 2800 to 3000 Hz. may be the "whine" that I hear.

[DaJMasta]

I sort of meant more of a sanity check - while zeroing out backround noise is useful, in a variable environment to corroborate a subjective (human) observation is a very easy way to convince yourself there's a big issue when the measurement doesn't actually show it.

In any case, you should be able to use the frequency content as your RPM indicator - if it goes up over time, then the fan is probably speeding up with increased load.  If you suspect vibration plays a part, you may be able to touch parts of the chassis near the fan or put a plastic piece through the grill (being careful not to obstruct the blades) to try and dampen any vibration of the fan itself.  While the design may not have emphasized silence, it also could be that there was a little wobble to the fan installed on the unit.


In any case, though, while it appears very fixable from the teardown photos by replacing the fan, if you are not comfortable doing so or don't think it's worth the effort, return is probably the best option if it bothers you.

[Roger Need]

There has been a lot of useful feedback on this thread.  Based on the comments above I made another series of measurements to make sure that the microphone was properly set-up (no AGC etc.) and to determine if a variable speed fan was being used. 

In order to confirm that the fan was speeding up with temperature I ran the tests in the unheated section of my shop.  The temperature there is 13C (55F) compared to the lab which is 21C (70F).  The first thing I noticed is that the unit started up with hardly any fan noise at all.  Even after 2 minutes in the unheated shop it was still quiet compared to what I find in the lab.  I recorded measurements for about 20 minutes and then plotted the spectrum vs. time.  The results can be seen below. The first graph shows noise at ambient and after 2,4, 8 and 16 minutes of operation. The change from ambient to 16 minutes and 2 to 16 minutes are shown on separate plots.  One can observe that over time the noise is increasing due to the fan speeding up.  Spectral peaks from 2300 to 2800 Hz are evident and may be due to fan noise or the air passing through the grill at a higher CFM.

There are only 2 wires on this fan so they must be using voltage control, without feedback, to increase the fan speed and airflow. This is not a good design choice if different fan suppliers are used.  This may account for Tautech's observation that new units are less noisy. A different fan would not have the same CFM vs. voltage characteristics and might be less noisy for the same voltage.  The other thing that occurred to me is that the fan control algorithm may have have changed in the latest firmware release (1.3.23 - Sept. 20, 2018).  My firmware (5.1.3.17) is one release behind the current one.  Since I am returning this unit I am reluctant to update the firmware.  Perhaps someone else may want to comment or try an experiment with the updated firmware.

I hope this investigation is useful to others owning one of these scopes or for those considering a purchase.

[tinhead]

For factory ‘new’ 2 and 4ch units there is a noticeable difference in fan noise levels....for October ‘18 produced units.

i have Oct 30th calibrated 4ch version, loud as shit and always running at full speed as well :\

[Rerouter]

Then perhaps they got louder after the change date? Or perhaps just a differemt noise distribution from different fan blade noise

Have any cold rooms you could run it in for a few minutes. May be able to figure out how things change with different temperatures.

[Roger Need]

Have any cold rooms you could run it in for a few minutes. May be able to figure out how things change with different temperatures.

The cold room is what helped me get to the bottom of it.  It started off much quieter than in my heated lab and it took much longer to reach max fan noise.   

Here is a link to a previous post on noisy fans in the SDS1104X-E and a fix...   https://www.eevblog.com/forum/testgear/siglent-1104x-e-noisy-fan-replacement/

In that post Bob Sava gives the part number of the fan. Here is a link to the specs.   http://www.szdosense.com/eng/products-detail.asp?cpid=177 A screenshot of the specs is below.   

I suspect the same fan was used in the initial release of the 1202X-E.   Anyone know the answer??  Is it the same fan in current production units?

[tinhead]

my SDS1204X-E (from around Oct 30th) have different fan, PAAD16025SL from Aavid Thermalloy, yeah even louder model :\

https://www.mouser.com/pdfdocs/Aavid-thermal-fans.pdf

[Performa01]

There are only 2 wires on this fan so they must be using voltage control, without feedback, to increase the fan speed and airflow. This is not a good design choice if different fan suppliers are used.  This may account for Tautech's observation that new units are less noisy. A different fan would not have the same CFM vs. voltage characteristics and might be less noisy for the same voltage.

Well, you should keep in mind that this is a low cost entry level device. Most DSOs are rather noisy and not many of them have any form of temperature control at all.

The solution might appear sloppy, but then the platform of the SDS1000X-E series is capable of monitoring the temperatures in critical components (SoC, FPGA, ADC, mainboard).  So a different airflow vs. voltage might affect the control characteristic - maybe even in a negative way - but at the end of the day, the fan will always get enough voltage to keep the temperature below the internally programmed threshold - if it is powerful enough in the first place, that is.

[Performa01]

my SDS1204X-E (from around Oct 30th) have different fan, PAAD16025SL from Aavid Thermalloy, yeah even louder model :\

https://www.mouser.com/pdfdocs/Aavid-thermal-fans.pdf

Yes, SDS1004X-E models have at least one additional ADC, which is traditionally the hottest component in there. So I would not be surprised if a slightly more powerful (and louder) fan has been fitted.

[tinhead]

Well, you should keep in mind that this is a low cost entry level device.

sure, on the other hand - based on my experience with Hantek gears (paying more = heatsink on ADC and better fan) - i thought it might be not bad idea to buy SDS1204X-E instead of cheating Siglent on the "license fee". That makes 230EUR diff for dealer, or 100EUR diif for Siglent, that's why expected better fan 

[ct1bxt]

Hi,

my 1202x-E is quite after power ON. After that the fan increases sped, but nothing special.
My main complain is the power LED that starts blinking as soon as I connect the power cable. I would like a real switch instead.

Rodrigo
   

[StillTrying]

I can't imagine how there'd be any fan speed increase without the humps at 750Hz moving quite a bit to the right.

[Roger Need]

I can't imagine how there'd be any fan speed increase without the humps at 750Hz moving quite a bit to the right.

You can see in the time plot that the overall noise level is increasing and it was measured 10 cm. from the exhaust port.  So I believe the fan is increasing in speed as the internal temperature rises.  The "humps at 750 Hz." are probably due to case and grill resonance and the amplitude would rise as airflow increases.

[Roger Need]

The fan specs posted earlier got me to take a close look at the air vents on the SDS1202X-E.  In the photo below you can see that about 1/3 of the fan is blocked by the external plastic case.  This has a considerable effect on the effectiveness of the fan.

The effectiveness of a fan is based on two parameters.  The first is the volume of air that the fan can move per minute which is usually expressed in cubic feet per minute (CFM).  The second is the fan static pressure that can simply be described as the resistance pressure that the fan has to blow against in order to exhaust the air in the desired direction. If a fan is blowing against high resistance pressure (like fan blockage) it requires more energy and delivers less air flow.   It also creates more noise.

The fan specs used in a similar scope are shown in the photo below.  It is clearly evident that the CFM of these small fans drops considerably as fan static pressure increases.  When the scope is cool the fan turns slowly and as heat is internally generated the voltage to the fan must be increased to increase airflow over the components inside.  Unfortunately, due to the the fan being blocked by the case and airflow resistance by the grill the fan must run at a higher speed, with more noise, than would be the case if the exterior plastic case had been designed to accomodate better venting. 

Changing the brand of fan would probably not result in lower fan noise with this case design due to the partially blocked fan exhaust.  I took a look at the SDS1104X-E photos and it does not appear to have much of the fan exhaust blocked.  Looks like a design oversight with the SDS1202X-E.  I highly doubt that they have retooled the case to get the lower noise output that Tautec posted earlier so one wonders how this was achieved.  Was it a change in the firmware algorithm for fan speed?

One possible modification would be to add a quiet inlet fan on the opposite side like the 1104X-E mod posted previously.  There is not much room due to the AC input connector.  A small fan would have to be used.

[Fungus]

I can't imagine how there'd be any fan speed increase without the humps at 750Hz moving quite a bit to the right.

Maybe those are a resonance in the case or a hum caused by air flowing over the grille.

[nctnico]

As mentioned to Roger via PM’s, I’m reasonably sure another member has added a series resistor to the fan to slow it some and reduce fan noise.
This topic would benefit from other owners experience if they would care to share what they’ve done.
There’s also adding rubber mounts to reduce resonant coupled noise........also mentioned by Performa01.

In my experiencel rubber fan mounts are a (well worth!) quick fix to take care of the low hum which couples/resonates into the casing. Getting rid of a high pitch wine is likely to need a different fan. As a rule of thumb the thicker the fan the less RPM it needs to move a certain amount air while producing the same pressure differential.

[Roger Need]

I contacted Amazon and they sent me a replacement unit.  This one was manufactured in November 2018 - the other one was produced in February 2018.  A side-by-side comparison was interesting.  The level of white fan noise is about the same but there is no high pitched whine in the replacement unit.  I don't know if the whine is coming from the switching power supply or the the fan.

According to the utility menu has been a change in the hardware and I will be making a new post about that.

[Dundarave]

As mentioned to Roger via PM’s, I’m reasonably sure another member has added a series resistor to the fan to slow it some and reduce fan noise.
This topic would benefit from other owners experience if they would care to share what they’ve done.
There’s also adding rubber mounts to reduce resonant coupled noise........also mentioned by Performa01.

In my experience rubber fan mounts are a (well worth!) quick fix to take care of the low hum which couples/resonates into the casing. Getting rid of a high pitch wine is likely to need a different fan. As a rule of thumb the thicker the fan the less RPM it needs to move a certain amount air while producing the same pressure differential.

Per Tautech's suggestion re: other's experience and nctnico's observation re: rubber mounts, has anyone actually taken steps to either replace the fan with a quieter one and/or added a series resistor and/or added rubber mounts? If so, I'd love to get the specs and sources for a replacement fan, rubber mounts & the resistor used.

I've got an SDS1104X-E (late-2018) that I'm very happy with, but my work area is very quiet, and I find myself turning off the scope when it's not being immediately used, which can be inconvenient at times, so I'd like to try to do something about it.  I checked out the May 2018 thread on the topic (i.e. Siglent SDS1104X-E noisy fan replacement, OP Bob Sava) but it discussed the fan being mounted on the "right side" of the scope, whereas my scope has the fan on the left side, so I wasn't sure if it was the same 1104 version. (Edit: I just realized the OP was looking at the scope from the rear as he was working on it, lol.)  He had added two fans...  I'm hoping for a less complex solution, i.e a simple combo of fan swap/resistor splice/rubber mount.

Has anyone done any fan mods for an 1104X-E or similar that they could share the details & parts sources of?

Thanks -

[tkamiya]

I'm afraid OP will have to find his own "comfort zone".  No matter how quiet or loud it is to others or what decibel meter says, perception of loud/quiet is very individualized.

I have a certain condition that makes me extremely sensitive to sound.  Also, I have a "dip" in sensitivity on one ear.  To me, high pitch sound seem louder than lower pitch sound.  (think mosquito at night!)  In quiet place, even a little noise sound louder.  Funny, I have a noise cancelling headset.  It only cancels repetitive sound.  Using it is sometimes worse from perceptive point of view as very little non repetitive noise comes right through.  Sometimes 10 dollar ear muff from Home Depot works better.

Fans are cheap to replace.  I've been going through a few that irritates me.  That said, my Siglent is pretty quiet and barely audible.  Since the fan is on back side of it, you can also be creative and try to remove noise that bounces off of a wall behind it.  I am uploading a photo of part of my lab.  On it, you'll see black and blue foam I bought from Amazon cheap.  White bar across it is my lighting.  Those foams are  thin but effective in preventing sound bouncing.

Run higher voltage fan with lower voltage power is also possible.  Often times, slowing it down is a good solution.  Some computer type fans are amazingly quiet, yet enough air to be effective.