Keysight 34461A Fan Noise

[Ahrenp]

Hi,

Long timer lurker, first time poster. I just got a Keysight 34461A and there seems to be quite a lot of fan noise, contrary to the reviews and posts I've seen about it. Along with what I would call typical 'fan noise/white noise' there also seems to be a louder low frequency hum/buzz. I'm just curious if this is typical for this meter? It's difficult to describe and when I tried to record the sound the hum didn't really pick up. It is somewhat annoying and louder than my nearby PC and Rigol DS1054z.

[TheSteve]

Hmm, that is odd - I have had a DS1054Z and it is much louder then my 34461A

[orbiter]

I don't believe its anything to worry about, I have the 34465A and it's fan is definitely not so quiet, it also has a rather audible whine to it as well.

[DaJMasta]

Fans can actually differ a bit in noise even of the same type, and it takes a very small amount of gunk to change it further.  If the manufacturer isn't making big claims about it being quiet, then there may not be a lot of checking done to be sure of it.

Fans do get noisier if the airflow is obstructed though, so if you have a bird's nest of cables in front of it, that could be contributing.  As for picking it up on a mic, make sure the gain is up and hold it close to the fan, if you can hear it at a distance, odds are good even a cheap mic can pick it up alright.

Don't have a 34461, but do have one on the way, maybe I can report back this week to see if mine is the same (hoping for quiet!  )

[Performa01]

Don't have a 34461, but do have one on the way, maybe I can report back this week to see if mine is the same (hoping for quiet!  )

I guess most of us hope for quiet instruments, rather than getting mini vacuum cleaners.
Unfortunately it appears most T&M manufacturers don't care about our hopes (cheap tiny fans, non-optimized airflow, no temperature control) ...

[slurry]

It should absolutely not be louder than a 1054Z.
I also have a 34461A and it's quiet, of course i can hear it but no more than a laptop.

[Ahrenp]

As for picking it up on a mic, make sure the gain is up and hold it close to the fan, if you can hear it at a distance, odds are good even a cheap mic can pick it up alright.

I was able to pick up the general fan noise, from across the room at that, but not the "hum" portion. Unfortunately I don't have a proper mic and was just recording the audio with my phone.

It should absolutely not be louder than a 1054Z.

If it were the same tone as the Rigol and I had them both running at the same time I probably would not notice the 34461A, but it's just different enough that I can still hear it buzzing away.

I realize they don't make any claims about it being quiet, and if it's normal I can deal with it, because otherwise it's an awesome meter. I would be lying if I said I wasn't a little bit disappointed though.

[billfernandez]

in mine the fan is quiet, but high enough pitched to be annoying.  No low frequency hum or rumble.

[BVH]

My now sold 34461A and my new 34465A have the same higher pitched annoying fan noise.  It's not the loudness but the irritating pitch.  Has no one tried to locate a generic, quieter replacement?

[Messtechniker]

I have the 34465A and it's fan is definitely not so quiet, it also has a rather audible whine to it as well.

Can confirm this for my 34465A. But I am known to be very
sensitive to any kind noise as I am running a small voice recording studio.
My 34465A lives is a separate lab room (house in very quiet rural
surroundings) and I always switch it off when I not need its capabilities
 - i.e. when my Voltcraft VC 940 will do instead. As to the fan in my
Hameg HMC8043 lab power supply, the Hameg people definitely did
a better job - rubber suspension and all so that I can leave it on all
the time (at low to medium loads that is). Anyway. Replacing the fan#
and improving its suspension will inevitably require a recalibration,
as the airflow is an important part of the equation.

[LaurentR]

I have had 3 of the 3446XA and they all had the same, not particularly loud but certainly annoying high-pitch whine.

Between the fact that it's tolerable and the difficulty to predict the effects of a reduces airflow on the calibration, this is one of the few pieces of test equipment I haven't refanned.
Unfortunately, this means that mine are off most of the time because I don't tend to leave them running when I don't really need them because of the whine.

I wish Keysight had picked a less whiny fan. The airflow is not all that high so there should be plenty of quieter fans with similar airflow.

[Ahrenp]

My now sold 34461A and my new 34465A have the same higher pitched annoying fan noise.  It's not the loudness but the irritating pitch.  Has no one tried to locate a generic, quieter replacement?

I ended up putting one of these in mine:
https://www.amazon.ca/gp/product/B00NEMGCIA/

[Messtechniker]

I ended up putting one of these in mine:
https://www.amazon.ca/gp/product/B00NEMGCIA/

What did this do to the calibration?
Measurements with a voltage/resistance reference
before and after the change please.

[Ahrenp]

I ended up putting one of these in mine:
https://www.amazon.ca/gp/product/B00NEMGCIA/

What did this do to the calibration?
Measurements with a voltage/resistance reference
before and after the change please.

I don't have the numbers to post here; I made the change a while ago, so it's up to you if you take my word for it or not, but voltage measurements were unchanged. Make this change at your own risk. Technically it probably should be re-calibrated, but I did not have an issue.

[Messtechniker]

Is anyone of the voltnuts around here prepared to try exactly
this fan with measurements before and after? 
Even so, I would very much prefer an endorsement of exactly this
fan by Keysight themselves. Probably never going to happen.
I myself do not have any voltage or resistance references precise
enough for checking this DMM.

[BVH]

I just installed the Noctua NF-A4x-10, 5 Volt, 40mm quiet fan in my 34465A.  Using a 5 Volt reference, I got the following VDC readings before and after:  Before 5.00062-5.00063.  After 5.00061-5.00062.  The very irritating fan "tone" or "pitch" is completely gone and the air movement noise is about the same.  I can now keep my meter on between 1-3 hour uses.  Definitely worth the change.

[Messtechniker]

Now that's some news! Thank you.
A Noctua NF-A4x-10 for my 34465A has been on
my shopping list for long time now. Since I can not check the
calibration after changing the fan, I was quite hesitant.
In view of your results, I will now go ahead.

[Gandalf_Sr]

I just installed the Noctua NF-A4x-10, 5 Volt, 40mm quiet fan in my 34465A.  Using a 5 Volt reference, I got the following VDC readings before and after:  Before 5.00062-5.00063.  After 5.00061-5.00062.  The very irritating fan "tone" or "pitch" is completely gone and the air movement noise is about the same.  I can now keep my meter on between 1-3 hour uses.  Definitely worth the change.

I have a 34461A that's:
a) Slightly noisier that I'd like
b) Recently calibrated
c) Well out of warranty

I might consider the fan replacement too.  I can get it from Amazon here https://www.amazon.com/Noctua-Cooling-Bearing-NF-A4X10-FLX-5V/dp/B00NEMGCIA

Is that the right one and do you have any other suggestions for vendors?

[iMo]

Sometimes it is enough to wire a 22-68ohm resistor in series with the fan's Vcc such the high pitch disappears (lower rpm).

[Messtechniker]

Well, its not any high pitch which is annoying.
Rather, its the howling sound the stock fan makes.

[iMo]

Cut the fan's Vcc wire, insert a 100-220ohm pot trimmer and adjust such it runs without the disturbing sound.. Replace with a 1W resistor afterwards. It could be the fan's rpm/air_volume is not linear and the fan is running too fast without good reason..
PS: replacing the original fan with a different XYZ one could have the same air pressure result as lowering the rpm (with help of the resistor) with the original one..

[Gandalf_Sr]

Does the 34461A need a 5V or 12V fan?  The Noctua NF-A4x10 5V is a 5V fan but you guys are talking about cutting "the 12V wire".

[iMo]

I fixed "12V" above, no idea what fan's Vcc is in 34461. In my 34401 the fan's Vcc is 0V. Decades back my first job with building a new PC was cutting the fan's wires with all fans in the box
Ideally do set the rpm with the trimmer (at the highest Tamb expected) such the measured external ref voltage will not change while the fan's noise is minimal. A nice Sunday's afternoon exercise

[HighVoltage]

Almost all my HP / Agilent / Keysight gear with a fan have received a 100 Ohm (1W) resistor in line with the power cable.

The fans still turn fast enough for good airflow and the annoying noise is gone.
And as a side effect, the fans will last many more years.

[iMo]

Almost all my HP / Agilent / Keysight gear with a fan have received a 100 Ohm (1W) resistor in line with the power cable.

.. with the fan's Vcc wire..