Scored a Agilent 34410A.

[pizzigri]

...and basically tried to learn as much as possible about it thru EEVBlog, and the search function. I found out that compared to the HP 34401A, there's a 1:500 amount of info in the forum, meaning, almost no one talks about it. I'm a bit dismayed, have I done the right thing to sell my beloved 34401 to get a 10?
It was a super deal from GB, about 550 US$ shipped for a basically brand new and still calibrated (due February  21) unit that looks and feels pristine.... so I could not pass it, and needed the funds for it.

I only had it for the past two hours and am just tinkering at this time - but one thing really stands out to annoy the heck out of me: the freaking fan noise is atrocious!

What are the opinions of the Forum GURUs about this meter?

ETA image

[Micke]

I did the exact journey as you, had a 34401A but upgraded to a 34410A 
I would say the 34410A is much better, did not regret the swap one second, some special highlights:
* Lower amps range down to 100µA on AC/DC
* Sampling/Digitizing AC (no AD637 or the like) putting this in the same class as other 3446xA TrueVolt meters (and even 3458A in ACV SYNC mode). This gives superior performance compared to 34401A.
* Ethernet
* Statistics with Min/Max/Avg/Standard deviation

Joe Geller did a comparison for low level ACV measurements:
https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/20_HP_Agilent/01_HP_3400B_20MHZ_True_RMS_Voltmeter/Geller%20Labs/34401A%20AC%20zero.pdf

[pizzigri]

That was actually very informative, although I dont think I'll ever need that capability of the 34410, it's really nice to know!

[Dr. Frank]

I've got a 34401A for about 30 years now (still goin' strong), and bought an additional 34465A 5 years ago.. and compared latter specification-and feature wise to its predecessors, the 34410A and 411A.
All the newer DMMs have much better comfort features, which I really miss on the 401A, like dual display, easy statistics, storage of power-down states, digitizing, much better current ranges and some others.
The fan noise of the instruments of that era including the counters is annoying, I've also heard of that, the 465A is much better in this instance. Maybe the fan can be replaced by a silent one, or a temperature controlled one... maybe you find some hints in the net.
But I really like the zero boot time of the 401A, (probably also on the 410A), as there is no cumbersome WIN CE operating system which takes a minute or so to boot.

In summary you made a big improvement by migration to the 410A!

Frank

 

[pizzigri]

Hello Frank,
Yes I absolutely need to solve the fan noise, I was looking around and Alas indeed it seems I have to leave it in, but a little TC board would help immensely. Relieved to know you approve!
Franco

[Kleinstein]

A temperature regulated fan can be tricky with a precision DMM:  it adds the fan speed and thus air speed as a new variable that has an effect on temperature gradients.

[jogri]

I've got a 34401A for about 30 years now (still goin' strong), and bought an additional 34465A 5 years ago.. and compared latter specification-and feature wise to its predecessors, the 34410A and 411A.
All the newer DMMs have much better comfort features, which I really miss on the 401A, like dual display, easy statistics, storage of power-down states, digitizing, much better current ranges and some others.
The noise of the instruments of that era including the counters is annoying, I've also heard of that, the 465A is much better in this instance. Maybe it can be replaced by a silent one, or a temperature controlled one... maybe you find some hints in the net.
But I really like the zero boot time of the 401A, (probably also on the 410A), as there is no cumbersome WIN CE operating system which takes a minute or so to boot.

In summary you made a big improvement by migration to the 410A!

Frank

As an owner of the data logging variants of the 401A and 465A (34970/DAQ970) i can attest to the boot time of the newer model: You push the power button of the 401, wait 2-3 seconds and you can take a measurement while you have to wait nearly a minute for the damn 465/970 to boot. Very annoying if you just want to take a quick measurement. Also, having ethernet instead of GPIB is a huge upgrade, GPIB is fine if you just want to connect it to one PC in the lab and have dedicated software but the virtual instrument interface over LAN is just way better: No extra software needed and you can control it from any PC in the network. The fan noise of my units didn't bother me (they are both rather quiet imo), but that's coming from a guy with a Tek 540 and an AFG310 on the desk and they both sound like an old vacuum cleaner choking to death.

Btw, you missed one really nice feature of the 410/465 generation: Capacitance measurement... Rather annoying if you need to switch between your DMM and a ESR meter/component tester when you are troubleshooting.

(I do have one question about the 410A: Does it also get rather warm in standby? My 34970A gets to ~35°C when it is in standby, and i don't know why it needs so much energy (heated reference temp junction mabe?))

If you absolutely can't stand the fan noise: Maybe look around for a Noctua fan of that size that offers a similar airflow/pressure? They tend to be rather quiet. Should be a 40mm fan, at least that's what my 34970 has (Edit: The fan is a 5V fan from Delta, model AFB0405MA).

[pizzigri]

Hi Jogri,
Sorry, I have had the 410 for just one day so I have no idea if it heats up or not, yet. Touching it feels cool, but I have not “pushed it” yet...
I was indeed checking capacitonce functionality but it doesn’t seem really mature, it immediately hits a limit with medium size electrolithic caps (ovld with a 470uf cap) and also accuracy is not exceptional. I do have an economical XWJ01 lcr meter and it’s light years ahead. However I totally agree that having it a button press away is a super bonus, especially for the smaller electrolithic caps that are after all the ones  more prone to failure....
I will search for a noctua fan and hopefully it will be quieter, otherwise i’ll have to wear headsets..   lol

[2N3055]

You shouldn't mess with the fan if you're not prepared to have it calibrated/adjusted afterwards. Whatever fan you put in it will be different and will change airflow, and internal temperature and it's distribution.
It's not a PC, it's a PPM level analog equipment....
Just saying...

[pizzigri]

You shouldn't mess with the fan if you're not prepared to have it calibrated/adjusted afterwards. Whatever fan you put in it will be different and will change airflow, and internal temperature and it's distribution.
It's not a PC, it's a PPM level analog equipment....
Just saying...

I am duly chastised.... will have to endure the excruciating whiszz of the fan.
Seriously, I connected the Agilent DMM utility (the latest I found is from 2013) and, BAM, it just works. Wow... also, boot is comparable to the 401a, it takes all of about 3-4 seconds.
Is there any risk of bricking the thing with a FW update? I’ e got 2.35, but on Keysight web the latest is 2.43

[Micke]

You shouldn't mess with the fan if you're not prepared to have it calibrated/adjusted afterwards. Whatever fan you put in it will be different and will change airflow, and internal temperature and it's distribution.
It's not a PC, it's a PPM level analog equipment....
Just saying...

Yes, I forgot to say the fan on the 34410A is the only negative compared to the 34401A 
On my 34410A I have put a switch on the back side, giving the possibility running fan on "jet engine mode" (original speed) or via a Noise-killer (used on PC´s in the old age...)
As an experiment this summer when I sent my 34410A for adjustment and calibration, I asked nicely if they could aid in an experiment, full calibration with fan on low and original speed.
The cal lab kindly participated in the experiment 
Air flow does matter, but as you say, it is on PPM level 
Unit was running on low speed fan for 2h before starting calibration, and prior to do first calibration with original speed, unit had been on over night.
Nevertheless, interesting experiment!

[Dr. Frank]

Micke,
that's an interesting experiment, which concerns all generations of HPAK DMMs, if you think a bit further, i.e. '401, '410/411, '465/470 and the 3458A.

It's not the (amount of) air flow itself, which matters, but the change of the internal temperature, and this affects the T.C. of the instruments only.

I also have some difficulties to imagine, which real observable effect this abstract term of "temperature gradients" should create, other than that... maybe offset voltages, but there are offset cancelling methods implemented.

Therefore, if you reduce the airflow, the internal temperature will rise, and the calibrated values will simply shift accordingly to their T.C.s.
The same happens, if you increase the room temperature, which can usually go up to 50°C.

Therefore, it would be possible to reduce the fan speed by controlling the internal temperature, which would additionally reduce the effective external T.C. to a certain degree. The calibration @ 23°C R.T. would have to be adapted. The 465/470 and 3458A are able to partly compensate this by their ACAL feature.

Frank

[jogri]

I think that's the reason why Keysight decided to include a thermometer in their newer DMMs: My DAQ970 will show you its current internal temperature as well as the temperature at which it was calibrated, and seeing this data i'm willing to bet that it tries to match those two as close as possible when its operating.

[bdunham7]

It's not the (amount of) air flow itself, which matters, but the change of the internal temperature, and this affects the T.C. of the instruments only.

I also have some difficulties to imagine, which real observable effect this abstract term of "temperature gradients" should create, other than that... maybe offset voltages, but there are offset cancelling methods implemented.

How does Fluke manage similar products without fans??

[pizzigri]

Ok, but then what’s the point of having a fan on at max speed all the time? It will lower the internal temp of precisely the same amount all the time instead of i.e. keeping it at a stable temp with a... well, temperature controller! I have not opened the meter (there are still valid cal stickers around it) so I don’t really know how it is inside , but the fact is that airflow should not change much depending on speed, it will follow the same paths, only the cooling power (Wind chill factor) will decrease IMHO.

[bdunham7]

Ok, but then what’s the point of having a fan on at max speed all the time?

I think it is a matter of controlling temperature gradients, not absolute temperature.  I recall that in another thread, a Keithley engineer was quoted as saying that they needed the fan in their DMM6500 to meet the accuracy specs on a budget, implying that there were other methods but that they cost more. 

[Robaroni]

I have long history with Agilent/Keysight meters. Originally bought a used 401A and replaced the display with a dying segment on one digit. Bought it for $600 a decade or so ago when they were still being sold by Agilent. Came with the optional 4 wire test leads, a hundred bucks extra or more new, really nice leads. Absolutely loved that meter!

A few years later I sold it for $550 when I upgraded for a 410A. Sure, it's a better meter but the fan killed me in my small lab whining on the bench all day long. I wanted to murder the thing, I even called Agilent to complain. Couldn't stand it any longer so I finally sold it and bought a 65A. Really great meter, love the thing. Takes six months to boot up but once it's up it's the cats meow.

Still missing my 401A, no fan super and fast turn on. Great, leave it on all day taking in data. Just found one on ebay - new old stock $549. Bought it! Merry Christmas a week early.

https://www.ebay.com/itm/NEW-Agilent-34401A-Digital-Multimeter-6-5-digits-New-in-The-Box/393044731082?epid=710140765&hash=item5b834aa4ca:g:3S8AAOSwjN5fsGs3

I think there are three or four left out of 14. One of the best meters ever made, how could I pass it up.

[mawyatt]

Nice find, new 34401A

I acquired a HP34401A and Agilent 34401A off eBay and repaired both. On the older HP the display is beginning to fade, so I'll need to replace this sometime. Also have a new KS34465A which is a beautiful instrument and shows the 34401 DNA, but I do not like the fan 

Most other instruments drown the KS34465A fan out, so not that annoying when other stuff is on.

So why do I have 3 of these DVMs Don't really know other than I can't part with the 34401A's since I grew up with HP and Tektronix instruments and why I also have 2 Tek 2465s 
 
They are like family 

Best,

[Robaroni]

I have long history with Agilent/Keysight meters. Originally bought a used 401A and replaced the display with a dying segment on one digit. Bought it for $600 a decade or so ago when they were still being sold by Agilent. Came with the optional 4 wire test leads, a hundred bucks extra or more new, really nice leads. Absolutely loved that meter!

A few years later I sold it for $550 when I upgraded for a 410A. Sure, it's a better meter but the fan killed me in my small lab whining on the bench all day long. I wanted to murder the thing, I even called Agilent to complain. Couldn't stand it any longer so I finally sold it and bought a 65A. Really great meter, love the thing. Takes six months to boot up but once it's up it's the cats meow.

Still missing my 401A, no fan super and fast turn on. Great, leave it on all day taking in data. Just found one on ebay - new old stock $549. Bought it! Merry Christmas a week early.

https://www.ebay.com/itm/NEW-Agilent-34401A-Digital-Multimeter-6-5-digits-New-in-The-Box/393044731082?epid=710140765&hash=item5b834aa4ca:g:3S8AAOSwjN5fsGs3

I think there are three or four left out of 14. One of the best meters ever made, how could I pass it up.

I don't mind the fan in the 65A, it's not annoyingly loud, I found the 410A obnoxious. I'm really a stickler about noisy fans in instruments. I can afford the 401A, Elon Musk has been very good to me this year, he bought me a new electronic load too!

[faraday]

You shouldn't mess with the fan if you're not prepared to have it calibrated/adjusted afterwards. Whatever fan you put in it will be different and will change airflow, and internal temperature and it's distribution.
It's not a PC, it's a PPM level analog equipment....
Just saying...

I am duly chastised.... will have to endure the excruciating whiszz of the fan.
Seriously, I connected the Agilent DMM utility (the latest I found is from 2013) and, BAM, it just works. Wow... also, boot is comparable to the 401a, it takes all of about 3-4 seconds.
Is there any risk of bricking the thing with a FW update? I’ e got 2.35, but on Keysight web the latest is 2.43

Did update mine no problem