Here is link to Keysight 34401A schematics

Hi

We use the 34401A as our base tabletop DMM

Was browsing through some specs, and found they even shared the schematics

From page 140 and forward:

http://literature.cdn.keysight.com/litweb/pdf/34401-90013.pdf

 

On Monday, 4 November 2019 15:05:06 UTC+1, Winfield Hill wrote:

klaus.kragelund@gmail.com wrote...

We use the 34401A as our base tabletop DMM
Was browsing through some specs, and found they even shared the schematics

From page 140 and forward:

http://literature.cdn.keysight.com/litweb/pdf/34401-90013.pdf

And there's extensive analysis of various portions of the
34401A in AoE III, plus more coming out in the x-Chapters.
These are part of our "Designs by the Masters" series, pp
342-347, 918-922 and 894-896. In x-Chapters, pp 353-355.


--
Nice, should be reading it more often. I have edition 1 and 3, but have not yet have had time to read edition 3

Cheers

Klaus

 

[Winfield Hill]

klaus.kragelund@gmail.com wrote...

We use the 34401A as our base tabletop DMM
Was browsing through some specs, and found they even shared the schematics

From page 140 and forward:

http://literature.cdn.keysight.com/litweb/pdf/34401-90013.pdf

And there's extensive analysis of various portions of the
34401A in AoE III, plus more coming out in the x-Chapters.
These are part of our "Designs by the Masters" series, pp
342-347, 918-922 and 894-896. In x-Chapters, pp 353-355.


--
Thanks,
- Win

 

[Winfield Hill]

klaus.kragelund@gmail.com wrote...

On Monday, 4 November 2019, Winfield Hill wrote:
klaus.kragelund@gmail.com wrote...

We use the 34401A as our base tabletop DMM

And there's extensive analysis of various portions of the
34401A in AoE III, plus more coming out in the x-Chapters.
These are part of our "Designs by the Masters" series, pp
342-347, 918-922 and 894-896. In x-Chapters, pp 353-355.

Nice, should be reading it more often. I have edition 1 and 3,
but have not yet have had time to read edition 3

Aha, you can start by reading those pages, they're were fun
to explore and write up, and should be fun to read. The HP
Agilent engineers were really on a roll. Looking at specs,
they've continued the process with their newer DVM versions.
They maintain or improve the accuracy for 1 PLC measurements,
while cutting the auto-ranging time to 5ms, and found ways
to make 20us 4.5-digit measurements with the same circuitry
(that's for the 34465A; I think it was 800us for the 34401A).
But they no longer publish schematics, so we can't figure
out how they did it. But of course, competitors who take
the time to reverse engineer, may be able to figure it out.


--
Thanks,
- Win

 

On Mon, 4 Nov 2019 04:15:43 -0800 (PST), klaus.kragelund@gmail.com
wrote:

Hi

We use the 34401A as our base tabletop DMM

Was browsing through some specs, and found they even shared the schematics

From page 140 and forward:

http://literature.cdn.keysight.com/litweb/pdf/34401-90013.pdf

My gripe about the 34401A is that the VF display kicks a huge amount
of noise into the input terminals. They partly hid that in software by
having AC measurements below some level jump to zero.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Miles, KE5FX]

On Monday, November 4, 2019 at 6:49:28 AM UTC-8, Winfield Hill wrote:

But they no longer publish schematics, so we can't figure
out how they did it. But of course, competitors who take
the time to reverse engineer, may be able to figure it out.

Yeah, if you publish your schematics in the service manual, the
Chinese will clone your device in about 30 days, give or take a few
hundred days depending on the economics of the product in question
and whether or not you gave them a sneak peek before it went into
production.

On the other hand, if you *don't* include schematics in the service
manual, the Chinese will clone your product in about 30 days, give or
take a few hundred days depending on the economics of the product in
question and whether or not you gave them a sneak peek before it went
into production.

Big two thumbs up for the "How they did it" sections in AoE3. It'd
be good to see more of them in future editions or X-chapters.

-- john, KE5FX

 

[RBlack]

In article <idf0selrk8t11fb74d4qhflmsnove2m8qu@4ax.com>,
jlarkin@highlandsniptechnology.com says...

On Mon, 4 Nov 2019 04:15:43 -0800 (PST), klaus.kragelund@gmail.com
wrote:

Hi

We use the 34401A as our base tabletop DMM

Was browsing through some specs, and found they even shared the schematics

From page 140 and forward:

http://literature.cdn.keysight.com/litweb/pdf/34401-90013.pdf

My gripe about the 34401A is that the VF display kicks a huge amount
of noise into the input terminals. They partly hid that in software by
having AC measurements below some level jump to zero.

We have a 34410A, a close relative of the 34401. I've never checked if
it suffers from the VFD noise issue but one thing that caught me out is
that the AC volts function has some sort of negative offset, which the
software pegs at zero, until it has warmed up. This is what I got when
I logged the ACV measurement, from a cold startup, with the input
terminals shorted:

<www.rblack01.plus.com/images/34410A-ACV-startup.png>

The first non-zero reading is after about 15 minutes. We have two of
these DMMs, I should try the other one sometime.

I was testing a low-noise PSU and wrongly thought it was below the
measurement limits of the instrument, until I did the same test later in
the day and found several millivolts of noise.

The data sheet says the readings are only guaranteed to be within spec
after a 90 minute warmup. Lesson learned: Always read the small print!