Two DVMs...

J

John Larkin

Guest
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.
 
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.
Click to expand...

Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
\"Old pinballers never die, they just flip out.\"
 
On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#
Click to expand...

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed
 
On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed
Click to expand...

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.
 
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.
Click to expand...

The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.
Click to expand...

At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
 
On Saturday, August 19, 2023 at 1:24:16 PM UTC-4, John Larkin wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <eh...@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.


The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.
Click to expand...

I seriously bet that\'s using \'mathematical\' compensation of some kind.
 
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs
Click to expand...

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.
 
On Sat, 19 Aug 2023 11:04:25 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

On Saturday, August 19, 2023 at 1:24:16?PM UTC-4, John Larkin wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <eh...@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.


The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.

I seriously bet that\'s using \'mathematical\' compensation of some kind.
Click to expand...

It\'s just a transistor and a zener.

The trick with reference transistors was to select a resistor to tweak
the operating current to get the tempco to zero. That\'s a nuisance in
production.

If I ovenize my references, the tweak could be automated, whatever
part I use.
 
On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.
Click to expand...

Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Sat, 19 Aug 2023 15:05:16 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.



Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs
Click to expand...

I\'m thinking about a baby board with some mosfet heaters in the
corners and a clever arrangement of references and thermistors towards
the middle. It could go on my main board on spacers, with a cover.
That could attenuate external temp changes by 50:1 maybe.

Four refs would cut the noise in half.

I could mux a nanovolt-resolution differential delta-sigma ADC between
multiple references and see if any is an outlier.

The potential customer has been talking about this for over a year. In
typical form, when they finally place an order they will want it in
three weeks.
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

[...]
Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.
Click to expand...

I have a Philips PM2518 which lost its fine calibration when the memory
battery ran out. It pre-dates the takeover by Fluke of Philips
Instruments and this one had stickers showing it was last calibrated by
the Luftwaffe in 2003.

Earlier this year I sent it off to Instrotech of Watford, who took a bit
of persuading that it was worth recalibrating. They succeeded, despite
a lack of information, and returned it to me promptly at a sensible
price with a proper Calibration Certificate.


Disclaimer: I have no connection with Instrotech other than as a
satisfied customer.

--
~ Liz Tuddenham ~
(Remove the \".invalid\"s and add \".co.uk\" to reply)
www.poppyrecords.co.uk
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 15:05:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.



Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs

I\'m thinking about a baby board with some mosfet heaters in the
corners and a clever arrangement of references and thermistors towards
the middle. It could go on my main board on spacers, with a cover.
That could attenuate external temp changes by 50:1 maybe.

Four refs would cut the noise in half.

I could mux a nanovolt-resolution differential delta-sigma ADC between
multiple references and see if any is an outlier.

The potential customer has been talking about this for over a year. In
typical form, when they finally place an order they will want it in
three weeks.
Click to expand...

The key thing about “analytically calculable” is that you can vary all
those sliders you keep wishing for, using only a plotting program.

In the present case, I expect that you’d find that you’d be better off
optimizing for maximum closed-loop bandwidth, and letting the geometry do
most of the work of smoothing out the gradients. (This is based on having
actually done something similar for a stabilized laser for a downhole
application.)

That means one sensor right up close to each heater, with a local feedback
loop wrapped around each pair.

The math isn’t complicated. It’s mostly the same as you’d need for your
spice model—conductivities and thermal masses and such—but with some
first-order estimates of diffusion delays based on the homogenous-material
model I linked to upthread.

Really repays the effort!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
 
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.
Click to expand...

Here there be dragons - and madness:

..<https://lists.febo.com/empathy/list/volt-nuts.lists.febo.com>

Joe Gwinn



I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.
Click to expand...
 
On Sat, 19 Aug 2023 20:44:49 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 15:05:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.



Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs

I\'m thinking about a baby board with some mosfet heaters in the
corners and a clever arrangement of references and thermistors towards
the middle. It could go on my main board on spacers, with a cover.
That could attenuate external temp changes by 50:1 maybe.

Four refs would cut the noise in half.

I could mux a nanovolt-resolution differential delta-sigma ADC between
multiple references and see if any is an outlier.

The potential customer has been talking about this for over a year. In
typical form, when they finally place an order they will want it in
three weeks.



The key thing about “analytically calculable” is that you can vary all
those sliders you keep wishing for, using only a plotting program.

In the present case, I expect that you’d find that you’d be better off
optimizing for maximum closed-loop bandwidth, and letting the geometry do
most of the work of smoothing out the gradients. (This is based on having
actually done something similar for a stabilized laser for a downhole
application.)

That means one sensor right up close to each heater, with a local feedback
loop wrapped around each pair.

The math isn’t complicated. It’s mostly the same as you’d need for your
spice model—conductivities and thermal masses and such—but with some
first-order estimates of diffusion delays based on the homogenous-material
model I linked to upthread.

Really repays the effort!

Cheers

Phil Hobbs
Click to expand...

Or keep my PCB pretty isothermal, measure temperature, and correct the
gain and offset errors with a pair of tweak dacs per channel. Or a 2d
polynomial!

Maybe bolt the critical PCB to a sheet of aluminum with a gap-pad
between, to keep the board pretty isothermal.

A heater would just be used at factory cal time to generate the
correction tables. Runtime, no heat would be applied, so gradients
would be minimal. I can delegate the coding!
 
On Sat, 19 Aug 2023 18:07:52 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:

On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

Here there be dragons - and madness:

.<https://lists.febo.com/empathy/list/volt-nuts.lists.febo.com

Joe Gwinn
Click to expand...

Yes, we\'d need one of those crazy expensive system DVMs to test and
calibrate units.

I could imagine an automated test/cal cycle taking a full day.
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 20:44:49 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 15:05:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.



Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs

I\'m thinking about a baby board with some mosfet heaters in the
corners and a clever arrangement of references and thermistors towards
the middle. It could go on my main board on spacers, with a cover.
That could attenuate external temp changes by 50:1 maybe.

Four refs would cut the noise in half.

I could mux a nanovolt-resolution differential delta-sigma ADC between
multiple references and see if any is an outlier.

The potential customer has been talking about this for over a year. In
typical form, when they finally place an order they will want it in
three weeks.



The key thing about “analytically calculable” is that you can vary all
those sliders you keep wishing for, using only a plotting program.

In the present case, I expect that you’d find that you’d be better off
optimizing for maximum closed-loop bandwidth, and letting the geometry do
most of the work of smoothing out the gradients. (This is based on having
actually done something similar for a stabilized laser for a downhole
application.)

That means one sensor right up close to each heater, with a local feedback
loop wrapped around each pair.

The math isn’t complicated. It’s mostly the same as you’d need for your
spice model—conductivities and thermal masses and such—but with some
first-order estimates of diffusion delays based on the homogenous-material
model I linked to upthread.

Really repays the effort!

Cheers

Phil Hobbs

Or keep my PCB pretty isothermal, measure temperature, and correct the
gain and offset errors with a pair of tweak dacs per channel. Or a 2d
polynomial!

Maybe bolt the critical PCB to a sheet of aluminum with a gap-pad
between, to keep the board pretty isothermal.
Click to expand...
None of that helps the bandwidth, which is what controls the rejection of
external forcing. That’s where the math comes in.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
 
On Sunday, August 20, 2023 at 3:12:23 AM UTC+10, John Larkin wrote:
On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <eh...@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed
I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.
Click to expand...

They don\'t use this.

https://en.wikipedia.org/wiki/Josephson_voltage_standard

Liquid helium is tricky to provide in a portable instrument. Jospheson junctions between high temperature superconductors ought to be able to do the same job

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=17550

but nobody seems to be selling one yet. You\'d still have to build in a Stirling engine refridgerator.

There\'s always the South Korean room temperature superconductor if it proves to be real.

--
Bill Sloman, Sydney
 
On a sunny day (Sat, 19 Aug 2023 11:48:09 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<cb32ei5glbddca82ufksi9f25kpht55gpj@4ax.com>:

On Sat, 19 Aug 2023 11:04:25 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Saturday, August 19, 2023 at 1:24:16?PM UTC-4, John Larkin wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <eh...@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.


The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.

I seriously bet that\'s using \'mathematical\' compensation of some kind.

It\'s just a transistor and a zener.

The trick with reference transistors was to select a resistor to tweak
the operating current to get the tempco to zero. That\'s a nuisance in
production.

If I ovenize my references, the tweak could be automated, whatever
part I use.
Click to expand...

I bought a voltage reference chip from Microchip, MCP1525? it was 1% +- 50 ppm per degree C
Good for most human things.
Caibrated my Chinese multimeters with it so they all show the same value...
 
On 8/19/23 19:39, John Larkin wrote:
On Sat, 19 Aug 2023 15:05:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-19 14:43, John Larkin wrote:
On Sat, 19 Aug 2023 17:49:52 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Sat, 19 Aug 2023 10:11:57 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 19 Aug 2023 12:43:24 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/19/2023 9:49 AM, John Robertson wrote:
On 2023/08/18 7:25 p.m., John Larkin wrote:
The Keithley 2001 is obsolete, so our test department is moving on to
a Keysight. They\'ll have to add a driver into our Python library.

They loaned me one to evaluate.

https://www.dropbox.com/scl/fi/vv1u2r1whendlxioihoma/Two_DVMs.jpg?rlkey=y0pbb1xhjl5na4004lfjoih6c&raw=1

Not too bad, considering that my Fluke hasn\'t been calibrated in human
memory.

I had to take six pics to get the numbers on the Fluke. Its VF display
heterodynes with my phone camera and makes a cool comet effect.



Is the Fluke meter not quite showing yet another digit in the photo?
Might that be an 8 or 9 as the .00000X digit?

If so, then indeed, it isn\'t doing badly!

John :-#)#

Maybe it\'s the Keysight that\'s off by ~10 uV
:)

Ed

I think there was one more digit that the phone camera missed.

But they agree to 1 PPM!

I have a request to design a board that will be a couple-of-PPM
accurate programmable voltage source. That\'s scary.

I\'m thinking of using several (or many) ADR420-series parts,
temperature controlled. Or a few LM199s, except it\'s obsolete.

ADR1000 is still available.

REF-01 is remarkably stable.

I wonder what those DVMs use.



The Fluke uses a \"reference transistor\", which is an NPN with a zener
in the emitter.



At a SWAG, three LTZ1000s and some software.

Cheers

Phil Hobbs

Great longterm stability. Maybe they\'ve been aged.

$93 from Digikey.



Could be. They\'re probably a bit cheaper if you buy lots at a time, but
there\'s obviously a lot of TLC involved.

Stabilizing the temperature adequately will require some care, for sure.
I sometimes put voltage references on paddles routed out of the PCB.
This is mostly to avoid shifts due to mechanical stress on the package,
but could come in very handy to (more or less) eliminate temperature
gradients.

A nice analytically-calculable geometry, e.g. a paddle within a paddle,
joined with two pairs of thin bars, would let one put two nested
temperature control zones in a small space.

Some nice squeaky styrofoam, and maybe a bit of wraparound metal here
and there to get rid of incidental vertical gradients, would probably do
a good job.

Cheers

Phil Hobbs

I\'m thinking about a baby board with some mosfet heaters in the
corners and a clever arrangement of references and thermistors towards
the middle. It could go on my main board on spacers, with a cover.
That could attenuate external temp changes by 50:1 maybe.

Four refs would cut the noise in half.

I could mux a nanovolt-resolution differential delta-sigma ADC between
multiple references and see if any is an outlier.

The potential customer has been talking about this for over a year. In
typical form, when they finally place an order they will want it in
three weeks.
Click to expand...

I would use a cheaper reference of known characteristics and use
software correction. Anyone can throw $100 ltz1000 at the problem,
but there must be a smarter way...
 
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