3458A reference boards on ebay
There is a seller letting a slow trickle of them out there... they seem to
be going for about $165. The current batch of two is around $100, but will
probably be bid up.
I just received one that I won. Seems to be working fine after a quick
breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem to
be going for about $165. The current batch of two is around $100, but will
probably be bid up.
I just received one that I won. Seems to be working fine after a quick
breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
----- Original Message -----
From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
drkirkby@kirkbymicrowave.co.uk
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Tuesday, January 27, 2015 2:24 AM
Subject: Re: [volt-nuts] 3458A reference boards on ebay
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem
to
be going for about $165. The current batch of two is around $100, but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a quick
breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
Dave:
The 002 reference boards have another label on them marked 03458-66519
which overlays the etched number on the PC board. As a matter of fact see
the new listing on evilbay 271754789913. The super ultra stable 2ppm is
marked 03458-66529 to the best of my knowledge.
Bill
and follow the instructions there.
Dave,
I'll be putting it in an enclosure to use as a reference. It will probably
be a smallish diecast aluminium box. It's what I did with my Geller SVR-T
and it compared very well with my Fluke 731B. I'll likely use Pomona 3770
binding posts for output (I used them to repair the 731B). I'll also use
the protection circuits from the Fluke 732 on the output - big reverse
diode, gas discharge tube and TVS as I recall (I plan to add these
protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard would
likely be OK; the socket spacing is 0.9" and the pin spacing 0.1". My
meters are also 6 1/2 digit (3456A and 34461A) so I'm not too concerned
with thermal EMFs with one count being 10uV on the 10V range. However, I
will try to avoid temperature gradients and keep the outputs close
together. I'll use star wiring for the 18V and ground as in the following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and
without. I'd add a few tantalum capacitors to the above design - on the
regulator outputs and on the 3320 resistor, along with protection diodes
for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be
reviewing that for ideas:
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
I actually have a couple of LTZ1000As here that I was going to DIY, but
never got around to getting the precision resisters . I think there is a
source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem
to
be going for about $165. The current batch of two is around $100, but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a quick
breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
These various Keysight/Agilent/HP references are selected during aging but are all identical in parts and layout. Most of these references improve with age and after time many standard references will meet or exceed the performance of 002 or even the 2PPm HFL boards.
The question on these eBay boards is are they ones that failed to meet factory specs. What I often wonder is in this era of JJA's why has no one built a better reference like has been done with Quartz oscillators for many decades?
Cheers;
Thomas Knox
From: wpgold3637@att.net
To: volt-nuts@febo.com
Date: Tue, 27 Jan 2015 08:20:50 -0800
Subject: Re: [volt-nuts] 3458A reference boards on ebay
----- Original Message -----
From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
drkirkby@kirkbymicrowave.co.uk
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Tuesday, January 27, 2015 2:24 AM
Subject: Re: [volt-nuts] 3458A reference boards on ebay
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem
to
be going for about $165. The current batch of two is around $100, but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a quick
breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
Dave:
The 002 reference boards have another label on them marked 03458-66519
which overlays the etched number on the PC board. As a matter of fact see
the new listing on evilbay 271754789913. The super ultra stable 2ppm is
marked 03458-66529 to the best of my knowledge.
Bill
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
Take a look at this site for some good info on using the 3458A reference:
http://www.maxmcarter.com/vref/
Tony H
When these boards are installed in a 3458A, the LTZ1000 is covered by a small, white, 'hat' that mounts with screws that pass through the two holes on opposite sides of the LTZ1000. I've never removed the board to see if there is anything on the bottom of the board that would cover the bottom of the LTZ1000.
Does anyone know what this 'hat' is constructed of or the HP/Agilent/Keysight part number of this item is? Is it available from Keysight?
In the 3458A the reference board is under a cover that covers about half of the top of the meter but not 'insulated' beyond that, except for the 'hat' referred to above.
It would appear desirable to find what that 'hat' is and see if something could be fabricated to 'insulate' the LTZ1000 for a 'do it yourself' standalone reference.
Would appreciate hearing anything about how the reference board is 'insulated' in the 3458A.
Thanks.
Joe
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Orin Eman
Sent: Tuesday, January 27, 2015 11:45 AM
To: Discussion of precise voltage measurement
Subject: [Bulk] Re: [volt-nuts] 3458A reference boards on ebay
Dave,
I'll be putting it in an enclosure to use as a reference. It will probably be a smallish diecast aluminium box. It's what I did with my Geller SVR-T and it compared very well with my Fluke 731B. I'll likely use Pomona 3770 binding posts for output (I used them to repair the 731B). I'll also use the protection circuits from the Fluke 732 on the output - big reverse diode, gas discharge tube and TVS as I recall (I plan to add these protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard would likely be OK; the socket spacing is 0.9" and the pin spacing 0.1". My meters are also 6 1/2 digit (3456A and 34461A) so I'm not too concerned with thermal EMFs with one count being 10uV on the 10V range. However, I will try to avoid temperature gradients and keep the outputs close together. I'll use star wiring for the 18V and ground as in the following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and without. I'd add a few tantalum capacitors to the above design - on the regulator outputs and on the 3320 resistor, along with protection diodes for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be reviewing that for ideas:
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
I actually have a couple of LTZ1000As here that I was going to DIY, but never got around to getting the precision resisters . I think there is a source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave Ltd) < drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they
seem
to
be going for about $165. The current batch of two is around $100,
but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a
quick breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
There is a bottom cover under the board.
On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jltran@att.net wrote:
When these boards are installed in a 3458A, the LTZ1000 is covered by a
small, white, 'hat' that mounts with screws that pass through the two holes
on opposite sides of the LTZ1000. I've never removed the board to see if
there is anything on the bottom of the board that would cover the bottom of
the LTZ1000.
Does anyone know what this 'hat' is constructed of or the
HP/Agilent/Keysight part number of this item is? Is it available from
Keysight?
In the 3458A the reference board is under a cover that covers about half
of the top of the meter but not 'insulated' beyond that, except for the
'hat' referred to above.
It would appear desirable to find what that 'hat' is and see if something
could be fabricated to 'insulate' the LTZ1000 for a 'do it yourself'
standalone reference.
Would appreciate hearing anything about how the reference board is
'insulated' in the 3458A.
Thanks.
Joe
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Orin Eman
Sent: Tuesday, January 27, 2015 11:45 AM
To: Discussion of precise voltage measurement
Subject: [Bulk] Re: [volt-nuts] 3458A reference boards on ebay
Dave,
I'll be putting it in an enclosure to use as a reference. It will
probably be a smallish diecast aluminium box. It's what I did with my
Geller SVR-T and it compared very well with my Fluke 731B. I'll likely use
Pomona 3770 binding posts for output (I used them to repair the 731B).
I'll also use the protection circuits from the Fluke 732 on the output -
big reverse diode, gas discharge tube and TVS as I recall (I plan to add
these protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard
would likely be OK; the socket spacing is 0.9" and the pin spacing 0.1".
My meters are also 6 1/2 digit (3456A and 34461A) so I'm not too concerned
with thermal EMFs with one count being 10uV on the 10V range. However, I
will try to avoid temperature gradients and keep the outputs close
together. I'll use star wiring for the 18V and ground as in the following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and
without. I'd add a few tantalum capacitors to the above design - on the
regulator outputs and on the 3320 resistor, along with protection diodes
for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be
reviewing that for ideas:
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
I actually have a couple of LTZ1000As here that I was going to DIY, but
never got around to getting the precision resisters . I think there is a
source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they
seem
to
be going for about $165. The current batch of two is around $100,
but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a
quick breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
--
John Phillips
I bought two HP-3458A ref boards from John Daly (he no longer has any more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
On Wed, Jan 28, 2015 at 9:40 AM, John Phillips john.phillips0@gmail.com
wrote:
There is a bottom cover under the board.
On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jltran@att.net wrote:
When these boards are installed in a 3458A, the LTZ1000 is covered by a
small, white, 'hat' that mounts with screws that pass through the two
holes
on opposite sides of the LTZ1000. I've never removed the board to see if
there is anything on the bottom of the board that would cover the bottom
of
the LTZ1000.
Does anyone know what this 'hat' is constructed of or the
HP/Agilent/Keysight part number of this item is? Is it available from
Keysight?
In the 3458A the reference board is under a cover that covers about half
of the top of the meter but not 'insulated' beyond that, except for the
'hat' referred to above.
It would appear desirable to find what that 'hat' is and see if something
could be fabricated to 'insulate' the LTZ1000 for a 'do it yourself'
standalone reference.
Would appreciate hearing anything about how the reference board is
'insulated' in the 3458A.
Thanks.
Joe
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Orin
Eman
Sent: Tuesday, January 27, 2015 11:45 AM
To: Discussion of precise voltage measurement
Subject: [Bulk] Re: [volt-nuts] 3458A reference boards on ebay
Dave,
I'll be putting it in an enclosure to use as a reference. It will
probably be a smallish diecast aluminium box. It's what I did with my
Geller SVR-T and it compared very well with my Fluke 731B. I'll likely
use
Pomona 3770 binding posts for output (I used them to repair the 731B).
I'll also use the protection circuits from the Fluke 732 on the output -
big reverse diode, gas discharge tube and TVS as I recall (I plan to add
these protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard
would likely be OK; the socket spacing is 0.9" and the pin spacing 0.1".
My meters are also 6 1/2 digit (3456A and 34461A) so I'm not too
concerned
with thermal EMFs with one count being 10uV on the 10V range. However, I
will try to avoid temperature gradients and keep the outputs close
together. I'll use star wiring for the 18V and ground as in the
following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and
without. I'd add a few tantalum capacitors to the above design - on the
regulator outputs and on the 3320 resistor, along with protection diodes
for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be
reviewing that for ideas:
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
I actually have a couple of LTZ1000As here that I was going to DIY, but
never got around to getting the precision resisters . I think there is a
source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave Ltd)
<
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they
seem
to
be going for about $165. The current batch of two is around $100,
but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a
quick breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
--
John Phillips
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
Well, the current supply isn't from John Daly as far as I know.
My sanity check is monitoring the output of the 3458A reference board with
an Agilent 34461A. I don't see any difference from when I was monitoring a
Fluke 731B. So, I have no evidence either way. This 'monitoring' mostly
shows the temp-co of the '61A which is in the order of 1ppm.
I have started a new test with the '61A monitoring the ratio of the 731B to
the 3458A reference. I'd prefer a differential test, but that doesn't work
as well with the 3458A output at 7.17750V and the 731B at 10V.
Orin.
On Wed, Jan 28, 2015 at 7:07 PM, Randy Evans randyevans2688@gmail.com
wrote:
I bought two HP-3458A ref boards from John Daly (he no longer has any more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
On Wed, Jan 28, 2015 at 9:40 AM, John Phillips john.phillips0@gmail.com
wrote:
There is a bottom cover under the board.
On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jltran@att.net wrote:
When these boards are installed in a 3458A, the LTZ1000 is covered by a
small, white, 'hat' that mounts with screws that pass through the two
holes
on opposite sides of the LTZ1000. I've never removed the board to see
if
there is anything on the bottom of the board that would cover the
bottom
of
the LTZ1000.
Does anyone know what this 'hat' is constructed of or the
HP/Agilent/Keysight part number of this item is? Is it available from
Keysight?
In the 3458A the reference board is under a cover that covers about
half
of the top of the meter but not 'insulated' beyond that, except for the
'hat' referred to above.
It would appear desirable to find what that 'hat' is and see if
something
could be fabricated to 'insulate' the LTZ1000 for a 'do it yourself'
standalone reference.
Would appreciate hearing anything about how the reference board is
'insulated' in the 3458A.
Thanks.
Joe
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Orin
Eman
Sent: Tuesday, January 27, 2015 11:45 AM
To: Discussion of precise voltage measurement
Subject: [Bulk] Re: [volt-nuts] 3458A reference boards on ebay
Dave,
I'll be putting it in an enclosure to use as a reference. It will
probably be a smallish diecast aluminium box. It's what I did with my
Geller SVR-T and it compared very well with my Fluke 731B. I'll likely
use
Pomona 3770 binding posts for output (I used them to repair the 731B).
I'll also use the protection circuits from the Fluke 732 on the output
big reverse diode, gas discharge tube and TVS as I recall (I plan to
add
these protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard
would likely be OK; the socket spacing is 0.9" and the pin spacing
0.1".
My meters are also 6 1/2 digit (3456A and 34461A) so I'm not too
concerned
with thermal EMFs with one count being 10uV on the 10V range.
However, I
will try to avoid temperature gradients and keep the outputs close
together. I'll use star wiring for the 18V and ground as in the
following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and
without. I'd add a few tantalum capacitors to the above design - on
the
regulator outputs and on the 3320 resistor, along with protection
diodes
for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be
reviewing that for ideas:
I actually have a couple of LTZ1000As here that I was going to DIY, but
never got around to getting the precision resisters . I think there
is a
source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave
Ltd)
<
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they
seem
to
be going for about $165. The current batch of two is around $100,
but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a
quick breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a
standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
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