Re: [volt-nuts] plastic caps on 3458A reference board
Frank, Thanks for the info. I've wondered about that. In the days of 3D printers and CAD/CAM, it might be possible to have a 'run' of these 'made to order', so to speak. I wonder if Linear Technology would have any information about them? Thanks again. Joe -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Frank Stellmach Sent: Wednesday, January 28, 2015 5:28 AM To: volt-nuts@febo.com Subject: [volt-nuts] plastic caps on 3458A reference board Hello Joe, yes the cap consists of two parts. The upper one serves for thermal isolation of the LTZ1000A TO99 case against the environment and therefore reduces the power dissipation of the oven. The part on the solder side is much more important, as it covers the solder joints and avoids air draught over these pins. That avoids these low frequency voltage variations, which are mentioned in the LTZ data sheet. Anyhow, there are no further shieldings around the PCB, so the solder joints of the OP Amp and the precision resistors are exposed to that air draught, maybe from the fan. That's a further engineering fault they made on this reference. (The other faults are the 95°C oven temperature, the use of the A version instead of the non A, and the use of R417,200k temperature compensation resistor, which is necessary for the non A version only.) The hat is not included in the BOM inside the CLIP, therefore can not be ordered from HP, obviously. It is a smooth, shiny plastic, resembles the one used around the LM399H. Wasn't latter one something like polysulphone? Maybe suitable pieces of polystyrol foam will do the job also. Frank ___ 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] plastic caps on 3458A reference board
Hello Joe, yes the cap consists of two parts. The upper one serves for thermal isolation of the LTZ1000A TO99 case against the environment and therefore reduces the power dissipation of the oven. The part on the solder side is much more important, as it covers the solder joints and avoids air draught over these pins. That avoids these low frequency voltage variations, which are mentioned in the LTZ data sheet. Anyhow, there are no further shieldings around the PCB, so the solder joints of the OP Amp and the precision resistors are exposed to that air draught, maybe from the fan. That's a further engineering fault they made on this reference. (The other faults are the 95°C oven temperature, the use of the A version instead of the non A, and the use of R417,200k temperature compensation resistor, which is necessary for the non A version only.) The hat is not included in the BOM inside the CLIP, therefore can not be ordered from HP, obviously. It is a smooth, shiny plastic, resembles the one used around the LM399H. Wasn't latter one something like polysulphone? Maybe suitable pieces of polystyrol foam will do the job also. Frank ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
this would be over-engineered, unless you have a lot of spare time or want to do this for fun. If you use plastic supports as they were used when these TO packages were common (these supports should still be available, they surround all pins and quality plastics were standard) and use any cap in addition on top of the case, thats enough blocking of airflow. you would put that into a closed box anyhow, with no air flow through fans or so. Gesendet: Mittwoch, 28. Januar 2015 um 15:00 Uhr Von: J. L. Trantham jlt...@att.net An: 'Discussion of precise voltage measurement' volt-nuts@febo.com Betreff: Re: [volt-nuts] plastic caps on 3458A reference board Frank, Thanks for the info. I've wondered about that. In the days of 3D printers and CAD/CAM, it might be possible to have a 'run' of these 'made to order', so to speak. I wonder if Linear Technology would have any information about them? Thanks again. Joe -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Frank Stellmach Sent: Wednesday, January 28, 2015 5:28 AM To: volt-nuts@febo.com Subject: [volt-nuts] plastic caps on 3458A reference board Hello Joe, yes the cap consists of two parts. The upper one serves for thermal isolation of the LTZ1000A TO99 case against the environment and therefore reduces the power dissipation of the oven. The part on the solder side is much more important, as it covers the solder joints and avoids air draught over these pins. That avoids these low frequency voltage variations, which are mentioned in the LTZ data sheet. Anyhow, there are no further shieldings around the PCB, so the solder joints of the OP Amp and the precision resistors are exposed to that air draught, maybe from the fan. That's a further engineering fault they made on this reference. (The other faults are the 95°C oven temperature, the use of the A version instead of the non A, and the use of R417,200k temperature compensation resistor, which is necessary for the non A version only.) The hat is not included in the BOM inside the CLIP, therefore can not be ordered from HP, obviously. It is a smooth, shiny plastic, resembles the one used around the LM399H. Wasn't latter one something like polysulphone? Maybe suitable pieces of polystyrol foam will do the job also. Frank ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
I needs to insulate electrical and thermal and metal would not do well. On Wed, Jan 28, 2015 at 11:36 AM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 28 January 2015 at 18:56, Charles Steinmetz csteinm...@yandex.com wrote: The problem is that an LTZ1000 (or LM399) runs hot enough that most plastics you find lying around won't stand up to it for very long (some of them melt almost immediately when you power it up). This is true even of polycarbonate, which is one of the most durable common plastics, and is why the original caps were made from polysulfone. Unfortunately, it also means that replacements may be hard to make by 3D printing, since the process depends on melting the base material. Best regards, Charles Is there any reason this cap is not made of metal? If its purpose is to restrict airflow by convection, metal will do. Copper sheet can easily be soldered to make something that would restrict airflow and s If you want thermal insulation, then PTFE rivited to a metal shield would provide a plastic that will not melt, and the metal would keep it in place, as its hard to form a box out of PTFE. It is not an easy material to glue, but nuts/bolts/rivits will work. 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. -- *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.
[volt-nuts] plastic caps on 3458A reference board
Well, my guess for poly-sulfone for the top cap was not that bad: The HP LTZ circuit, and also the LM399, were heated to about 95°C, and therefore, you need a thermally insulating plastic, which can withstand that temperature. Poly sulfone is able to do so, whereas poly-styrene is OK for 70°C maximum, like in 45°C designs. It would be OK also for that amateur purpose, if it's thick enough: The inner layer would deteriorate over time, but the outer side would still isolate enough. If the whole PCB is placed inside a shielding box, the solder side cap can be omitted, of course. I would place a thin sheet of poly styrene underneath the PCB to thermally insulate the circuit. Frank ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
Dave wrote: If you want thermal insulation, then PTFE ... John wrote: I[t] needs to insulate electrical and thermal and metal would not do well. Two machined pieces of glass-filled PTFE with holes to pass screws or plastic rivets through should work pretty well. You want some thermal insulation, but not too much (there has to be a heat flow path to ambient to allow the heater to work at a reasonable fraction of its capacity), so the thickness of the top part would need to be right and some experimentation might be required. I've made a number of machined parts out of plain PTFE and glass-filled PTFE -- either one is definitely do-able. Straight PTFE is subject to cold-flowing, so if you used that some thought would need to be given to the through-bolts so everything would stay tight. Belleville washers are one common solution. But glass-filled PTFE is harder and more stable, and is the better choice for this job. I've never machined polysulfone, but it is routinely done, so that is another choice. It is also available with glass filling. Once a design was set and programmed, a small CNC mill could zip out enough parts to fill the next 100 years' volt-nut needs in ten minutes. For those who haven't seen one, here is a top view of a 3458A reference board showing the LTZ1000 with its hat on: http://cache.amobbs.com/bbs_upload782111/files_17/ourdev_466753.jpg. As Frank noted, the bottom piece (not shown) is very important because it insulates the thermocouple joints where the part is soldered to the board. Best regards, Charles ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
Poul-Henning wrote: I've often wondered what would happen if you put one of these circuits (xtal, vref etc) in a suitable small box, and filled the box with with aerogel powder: * * * I'm pretty sure you'd get very stable temperatures, my worry is that you'd get too high stable temperatures... I think over-insulation is a very real worry, given what the web site says about the thermal insulating properties. The properties they described seem to be those of a solid block or sheet -- the powder may not be quite as good -- but still, it seems like you'd be going a long way toward emulating a dewar, and it is very easy to over-insulate an oscillator or other circuit with a dewar. Another possibility is glass microballoons (also called microspheres), which are just what they sound like. They are a very common filler for epoxy when a featherweight composite is required. Either one would probably be kind of messy Best regards, Charles ___ 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] plastic caps on 3458A reference board
Most low-end 3D filament printers can print in either PLA, ABS, or even nylon. PLA prints are known to distort in a hot car. ABS is extruded at around 250C. I think nylon is a bit higher. I would think that ABS would work well.There are now some low-ish cost (like under $3000) stereo-lithography printers available that print by scanning a liquid resin with a laser. Some of those resins are good for higher temperatures. The low end resins have a glass transition temperature of around 100C. Another possibility is to make a mold and cast the parts out of epoxy. Epoxies that can handle over 400C are available. ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
Hi, I wouldn't completely discount 3D printing due to temperature. There are companies claiming to print the high nickel super alloys. It's questionable whether the plastics are available in the form needed, but laser sintering technologies appear to be out there now. If stock is available in raw form, for a few 'one off' items CNC would probably be the way to go. Anyone have a few bars of this stuff laying around? ;) Dan The problem is that an LTZ1000 (or LM399) runs hot enough that most plastics you find lying around won't stand up to it for very long (some of them melt almost immediately when you power it up). This is true even of polycarbonate, which is one of the most durable common plastics, and is why the original caps were made from polysulfone. Unfortunately, it also means that replacements may be hard to make by 3D printing, since the process depends on melting the base material. Best regards, Charles ___ 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.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
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.philli...@gmail.com wrote: There is a bottom cover under the board. On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jlt...@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-boun...@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) drkir...@kirkbymicrowave.co.uk wrote: On 27 January 2015 at 09:16, Orin Eman orin.e...@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
Re: [volt-nuts] plastic caps on 3458A reference board
Hi, for me, the obvious solution was a heat-resistant spacer - a EPDM O-Ring in my case - to fix a hat which is a bit wider than required, which was a simple dustproofing cap for a vacuum port (a bottle cap might also work). The thin air layer in between is not expected to do too much harm. This seems to be PP in my case, but as it is already a bit insulated, not much harm would be done even with a hotter Ref. On the underside (low distance to wall of metal box), I had either a piece of foam or nothing - i forgot. Frank, do you still know as you inspected it? Also, would everybody who wants a heat resistant cap please stand up - thank you - and now would everybody sit down who expects less than 50 deg C inside the reference box ? Go for simple isolation, invest in the right resistor to do the 45/55 degree hack and enjoy your lower drift. Epoxy formed in a silicon mould would be the way I go for heat resistant insulation parts. Hendrik ___ 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.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
Am 29.01.2015 04:07, schrieb Randy Evans: 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 Hi Randy, Noise bursts, especially if they get back on track again, sound like electromagnetic interference from your short description. If applicable, turn of the CFL or LED lighting, replace the switch-mode power supply with a linear one or even better a battery,, try a known non-reject in place of the ebay reference module, spread some capacitors on/around the module and/or invest in a metal box. Hendrik ___ 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.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
I think teletekj...@gmail.com has some that were removed from working unit to upgrade to the more stable board. On Wed, Jan 28, 2015 at 7:07 PM, Randy Evans randyevans2...@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.philli...@gmail.com wrote: There is a bottom cover under the board. On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jlt...@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-boun...@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) drkir...@kirkbymicrowave.co.uk wrote: On 27 January 2015 at 09:16, Orin Eman orin.e...@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?
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
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 randyevans2...@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.philli...@gmail.com wrote: There is a bottom cover under the board. On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jlt...@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-boun...@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) drkir...@kirkbymicrowave.co.uk wrote: On 27 January 2015 at 09:16, Orin Eman orin.e...@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
Re: [volt-nuts] plastic caps on 3458A reference board
On Wed, Jan 28, 2015 at 10:56 AM, Charles Steinmetz csteinm...@yandex.com wrote: I'd think a couple of pieces of pink (non-conductive) closed cell antistatic foam, one hollowed out a bit with a penknife, would work well. It would both shield from airflow and provide insulation. The problem is that an LTZ1000 (or LM399) runs hot enough that most plastics you find lying around won't stand up to it for very long (some of them melt almost immediately when you power it up). This is true even of polycarbonate, which is one of the most durable common plastics, and is why the original caps were made from polysulfone. There seem to be many examples using pink foam as insulation over on the EEVBlog forum thread and no complaints at all about the foam melting... However, they are using DIY boards for the LTZ1000(A), not the HP 3458A board. I guess it's time to go and apply some pink foam to my board. Orin. ___ 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.
Re: [volt-nuts] plastic caps on 3458A reference board
On 1/28/2015 9:00 AM, J. L. Trantham wrote: In the days of 3D printers and CAD/CAM, it might be possible to have a 'run' of these 'made to order', so to speak. I'd think a couple of pieces of pink (non-conductive) closed cell antistatic foam, one hollowed out a bit with a penknife, would work well. It would both shield from airflow and provide insulation. ___ 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.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
There is a bottom cover under the board. On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jlt...@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-boun...@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) drkir...@kirkbymicrowave.co.uk wrote: On 27 January 2015 at 09:16, Orin Eman orin.e...@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
Re: [volt-nuts] plastic caps on 3458A reference board
On 28 January 2015 at 18:56, Charles Steinmetz csteinm...@yandex.com wrote: The problem is that an LTZ1000 (or LM399) runs hot enough that most plastics you find lying around won't stand up to it for very long (some of them melt almost immediately when you power it up). This is true even of polycarbonate, which is one of the most durable common plastics, and is why the original caps were made from polysulfone. Unfortunately, it also means that replacements may be hard to make by 3D printing, since the process depends on melting the base material. Best regards, Charles Is there any reason this cap is not made of metal? If its purpose is to restrict airflow by convection, metal will do. Copper sheet can easily be soldered to make something that would restrict airflow and s If you want thermal insulation, then PTFE rivited to a metal shield would provide a plastic that will not melt, and the metal would keep it in place, as its hard to form a box out of PTFE. It is not an easy material to glue, but nuts/bolts/rivits will work. 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.
