Author Topic: Ultra Precision Reference LTZ1000  (Read 410018 times)

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Online TiN

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Re: Ultra Precision Reference LTZ1000
« Reply #625 on: March 10, 2014, 01:58:30 AM »
I'll do all that later, when recovering schematics.
I just don't want to disassemble meter every time, for this or that, it's still likely in cal.
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Online Andreas

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Re: Ultra Precision Reference LTZ1000
« Reply #626 on: March 10, 2014, 07:48:03 AM »
Somewhat off topic but since the LTZ needs precision resistors too:

perhaps this fits to Franks results for the TC of the resistors.

With best regards

Andreas
 

Online casinada

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Re: Ultra Precision Reference LTZ1000
« Reply #627 on: March 11, 2014, 03:37:52 AM »
Is anybody familiar with this unit?
VALHALLA 2720GS
http://www.adret-electronique.fr/valhalla_2720/adret_valhalla_2720.html

It has 0.01 ppm and suppose to be able to calibrate 8 1/2 digit DMMs :)
10.0000000V :)
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #628 on: March 11, 2014, 03:56:11 AM »
I am a big fan of Valhalla gear and saw this unit before.
But so far I have never seen a real one and only have seen very litte details. 
see att. Prices and HSR specs
« Last Edit: March 11, 2014, 04:04:08 AM by quarks »
 

Offline CaptnYellowShirt

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Re: Ultra Precision Reference LTZ1000
« Reply #629 on: March 11, 2014, 03:58:30 AM »
"2 Year Spare Parts" ?

Does it require regular oil changes?
 

Offline Mickle T.

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Re: Ultra Precision Reference LTZ1000
« Reply #630 on: March 11, 2014, 04:05:28 AM »
Valhalla 2720GS = Solartron 7081 (PWM ADC) + Datron 4000A (8x 1N829 zeners and PWM DAC)  ;D

2720GS has a very old and noisy PWM type ADC for a such measurements. 0.01 ppm resolution is absolutely useless.
 

Online TiN

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Re: Ultra Precision Reference LTZ1000
« Reply #631 on: March 11, 2014, 11:34:21 PM »
There is dead one on ebay for sale for a while for 1K.

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Offline babysitter

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Re: Ultra Precision Reference LTZ1000
« Reply #632 on: March 12, 2014, 06:44:15 AM »
Freshly calibrated [email protected] arrived from cal today, will measure my LTZ source soon :)
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Online Andreas

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Re: Ultra Precision Reference LTZ1000
« Reply #633 on: March 12, 2014, 04:41:58 PM »
Freshly calibrated [email protected] arrived from cal today, will measure my LTZ source soon :)

Too late: you are already outside the 24hrs calibration window.
For the 90 days tolerances the accuracy is +/- 190uV for a 7V source.

And did you measure the 34401a before shipping?
Or how can you tell that the device did not drift during transport back from calibration?

With best regards

Andreas
 

Offline babysitter

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Re: Ultra Precision Reference LTZ1000
« Reply #634 on: March 12, 2014, 07:26:23 PM »
Hi Andreas,

its too late to use the 24h-window, yes.
But its not too late to do exactly what I am able to do, although it will be one more day I am afraid.

I have a second 34401A sitting here which was compared to the cal'd one right before shipping, should be able to give a hint from it how the difference between departure and (late) arrival is.

However, Agilent screwed up a bit this time, the meter was out for about one month, they requested more and more order confirmations totalling at 3 (upfront at InfoLine, on paper with signature in the box and after their 3rd request as email again), cal was on 6th and arrived here on 11th.

It only gives a bigger window of where the actual voltage might be. But I dont expect the LTZ to have wandered too far.

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Offline DiligentMinds.com

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Re: Ultra Precision Reference LTZ1000
« Reply #635 on: March 13, 2014, 08:02:10 AM »
Hello fellow forum users,

I just finished with a telephone conversation with Bob Dobkin, and he was short on time, so I was not able to get all of the answers to every question I [and we] had, but here are the ones I was able to get:

1) [FYI]:  The applications circuits in the LTZ1000 data-sheet and other ap-notes were designed by Bob Dobkin, not Jim Williams.

2) Regulation in the LTZ1000 is more about controlling the power rather than controlling the voltage.  If you accurately control the power, voltage stability will be achieved as a by-product.

3) The LTZ1000A has a different die attach than the LTZ1000, but they are both isolated quite a bit from external lead stress.  Both of them will respond a small amount to lead stress, but the 'A' version if far less susceptible to this.  Bob said that this can show up as a drift in output voltage with changes in barometric pressure.

4) It's been 20 years, so he didn't know the exact numbers, but Q1 is only rated to a few hundred micro-amps of collector current.  [This means my single-resistor idea will *not* work! -- back to the original circuit from the ap-note!]  Q2 will have a max rating of around 1mA, and the Zener can take quite a bit more.

5) They *could* make a model for LTspice, but the temperature effects are very difficult to simulate, and the market need is not large enough to support the development effort [my words].  He said the best way is to build the circuit and test it out in real life.

6) After telling him that I wanted a voltage transfer device, he said a better way might be to use [at least 6] LM399's in parallel [like the Bob Pease idea].  He said that the burn-in procedure would be to operate these in an oven set to 125C for 2 weeks, which would be equivalent to 1000's of hours of normal operation.  Any LM399's that are drifting too much after that can be replaced [i.e., you burn-in more than you need, and select the best units for the array].  The LM399 is much more sensitive to board stress than the LTZ [because the LTZ has a special mechanical arrangement in the die mount]-- so the LM399 should be mounted off of the PCB a little bit to allow for this.  The long term stability of the array of LM399's will be directly related to the power required to run the heater-- and this can be minimized with insulation-- the more the better!  The LM399's do not age when they are turned off, and have almost no hysteresis-- so keeping the reference *off* until a few hours before you need to use it [and/or calibrate it] is the best way to keep the long-term drift minimized.

7) Note that for LM399-based designs, the slots in the PC board [plus a lot of insulation top and bottom] make sense-- Bob said that the less power the heater requires, then the more stable the output voltage will be.  So, in this case, the slots [plus insulation] are helping with this.  Oh-- and he also said that the LM399 should be run at about 1mA of Zener current for best stability.  The more stable you can make the Zener current, the more stable will be the output voltage.  He said that there is about 1uV of voltage change for 1uA of current change.

8: All voltage references *do* age faster at higher temperatures.  So, since the LTZ1000 can be run about 10-deg-C lower than the 'A' version, it will have lower [about 1/2] long-term drift than the LTZ1000A under otherwise identical conditions.  [But, the 'A' version has *other* differences that are positive-- my words.  There are other sources of drift that the 'A' version is less susceptible to-- barometric pressure changes is one of them].

9) For the LM399 and both of the LTZ parts, he said a good burn-in routine would be to operate them at 125C [in an oven] for 2 weeks.  After that, you can cycle the power on and off 10 to 15 times at normal operating temperature, and this will get them to settle down.  This process should remove most of the initial drift that these devices exhibit.  [So, my initial guess for a burn-in cycle was pretty good-- there is nothing wrong with a burn-in 10 times longer than this.]

10) If properly insulated, an LM399 can have a ppm/K figure of between 0.1ppm/K to 0.2ppm/K-- the data sheet is *very* conservative.  [Note that the DMM manufacturers are not insulating these other than the plastic insulator that they come in-- they would benefit by better insulating the top and bottom of the LM399 to keep the heat in, and the heater power down.]

11) They are working on releasing more parts in the LS8 [8-pin ceramic LCC] package-- they should be coming out later this year.  Some of the parts will not fit in the LS8, and they will have to use a larger ceramic LCC for those.  He said the 1021 series will also be on the list of parts that will be released in LS8.

12) The ceramic LCC's have Kovar in them to get out of the package-- so, you don't get away from the thermal EMF problem, and these parts should be insulated from air currents [just like the TO-style packages] after they are mounted on the board.

13) The LTZ parts do not need to be spaced above the PC board like the LM399 does due to the unique mechanical de-stress design inside the package.

14) They will not be building a reference design for the LTZ part-- this is a niche product that does not warrant the development time.  [That does not mean that *we* cannot come up with our own reference design!  Let me think about this-- perhaps if there is enough interest, I can take the risk to do this...]

15) The TO packages are filled with *DRY AIR*-- not even nitrogen-only [so you would expect some degradation from this-- my words]-- but, Bob says that they don't have any parts that are degraded by this.

16) The LTZ1000 will use a lot more power than the LTZ1000A, so for battery operated circuits, it's best to go with the LTZ1000A, and insulate it to save power.

17) There is probably not a scenario where you can get zero-TC out of the LTZ-- he said you probably would have to operate Q1 at around 1uA, and that is not practical.

18) He said that it is not necessary to use the LTC2057, as the drift and noise of the Zener contribute far more than the LT1013.  Bob said that you could use almost any precision op-amp, and the drift would not be affected by much even by the less precise amps.  [I'm still going to use the LTC2057 anyway-- they are as cheap as popcorn, and have very little noise.  Since I *do* need a zero-drift amp in the follow-on boost circuitry, and it's more economical to keep the number of unique parts on the BOM as low as possible.]

19) The Zener in the LTFLU-1 is the exact same one as is in the LTZ1000.  He said that even though the exclusivity portion of the contract with Fluke is no longer in effect, they are not going sell these to the public because they don't want to anger a customer that buys millions of dollars in other parts from them.  Even if they did want to sell it to others, it has not been characterized and there is no data sheet-- so there would be a lot of work just to build that.  It's just not going to happen...

20) Bob said that he would join this forum, but he doesn't have enough time in the day to deal with what he already has to do-- so, it is not likely that he will participate.  He said that I can email him with any questions I [we] have in the future, and he will do his best to answer them.

That's about all we could fit in.  I hope that helps everyone-- it sure helped me a lot, as I was able to see that my "single resistor" design would not work.  Bob said the that the LTZ would probably not be destroyed by my circuit [because "the LTZ can take a lot of abuse"], but it still would not ever be reliable even if it did work in the laboratory.

I was furiously taking notes during the phone call, and so I may have missed a few things-- if I remember anything I missed I will post it.

Regards,
Ken
« Last Edit: March 13, 2014, 08:05:23 AM by DiligentMinds.com »
 
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Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #636 on: March 13, 2014, 08:41:00 AM »
Thanks for sharing all this information.

Quote
7) Note that for LM399-based designs, the slots in the PC board [plus a lot of insulation top and bottom] make sense-- Bob said that the less power the heater requires, then the more stable the output voltage will be.  So, in this case, the slots [plus insulation] are helping with this.  Oh-- and he also said that the LM399 should be run at about 1mA of Zener current for best stability.  The more stable you can make the Zener current, the more stable will be the output voltage.  He said that there is about 1uV of voltage change for 1uA of current change.

9) For the LM399 and both of the LTZ parts, he said a good burn-in routine would be to operate them at 125C [in an oven] for 2 weeks.  After that, you can cycle the power on and off 10 to 15 times at normal operating temperature, and this will get them to settle down.  This process should remove most of the initial drift that these devices exhibit.  [So, my initial guess for a burn-in cycle was pretty good-- there is nothing wrong with a burn-in 10 times longer than this.]


That confirms the way I realized my first LM399 reference, a slotted pcb design with a thermal encapsulation on both sides and a thermal burn-in of the board for more than 300h, but sure without powering the circuit, as I had no adequate cables at hand. The reference seems to be very stable and that makes me believe that the humidity depended drift I can observe is the drift of the 34401As reference itself, because all the mentioned actions are not realized in this DMM.

Once again, thanks for sharing.
Prema 5000 | Prema 5017 SC | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Keithley 181, Prema 5017 SC, 34401A, 34410A, HDO6054 and other goodies at work
 

Online Vgkid

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Re: Ultra Precision Reference LTZ1000
« Reply #637 on: March 13, 2014, 09:51:39 AM »
Thnks for sharing Dilligentminds
If you own any North Hills Electronics gear, message me.
 

Offline quantumvolt

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Re: Ultra Precision Reference LTZ1000
« Reply #638 on: March 13, 2014, 10:34:34 AM »
Thank you very much to Bob Dobkin and to you DiligentMinds.com.

I have been working a lot with the SZA263-type AmpRef/RefAmp circuit, and have found that HP used the circuit/component already in 1963, while Fluke seems to use it first time around 1971. The circuits are so similar that it is imo unreasonable to argue for any originality in the Fluke 731A.

So may be it could be an idea for US based volt-nuts to contact Fluke and ask them to "free" the LTFLU-1.
 

Offline CaptnYellowShirt

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Re: Ultra Precision Reference LTZ1000
« Reply #639 on: March 13, 2014, 11:02:36 AM »
Did you happen to get an address that we could send a thank you card to?
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #640 on: March 13, 2014, 11:54:25 AM »
 :-+ great information
Thanks a lot for sharing
 

Offline robrenz

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Re: Ultra Precision Reference LTZ1000
« Reply #641 on: March 13, 2014, 12:41:22 PM »
Thanks for the great information :-+

That gives me confidence to continue my practice of only turning on my 8846A when using it.

Offline DiligentMinds.com

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Re: Ultra Precision Reference LTZ1000
« Reply #642 on: March 13, 2014, 01:05:55 PM »
Thank you very much to Bob Dobkin and to you DiligentMinds.com.

I have been working a lot with the SZA263-type AmpRef/RefAmp circuit, and have found that HP used the circuit/component already in 1963, while Fluke seems to use it first time around 1971. The circuits are so similar that it is imo unreasonable to argue for any originality in the Fluke 731A.

So may be it could be an idea for US based volt-nuts to contact Fluke and ask them to "free" the LTFLU-1.

Good luck with that!  Fluke was purchased by the evil Danaher corporation (along with Keithley and Tektronix)-- they pretty much fire everyone over the age of 30 [thus losing the people that actually know *why* things were done in the past], then they cancel anything that isn't making huge profits, and then milk their "captive customers" for everything that they are worth.  I seriously doubt if they are going to budge even one inch in giving us access to *anything*.  But you can *try*... Let us know how that goes!
 

Offline DiligentMinds.com

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Re: Ultra Precision Reference LTZ1000
« Reply #643 on: March 13, 2014, 01:06:56 PM »
Did you happen to get an address that we could send a thank you card to?

No, I did not, but you can probably send it to the main office in Milpitas, CA and it will get to him.
 

Offline DiligentMinds.com

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Re: Ultra Precision Reference LTZ1000
« Reply #644 on: March 13, 2014, 01:13:10 PM »
I'm thinking of buying one or two of those SZA263's and one or two of the LTFLU-1AH's-- just to "play with" [for my own personal edification, as I know they will *never* be available to the public]...  Does anyone know if the one's for sale on "fleaBay" are the "real deal" [or is it some kind of scam]?

I suppose I could build a "poor man's" version of a Ref-Amp with the 7V Zener part of an LT1034, and a 2N2222A [or maybe a low-noise RF transistor?]-- then put those in a hermetic package of some sort [*after* I bake them in the oven long enough to remove any water the epoxy has absorbed].
« Last Edit: March 14, 2014, 11:47:50 AM by DiligentMinds.com »
 

Offline quantumvolt

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Re: Ultra Precision Reference LTZ1000
« Reply #645 on: March 13, 2014, 01:24:49 PM »
Thank you very much to Bob Dobkin and to you DiligentMinds.com.

I have been working a lot with the SZA263-type AmpRef/RefAmp circuit, and have found that HP used the circuit/component already in 1963, while Fluke seems to use it first time around 1971. The circuits are so similar that it is imo unreasonable to argue for any originality in the Fluke 731A.

So may be it could be an idea for US based volt-nuts to contact Fluke and ask them to "free" the LTFLU-1.

Good luck with that!  Fluke was purchased by the evil Danaher corporation (along with Keithley and Tektronix)-- they pretty much fire everyone over the age of 30 [thus losing the people that actually know *why* things were done in the past], then they cancel anything that isn't making huge profits, and then milk their "captive customers" for everything that they are worth.  I seriously doubt if they are going to budge even one inch in giving us access to *anything*.  But you can *try*... Let us know how that goes!

I sure will  >:D  Nothing to lose...

I do however not expect much. After seeing the 6-in-1 launch timer/clock running negative overtime far to long after count-down, I sent an email to Tek's Quality Dept. The timer was taken away a few hours later. But they didn't thank me - they are now repeatedly filling my email inbox with US located seats for some post-launch sessions.

But I have seen a video on YT with Fluke's Chief Corporate Metrologist Mr. Jeff C. Gust. If it is not all circus for the masses, I suppose he will at least answer my mail.

I'll be back in due time  :-BROKE
 

Offline CaptnYellowShirt

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Re: Ultra Precision Reference LTZ1000
« Reply #646 on: March 13, 2014, 01:45:38 PM »
Did you happen to get an address that we could send a thank you card to?

No, I did not, but you can probably send it to the main office in Milpitas, CA and it will get to him.

I'm going to send him a thank you card from the [Volt-Nuts].

I think it'd be nice if he could see the international cross section of people that have benefited from his advice. PM me if you want your name or handle in the signed-by section. Include what you want to be called and a city and country if you don't mind.

I'll post a picture of the card before I send it.
 

Online TiN

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Re: Ultra Precision Reference LTZ1000
« Reply #647 on: March 13, 2014, 03:59:16 PM »
Great, thanks!

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Offline DiligentMinds.com

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Re: Ultra Precision Reference LTZ1000
« Reply #648 on: March 13, 2014, 04:32:06 PM »
Did you happen to get an address that we could send a thank you card to?

No, I did not, but you can probably send it to the main office in Milpitas, CA and it will get to him.

I'm going to send him a thank you card from the [Volt-Nuts].

I think it'd be nice if he could see the international cross section of people that have benefited from his advice. PM me if you want your name or handle in the signed-by section. Include what you want to be called and a city and country if you don't mind.

I'll post a picture of the card before I send it.

No need for the private message-- you could find out who I am anyway just from the domain name registration for DiligentMinds.com ...

You can sign my name "Ken Peek from Las Vegas, NV, USA -- DiligentMinds.com".

Thanks!
« Last Edit: March 13, 2014, 04:34:36 PM by DiligentMinds.com »
 

Offline CaptnYellowShirt

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Re: Ultra Precision Reference LTZ1000
« Reply #649 on: March 13, 2014, 04:39:19 PM »

No need for the private message-- you could find out who I am anyway just from the domain name registration for DiligentMinds.com ...


The judge said I have to stop cyber-stalking people ... its part of my parole.  ;)

Your name will be the first on the list.
 


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