Author Topic: Group-buy for 10V LTZ1000A reference? [Completed, no more boards].  (Read 1415 times)

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Offline TiN

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Considering Decided to make 10 completely assembled and tested modules to provide +10.00000 +/-4 ppm buffered output.
One of the challenges is cost and time involved to test and calibrate these things.

Device is based around xDevs.com FX module PCB, which have next design specifications:

Reference source: LTZ1000ACH with datasheet schematics, using LT1013ACN.
LTZ Temperature SP: 13K/1K which provide about +55C oven temp
Resistors: VPG BMF HZ for 120ohm, temperature SP. PTF56 5ppm/K for 70-80K bias resistors
Output 7V->10V stage: Chopper opamp ADA4522-2 in SO8, Hermetic resistor network or BMF resistors. Each unit adjusted by trim resistor for tight output tolerance.
Onboard supply: Linear LT3042 LDO, configured for +11V output to LTZ circuit.
PCB: 4-layer FR4 with ENIG plating
Input power requirements: +12V and -12V.
Power consumption : ~0.6W when operated with +24C ambient
Additional features : isolated section with I2C EEPROM with calibration data/config/history (RPI python app to be provided to maintain data), MAX6610 PCB temperature sensor for tracking
Calibration traceability: <4 ppm to 732B, uncertain with 0.6ppm.
Expected performance: <4 ppm/year long-term stability, <0.1ppm/K tempco over 18-28C ambient temperature.
Assembly type: Hammon metal box with Pomona 3770 low-thermal binding posts.

I'd like to check if there is any interest in expensive hobby-level reference among the members here.
If enough people would be willing to buy one, it will be easier for me to pull the trigger and tie in 4-5K$ into this project.
Estimated delivery date would be March 2018, with final good cost $500 USD.

Specs above are on safe side, so the module likely to be 2-5 times more stable, however I wouldn't guarantee it just yet. There is no replacement to actually running reference for 3+ years to determine actual long-term annual stability.

Feel free to comment :)

Member list, who interested in module

montemcguire - 1 unit [CONFIRMED]
dr.diesel - 1 unit
chriswebb - 1 unit
PeLuLe - 2 unit
MM - 1 unit [CONFIRMED]
bck - 1 unit [CONFIRMED]
USA cal club - 1 unit [CONFIRMED]
CM - 1 unit [CONFIRMED]
zucca - 1 unit

No more units available., unless somebody change their mind.

Prototype board overview, test data samples



Initial output after first assembly.


« Last Edit: December 09, 2017, 07:55:00 PM by TiN »
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Offline Vgkid

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #1 on: December 06, 2017, 04:24:58 PM »
Sounds interesting, I would do it if I ever get the money. That would be around 6mo + from now.
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Offline montemcguire

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #2 on: December 06, 2017, 05:33:16 PM »
I'd buy one - count me in!
 

Online lukier

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #3 on: December 06, 2017, 10:40:23 PM »
Does it really need -12V? It would be much simpler to have just one battery (12V lead-acid or 4x18650 LiPo).
 

Offline dr.diesel

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #4 on: December 06, 2017, 11:29:10 PM »
Count me in, prepay is no problem to help offset costs.

Offline maxwell3e10

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #5 on: December 07, 2017, 12:33:45 AM »
Sounds interesting. What would be the specification for 0.1 to 10Hz rms noise? That is primarily what I am interested in.
 

Offline mimmus78

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #6 on: December 07, 2017, 12:45:32 AM »
I'm interested too but as I'm building my own version I'm not interested in buying one.

I have a DHL contact with good fee for international shipping ... I can offer few trips for free is some of this board wants to became a traveling standard among EU guys or for just a stop and go.
« Last Edit: December 07, 2017, 12:50:43 AM by mimmus78 »
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Offline nidlaX

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #7 on: December 07, 2017, 12:54:15 AM »
I'm interested, but it's only a run of 10 units?
 

Online chriswebb

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #8 on: December 07, 2017, 03:17:57 AM »
I'd also be interested in picking up a unit if available.
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Offline Kleinstein

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #9 on: December 07, 2017, 04:35:10 AM »
Does it really need -12V? It would be much simpler to have just one battery (12V lead-acid or 4x18650 LiPo).

The circuit should run with less than -12 V. It should be possible to make it run on just a single supply, maybe 14 V. For battery operation something like 12 V min would be nice, but this would not leave much room for driving both the positive and negative side. So getting it down to 4 Li Cells could be a little tricky.
 

Offline TiN

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #10 on: December 07, 2017, 04:47:53 AM »
montemcguire, dr.diesel, chriswebb - OK, I'll keep you guys in mind.

Quote
Does it really need -12V?
-3V can be fine too, I checked today, output change was less than 0.4ppm.
But I will be validating only +12/-12 +/-5%. Negative voltage is used on the output stage, not the LTZ-ref itself.

Quote
Sounds interesting. What would be the specification for 0.1 to 10Hz rms noise?
I expect ~3 uV perhaps. Will know better once I test first 3 prototypes I have now.

Quote
I'm interested, but it's only a run of 10 units?
Even to make 10 boards, lot of time and money will be tied in, so I'd rather spend some resource for other projects, using this reference, instead of making just the reference. I originally did not plan to make any extra's at all, and still need to run the numbers to pull the trigger.

Also each output resistor network must match the used LTZ chip value, so it's NOT simple assemble/hook to fancy meter/write value/sell process.
« Last Edit: December 08, 2017, 10:42:15 PM by TiN »
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Offline pelule

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #11 on: December 07, 2017, 05:31:52 AM »
Count me for 2 (if such many left available), min. 1.
Prepayment possible.
BR
/PeLuLe
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Offline wn1fju

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #12 on: December 07, 2017, 06:55:29 AM »
Could I buy one volt for $50USD ???
 
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Offline VintageNut

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #13 on: December 07, 2017, 11:36:41 AM »
Hi TiN

I am curious about the 0.1 ppm/deg C temp dependency. If the temp changes +/- 3 deg C, then the output will change +/- 3uV?

The temp in my home/office can change +/- 5 deg, which is 10 deg p-p. That would translate to 10uV p-p or 1 ppm p-p.

My 731B which cost $250 is pretty much that good for temp dependency.

I think that if your LTC ref were in an oven like the KE DMM7510, THAT would be very attractive. \

One reason that I like my DMM7510 so much is that the ovenized reference makes the DMM rock solid stable in my home/office where the temperature is not stable.


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Offline TiN

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #14 on: December 07, 2017, 12:00:57 PM »
VintageNut
Will have to see if can do better. Current data looking like this:



Ignore the steep jump on the end, that shows reference ran out of oven thermal margin, with resulting +150ppm raise of zener voltage and output voltage.
« Last Edit: December 07, 2017, 09:22:28 PM by TiN »
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Offline texaspyro

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #15 on: December 07, 2017, 01:00:24 PM »
So 17 uV over 10 degrees C...

My ancient scrap heap salvaged EDC MV100 seems to drift around 20 uV over 3 degree C... not too shabby for an un-modified, non-ovenized 1N829 zener diode referenced clunker with a 6 decade adjustable divider... I've been looking at seeing what some LTZ1000 / LM199 / better chopper love could do for it.
 

Offline bson

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #16 on: December 07, 2017, 02:44:21 PM »
I'd be interested in a few (say 3) known to be genuine LTZ1000 references, just the parts without a board - if you can get a few extra!
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Offline TiN

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #17 on: December 07, 2017, 03:27:08 PM »
So 17 uV over 10 degrees C...

Actually more like 22 uV over 22.6C, here's live data.
So that's about 1uV/C, or -0.1ppm/K.

LTZ reference itself was tested last week to ~-0.03ppm/K over 20-50C span. TC is not exactly linear due to compensation.
Sweet spot with nearly zero TC is to run with ambient temp 30 to 40C.

I'd suggest to move discussion about the design to thread.

There will be no parts/kits, only fully assembled and tested module is in question.
« Last Edit: December 07, 2017, 03:32:04 PM by TiN »
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Offline texaspyro

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #18 on: December 07, 2017, 03:36:13 PM »
I already have a couple of 732A's and a 732B,  but if you need a another taker to meet your minimum build I'm game.  Might even be interested, otherwise.

The main difficulty I see with the unit is the +/- 12V power.   I'd like to do a small unit with LiPo (18650) backup batteries.  There are some nice, isolated, low noise DC-DC's out there that should be able to take care of that.. hopefully without slathering the system with switching noise.
 

Offline Echo88

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #19 on: December 07, 2017, 08:49:33 PM »
Maybe a capacitor charge pump suffices for the negative voltage while ensuring low noise? Or a big LED + solarcell.  ;D
 

Offline DiligentMinds.com

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #20 on: December 08, 2017, 03:24:08 AM »
Maybe a capacitor charge pump suffices for the negative voltage while ensuring low noise? Or a big LED + solarcell.  ;D

The Fluke 732B uses a charge pump for a small negative voltage (5V?) that is used for the force/sense on the (-) output, and also for the ground current compensation on the Zener and 7V/10V resistor divider chain.  This (IMO) is extreme overkill, where a single-point ground would suffice without adding more amplifiers to create extra noise and drift over time.
 

Offline zucca

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Re: Group-buy for 10V LTZ1000A reference?
« Reply #21 on: December 08, 2017, 09:54:16 PM »
TiN let's the magic happen, it's Xmas time!

I am in. Yes Yes Yes!

PS: anyone with connections for custom resistor arrays/dividers (Fluke 2464707)

http://www.eevblog.com/forum/metrology/tin-livestreaming-layout-of-new-ltz1000a-10v-reference-module/msg1345273/#msg1345273

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Can't love what you don't know. Zucca
 

Offline TiN

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Re: Group-buy for 10V LTZ1000A reference? [Completed, no more boards].
« Reply #22 on: December 08, 2017, 10:26:58 PM »
zucca
OK. What did you do with previous ref, btw? :)

ALL
No more boards, so far I got all allocated, unless somebody from the list wanna change the mind.
Ordering parts (LTZs from LT direct, resistors from VPG direct, rest are from Digikey) next week.

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Offline zucca

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Re: Group-buy for 10V LTZ1000A reference? [Completed, no more boards].
« Reply #23 on: December 08, 2017, 11:02:54 PM »
zucca
OK. What did you do with previous ref, btw? :)

I needed first a HP 3245A, now I am going to upgrade it...
Following your path.. very slowly my friend.
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Can't love what you don't know. Zucca
 

Offline TiN

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Re: Group-buy for 10V LTZ1000A reference? [Completed, no more boards].
« Reply #24 on: December 11, 2017, 03:49:16 PM »
LTZs, opamps and LDO's ordered from LTC  ::).
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