Author Topic: Ultra Precision Reference LTZ1000  (Read 759448 times)

doktor pyta, pansku and 3 Guests are viewing this topic.

Online pitagoras

  • Regular Contributor
  • *
  • Posts: 115
  • Country: ar
Re: Ultra Precision Reference LTZ1000
« Reply #2075 on: December 18, 2017, 02:20:09 pm »
I've shared my board at OSHPARK too, if anyone is interested.

https://oshpark.com/shared_projects/DmMENXtg

It was going to be PX but it has been taken  :)

So it has become QX, much better for the logo  :P 
 
 
The following users thanked this post: quarks, Echo88, cellularmitosis, chuckb, Inverted18650

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Ultra Precision Reference LTZ1000
« Reply #2076 on: December 18, 2017, 04:09:44 pm »
Digilent:

It doesn't matter if you believe me or not re: '2057 input chopper noise.  You're welcome to pay my client for the documentation - otherwise just pay no attention.  Consider the free advice clue as worth exactly what you paid for it. That's as far as I can go on a public forum.

What does matter is LT specifically recommends against a '2057 for various reasons, unnecessary excess noise across the Zener is one of them.  These are the people that manufacture the part.  I would guess they have some knowledge of what works and what doesn't, and they handle a lot more design feedback from volume manufactures.  They have about zero economic reason to even sell LTZ's in small orders, so be glad they even do that.  The fact that they even discuss design know-how is an added bonus.

For the gazillionth time:  It is true that other amps will work as the LTZ current driver, but the "1013 is hands down the best amp to use for the right mix of current and voltage noise.  It is tailor- made to be the LTZ's companion.  That is the part to use, and that is the part they will stand behind on datasheet specs.  When you talk to LT apps engineering, that's what they tell you - at least that's what I've gotten on more than one occasion when I ask about "upgrading" to a chopper amp.  There is just no reason to do that.  Remember you're using the amp as a CURRENT driver, and the zener + transistor stability will overwhelm whatever small Voffset you've got on the '1013.

Check your specs - we've never seen an hfe on the the LTZ transistors as low as 50.  Typical is 200, the range is 80 to 450.  A small Voffset on the current driver amp is not going to result in significant Vref change.

There are lots and lots of older "standard" 3458a's that work just fine to "002" high stability option specs - we have several that don't drift a ppm per year.  That means the board design is not the main contributor to drift - it's the LTZ die itself (and scope of normal drift variation part to part), and that is far beyond anyone's "hand tuned" control.

Go ahead, try it - remove the ground current cancellation resistor on that 3458a Vref board and let me know what happens as the ambient temperature changes....and let me know if it's not pretty smart to use a sub-penny carbon resistor (fancier types not required here) to reduce ground current at the module header pins....  I really don't see designers flailing around: I see a smart, well thought out design that produced the most successful DMM in history - and a DMM that has outsold and out-lasted every competitor design over time.  Am I wrong?

If there were a better way to do it we'd have it after 30+ years.  You're more than welcome to produce a better Vref replacement that works in production.  Hopefully Keysight will be able to at some point...
« Last Edit: December 18, 2017, 05:01:26 pm by MisterDiodes »
 
The following users thanked this post: Echo88, cellularmitosis, floobydust, hwj-d, TWMIV

Offline cellularmitosis

  • Supporter
  • ****
  • Posts: 1038
  • Country: us
Re: Ultra Precision Reference LTZ1000
« Reply #2077 on: December 18, 2017, 05:08:32 pm »
Update the HP A9 reference board clone (03458-66509):

I figured out how to scale and align TiN's images (see https://xdevs.com/article/volt_xfer/) on top of kicad screenshots (using gimp) and dialed in all of the dimensions.  They match up pretty closely!  (see attached overlays).

Also, I've managed to squeeze in room for hermetic footprints on R413 and R415.  The footprints are backwards compatible, so you can populate this board with original HP components, or upgrade the critical  resistors to hermetic packages.

This version of the board is intended to mimic the original board as closely as possible, with the option of upgrading the resistors, but in a future version I'd like to explore diverging from the original design a bit, perhaps with the "R60" mentioned above, etc.

I was a bit surprised to find that the LTZ isn't perfectly centered between the two mounting holes.  I decided to err on the side of reproducing HP's error.

v2 OSHPark link: https://oshpark.com/shared_projects/jP5xkfJy

github: https://github.com/pepaslabs/hp-03458-66509-clone
« Last Edit: December 18, 2017, 05:10:39 pm by cellularmitosis »
LTZs: KX FX MX CX PX Frank A9 QX
 
The following users thanked this post: quarks, mimmus78, Echo88, chuckb, hwj-d

Offline Dr. Frank

  • Super Contributor
  • ***
  • Posts: 1522
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2078 on: December 18, 2017, 06:44:02 pm »


Well, if this is being done for the reasons that you state-- and what you are saying sounds reasonable, then why are they bothering when it's an offset, and as long as the offset does not change then it doesn't matter?  Why in the heck would they use a very noisy carbon-film type resistor for this.  There is really something goofy going on here-- I think somebody was desperately plastering band-aids all over this design-- with the hope of being able to "fix" a number of issues-- instead of just re-engineering the whole circuit and layout.  The whole design looks as though they were flailing about without really understanding what they were doing.  Those engineers are no longer at HP (or Agilent, or Keysight) anymore-- so we may never know what the hell they were up to.  I guarantee you this-- I could design a much better Vref replacement for the 3458A than factory; and if I can do it, then why don't THEY do it?


Hu, Carbon?
In the BOM, R419 is specified TF (usually Thin Film), TC100.

And on my A9 board, it really looks like a Thin Film resistor, not at all like a carbon type.
(and it's definitely 1%, brown ring, also visible on other boards. Carbon resistors are 10% at best)

Again, the whole reference circuit is not directly fed into the A/D circuit, but is routed over at least three connectors, which might well change their resistance.

In the Fluke 5440 and 5720, they treat this GND star point and supply current problem much nicer, just lay both schematics side-by-side.

That's also the reason, why I  designed a big star point into my latest design as a stand-alone 7 / 10V reference, but I would also have some trouble with GND, if I would use my modules inside another circuit.

Frank
« Last Edit: December 18, 2017, 09:04:53 pm by Dr. Frank »
 
The following users thanked this post: Inverted18650

Online Echo88

  • Frequent Contributor
  • **
  • Posts: 426
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2079 on: December 18, 2017, 09:15:19 pm »
Man, so many new open source LTZ1000-boards, but no LTZ1000A available....  :-DD
Maybe we can gather all open source LTZ1000-boards in a new thread/post?

Special thanks to cellularmitosis, who apparently needs no sleep and produces a new board every few days.  ;D
« Last Edit: December 18, 2017, 09:19:52 pm by Echo88 »
 
The following users thanked this post: cellularmitosis

Offline BU508A

  • Frequent Contributor
  • **
  • Posts: 392
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2080 on: December 18, 2017, 10:04:58 pm »
A seller on AliExpress is offering this LTZ1000 board (no affiliation):

https://www.aliexpress.com/item/Ltz1000-ltz1000a-PCB-circuit-board-thickness-1-0mm-size-62mm-62mm/32829991789.html



And there is a seller which is selling LTZ1000ACH, but I'm not sure if I would buy them (no affiliation):

https://www.aliexpress.com/item/5PCS-LOT-LTZ1000ACH-LTZ1000/32757679028.html
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Offline mimmus78

  • Supporter
  • ****
  • Posts: 645
  • Country: it
Re: Ultra Precision Reference LTZ1000
« Reply #2081 on: December 19, 2017, 11:38:21 am »
Update the HP A9 reference board clone (03458-66509):

I figured out how to scale and align TiN's images (see https://xdevs.com/article/volt_xfer/) on top of kicad screenshots (using gimp) and dialed in all of the dimensions.  They match up pretty closely!  (see attached overlays).

Also, I've managed to squeeze in room for hermetic footprints on R413 and R415.  The footprints are backwards compatible, so you can populate this board with original HP components, or upgrade the critical  resistors to hermetic packages.

This version of the board is intended to mimic the original board as closely as possible, with the option of upgrading the resistors, but in a future version I'd like to explore diverging from the original design a bit, perhaps with the "R60" mentioned above, etc.

I was a bit surprised to find that the LTZ isn't perfectly centered between the two mounting holes.  I decided to err on the side of reproducing HP's error.

v2 OSHPark link: https://oshpark.com/shared_projects/jP5xkfJy

github: https://github.com/pepaslabs/hp-03458-66509-clone

Nice I think I will use it to build and age a A9 replacement for my 3458a. The one actually inside is friend of TiN little jumpy.
« Last Edit: December 19, 2017, 11:44:23 am by mimmus78 »
 
The following users thanked this post: cellularmitosis

Offline 3roomlab

  • Frequent Contributor
  • **
  • Posts: 779
  • Country: 00
  • A long long time ago, in a land far far away ...
Re: Five new kids on the block - Ultra Precision Reference LTZ1000
« Reply #2082 on: December 19, 2017, 12:33:39 pm »
I have assembled and tested my 5 new LTZ1000 reference boards.

They all are based on Andreas schematic, providing additional EMI filtering for great immunity against RF and mains disturbances.

ive been playing with eagle, i wonder, has anyone been succesful in totally laying this entirely on 1 side? i must say i have no success.
« Last Edit: December 22, 2017, 01:00:08 pm by 3roomlab »
Hayao Miyazaki - "there is no nuclear power here (at studio ghibli)"
Feynman - "What Do You Care What Other People Think?"
 

Offline Macbeth

  • Super Contributor
  • ***
  • Posts: 2453
  • Country: gb
Re: Ultra Precision Reference LTZ1000
« Reply #2083 on: December 19, 2017, 12:52:12 pm »
And there is a seller which is selling LTZ1000ACH, but I'm not sure if I would buy them (no affiliation):

https://www.aliexpress.com/item/5PCS-LOT-LTZ1000ACH-LTZ1000/32757679028.html

I wouldn't touch them with a bargepole. Straight off the bat no manufacturers logo and no date code.
 

Offline cellularmitosis

  • Supporter
  • ****
  • Posts: 1038
  • Country: us
Re: Five new kids on the block - Ultra Precision Reference LTZ1000
« Reply #2084 on: December 19, 2017, 04:32:44 pm »
I have assembled and tested my 5 new LTZ1000 reference boards.

They all are based on Andreas schematic, providing additional EMI filtering for great immunity against RF and mains disturbances.

ive been playing with eagle, i wonder, has anyone been succesful in totally laying this entirely on 1 side? i must say i have no success.

Dr. Frank has!  http://www.eevblog.com/forum/metrology/mx-reference/msg1297126/#msg1297126

edit: actually he used two jumper wires, so *almost* entirely on one side.  I put a copy of his design on OSHPark: https://oshpark.com/shared_projects/gl2aXmlh
« Last Edit: December 19, 2017, 04:35:00 pm by cellularmitosis »
LTZs: KX FX MX CX PX Frank A9 QX
 

Offline borghese

  • Regular Contributor
  • *
  • Posts: 63
  • Country: si
Re: Ultra Precision Reference LTZ1000
« Reply #2085 on: December 20, 2017, 04:37:39 am »
You have to load the appropriate DRU file for 1 layer; for example "Multi-CB_1L_125um-Tracks_OL35um.dru". File attached, just rename from TXT to DRU
Regards
Cheers
Borghese
 

Offline 3roomlab

  • Frequent Contributor
  • **
  • Posts: 779
  • Country: 00
  • A long long time ago, in a land far far away ...
Re: Five new kids on the block - Ultra Precision Reference LTZ1000
« Reply #2086 on: December 22, 2017, 12:11:26 am »
I have assembled and tested my 5 new LTZ1000 reference boards.

They all are based on Andreas schematic, providing additional EMI filtering for great immunity against RF and mains disturbances.

ive been playing with eagle, i wonder, has anyone been succesful in totally laying this entirely on 1 side? i must say i have no success.

Dr. Frank has!  http://www.eevblog.com/forum/metrology/mx-reference/msg1297126/#msg1297126

edit: actually he used two jumper wires, so *almost* entirely on one side.  I put a copy of his design on OSHPark: https://oshpark.com/shared_projects/gl2aXmlh

i know he did, i quoted his post in my question. i should re-word the Qn as : did anyone else have success in a strictly 1 layer layout w/o using jumpers?

this is my whimsical layout which i did for fun and somewhat curiosity
https://3.bp.blogspot.com/-fUTVzhfdWqY/Wjuw9s3vnXI/AAAAAAAAC30/BwFihqLtVVcEBqPCOMeiwlxS7IgqzYitQCLcBGAs/s1600/LTZ1k_11%2Bcopy.gif
i included the "RR0" which on LTZ pdf page6, is for finding an unstabilized TC compensation (but now i think it is a useless inclusion :/). the idea is to do the construction manhattan style, so no leads will be visible on the rear. the size is based on a IP67 plastic box 100x68mm. i dont suppose i have seen anybody create their favourite project box as a piece of component?

in my version, i had to use ground plane to connect capacitors :( (i also have to "jump" VREF to the 2nd op amp). which lead me to think, since capacitors do not really need to track temperatures and influence overall tempco, it should be possible to flip all the capacitors to the flipside of the PCB and have them out of the way of all the resistors on the front side.



*update
well i wasnt quite satisfied, and i think i managed to really fit all into 1 layer.

https://2.bp.blogspot.com/-ggDXXGuKW-A/Wjvgm3jeewI/AAAAAAAAC4I/rGwKasaRdf8qRVw13cVOsFrf3OUn19GxgCLcBGAs/s1600/LTZ1k_11B%2Bcopy.gif
« Last Edit: December 30, 2017, 08:55:46 am by 3roomlab »
Hayao Miyazaki - "there is no nuclear power here (at studio ghibli)"
Feynman - "What Do You Care What Other People Think?"
 
The following users thanked this post: cellularmitosis

Offline Galaxyrise

  • Frequent Contributor
  • **
  • Posts: 526
  • Country: us
Re: Ultra Precision Reference LTZ1000
« Reply #2087 on: December 22, 2017, 02:39:00 am »
The gain of the temperature compensation transistor reduces to about 50 when the base and collector are at the same voltage (which is where this circuit biases the transistor)-- so the high hfe listed in the data sheet is misleading. 

Isn't this the condition in which I measured 200?
I am but an egg
 

Online Kleinstein

  • Super Contributor
  • ***
  • Posts: 4606
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2088 on: December 22, 2017, 03:05:30 am »
For the sensitivity to the OP it is not Hfe that matters, but the voltage gain of the transistor stage. This is about 6.5 V / (kT/e) or about 200, depending on the temperature. The early effect might reduce this gain a little, but not that much. The input side is rather low impedance and the collector side is usually much higher impedance - so the actual Hfe does not matter as long as it's in a reasonable range and not much below 1.


 

Offline TiN

  • Super Contributor
  • ***
  • Posts: 3617
  • Country: tw
  • xDevs.com
    • xDevs.com
Re: Ultra Precision Reference LTZ1000
« Reply #2089 on: December 22, 2017, 04:04:05 am »
3roomlab, or cellularmitosis should make single-layer LTZ ref with large pads, so we can order metallized ceramic board to make hermetic LTZ ref :).
Put some VAR resistors, get kovar tubes for feedthru copper pins and seal it all in vacuum or argon filled tube. 

Likely there would be no difference in performance, but it would look neat. Maybe toss an orange LED or two on the base to give it warm fuzzy glow too  :popcorn: .
xDevs.com YouTube | Have test gear documentation to share? Upload here! No size limits, firmware dumps and teardown photos welcome.
 
The following users thanked this post: kj7e

Online beanflying

  • Frequent Contributor
  • **
  • Posts: 837
  • Country: au
  • Toys so very many Toys.
Re: Ultra Precision Reference LTZ1000
« Reply #2090 on: December 22, 2017, 01:21:48 pm »
3roomlab, or cellularmitosis should make single-layer LTZ ref with large pads, so we can order metallized ceramic board to make hermetic LTZ ref :).
Put some VAR resistors, get kovar tubes for feedthru copper pins and seal it all in vacuum or argon filled tube. 

Likely there would be no difference in performance, but it would look neat. Maybe toss an orange LED or two on the base to give it warm fuzzy glow too  :popcorn: .

I would prefer a 5 digit Nixie voltmeter on the front please  :)
Coffee, Food, R/C and electronics nerd in no particular order :)
 

Offline branadic

  • Super Contributor
  • ***
  • Posts: 1132
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2091 on: December 29, 2017, 06:19:26 am »
Prema Semiconductor used a slightly different circuit to power the LTZ1000 from 12V in Prema 6048. I found two circuit diagrams with slighlty different resistor values in two different manuals. Would be interesting to see what they finally assembled.

-branadic-
Prema 5000 | 2x Prema 5017 SC | GenRad 1434-G | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, Keithley 2182A, HDO6054, Keysight 53230A and other goodies at work
 

Offline 3roomlab

  • Frequent Contributor
  • **
  • Posts: 779
  • Country: 00
  • A long long time ago, in a land far far away ...
Re: Ultra Precision Reference LTZ1000
« Reply #2092 on: December 29, 2017, 08:50:19 am »
i dont know if my eyes are playing tricks ... but what does the red resistor do?
Hayao Miyazaki - "there is no nuclear power here (at studio ghibli)"
Feynman - "What Do You Care What Other People Think?"
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 1722
  • Country: ca
Re: Ultra Precision Reference LTZ1000
« Reply #2093 on: December 29, 2017, 10:29:34 am »
Not an expert here, but in ref PCB layouts, there's two grounds- the high-current heater return and the reference (-).
They are separated to minimize any heater-induced I2R voltage drop across ground from shifting the 0V reference point and causing uV offset error.

Your PREMA schematic just seems to use one symbol though, as some CADD software cannot understand two ground (nets) that are connected together at the PSU central grounding point. I don't have a 6048 or 6047 PCB to look at both sides.

The 10R resistor between them is usually to avoid big trouble if one ground is open circuited, and to lower Q for any RF picked up between the two ground traces.
 
The following users thanked this post: 3roomlab

Offline 3roomlab

  • Frequent Contributor
  • **
  • Posts: 779
  • Country: 00
  • A long long time ago, in a land far far away ...
Re: Ultra Precision Reference LTZ1000
« Reply #2094 on: December 29, 2017, 02:50:11 pm »
Not an expert here, but in ref PCB layouts, there's two grounds- the high-current heater return and the reference (-).
They are separated to minimize any heater-induced I2R voltage drop across ground from shifting the 0V reference point and causing uV offset error.

Your PREMA schematic just seems to use one symbol though, as some CADD software cannot understand two ground (nets) that are connected together at the PSU central grounding point. I don't have a 6048 or 6047 PCB to look at both sides.

The 10R resistor between them is usually to avoid big trouble if one ground is open circuited, and to lower Q for any RF picked up between the two ground traces.

i could not get my head around it. so i dump something into FEMM 4.2 to visualize it
pic1 describes the approx currents and the 10R between the 2 sides, each with its own 0v (cyan)
pic2 is the same currents, but all traces are approx 6mil (no 10R)
pic3 same again, left side is approx 200mil trace, right is 6mil trace (no 10R)
pic4 is 6mil only 1 GND (no heater GND)

the simulation idea behind 6mil and 200mil trace comes from saturn PCB
6mil 1 oz PCB 1 inch long loaded @ 0.1mA returns a potential diff of about 0.011v
230mil 1oz PCB 1 inch long loaded @ 5mA returns a potential diff of about 0.011v (2oz PCB will only need about 150mil wide)
esp for VREF end, i wonder how much of these traces should be balanced between sourcing and draining. it would be a crazy matching exercise, this reminds me of that zero ohm thread, trying to find the zero current point inside a thick copper piece.

i also assume that the GND return current posing the most problem is the heater as the current varies with changing temperature.

but since swapping these around in simulation for GND, it appears as long as all returns appear at exactly the same star point, it doesnt seem to need a 2nd heater return? what did i miss? (assume the left side GND is the master)
maybe the better question is, since pin 3 potential is referenced to the GND thru R1, how could a seperated heater return create a more stable GND point since it is the only GND? if GND shifts, wouldnt VREF also shift and result in no change? (i assume a low noise LDO is on board and the V supply is always "constant")


i went a little further in FEMM 4.2 simulation. the animated gifs alternate between 2 diff current returns. however the more i look at these, i seem to confuse myself more

assuming zero volts is the black hole, it prevents a current return disturbance on the right from affecting the 1 on the left.


i need to emphasize, i am assuming by simulations.

this is with/without the 10R linker. i am unsure what to make of it.


i can assume since all GND labels are not really zero, what does come close to a full negation? huge capacitor as sinker?


(the txt file needs to be renamed *.FEC for use in FEMM 4.2)
« Last Edit: December 31, 2017, 07:03:59 am by 3roomlab »
Hayao Miyazaki - "there is no nuclear power here (at studio ghibli)"
Feynman - "What Do You Care What Other People Think?"
 
The following users thanked this post: floobydust

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 1722
  • Country: ca
Re: Ultra Precision Reference LTZ1000
« Reply #2095 on: December 31, 2017, 07:41:34 am »
Colourful sims, what I expect for showing the electric field in copper PCB traces. Learned about the "river mouth" being something to consider.

My theory for the Prema 10R resistor - it does nothing at DC as the PCB trace resistance is comparatively low, unless for open-circuit protection on the Kelvin zener (-).
Or, it's to fool the CAD software. But at high frequencies, RF, the twin trace inductance is now at play and I suspect that another reason for it.

Copy pasta from http://www.electronicdesign.com/analog/what-s-all-ltz1000-stuff-anyway:

"Some folks put a dummy resistor in the schematic to separate those grounds into different nets. However, Mark Thoren, staff scientist at Linear Technology says, "Dummy resistors separating 'grounds' are a recipe for disaster, and I see disasters related to this practice all the time. One of the first things to look for when reviewing a customer's schematics is multiple ground symbols without a good reason for them."

'Do be aware of the return currents causing drift problems. [Carl] Nelson comments, “Current out of pin 7 is about 6.5 V/R2 + 6.5 V/R3 = 186 uA. Current out of R5 is about 550 uA.  Current from R1 (same as the Zener current) is about 4 mA.  These currents should be routed separately to the low side of the reference output. If a single trace is used, and the trace resistance is 0.4R , voltage drop in the trace will be 1.9 mV. Copper has a thermal coefficient of 0.0038/°C, which generates 7 uV/°C in the trace, equal to about 1 ppm/°C in the reference.  This is about 20 times higher than the expected drift of the part’s design intent.”
 

Offline guenthert

  • Regular Contributor
  • *
  • Posts: 195
  • Country: us
Re: Ultra Precision Reference LTZ1000
« Reply #2096 on: January 02, 2018, 02:42:46 am »
Copper has a thermal coefficient of 0.0038/°C, which generates 7 uV/°C in the trace, equal to about 1 ppm/°C in the reference.  This is about 20 times higher than the expected drift of the part’s design intent.”
There he lost me.  What "thermal coefficient" is meant?
 

Offline Andreas

  • Super Contributor
  • ***
  • Posts: 2099
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2097 on: January 02, 2018, 04:13:54 am »
If a single trace is used, and the trace resistance is 0.4R
How long are your traces?
I usually use minimum 24 mils which have 0.9R per meter with 1 oz copper.
Usually you should use Kelvin sensing for the zener voltage.
Within the resistor loops you have at least a reduction factor of 100 for the resistance changes.

There he lost me.  What "thermal coefficient" is meant?
0.385%/K is the thermal resistance change of pure metals like copper, platinum etc.

with best regards

Andreas

 
The following users thanked this post: guenthert

Offline TiN

  • Super Contributor
  • ***
  • Posts: 3617
  • Country: tw
  • xDevs.com
    • xDevs.com
Re: Ultra Precision Reference LTZ1000
« Reply #2098 on: January 02, 2018, 08:37:52 am »
Happy New 2018 to all voltnuts. Wish you all guys short LTZ lead-times and smooth stable voltages.
Little present on my LTZ data. I had my references turned off for few weeks, and just in mid-December I put them all back in new box and powered backup.
Since then all 8 references are scanned non-stop using HP 3458A and Keithley 7168 nV scanner card.

So far:



Modules:

Channel 1: KX 7V LTZ1000 reference.
Channel 2: KX 7V LTZ1000 reference.
Channel 3: KX 7V LTZ1000 reference.
Channel 4: HP 3458A STD A9 reference
Channel 5: xDevs.com FX 10V reference prototype.
Channel 6: KX 7V LTZ1000 reference prototype.
Channel 7: KX 7V LTZ1000 reference prototype.
Channel 8: xDevs.com FX 10V reference prototype.

P.S. Over last year I got 8M of pageviews, which is amazing to me, given the narrow niche of my projects.  :-+
xDevs.com YouTube | Have test gear documentation to share? Upload here! No size limits, firmware dumps and teardown photos welcome.
 
The following users thanked this post: dr.diesel, cellularmitosis

Online Kleinstein

  • Super Contributor
  • ***
  • Posts: 4606
  • Country: de
Re: Ultra Precision Reference LTZ1000
« Reply #2099 on: January 02, 2018, 09:18:21 am »
Looks like the 3458 got an extra 0.2 to 0.3 ppm shift by Christmas. At least all the curves seem to shift in parallel - so the more likely cause would be the meter.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf