Ultra Precision Reference LTZ1000

[alex-sh]

I think I have a similar experience with my first LTZ1000A.
CORRECTION: As soon as the board is assembled, the buffered output is giving me 7.11793.
Exactly the same of the 10.0000V V Ref b. Resistance between pin 2 and pin 6 LTC1052 is around 16.2kOhm, but OpAm is not working.
Not sure what the problem is though.

I am not sure what happened as I was very careful assembling the reference...


 PS Any idea where to source LTC1052??? Its obsolete
      Any direct replacement? TLC2654ACP?

One of my LTZ1000 reference circuits failed.  The LTC1052 output was oscillating and the failure occurred when I placed the circuit in a homemade cooler/foam box to measure its temperature performance.  I assume a static charge destroyed the LTC1052.  After replacing that IC, all is back to normal.

The LTC1052 is a CMOS device and perhaps should not be placed in a foam box?  A partial schematic is included ... you might recognize the good work of Dr. Frank.

[blackdog]

Hi alex-sh,

Have you considered that your measuring leads are a capacitive load on your circuit?

Chopper opamps do not like capacitive loads, see the datasheet for more details.

Your NTC is hanging loose, it can never give a stable reading this way.

Kind regards,
Bram

[alex-sh]

Hi alex-sh,

Have you considered that your measuring leads are a capacitive load on your circuit?

Chopper opamps do not like capacitive loads, see the datasheet for more details.

Your NTC is hanging loose, it can never give a stable reading this way.

Kind regards,
Bram

Hi,

No. I do not see the same behavior on other LTZ1000 modules with the same leads.
Why do you think NTC is a problem? I wanted it to be long enough to read a temp around LTZ1000A

[blackdog]

Hi Alex,

Stability
Just because another module seemed "stable" does not mean that other modules will then also be stable....
There is always component spread even if you use the same parts with the same schematic and circuit board.

It is up to the builder to figure out to what extent a schematic and setup is stable.

NTC temperature measurement
Ask yourself, what are you measuring at the position where that NTC is hanging?
Is the draft (there always is) coming from the direction of the LTZ1000's legs or from some other direction, does the circuit board stay horizontal or is it mounted vertically?

And also don't forget that the wires of the NTC are a fair part of determining the measured temperature.

Can you show "your" schematic here that you built on the circuit board?
You may have made minor modifications that could be important.
Of course with the component values you used that are on the circuit board.

Then it will be easier to help you identify the cause of the instability.

Kind regards,
Bram

[Kleinstein]

 PS Any idea where to source LTC1052??? Its obsolete
      Any direct replacement? TLC2654ACP?

The TLC2654 sees to be a little lower in noise and higher bias. The ICL7650 would be on the other side with lower bias, higher noise. The exact values can scatter.
For the amplifier from 7 to 10 V one may also change to another AZ OP amp that can withstande a 12-16 V supply, like LTC2057 or MCP6V51 or OPA189. These are lower voltage noise, but even higher bias and don't need external capacitors.

[alex-sh]

Hi Alex,

Stability
Just because another module seemed "stable" does not mean that other modules will then also be stable....
There is always component spread even if you use the same parts with the same schematic and circuit board.

It is up to the builder to figure out to what extent a schematic and setup is stable.

NTC temperature measurement
Ask yourself, what are you measuring at the position where that NTC is hanging?
Is the draft (there always is) coming from the direction of the LTZ1000's legs or from some other direction, does the circuit board stay horizontal or is it mounted vertically?

And also don't forget that the wires of the NTC are a fair part of determining the measured temperature.

Can you show "your" schematic here that you built on the circuit board?
You may have made minor modifications that could be important.
Of course with the component values you used that are on the circuit board.

Then it will be easier to help you identify the cause of the instability.

Kind regards,
Bram

Hi,

Please see attached the schematic. This is a modified Dr Frank module. I have built several of these without any issues, but LTZ1000
This one is LTZ1000A with corresponding 1K/13k divider. Something is not working correctly on the LTC1052 side...

Regards
Alex
 

[alex-sh]

Ok, what would you recommend as a direct replacement?

Hi Alex,

Stability
Just because another module seemed "stable" does not mean that other modules will then also be stable....
There is always component spread even if you use the same parts with the same schematic and circuit board.

It is up to the builder to figure out to what extent a schematic and setup is stable.

NTC temperature measurement
Ask yourself, what are you measuring at the position where that NTC is hanging?
Is the draft (there always is) coming from the direction of the LTZ1000's legs or from some other direction, does the circuit board stay horizontal or is it mounted vertically?

And also don't forget that the wires of the NTC are a fair part of determining the measured temperature.

Can you show "your" schematic here that you built on the circuit board?
You may have made minor modifications that could be important.
Of course with the component values you used that are on the circuit board.

Then it will be easier to help you identify the cause of the instability.

Kind regards,
Bram

Hi,

Please see attached the schematic. This is a modified Dr Frank module. I have built several of these without any issues, but LTZ1000
This one is LTZ1000A with corresponding 1K/13k divider. Something is not working correctly on the LTC1052 side...

Regards
Alex

[alex-sh]

My LTZ1000A is covered to minimise any draft - both the head and the legs.
I am measuring the temperature of environment next to LTZ1000A module.
This is a horizontal board.

Schematic is attached to the previous post.

Hi Alex,

Stability
Just because another module seemed "stable" does not mean that other modules will then also be stable....
There is always component spread even if you use the same parts with the same schematic and circuit board.

It is up to the builder to figure out to what extent a schematic and setup is stable.

NTC temperature measurement
Ask yourself, what are you measuring at the position where that NTC is hanging?
Is the draft (there always is) coming from the direction of the LTZ1000's legs or from some other direction, does the circuit board stay horizontal or is it mounted vertically?

And also don't forget that the wires of the NTC are a fair part of determining the measured temperature.

Can you show "your" schematic here that you built on the circuit board?
You may have made minor modifications that could be important.
Of course with the component values you used that are on the circuit board.

Then it will be easier to help you identify the cause of the instability.

Kind regards,
Bram

EDITED: Solved! One of jumper wires had a bad connection and it was not noticeable at all. The lesson learnt - double and triple checking everything

[Villain]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

[arcnet]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

Buy some 03458-66509 or 03458-66519... More seriously: I don't know. Currently I'm offering my customers to get LM399-based references instead which will be replaced when the LTZ1000 or ADR1000/ADR1001 are available (again)...

[Ole]

Additionally the Vishay Precision Website (www.vishaypg.com) is also unavailible

[quarks]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

Send me a PM I have some in stock

[The Bootloader]

I recently got 2 LTZ1000A, directly from Analog. The leadtime was insane, but at least I got them, and it rewarded to be patient... I am now looking for a nice reference design. Any suggestion as to which one I should build? I have noticed there are a few designs available.

[Villain]

I recently got 2 LTZ1000A, directly from Analog. The leadtime was insane, but at least I got them, and it rewarded to be patient... I am now looking for a nice reference design. Any suggestion as to which one I should build? I have noticed there are a few designs available.

If i would have two chips i would build one Dr Frank's and one TiN's design. Just to have some variety and maybe compare (comparing one with one is not much statistics to go with but oh well)

[Andreas]

Hello,

Cellularmitosis has published some PCBs of 7V LTZ designs on his GitHub.

E.g:
https://github.com/pepaslabs/dr-frank-ltz1000

https://github.com/pepaslabs/px-ref

The leadtime was insane.

I hope you have already ordered the necessary precision resistors.
Otherwise you might have to wait another 6-14 weeks.

The stability of those references also depends on mechanical design (air drafts)
and EMI disturbances (mobiles / LED lamps) in your environment.

Which design to choose is mainly dependant on your personal preferences.
- dual supply / single / battery powered supply
- 7V / 10V output
- your environment conditions

with best regards

Andreas

[Haasje93]

Hi,

I found mine LTZ1000 PCb and parts in a forgotten corner in my home lab, it's a shame i know..
I am busy with completing the PCb and i have already made the housing.
I have a question about the LTZ1000, I have red that the LTZ must not be mounted directly against the PCB. There has to be some room between them, i have also red that you should protect the leads againt any drafts. I found a bag of teflon tubing, i figured that i can put a single piece of tube around every lead to protect it against drafts. What do you think?

Kind regards,
Christiaan

[Andreas]

Hello,

I usually put some foam around the whole LTZ (including the leads)
And of course do not forget the soldering side of the PCB.

https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg250759/#msg250759

Others use a plastic cap over the LTZ.

with best regards

Andreas

[branadic]

There is also the simplified LTZ reference circuit based on W/F7000 available,that only needs one "better" resistor and is otherwise using resistor networks, no need to spend gold on expensive components with long lead-times.

-branadic-

[The Bootloader]

https://github.com/pepaslabs/dr-frank-ltz1000

https://github.com/pepaslabs/px-ref

Awesome, looks like two solid designs. Not sure yet which one I want.
I don't mind 7V or 10V, I think it does not make a big difference.
I would say, instead, that I would rather do whatever circuit performs the best.

I hope you have already ordered the necessary precision resistors.
Otherwise you might have to wait another 6-14 weeks.

Yes, thankfully, there was a group order a few months back and I got 120, 1K, 12.5K, 2x70K. I regret (a lot) not getting more than one set, but heh, better than nothing and enough for one reference with typical circuits. They are not the famous VHP100 series, but should still perform well.

The stability of those references also depends on mechanical design (air drafts)
and EMI disturbances (mobiles / LED lamps) in your environment.

I plan to just put the damn thing into a block of foam. Brute force method

Which design to choose is mainly dependant on your personal preferences.
- dual supply / single / battery powered supply
- 7V / 10V output
- your environment conditions

What I would like is to get something like a Fluke 732A in terms of features. I would love to have something that can be AC powered, but also run on battery for up to a few days so I can move it around freely or even ship it (cal club heh?) and not worry about power outages.

Thank you so much Andreas for the valuable feedback. Helped me make progress in my thoughts about what I will build. Still not sure yet, I need to continue digging in the rabbit hole.

There is also the simplified LTZ reference circuit based on W/F7000 available,that only needs one "better" resistor and is otherwise using resistor networks, no need to spend gold on expensive components with long lead-times.

-branadic-

This one? https://xdevs.com/article/b7000/
Interesting design - it seems like it does require quite a bit more initial trimming than the other designs, but that allows for reduced TC with lower cost components.

Aaarg another design to consider building

Would be interesting to build one of the standard design, and one of this design to compare them. But sadly, with a sample size of only one LTZ per design type, I think I would be comparing the actual LTZs and not the designs.

[alex-sh]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

Yes, it is a disaster.
Not just for LTZ1000
I have been waiting for LTC6655 in ceramic for months now.

[alex-sh]

That's what I do for my references as well.
1. Put a plastic cap on top of LTZ1000. Ideally it should cover the LTZ1000 and leads. I do not solder LTZ1000 "on the board". It is slightly elevated above the board.
2. If not - cover LTZ1000 leads with a foam.
3. cover soldering pads on the other side of the PCB with foam.

Hello,

I usually put some foam around the whole LTZ (including the leads)
And of course do not forget the soldering side of the PCB.

https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg250759/#msg250759

Others use a plastic cap over the LTZ.

with best regards

Andreas

[iMo]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

Yes, it is a disaster.
..

Could it be they are going to discontinue the LTZ1000? They source vendors till the stock is empty, the vendors are changing their designs to the ADR1000 or ADR1001 already. It has no sense to manufacture three almost identical references, especially the ones in metal..

[syau]

anyone know where to source ltz1000ach nowadays without 100 weeks lead time?

Yes, it is a disaster.
..

Could it be they are going to discontinue the LTZ1000? They source vendors till the stock is empty, the vendors are changing their designs to the ADR1000 or ADR1001 already. It has no sense to manufacture three almost identical references, especially the ones in metal..

Did a Mouser back order on 22 Oct, received 11 Jan.

[RikV]

Is the project documentation on the FXref (TiN) publicly available? On Hithub or something? I'd like to build one but I am unable to find the necessary documentation (especially the gerbers).

[Tj138waterboy]

https://xdevs.com/article/792x/