Electronics > Metrology

LM399/ADR1399

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miro123:
Hello,
I've started an new software project.
it contains only four LM399.
The goals are
  - create model of each LM399
  - find best and worse of them
  - real time report of estimated voltages on each channel
  - much better performance than classical analog approach - averaging.

Project is more software related can be applied to multichannle LTZ1000. ADR1000s. I have limited knowledge in low level voltage measurements.- build two projects with ADS1256+PGA280 and just started with evaluating ADS125h02

Description is available @
https://github.com/mirtcho/LM399/wiki


Suggestions, remarks and critiques are welcome.

dietert1:
Creating a Maxwell demon for voltage references is an ambitious project. You may need AI and a lot of example data for teaching it. Guess it starts by making one or more hardware setups to collect data. That is the state of my own work. I share your idea that similar methods will be applicable to different types of zeners. As Mr. Frank commented somewhere: "A good zener reference is constant but sometimes goes up or down by 0.1 ppm."
At the same time i know that all my setups contain errors, like connectors made of brass, imperfect Guard schemes and the like. The Arroyo temperature controllers i am using for some LTFLU references aren't perfect either. So it's important to keep up mood and resolve errors like the moving LM399 caps causing popcorn noise or RF from a WLAN router causing shifts.

Regards, Dieter

Kleinstein:
With LM399 reference I quite often see jumps between 2 discrete level, like an upper and lower level, but relatively little noise while at the level. So if one could know which level is currently present.

For the measurements I would consider to only read the difference of each reference relative to the average of some 4 (maybe more) references.
This would lower the demand on the ADC(s) and one could monitor multiple channels.

DavidKo:
I have checked the ADS1256 datasheet and I think that you cannot directly hook it to the reference (max input voltage should be+-5V) without divider.

miro123:

--- Quote from: DavidKo on October 22, 2021, 11:39:45 am ---I have checked the ADS1256 datasheet and I think that you cannot directly hook it to the reference (max input voltage should be+-5V) without divider.

--- End quote ---
The ground between two parts is shifted with 4,5... 5V. On such way the LM399 7v comes somewhere  in the middle of ADS1256 range.

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