Electronics > Metrology

ADR1399 reference

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bastl_r:
Hi

What did you use to measure the reference voltage? It is advisable to measure it with a measuring device with an input voltage divider in the G-Ohm range. I once had an aha-experience on my Solartron 7066 when I wanted to check the reference voltage before the buffer. The standard 10MOhm of the 34401a was not enough and the voltage dropped a few 10µV...
Whether this also applies to the ADR1399 I cannot say at the moment.

Greetings bastl_r

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misterpulcri:
Hi all and thanks for your replies. I should explain my objective and reason for constructing an ADR1399 based voltage reference. 

My "best" DMM is an ancient Fluke 8050A and I wanted to check the calibration of this device. I need to be able to measure down to 100s of uV which this meter will not do, but I wanted to ensure I was ballpark in the mV range.

I construct Eurorack synthesiser modules which use the 1V/octave system for voltage to pitch  i.e. note C0 = 0v, C1 - 1.0v etc. Each octave is divided into 12 semitones and each semitone is a 0.0833V increment.

Mouser sent a product announcement for the SMT version of the ADR1399 so I investigated and purchased the through hole version naively thinking that if I built the circuit in the datasheet adjusting my shunt value to ensure 3mA for the Zener, 7.05 volts would be present at the reference output and I could gain a degree of confidence in my meter calibration at least down to the mV range.

Before cominng here I did experiment with different shunt values to swing from <3mA up to 5mA and also varied my supply voltage etc and always seeing 6.920V.
I now know that my voltage reference build is fine and is accurate and stable at 6.920 instead of 7.050V  :)

Thanks again for taking the time to look at my naive newbie experiments, I will most likely purchase a new DMM that gets me into the uV range.

Thanks

Sean

Kleinstein:
When the layout is right, the ADR1399 has a rather low output impedance (< 0.1 ohm) and should be OK even with a meter with 10 M input impedance.

The ADR1399 is however the totally wrong way to hope for an absolute value of the voltage. There is quite some tolerance in the voltage, but that value is quite stable.
There are other reference chips for a good accurate initial value (e.g. Ref102C or max6126A) : better accuracy, but not as stable.

dazz1:

--- Quote from: JodelJonny on April 19, 2023, 07:16:27 am ---I could post the KiCad, Gerber and BOM file for the circuit I build if that fits your need. But they are pretty messy since that was my first design in KiCad.
I would need at least a few days to clean up the most important errors.

--- End quote ---

Hi
I like your design.  Simple single purpose, no unnecessary complexity.
If you haven't already, could you clean and post your files please?
Are there any changes or improvements you would make?

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