Electronics > Metrology

Nanovolt design challenge - build and show your own nV-meter in 256 days [DONE]

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Input protection is a different topic than effects related to input bias currents...
Input protection has to be designed to a given spec - which determins the effort one has to put into the protection.
There are two main strategies that can be combined arbitrarily: current limitation and voltage limitation.
In the usecase of ultra-low voltage measurements a current limiting impedance can in fact cause problems. In this case it is possible to use a cascaded voltage limitation with a first set of anti-parallel diodes against a guard (with a low voltage difference to the input) and a second voltage limiter against the supply rails or transil diodes. An example for this approach is the ADA4530. One has to be aware that the source is the current limiting element in this case.
A trap to avoid is the choice of diodes that have a package that is transparent for IR or visible light...


--- Quote from: ferret_guy on January 12, 2022, 04:21:01 pm ---I have been working on and off. Got my prototype PCB back and did some noise and input current testing.

Here is a photo of the current PCB:

--- End quote ---


First off all, i want to say that i am following this thread with interest. I am learning new stuff am i am looking forward to what everyone has come up with. :)

By seeing the above picture i saw something that was not as it is supposed to look. The capacitors below the 4 amplifier, the solder joints don't look right to me.
And it look like there is a short on the left IC above the raspberry pi.

Kind regards,



46 days, I am curious whats come.

Best regards

I’m interested to see what folks are going to come up with for this as well. Been quiet though so not sure how many folks are actively working on it.

What’s next TiN? A millOhm meter?

I haven't received any projects or WIP items from anyone, so I believe this contest is a flop at this point.
But who knows, maybe there will be 10 projects published on last day.  :-//


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