Hi,
Hi Klaus, but then you would probably not be able to design this circuit since there are too many unknows for your method to even get started.
I´m a professional high precision electronics designer for decades now.
I guess I´ve experienced a lot of difficulties .. and I´ve solved a lot of them.
Decades ago for example I`ve designed an X-Ray meter with 2Ch, 10kSmpl/s ... with a resolution down to 7pA ... and a trigger at 30pA. I had almost no specification about sensors ... and algorithm. And especially when there is a lack of information one needs to investigate about the physical limits.
Doing a lot of tests and math ... to find out
wich part of the circuit
is critical.
From my experience I can say I never had a fully specified task from the beginning. It always is part of the designer to make the specifications complete.
Only doable math has been done in this case.
OK. Shakespeare said: well roared, lion.
Then prove me wrong with my opinion, that the drift of the power supply voltage of your circuit overrules the expectable grounding errors by several decades. I guess this is (one of) the biggest error source in your circuit, indeed I expect the errors caused by power supply noise and drift maybe to be higher than your entire "sensor measurement signal range". It may be higher than OPAMP errors, noise errors, offset drift errors and ADC errors combined.
I did not do the math .. but you said you did! So it should be simple to show. Or at least an estimation.
And how would any math sort out the potential grounding issues?
This is exactly the problem. You don´t see that the grounding issue is no issue at all in your system ... because other errors are way bigger.
No need to sort out a problem that does not exist.
Just look at the results of your math. They show you.
Do you know that independent errors add by using squares?
Do you also know what this mathematically means?
An example: Let´s say you have three error sources: The one introduces 30mV, the other 5mV and the other 3mV.
So the total expectable error is: 30.5mV
You may do handstands on the 5mV and 3mV errors, you may invest hours, weeks of discussion ...
and even if you manage to reduce both of them to 1/10th ie, 0.5mV and 0.3mV ... you still have about no improvement. It still will be about 30mV of error.
But if you reduce the 30mV error by a tiny bit only ... down to 29.4mV (just by 0.6mV)... it already
overrules all effort to reduce the other two errors.
Do you understand that it´s much easier to reduce the error of 30mV down to 29.4mV (reduced by 2%) than to reduce 5mV down to 0.5mV (reduced by 90%)?
It´s better to reduce the one by 0.6mV than reducing the other by 5mV. You just need to focus on the bigger one. That´s what science tells.
This mathematically shows it has no significant impact on performance to reduce the smaller errors even more.
This example uses just a ratio of 1/6 ( 30mV vs 5mV) .. in your circuit I expect the ratio to be much bigger ... making things worse.
I know there are people who ignore physics and math ..
Their goal is to reach the north pole .. but they decided to go along the equator. And nobody is allowed to tell them to change their direction. They want to talk about speed, gravitation and everything else. They don´t want to rethink their decision... or follow rules of physics and math. They go their way.
It´s your job, it´s your effort, it´s your application ... My post is a just well meant "recommendation" .. nothing more. Like a map showing the path.
Still it´s your choice which direction to go.
Klaus