Hi,
I´ve already exlplained it:
and prone for leakage current errors
****
I can´t find a specificaton about your expected accuracy.
Did you do some calcuations on your own?
Depending on your specifications...
* an electrolytic capacitor may fail because the leakage currents
* a ceramics capacitor may fail because it´s unlinearity (depending on ceramics type, temperature range, expected precision, and your signal voltage range)
* thus I assume you need a good film capacitor.
The higher the capacitance value, the higher the current, the lower the external error influence.
Thus if you use a good 100uF foil capacitor ( wich costs 10 ... 100 times of a microcontroller)
and you have a 10mV/min rate and you want the leakage current error to be less than 10% then the total leakage current needs to be less than 2nA = 0.002uA.
Total leakage current = Capacitor leakage current + PCB leakage current + wiring leakage currents + measurement amplifier input current + all other leakage currents....
now there may be flux residuals, humidity that changes with daytime, temperature....
Not impossible, but you need (to be) a good electronics designer.
Klaus