I got this pH sensor board circuit design from one of the forum discussions. Can anyone please explain the significance of the resistors and capacitors used? I am new to the circuit design.

 

hi jv,
The resistors R1 and R form a potential divider for the 5V, the voltage at the junction is ~+1.6v.
This voltage is applied to the shell of the sensor, so the centre voltage signals are referred to this potential.
So for no centre signal, the adc out is at the same ~+1.6v

The OPA is configured as a non inverting unity gain buffer.

The C2 is power line decoupling.

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thank you very much. Then what about the c1 capacitor?

 

thank you very much. Then what about the c1 capacitor

Hi,
It is to decouple the junction to 0V, of two resistors from possible electrical 'noise' on the 5v supply rail.
Similar purpose to the C2, decoupling

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Thank you very much

 

Hi jv,
These two simulations show the effect of C1 decoupling of a test 'noise' on the power rail.
Left image no decoupling.

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I want to know how to learn all these topics and build the circuits. In which topics should I gain more knowledge?

 

Where can I simulate these circuits? What happens if I use 100uF instead of 100nF?

 

hi,
I use LTSpice, as do many other members, it is a free program

It has a steep learning curve, but well worth the effort.
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https://www.analog.com/en/resources/design-tools-and-calculators/ltspice-simulator.html