Dear I am making a prototype of a bubble sensor using a capacitor. I would like to ask if anyone has a diagram of how, on the principle of capacitor capacity, they can detect air bubbles in oil
i found this sketch on the internet so it can serve as an aidonly the capacitance change measurement scheme is needed and not the rs232 io test kit

 

The capacitor, in your case, are the three conductive plates on edge of the PCB holes where your tubes pass. The capacitance is going to be small because the plate size of each conductor is small. The good news, you are looking for changes in capacitance as each bubble passes. The mode of operation is based on changes in dielectric constant of the material between the plates. A gas bubble has a relative dielectric constant very close to 1. And your oil will likely be in the range of 2.5 to 3.5. Larger bubbles will give a larger signal as they pass. Very slow moving bubbles may be difficult to detect because the change in dielectric constant is very slow (but depends on your circuit and operating frequency).
Capacitive sensors ICs are available and a microcontroller can connect to them easily with serial communications. Some can detect changes in the Atto-farad range so the small plate size may not be a problem. Good luck.

example part
https://www.ti.com/lit/ds/symlink/f...=https%3A%2F%2Fwww.ti.com%2Fproduct%2FFDC2214

 

Thanks