I would either use an ultrasonic sensor such as the HC-SR-04 or a laser sensor like the VL53L0X as both do not require direct contact. The VL53L0X is the preferable choice as its only measures a small surface area "the size of the laser" where as the HC-SR-04 measures a large surface area growing rapidly as the range increases, and since you want to measures solution within a beaker a laser would be best IMO...
Thanks! I ended using a non-contact sensor. Which is actually working just fine.
Failed the chem class? Both gold and platinum are non-reactive with sulfuric acid and should be readily available to you.
that's very unpolite. You have no idea what conditions my project is under and you try to judge people knowledge?
Use weight ?
my experiment is constantly in a hot plate, I would be complicated to add another layer to that.
How, incidentally, is the beaker being filled or emptied? By something controllable by electricity such as a pump or a heating element?
Search also for capacitive proximity detectors for liquid level detection.
the solution is slowly evaporating, but since it's running for 2+days I need to top off the volume. But thanks for your suggestion, I'll keep that in mind if needed.