I’m building a bubbler-style pneumatic water level sensor. The simple functionality of this sensor is to release a stream of bubbles at the bottom of the vessel, measure the air pressure in the tube, convert air pressure to height of water column.
While I have the basic electronics sorted out (along with some code that reveals just how clueless I am), I still have to wrap my head around the physics, specifically the differences in pressure that will be seen during the formation and separation of bubbles at the end of the bubbler tube.
Does anyone know of convenient software that will allow me to take “high speed” video (240fps from an iPhone for example), along with rows of data from the sensor, and produce an animated line graph superimposed on the video playing back at “normal” frame rates of, say 30fps?
I plan to synchronise the video with the telemetry using LEDs visible in the video stream.
Also, does anyone understand the physics involved? When attempting to solve the Young-Laplace equation to derive maximum pressure from radius and surface tension, I end up with a bubble on a 4mm tube producing a pressure equivalent to 0.5cm of water (about 0.007psi, with PSI being the units reported by my pressure sensor).
My plan with the high speed video is to record a few seconds of bubbles being formed and then escaping the tube, overlaid with a scrolling graph showing the measured surface tension, just to confirm where maximum and minimum pressures are observed.
 High level design of bubbler level sensor from Benoit Drooghaag, “Rain water tank level,” http://playground.arduino.cc/Main/Waterlevel
 Arduino code and Fritzing designs for my bubbler water level sensor: https://github.com/AlexSatrapa/Arduino/tree/master/Bubbler
 Young-Laplace applied to bubbles forming at the mouth of a capillary immersed in liquid from Krüss, “Bubble pressure tensiometer,” http://www.kruss.de/services/education-theory/glossary/bubble-pressure-tensiometer/