Principle
Powered by the thread Alternative to the Spindle, the idea was born to reproduce the commercially available electronic tildting spindle.
The system is based around the use of a heeling (or tilting) cylinder, an ingenious and easy concept - you do not need any external reference (except for gravity) and the cylinder is extremely easy to keep clean. The inclination angle changes in relation to the buoyancy and thus directly in relation to the sugar content. There is an angle formed between the center of mass and the center of bouyancy depending on the density of the fluid.
Therefore the idea is to place a Wifi-enable IoT device with an accelerometer and temperature sensor in a floating cylinder. The system will measure the sensors and every x-minutes it will connect to the Wifi and sends its tilt angle, temperature and battery voltage to a cloud service like Ubidots.com to store the data.
With an update interval of 30min it was possible to achive a battery lifetime of almost 3 months!
Actually, this is the “metacentre”, the cylinder will tilt as the liquid density changes in relation to its center of mass and center of bouyancy. The angle of tilt can then be measured.
It is possible to trim the cylinder by adding a few grams on the bottom so that the cylinder is more upright, or on the lid, so that it is more tilted.
The software calculates the Euler angle for X and Y from the XYZ acceleration values and forms the absolute angle. We compute these with the calibrated parameters to ° Plato, SG or similar by correlating to measured references.