The aim of this project is to help scientists to understand the nature of chaotic water level changes in Ozerna cave (Ternopilska oblast, Ukraine). Traditionally scientists were using stationary rullers in different parts of the cave to collect data about water level dynamics, but the readings in some parts of the cave can be made only a couple of times a year due to significant difficulties of getting there. So I decided to make an electronic data-logger.
Main requirements:
Ultrasound sensors were tested, but accuracy was poor, and the large water surface was needed for stable work.
The main problem with barometric sensors is that one sensor is not enough to measure water level. Second sensor is needed to compensate atmospheric pressure fluctuations
There is a similar to my project - The Cave Pearl Project. I've asked them a couple of questions, and Edward Mallon kindly gave me some advices about using barometric pressure sensors under water. I've decided, that MS5803-05BA sensor fits my requirements the most.
The device consists of main and underwater units connected with 20m cable. The main unit is built around STM32L152RD microcontroller. It has microSD card slot and batteries inside. Underwater unit consists of sensor, STM8S003 MCU and differential pair driver. It is hermetically encapsulated with thermal glue.