Pressure sensor

For the project, we use MS5837-30BA (Bar30 High-Resolution 300m Depth/Pressure Sensor) from Bluerobotics .

The description of the sensor from http://www.bluerobotics.com/store/electronics/bar30-sensor-r1/ :

The Bar30 pressure sensor is a high-pressure, high-resolution pressure sensor that is sealed from the water and ready to install in a watertight enclosure on your ROV or AUV. With 0.2 mbar resolution, it has an amazing depth measurement resolution of 2mm in the water column!

The sensor is the Measurement Specialties MS5837-30BA, which can measure up to 30 bar (300m/1000ft depth) and communicates over I2C. It operates on 3.3V I2C voltage but can accept power input up to 5.5V. It comes standard with a 4-pin DF13 connector that is compatible with most DroneCode compatible boards including the APM2.6, PixHawk, and others.

This sensor includes a temperature sensor accurate to ±1°C, with data also accessible through I2C. If you need something with more temperature accuracy, please check out the Celsius Temperature Sensor.

The anodized aluminum body was designed around the cable penetrator design and is compatible with all of the watertight enclosures.

To summarize, there are some noticeable features:

0.2 cm resoulution (in freshwater), but not confusing with absolute accuracy.

measure up to 30bar = 30*1000 mBar = 30*1000*0.01 m = 300 m

From datasheet of the sensor, the accuracy +/-50 mBar (aka. +/-50cm in freshwater)

By experiment and from Bluerobotics' forum:

There is significant drifting of absolute value

Problem of repeatibility of the values. Fonz (fernandoFonseca) recommends using Sparkfun Breakout MS5803-14BA (but not waterproof)

After some period of time (can be up to 1 hour), values read from the sensor become stable