Bar30 inaccuracy/drift

Blue Robotics Products Sensors
1

As i have posted here, I am trying to make the Bar30 sensor work with the BlueBoat.

I am now using an Arduino-style microcontroller to read its sensor values. I am using the Bluerobotics MS5837 library.

There is however an issue: The measured pressure (and thus also depth) drifts while submerged in water!

If I have the sensor just lying on the bench, it should output atmospheric pressure and 0.00m in depths. That is what it does.

However: If I submerge it in a glass of water the reading goes from the correct 0.16m to 0.00m in a matter of minutes! It even becomes negative!

Note: The cable is in total around 500mm, but I guess a bad I2C connection would result in erroneous behavior – losing connection etc. – and not drifting sensor output.

Could this be a defective sensor or am I doing something wrong? The sensor is mounted in an M10 hole in a proper enclosure (I have checked, the inside stays dry.)

2

Hi @jobotics, does it stabilise after some time?

The Bar30’s absolute accuracy is ~2m in fresh water[1], and the values you’re reporting are still well within that. The sensor resolution is much finer than that, so it can track quite small movements relative to an initial offset, but there is expected to be some drift over time (including as the gel covering absorbs some water),

If the drift is excessive (in rate or extent) then I’d recommend submitting a product problem report so our support team can help determine what’s going wrong, and replace the sensor if it’s defective.

  1. See the technical details or datasheet on the product page for more specific values and conditions ↩︎

3

Hi @jobotics -

How long did you leave the sensor in the glass of water? It’s important to not let it soak for more than 24 hours! If not, that does sound like your sensor is out of spec - reach out via the help center, report a problem with a product, including your order number as a next step!

4

Thanks for your input. The sensor was only submerged for a few minutes and the drift started immediately after submersion. Out of the water there was no drift.

I got a decrease in pressure after submersion of around 20mbar within that time frame.