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Bar02 negative pressure reading

I am using an Arduino Nano to read the pressure data from 2 Bar02 sensors. They are connected via an I2C multiplexer TCA9548A and each sensor has an I2C level converter. I have both sensors out of the water and one seems to be working fine and showing a pressure of 1017 mbar. However, the other sensor reads a negative pressure of -14 mbar. The sensor that reads the correct pressure works fine when connected to either of the level converters, which makes me think that the multiplexer and the level converters are working properly. Does this mean that one of the sensors is faulty? If so, what could cause this? The sensor has not been used before.

Thanks for any suggestions.

It could maybe be incorrectly calibrated, or be faulty? The sensor datasheet doesn’t seem to specify a way to change the calibration, although it does allow you to read the calibration data, and provides a ‘Cyclic Redundancy Check’ (page 13) to verify that the stored calibration data is at least valid (but not necessarily anything about how correct it is).

I’d suggest you start out by checking the CRC, and also comparing the calibration values to those from the working sensor, to see if they’re at least in a similar range. Also worth seeing how the values change in the water over a known distance - it’s precise enough that you should be able to test even just in a cup/bucket of water.

Thanks for the valuable advice. When testing in a cup of water, the non working sensor does not change its values which probably means that the sensor is indeed faulty. I will also look into the CRC. While testing, I noticed what seems to be a tiny hole in the gel. I wonder if it is possible to refill the gel. If so, is there a particular gel that would work?

Seems like a reasonable conclusion.

Unfortunately there isn’t anything mentioned about this in the datasheet, and it doesn’t include any information about which gel is used. Most likely you’ll need to get it replaced/refunded. Assuming you bought it from Blue Robotics, you can contact support@bluerobotics.com :slight_smile:

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