BA02 sensor now producing strange results

Blue Robotics Products Sensors
1

I am having problems with two BA02 sensors. I am using them with an Arduino MKR1200 which runs on 3.3Volts.

The first one is reporting about 20mb too high when compared to other atmospheric pressure measurements I have in the lab. (I have mentioned this in another topic already)

I purchased another one. This started producing correct atmopheric pressure results similar to other lab measurements, however after leaving it running for a couple of days it is now doing this:

Pressure: -1168.00 mbar
Temperature: -13.24 deg C
Depth: -21.61 m
Altitude: nan m above mean sea level
here
Pressure: -1168.00 mbar
Temperature: -13.24 deg C
Depth: -21.61 m
Altitude: nan m above mean sea level
here
Pressure: -1167.00 mbar
Temperature: -13.23 deg C
Depth: -21.60 m
Altitude: nan m above mean sea level

I am not using the Blue Robotics i2c converter, but I thought it should be OK since my Arduino MKR is running at 3.3 Volts.

So do I have to use the Blue Robotics i2c level converter? i.e., is there something on the i2c converter board that means it has to be used even if you use it with a 3.3 Volt micro controller?

Or are my sensors faulty?

Thanks

2

Has the sensor been submerged for this amount of time? Does anything change when you power cycle it?

From the other topic:

3

I have not tested these sensors in water yet.

My first BA02 sensor

This sensor produces atmospheric pressures that seem too high. I have it on the bench now and its been showing around 1034mb all afternoon. Meanwhile I have two other different types of pressure sensors ( SparkFun Barometric Pressure Sensor Breakout - BMP180, and a SparkFun Pressure Sensor Breakout - MS5803-14BA) on another Arduino showing between 1005mb and 1007mb. I am tending to believe these two sensors.

My second BA02 sensor

This is really odd. I powered it on again this morning and initially it started to show up atmospheric pressures close to my other sensors. However, after monitoring the output I could see it drifting down, both in temperature and pressure

e.g. for example at
11:33 Prs of 924mb, tem 22.24 degreeC
11:49 Prs of 874mb, tem 21.48 degreeC
12:10 Prs of 816mb, tem 20.67 degreeC
…
13:10 Prs of 656mb, tem 17.69 degreeC
13:36 Prs of 600mb, tem 17.64 degreeC

by 14:18 it had reached 468mb.

Any ideas on what to to try next?

4

Please contact support@bluerobotics.com for a replacement. Please note that you need to consider the error margins in the measurements of both sensors to determine whether or not two different devices really do or do not agree on a single measurement.

5

I am having a similar problem with a new Bar02 sensor.

On the bench it reads 1031hPa, all my other sensors read 997hPa+/-2. My other sensors are BME280’s.

I will do more testing of it tomorrow, with it submerged, but the previous (failed) Bar02 read the same as all my other pressure sensors in air.

This is a depth sensor that I have had running for 5 months, I just replaced the failed Bar02, and now the readings are way off.

Is there a problem with the calibration factors on these sensors? Or has something else changed?

6

I got replacements for my Bar02 (one was broken and one was reading pressure too high). However, these new ones are also over reading pressure in air by around 25mb when compared with a couple of different types of atmospheric sensor I have in the lab.

I have not had chance to test these in water yet - I am hoping that its a linear problem and I can just adjust the readings.

I am using them with an Arduino MKRFox1200 which runs are 3.3Volts, so I have not used the I2C level converter.

7

In our vehicles, we calibrate the pressure readings by taking the air pressure reading to be zero depth. This is analagous to taring a scale.

The readings will be linear and accurate in relative terms, and you can simply subtract whatever offset you need to get the readings that you desire.