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Bar02 Depth/Pressure Sensor Calibration

(Evan McCaulley) #1


I am designing a water level monitor for a holding tank and would like to use the Bar02 sensor for some high accuracy readings, with a raspberry pi reading it. My only concern is calibration, the tank is long and wide but only 4-5 ft deep and I’m at around 7000ft in elevation. To get accurate depth readings should I use a second sensor above the surface or is there a way I can calibrate it? if I can calibrate it how frequently should I calibrate it? I know these are usually used in submersible vehicles, but this design will be stationary, so it won’t be able to know the pressure when it enters the water.

I was debating using 2 sensors so I wouldn’t have to re-calibrate the sensor ever and it could just stay submerged indefinitely. When I was looking at the code there didn’t appear to be a way to distinguish between 2 sensors on python, am I missing something?

Thanks all for your input!


If you can put an ultrasonic sensor at the top i would go with that as it would be a lot easier. IF you want to use a sensor like the Bar02 I would get a barometric pressure sensor to correct your values. I ran into a problem similar to that with one of my projects. The barometric pressure can skew your level data way off if not corrected for.

Also, if you are going to use 2 of the same sensors via i2c I would use a multiplexer to read them.

(Evan McCaulley) #3

The ultrasonic sensor was my initial plan, but when I looked into the holding tank it is filled with roots. The only way I could think of to get around it is a high quality pressure sensor.

Think the barometric pressure sensor would be of similar calibration to cancel out the correct amount of pressure for the other sensor? this is why I was thinking the same sensor.

If I go for dual sensors and the multiplexer, would I have to reinitialize the sensor before taking new readings, or could I just switch between the two whenever?


With or without the roots you’ll probably have the same problem with water displacement one way or another.

An individual barometric pressure sensor would be a lot easier and cheaper than using an extra sensor that are made for use underwater. But i guess it depends on the environment you will have it in.

I’ve used adafruit’s multiplexer and you can just switch between the two no problem you just have to make sure both are initialized in the setup.

(Nicholas Waterton) #5

I am using the BAR02 for a similar project. I used a BME280 to read atmospheric pressure, which worked perfectly.

The only issue I have run into is that after about 5 months of operation, the BAR02 has now failed (shorts the i2c bus when plugged in).

Not sure why, I’m replacing it now. Maybe the rear is not as waterproof as hoped (it’s potted), or maybe it’s not good for extended immersion in a tank.

(Jacob) #6

I have seen this observation from others. The sensors apparently break after extended immersion.