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Bar02 Alternative?

I have been using the Bar02 for a couple of years now. The problems I have with this sensor are:

  • Sensors fail after about 4 months submerged (I can’t dry them out every day)
  • Drift over time is significant
  • Offsets can be large, so I have to calibrate each sensor individually, and track which sensor is which, so I can apply the correct offset
  • Drift with temperature is significant, making readings unreliable when temperature fluctuates.

I am attempting to measure shallow depths (less than 1 m), so accuracy is critical, and the drift on these sensors is poor. The sensor stays in the water for up to 6 months (being pulled out when the water freezes - Oct to April).

I see that you have a Bar100 based on the Keller LD series. I was wondering if it were possible to produce a high accuracy equivalent to the Bar02, but using one of the lower range Keller LD sensors? say the absolute 0-1 bar or 0-3 bar sensors.

This would eliminate all the complicated libraries as the calculations are performed within the sensor, and should allow a more stable and accurate sensor.

I understand that it would be more expensive than the Bar02, but I am currently on my fifth Bar02 in 2 years, so I’ve already spent nearly $500 on sensors that just aren’t very good. I would happily pay for a more accurate, reliable sensor, that would hopefully last 6 months submerged.

I’m using a RPi to read the temperature/pressure, as well as several other sensors (including barometric pressure to derive a depth reading).

What do you think? would this be possible? even as an experiment?

Thanks.

You don’t have to get the sensor wet to measure the depth. In water treatment plants they have a flexible reservoir of air submerged with a capillary air tube running to the sensor at the control room. Since the air is weightless (almost) the pressure is the same at the end of the tube. I plan to have the Bar02 in my pi enclosure in the dry so I never have to dry it.

Best of luck with that.

I’m not sure that keeping a flexible reservoir of air submerged in a tank with a capillary tube connected to a pressure sensor outside is going to be all that easy. Not with a BAR02 anyway, it has no tube connection.

How do you keep a flexible air reservoir submerged anyway? I have a buried, shallow, stainless steel tank that I’m measuring water depth in.

It is how professional instrument suppliers do it. The reservoir is a weighted butanol bladder. The volume just has to be enough to handle the depth range without completely deflating, hence the capillary tube which reduces the air volume to a minimum. Why can’t you simply attach the end of the tube to a bar02 fitting? The air is a sealed dry system, perhaps filled with dry nitrogen gas. I haven’t built my own yet! You could attach the bladder to the floor. In my tank it is a bit deep, but not turbulent.