Ultrasonic Stream Depth Sensors

Tom, I checked out that new sensor, the I2C interface from Maxbotix is a new feature, it might be handy, but I think the serial output is just as easy to use. My main concern is that the 7040 model is kind of a general purpose rangefinder used for object detection, usually indoors. In the datasheet, it warns that different target sizes will result in different range measurements, even if they are at the same distance. Basically, there is no filtering or target size compensation. The MB7389 model that I use is specifically designed to measure water level, so it has a special filter that returns the largest signal (the water surface), so all other sources of noise and reflections are ignored.

And most importantly, the MB7389 has internal temperature compensation that is applied at each power-up. Without this, the varying temperature of an outdoor environment will make a non-compensated sensor rather inaccurate. And my recent tests have shown that we need to also use the maxbotix external temperature compensation sensor (only $5) in order to eliminate all of the effects of temperature variations.

I’ve had many communications with the technicians at Maxbotix in the past year, and they assured me that the MB7389 is the best model for water level measurements with TTL-level serial output, so I would recommend that you try that one.

The rest of your post on your blog sounds interesting. That’s the kind of content we’d like to have here on this site as well, so you should post it here on a blog post so users here can comment easily on it.

Steve – I gather this, rather than the blog, is the best place for questions.

So, any idea when you might have a new design for the ultrasonic level kit ready to post? W. Oregon has wet winters and dry summers so it would help my planning if I knew whether we might get this built and installed this wet season or we should just plan on getting this running for next fall.

Hi..i am a new user here. As per my knowledge in the datasheet, it warns that different target sizes will result in different range measurements, even if they are at the same distance. Basically, there is no filtering or target size compensation. The MB7389 model that I use is specifically designed to measure water level, so it has a special filter that returns the largest signal (the water surface), so all other sources of noise and reflections are ignored.

assemble pcb

You are not missing something. It would be more accurate to say “ultrasonic stage height sensors”, because depth is merely retrieved, not sensed. This is problematic when one cannot easily survey the sensor as you said, even more problematic for sensing streams with moving beds. Presently, something like a pressure transducer can measure depth in-situ, but non-contact methods almost universally require an a priori stage-depth relationship. In the early 2000s, the USGS (John Costa, Kurt Spicer, et. al.)showed it’s possible to measure depth with ground-penetrating radar, but that’s not exactly economical or practical.

One of my current projects is tacking exactly that problem. It’s not ready for prime time yet, but if you are working on similar technology and wish to collaborate, feel free to private message me.