Using ultrasonic level sensors on a complex water surface

Undergrads and I study river erosion of simulated bedrock in a 14-cm wide water flume. In this summer’s research, we need a good way to characterize the water surface profile in a non-stationary and non-uniform flow field illustrated by this still from a research video. The hydraulic jump moves up- and down-stream and is quite irregular in time and space with boils and waves.

The measurements here are in cm.
Can we place a series of ultrasonic sensors above the flow? The top is 30 cm from the bottom, and the water is 3-10 cm deep. We would like to track the water surface at the minima (103 cm upstream in the photo) and at the top of the jump (90 cm) and if possible, more locations in between. We are measuring pressure and other aspects of the setting at 100 Hz, and would love that kind of information for the water surface too. I know that other flume experiments have made use of the Massa mPulse sensors (but perhaps under more uniform flow conditions).
Will the uneven surface make a poor surface to detect?
Will multiple sensors interfere with one another?
What would be the best type of sensor?
Thanks, Dr. Dave

Greetings and welcome to the Forum, that looks like an interesting study, the power of water has fascinated me since I was young.

We have a wide variety of ultrasonic sensors available here. Many of these sensors may work for your application, but it depends on quite a few factors. Of those options we currently have these in stock.

First and foremost, I have by no means searched every datasheet but of the ones I did go over the minimum sensing distance was typically 30-50cm so the top of your tank would be too close to use them and would require redesign in order to work.

The ones I looked at when referencing water levels did seem to indicate larger flat bodies of water and may or may not be able to adjust quickly enough. However, the ones that sense the closest object rather than the largest object may be able to sense the top of the wave vs the rest of the water just fine. I do not have enough experience with these sensors to know, hopefully someone with more knowledge has a suggestion. Otherwise it will just take some good old fashioned experimentation with the sensors to figure out which works best.

As far as whether or not they work well in the same area some said they did and others did not. The ones that did typically had some type of filtering so that is something to watch for.

There is no easy way to filter these things out to narrow down the search so this will require reviewing the datasheets for each sensor to find the ones that will suit your application.

To get you started I thought the HRXL-MaxSonar-WR series looked promising and they had a thorough datasheet that should be helpful in your selection. They have models specifically stated for water level. They also have the detect first object type I spoke of earlier. They state in the datasheet that they are filtered and can be used in the same area. Of those options we currently have these in stock.

Please let us know if we can be of further assistance.

Good luck in your search, if you find what you’re looking for let us know how it goes!

I would expect ultrasonic sensing to pose some difficulties at the scales indicated, for the various reasons suggested; cross-sensor interference, noise due to uneven surfaces and surfaces non-orthogonal to the sensor, scale of acoustic beam width relative to measured features, etc. Getting more detailed information on the referenced experiments using such sensors might be illustrative as to their capabilities.

Structured Light Scanning (SLS) techniques might be a thing to consider due to potential for good spacial and temporal resolution, though I could imagine complexities there due to the optical properties of the fluid. It might be possible to limit that with use of dyes or such to reduce transmission without totally mucking up the rheological properties of the water though.

One could also consider the possibility of simpler machine vision techniques simply looking through the side of the tank to more or less automate reading the scales drawn there at high speed, but this would probably come at some cost of distortion due to boundary layer effects at the fluid/container interface rather than at mid-stream.where I suspect you’d prefer to measure.

Unfortunately I don’t believe that we have well-prepared resources to guide the selection and application of tools for either approach at present, but perhaps the ideas will give you something to run with.

Hi harbord,

You could consider using a time-of-flight -sensor.
ST’s VL53L7C can measure 8x8 zones and water is (if I recall correctly) opaque at 940nm.

heke, AsamaLab