Ultrasonic Sensor Detection for Sludge

Hello All,

More of a sensor questions here:

I am working on a project where I am using an ultrasonic sensor to detect the level of sludge build up in a tank or pipe. I plan to install the ultrasonic sensor at the top of un upside down TEE fitting that is installed in-line of a sanitary pipe.

The goal is to be able to measure the build up of sludge at the bottom of the pipe using the ultrasonic sensor at the top of the TEE pointing down.

My questions is: Will the ultrasonic sensor be able to detect the build up of sludge at the bottom of the pipe? even considering the fact that water will be passing through periodically?

Not very easily, no.

First you’d need a waterproof sensor.

Then you’d need a sensor that wasn’t confused by reflections from the pipe or imperfections in its joints

Finally, no, you can’t see through water: you’d have to look at the maximum range during the periods with no water. If that gets smaller, maybe you have sludge.

But if it gets smaller and stays smaller, you have to figure out if you’re looking at ever-present flow, or if you’re looking at sludge. Maybe you could look at noise as an indicator of turbulent flow, but maybe there’s just standing water easily mistaken for sludge…

Also it’s not going to work well in a round pipe, since the range to the “floor” varies with the curvature.

And if you’re looking for only small amounts of building, you’re going to have to calibrate for temperature since the speed of sounds changes.

Probably you want to try something else; but maybe you could get it to work with a really fancy DSP setup able to distinguish multiple reflections and not just one.

Needless to say, doing this with the Arduino-project hc-sr04 type sensor is a complete non-starter.

Hi @Gianpaul, one of the biggest manufacturers of ultrasonic sensors is Maxbotix. Their datasheet for their main range of sensors states:

Applications requiring 100% reading-to-reading reliability should not use MaxSonar sensors at a distance closer than 50cm.


Because of ultrasonic physics, these sensors are unable to achieve 100% reliability at close distances.

If you are measuring inside a large diameter, e.g. public sewer, pipe then you may be ok but use inside a small diameter pipe is unlikely to work using ultrasonics.

You might consider using a conductivity sensor. A change of the salinity of the water should also change the conductivity level.

This might work or not (https://www.researchgate.net/publication/228779922_Conductivity_measurements_for_controlling_municipal_wastewater_treatment)

Or capacitive differences - sludge build up may have an impact on a touch sensor.

Or some optical sensor(s) embedded in the pipe.

Or a section of transparent pipe with some optical sensor(s).

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