Ultrasonic level transmitter in 10" dia. tank having agitator with top mounted motor


Thread Starter


Can any ultrasonic level transmitter be installed on a tank 10" dia. and 5 ft. height with top mounted motor for agitation? The tank has slurry in it.
Yes it can, but you will you will get echoes off any imperfections in the wall. (You did mean 10 inches diameter, a 10 foot tank would be easy.) I doubt you will be able to read below the agitator but it's not usual to do that anyway.

From the size of your tank I assume it's a pilot plant, a better choice might be a bottom mount DP level transmitter or even a bubbler setup and regular DP. Weight is also a good method for a pilot plant.

Hope this helps,
Yes, but there are some serious issues. I'd look at a load cell instead.

First, the size of the vessel is problematic. There are very small diameter ultrasonic transmitters around that can be used, however the standard size is 2" to go through a 2" standard female connector on the top of the tank. If you use a sensor with a very long waveguide you may be able to avoid sidewall interference.

The agitator will give you two problems. First, it will be swinging repeatedly through the beam, and will cause errors unless you can do multiple blanking... but then if your level drops to around the level of the agitator repeatedly, that would be a non-starter.

The other problem with ultrasonics in an agitated tank is that there is essentially no level in an agitated tank. There is either a severe turbulence or a vortex. What you want to know is the variable "what the level would be if I were not agitating the tank right now." That's not a measured or measurable variable with an ultrasonic sensor-- it is an inferred variable, or a calculated variable.

That's why I like a load cell better. Unless the density of the fluid is changing radically, you will be getting a better "level" variable than by using an ultrasonic sensor in your application.

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Yes, I'm also thinking on that option. Can you guide me what will be the distance between the two tubes (size?) and what height it will be inside the tank? Mind it it has also agitator in the tank. What will be the total cost including DP?
For a bubble tube it can be any size, although I wouldn't go less than 1/2". File a small notch at the tip so the bubbles come out in a small stream.

I normally like to end the tube level with top of pump suction, but it depends on where you consider the zero to be. If it's an open tank you only need one connection from tube to DP cell HP port, and you will need a small flow of gas, e.g. 0.1 LPM from a rotameter or some other flow restricting device.

In lieu of a bubble tube, you can also inject air at a bottom nozzle. Send me a sketch if you like and I can make some suggestions. Probably < $2,000

roy_matson at yahoo dot ca
If you haven't been dissuaded from using ultrasonics by now, let me give you yet another difficulty - all commercial ultrasonic transmitters that I am aware of, use the same transducer internally for listening for echo as they do for creating the ultrasonic (excitation) ping. Since the transducer has to 'ring down' or damp out its own excitation oscillations before the transducer can effectively listen for the return echo, there is an inherent 'blanking zone' extending about a foot (300mm) from the face of the transducer outwards, within which an echo measurement can't be made because a pulse's echo would return so quickly as to coincide with the ring down period.

This doesn't matter on a 30' (10m) tank that only fills to 90% capacity, but it severely affects short (5 ft/2m) shots by limiting the usable range, especially when mounting to avoid covers or agitators might lower the mounting position even closer to an operating level.

A suggestion or two were made to weigh the vessel to determine the level and I'd recommend that also. Sartorius has a unique mounting technology for their industrial load cells (not commercial scales) that eliminates the effects of vibration due to agitation. I saw a video the salesman had and was impressed enough to try a set and the video is true, the response is very fast because there's no need for filtering to avoid the noise one expects with agitation induced vibration.

Carl Ellis


It is better to avoid ultrasonic measurement for this size of the tank where agitator is also present (seems for experimental purpose).

There are other type of measurements cheaper available like loadcells, bubble tube with DP transmitters, etc., but they depend on the fluid and other operating conditions.

What is load cell, and how does it work? Please give me some details of this type of measurement.