What is false echo suppression?


A few weeks ago, I wrote about problems a customer encountered trying to move a functioning radar level device from one tank to another. With a little light reading of the user manual, and one change on the radar, the situation was resolved. 

People are usually familiar with the concept of false echo suppression: looking at a tank and mapping out the obstructions that can cause false readings, like baffles, ladders, tank braces. But the Siemens products we work with do it a little differently. It’s a built-in feature on Siemens ultrasonic and radar level devices, and only takes five minutes to run.

Self-Learning Echo Suppression Technology

Siemens calls it “Sonic Intelligence”, their patented echo suppression algorithm. It’s built into all Siemens non-contacting level instruments. You don’t need a laptop PC or any special software, just the infrared handheld programmer you ordered with your level device.

You’ll run the self-learning algorithm when the tank is empty or nearly empty. To make it work properly, all you need to know is (a) the actual material level, and (b) the distance from the transducer face to the material level.

  1. On the handheld, select parameter P838, and key in the distance from the transducer face to the material level… minus 0.5 meters (1.64 feet).
  2. Select parameter P837, press 2, and press ENTER.

After a few seconds, the level device calculates the new echo profile, and automatically modifies the filter around the area of obstruction to ignore the echo.

Self-learning ech suppression technology shown on charts, before and after

Before: The BLUE line represents the echo being returned to the level instrument, including all echoes from obstructions. The RED line represents a default, out-of-the-box filter applied to the unit to suppress the nominal noise returned with the echo. The first echo bump might be from an agitator or tank brace, but it’s the second signal you really want: the reflection from the surface of the level being measured.

After: With just a few pushes of your handheld programmer buttons, the level unit “learns” where the false echoes fall between the device and the material level. The RED line represents the “learned filter” that is set above the false echoes. All that’s left is the true echo from the material surface.

But remember, if you move the level device from one tank to another, you have to let the unit re-learn where the false echoes are. Otherwise, it remembers its last configuration, which may not prove true in the new tank installation.

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Lesman Instrument Company is the authorized Siemens representative in Illinois, Indiana, Missouri, Paducah KY, Wisconsin, and Michigan’s Upper Peninsula. If you are located outside that area, you can find your local sales office or get technical assistance by calling 800-365-8766.

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  1. #1 by Rick Frauton on January 23, 2012 - 7:27 am

    As any good tech support rep will tell you, RTFM is usually the best solution to most product application issues. RTFM is extremely effective. Most manufacturers include RTFM inside the shipping carton and online, just in case it gets lost. Please, read the FREE manual.

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