Level measurement


Thread Starter

Alvaro Rodriguez

Need analog level measurement from silos containing products such as powder sugar, oats, corn powder. All these products generate dust when filling the silo, that can interfere with the sensor. Any suggestions ?

Endress+Hauser is making such a sensors with name of guided microwave , which the micro waves are passing through a Hard mettalic cable till
the end of the bin i.e from top to bottom.

The disadvantage is you need to clean the guide once in every two weeks for accumulated power coatings.

contact nearest endress + Hauser representative near to you.



Daniel Chartier

Siemens Moore makes ultrasonic and radar-based level tranducers that can be specked for different dust densities. Contact your local Siemens rep. for specifications.

Hope this helps,
Daniel Chartier

Larry Kolbert

Laser is a possibility. Would need to install a 'window' (could be lexan) for an optical sight path into the vessel. A spray ring would be used to direct air/nitrogen onto the window to keep it free of dust.

For detailed info, look at:


The product is an Accu-Pulse.

There is also a controller called Milltronics which is designed specifically for your type of application. Milltronics' transducers (sensors)are
self-cleaning, because the sensor is vibrating, thus makes it less maintenance. If you need brochures for this, contact me or contact Milltronics, "http://www.milltronics.com":http://www.milltronics.com .


I do not like probes in silos for a number of reasons: maintenance requirements, installation aggrevation, potential for imparting a large load to the silo roof as material levels rise. Non-contact is far better if the application is workable, there are no obstructions in the path of the signal and your expectations are reasonable.

If the measurement is not essential during filling operations and/or there is not a huge amount of dust generated during fill, ultrasonic is a good choice and Milltronics is an excellent vendor. High dust levels in the ullage space could prevent proper operation during filling, particularly when the silo is nearly empty.

Unguided microwave (sometimes called radar) is generally less affected by dust but often has trouble with the distance between roof and floor of larger silos. If you can get AC power to the silo roof, you can use a high powered radar to
overcome this to some extent. Get some dimensioned sketches together (including access ports and any internal obstructions)
and talk to Milltronics, E&H, Krohne.

I strongly encourage you to include both a high and a low level switch - simple capacitance type would be choice A - inserted horizontally. This will provide overfill protection (in event of dust or the actual material falling thru the signal path) and underfill protection (since low levels are when the signal to noise ratio will be at its minimum).

Joe Hohn

Roger W. Harte

Milltronics has excellent level sensors.

Roger W. Harte
EWA Technologies, Inc.
Suite 500
13873 Park Center Rd.
Herndon, VA 20171

Nassir Abedi

Think a basket type level mesuerment system should be good for your application. It works on the priciple of weighing of a basket hanging
from a winder on a loadcell. As attachment I'll send you two pictures.
Those are part of my exam in interfacing course.
Best Regards

Nassir Abedi(Mr.)
K. N. Toosi University of Technology
P. O. Box 16315-1355
Tehran 16314
E-mail: [email protected] or [email protected]

Larry Kolbert

Laser is a viable option. Unlike sonic level systems, laser has a .3 degree beam which is unaffected by angles of repose which would adversely affect the sonic systems. No need to go through the excercise of looking at multiple return signals over time to set up software. Dust would be a consideration but once settled, laser is good to 5 mm, plus/minus.



This may be new name for some but was previously known as TN Technologies/Kay Ray/Sensall.

Approach 1: Check out Drexelbrook's "KoteShield" capacitance probe. Supposed to avoid problems with coating, though I haven't tried it.

Approach 2: Try a servo type displacer unit. This unit keeps the displacer float retracted when not measuring height of the material. To measure, it lowers float until tension on the cable drops. Measurements can be on a scheduled or demand basis, depending on yoiur needs. Check
out Endress-Hauser and Varek for these devices. I have used this type on Fluid Bed Catalytic cracker (FCC) catalyst hoppers with good results.

John Beck
Control System Specialist - Retired

Scott Rosenke

From my many years of level experience because of dust in the air and builup on sensors do not not not use ultrasonic, laser, non-contact laser or RF capacitance!

The only proven method out there is microwave radar signals going through a cable. The first guys comment is good and you don't have to clean the probe. If you want us to futher engineer this we would be glad to help you out with a 100% performance guarantee. If it does work we give you your money back. Thanks.

Kevin Hambrice

Mr. Rodriguez,

KTEK offers a number of level measuring instruments. Two products in particular have been successful in the applications you have mentioned: (1) MT2000 - Guided Wave Radar (2) LM02 Laser.

Can you supply additional application information?

Kevin Hambrice
225-673-6100 x172
I have ten years of experience with ultrasonics and radar on solids materials in a wide range of applications from foodstuffs to mining to chemical powders to the cement industry. Ultrasonics from Siemens Milltronics is very effective on the materials you mentioned (sugar, grains, corn, etc.) where the dust levels are relatively low to medium. Where dust levels are severe (like cement silos or flour during filling) then a radar instrument like the Siemens LR400 is suggested. Our experience with laser systems is that if you can't see the material with your own eye (too much dust) then the laser won't be able to see it either.