Listen in tutorial: Electromechanical level sensor / switches

Vibrating / rotating probe level sensors still good choices in the right applications.


While we’ve considered many high-tech types of instruments in this newsletter, readers appreciate basic technologies too. For example: electromechanical level devices that use vibrating probe or paddle wheel sensors still have many useful applications. ( Listen in: Don Koeneman, application engineer for Ametek’s Drexelbrook division, comments on electromechanical level devices .)

These two technologies are similar in that they insert a moving device into the tank contents and determine the presence of liquid or dry material by the way in which it interferes with the motion. A vibrating sensor extends a small tuning fork or rod into the material that is attached to a piezoelectric crystal. If there is nothing around the probe, it can vibrate at its normal frequency. If immersed in liquid or solid material, it can’t vibrate as easily, and the system will detect the difference.

A paddlewheel sensor extends a multi-bladed wheel or a flag into the tank and turns it slowly. Immersion in liquid or solid material will interfere with its rotation, which can be detected.

These approaches have some limitations:

  • They provide only a point level reading, so use them in appropriate applications.

  • Both use moving parts so there is some mechanical delicacy. Don’t position them where product can fall on the probe or protect it with a baffle.

  • Both are relatively high power consumers. If you’re concerned about having the lowest power devices possible, there are better choices.

  • Equipment vibration can be problematic.

  • Product build-up on the probe can interfere with accuracy.

  • Things that move need maintenance.

But there are some characteristics that keep customers coming back:

  • They are generally very reliable;

  • Typically low cost;

  • Often no calibration is required;

  • Liquid/solid characteristics (conductivity, dielectric, etc.) are largely inconsequential;

  • Relatively immune to foam, (although this varies);

  • Can be made in sanitary configurations;

  • Easy to position and place; and

  • Many configurations are available.

These are generalities, so discuss specifics for your process with your instrumentation provider. Vibrating and paddle wheel sensors are available from a variety of suppliers, including:

Babbit International
Drexelbrook (Ametek)
Monitor Technologies
Sapcon Instruments

You can also search online at the Control Engineering Supplier Search .

—Peter Welander, process industries editor, ,
Control Engineering Process Instrumentation & Sensors Monthly
Register here and scroll down to select your choice of free eNewsletters .

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me