Automation Products Group is a designer and manufacturer of liquid level sensor and pressure transducer products. The company publishes a blog covering a variety of level sensing subjects. Recent entries include "Myth Busted: Floats Don’t Stick on Continuous Float Level Transmitters," "A Local Display for a Level Sensor (or 10)," "The Seven Deadly Sins of Pump Control" and "Five Tips for Using Battery-Powered Level Sensors on Your Remote Tanks." The direct link is at bit.ly/RtSCfJ.
Automation Products Group
ADAPTIVE LEVEL CONTROL
The tuning of level controllers can be challenging because of extreme variation in the process dynamics and tuning settings. Control system studies have shown that the most frequent root cause of unacceptable variability in the process is a poorly tuned level controller. The most common tuning mistakes are a reset time (integral time) and gain setting that are more than an order of magnitude too small. This article provides a fundamental understanding of how the speed and type of level responses varies with volume geometry, fluid density, level measurement span and flow measurement span for the general case of a vessel and the more specific case of a conical tank. It also discusses how tuning settings change with level dynamics and loop objectives, and the opportunities opened by the use of an adaptive controller for all types of level applications. The direct link is at bit.ly/1jUUJ97.
THE BEST WAY TO MEASURE LEVEL
This free PDF begins with the observation that every technology for level measurement works—when applied correctly. The paper discusses the most popular level measurement technologies used, outlines their advantages and disadvantages, and tells where they are best applied. The pros and cons of RF admittance, capacitance, ultrasonic, radar, nuclear, differential pressure and bubblers are analyzed. The direct link is at bit.ly/1nqlzWA.
Drexelbrook Engineering Co.
LIQUID AND FLUID LEVEL MEASUREMENT
The four major level measuring technologies for fluid and liquid applications are ultrasonic, capacitance, submersible and radar. This tutorial gives an overview of these technologies, including the advantages and disadvantages in an application context. The tutorial includes a short video. See more at: bitly/1k9DACD.
Process Industry Forum
LEVEL MEASUREMENT EBOOKS
This site offers a variety of free, downloadable PDFs on a variety of process control subjects. Among those available on liquid, solid and slurry measurement are Measurement of Level, Humidity and pH, Radar Level Measurement Basics, Ultrasonic Level Measurement Basics, and The Siemens Level Measurement Guide. For more information, go to http://bit.ly/RtJGqI.
LEVEL CONTROL METHODS
The following link provides a brief overview of the various methods of level control, including both adjustable and non-adjustable level control and modulating level control. It also contains a list of a variety of level controller types and their uses, and a brief summary of steam flow control applications. The direct link is at bit.ly/1nqeDuZ.
SOLIDS LEVEL MEASUREMENT
Measuring solids in bins, silos or hoppers presents very different challenges from measuring liquids. The need to convert level to volume and mass, as well as the nature of the material itself,
which often behaves in a manner that makes securing a level measurement difficult or makes the accuracy questionable, all present difficulties. This white paper discusses these challenges and how to address them to ensure accurate solid level measurement. It covers several possible approaches to level measurement, and discusses the strengths and limitations of each one.The direct link to this free, 26-page PDF is at bit.ly/1kivEnV.
RADAR LEVEL MEASUREMENT HANDBOOK
Radar Level Masurement — The User’s Guide by Peter Devine is a free, downloadable, 154-page PDF covering the history of radar technology, the physics of radar, antennas and their installation and radar level measurement techniques, including continuous wave radar measurement and more. The direct link is at bit.ly/1muDo5N.
VEGA Grieshaber KG