Is it water or orange juice?

11/12/2010


Dear Control Engineering: I am working in the process to automate a pasteurizer. I am looking for a sensor technology to detect the change from water to orange juice, and from orange juice to water in the output process. It has a color sensor, but it doesn't detect the change all that well. Do you know a better sensor? Thank you. –Erick

When looking at a question like this, we have to think about how water is different from orange juice, and then which of those differences is the easiest to detect or quantify. Apparently color, the most obvious choice, isn’t good enough, so what are some of the other possibilities? Orange juice is more acidic and has more sugar in it, so those might be more practical to detect. I asked Jim Gray, application manager at Rosemount Analytical Instruments for some suggestions. He says, “I think conductivity using a toroidal sensor would be the way to go. That would be the easiest from a maintenance standpoint. The conductivity of OJ should be greater than the conductivity of water, although I don’t have any number handy. The problem with pH would likely be the sensor drying out when the process is down. A Coriolis flowmeter would provide a continuous inferential measurement of concentration but is much more expensive. Conductivity should be sufficient for a status indication.”

A toroidal conductivity sensor.A toroidal conductivity sensor is a doughnut-shaped probe that inserts into the process liquid stream. The toroid itself has two coils. One is powered and creates a magnetic field. The second is a receiver. The current induced in the receiver is in proportion to the conductivity of the surrounding liquid. The probe can be encased in an appropriate grade of plastic to withstand the process liquid. Units are available that are designed for sanitary applications in food processing.

--Peter Welander, pwelander@cfemedia.com



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
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.
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how motion control advances and solutions can help with machine control, automated control on assembly lines, integration of robotics and automation, and machine safety.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

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

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
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