Is it water or orange juice?


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,

No comments
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
Commissioning lighting control systems; 2016 Commissioning Giants; Design high-efficiency hot water systems for hospitals; Evaluating condensation and condensate
Solving HVAC challenges; Thermal comfort criteria; Liquid-immersion cooling; Specifying VRF systems; 2016 Product of the Year winners
MEP Giants; MEP Annual Report; Mergers and acquisitions; Passive, active fire protection; LED retrofits; HVAC energy efficiency
Driving motor efficiency; Preventing Arc Flash in mission critical facilities; Integrating alternative power and existing electrical systems
Putting COPS into context; Designing medium-voltage electrical systems; Planning and designing resilient, efficient data centers; The nine steps of designing generator fuel systems
Designing generator systems; Using online commissioning tools; Selective coordination best practices
As brand protection manager for Eaton’s Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.
click me