Design of a Contactless Conductivity Sensor Used in the Treatment of Industrial Waste Liquids
Challenges
Our client is a North American manufacturer of chemical reduction and metal extraction systems for liquid solutions. Its systems are used across a wide range of sectors and industries, in applications such as medical imaging (X-ray), non-destructive testing, photo development, and printed circuit board production.
One of the systems our client offers entails degrading the metal content of certain solvents used in etching operations and recycling the used liquids. To do so, the company must measure the conductivity of liquids before and after recycling to assess product quality. It therefore called on Cysca Technologies to design a sensor able to detect the conductivity of various used liquids, without galvanic contact.
Solutions
Once recycled, the liquids present very low levels of conductivity, which makes measurements difficult. Cysca’s approach involved synchronous demodulation, similar to what is used in radio communications.
To achieve its ends, the Cysca team used two copper-wound magnetic cores, set a few millimeters apart and coated in silicone or epoxy to achieve galvanic isolation. The setup forms a poorly coupled transformer. When the winding of the primary core is excited by an alternating voltage, it generates a magnetic flux, a portion of which couples to the secondary core and produces alternating voltage at the secondary core winding. The magnetic flux coupled between the two cores is then influenced by the conductivity of the liquid, in such a way that the voltage measured at the secondary varies according to the conductivity level of the liquid. The problem is that the voltage measured is very low and buried in noise. To extract the signal, we want to measure from the noise, we implemented a synchronous demodulator followed by a series of low-pass filters and decimators, much like what is used in radio.
The system was completed using a digital signal processor with implemented algorithms.
Results
Once the sensor was designed, testing was conducted in close cooperation with the client to assess sensor effectiveness in various liquids with controlled conductivity levels.
This project was a first for our teams and helped further expand our skill sets when it comes to signal processing. The design of the contactless sensor fully met the business requirements of our client, who was then able to market new processes using a proven conductivity-measurement solution.
Project Services and Industries
Electronic Design
Software Engineering
Medical Equipment, Industrial Equipment, Photography and Printing
Environment (recycling and green processes)