Researchers at the University of California Santa Barbara have found a way to replicate the functionality of a sensitive but expensive conductivity probe with low cost electronics.
Paolo Luzzatto-Fregiz, a mechanical engineer at UC Santa Barbara, was frustrated with repeatedly breaking the delicate tip of conductivity probes. Conductivity probe tips consist of four small platinum electrodes housed in glass. The fragility of the probe tip was matched by its high sensitivity, allowing it to make measurements in tiny volumes of water.
Luzzatto-Fegiz is an expert in fluid dynamics. According to him, while the probes work well, they are expensive and fragile, making it expensive to do complicated experiments in the lab.
The fragility of the tip also limits the kind of experiments that can be done in the field, due to the risk of collision, or stray debris coming into contact with the millimetre-thick tip.
"It also limits the kind of teaching that could be done with it, for example in oceanography," Luzzatto-Fegiz said. "It would be great to send out a bunch of undergrads in your labs to use these things but you can’t reasonably afford to do that."
Inspired by the rise in maker culture, particularly with DIY electronics, he decided to engineer his own solution.
He worked with his childhood best friend, Marco Carminati, a microelectronics and sensors expert from the Politecnico di Milano. Together, the two engineers used off-the-shelf products to design and build a conductivity probe that not only costs a fraction of the conventional one, but also achieved close to the same sensitivity while being more versatile and robust enough to withstand the occasional knock.
The main design challenge was to replicate the probe tip with its closely spaced electrodes. The engineers did that by cannibalising a micro USB connector plug. Carminati came up with the idea, according to Luzzatt-Fegiz.
"What you do is you essentially peel off the outer metallic shield and expose these gold-plated electrodes and they’re perfect," said Luzzatto-Fegiz.
The device, which the engineers dubbed Conduino, after its functionality, and the fact that it is Arduino-based, is modular and customisable, and can be USB-powered, making it extremely portable. It can also be built for a couple of hundred dollars, and incorporates several sensors operating in parallel, as opposed to the single sensor of the commercially available device.
While some experiments and operations require conventional instruments for the finest, highest-resolution measurements, the Conduino achieves the same level of performance as the commercially available devices for most applications.