Micro-USB Connector Pins as Low-Cost, Robust Electrodes for Microscale Water Conductivity Sensing in Oceanographic Research

Motivated by the widespread need to sense water conductivity in oceanography, as well as in other applications in fluid dynamics and environmental monitoring, we propose using the exposed gold-plated pins of readily available micro-USB connectors as miniaturized, parallel finger electrodes. Since the electrodes are 600 μm apart, they grant sub-mm spatial resolution, suitable for most applications. Standard micro-USB cables are an ideal, ready-to-use solution, since they are shielded, are preassembled in different lengths, and enable 2 and 4-wire measurements. In order to take full advantage of these USB probes, we have designed a custom, open-source 4-channel measuring circuit, named "Conduino", consisting of a low-noise (SNR = 60 dB) shield board coupled to an Arduino microcontroller. Experimental results demonstrate sensing performances comparable with state-of-the-art reference instrumentation (0.1% resolution in the 0.1-15 S/m range), with significantly lower cost and increased versatility and reliability.