<p>Systems and techniques for probing interfaces between electrodes and conductive solutions. In one aspect, devices can include a time variable source of power configured to output power that varies in time over a pair of output conductors, an electrode connected to a first of the conductors, an extrinsic inductive impedance connected between the pair of output conductors, and an impedance sensor connected to one or both of the output conductors and configured to measure net impedance between the pair of output conductors based on a known current or voltage output by the time variable power output. The measured net impedance includes the extrinsic inductive impedance and an impedance of the interface. The electrode is configured to be submersed in a conducting solution and form an interface with the conducting solution.</p>
