Abstract：As a non-invasive neurostimulation technique, multi-channel transcranial electrical stimulation has high focus and flexibility. However, the increase in the number of electrodes also increases the risk of electrode failure, and the requirements for the safety and reliability of the electrical stimulation device are more stringent. The electrode impedance can reflect the skin contact status and the electrochemical changes of the electrode, thus the online monitoring of the electrode impedance helps to improve the safety during electrical stimulation. Due to the crosstalk problem in multi-channel electrical stimulation, the direct measurement of electrode impedance has a large error. This paper proposes a new online impedance measurement method suitable for multi-channel electrical stimulation, which realizes crosstalk decoupling by superimposing short-term and small-amplitude current disturbances on the stimulation waveform, thereby measuring the impedance of each electrode and realizing the location of the faulty electrode. A composite amplifier enhanced Howland current source circuit was designed, and a multi-channel and a multi-mode transcranial electrical stimulation device was built using FPGA controller. Finally, a series of human body experiments were carried out through this device, the on-line monitoring of electrode impedance based on the current perturbation method was realized, and the faulty electrode was located in several types of common electrode poor contact experiments.
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