A comparison of power measurement techniques and electrical characterization of an atmospheric pressure plasma jet

In the last two decades a growing interest has been shown in the investigation of atmospheric pressure plasma jets (APPJs) that operate in contact with liquid samples. In order to form a complete picture about such experimental systems, it is necessary to perform detailed diagnostics of plasma jets, as one step that will enable the adjustment of system properties for applications in different areas. In this work, we conducted a detailed electrical characterisation of a plasma system configuration used for water treatment. A helium plasma jet, with a pin electrode powered by a continuous sine wave at a frequency of 330 kHz, formed a streamer that was in contact with a distilled water sample. An electrical circuit allowed the monitoring of electrical signals supplied to the jet and also to the plasma itself. An electrical characterisation together with power consumption measurements was obtained by using two different methods. The first method was based on the direct measurements of voltage and current signals, while in the second method we used 'Lissajous figures'. We compared these two methods when used for discharge power estimation and addressed their advantages and limitations. The results showed that both of these methods could be used to successfully determine power consumed by a discharge in contact with water, but only when taking into account power dissipation without plasma.