Shielding effectiveness of liquid electrolyte

Abstract

The paper aims at the investigation of a liquid electrolyte effect on electromagnetic radiation. The liquid electrolyte could represent an interesting solution against electromagnetic interference for devices using transparent covers, such as security cameras. Currently, the way how to protect transparent areas is a fine metallic grid or polymer material; however, this solution could reduce the transparency through the protected part. The paper describes different types of electrolytes and compares their shielding effectiveness. The experiment includes a plastic packing, metallic electrodes, liquids, laboratory power supply, a coaxial transmission line with receiving and transmitting conductors, source of electromagnetic radiation, and test receiver. The liquid consists of weak and strong acids and bases, such as acetic acid, sulfuric acid or sodium chloride which have different conductivity. There are also various materials for electrodes affecting the conductivity and consequently, the ability of the electrolyte to eliminate the effects of electromagnetic interference. The kind of electrode affects the amount of received and delivered ions between anode and cathode. Shielding effectiveness of electrolyte depends on more unstable parameters compared to conventional metal materials. Temperature and concentration of solution affect the electrolyte conductivity; thereby, the reproducibility could be problematic. Strong electrolytes initially have a rapid increase in conductivity; however, high amounts of ions cause their interaction and decrease in conductivity. Weak electrolytes have a similar course, but the conductivity achieves many times lower values. Measurement is provided according to the ASTM D4935 methods, and it involves a discontinued inner and flanged outer conductor. Samples and the conductors are isolated from external sources of electromagnetic interference by special absorbent materials. The conclusion describes the contribution of the paper. © 2019 IEEE.