APK Identification ECG Solid GEL Electrodes, commonly Ag/AgCl (silver/silver chloride) type, consist of a conductive sensor, electrolyte gel, adhesive, and backing material. The Ag/AgCl sensor, usually on a conductive ABS plastic stud, minimizes signal noise and impedance, while solid gel acts as an interface, with foam or non-woven fabric backing.are a type of sensor that monitors heart signals. This arrangement translates the heart's ionic electrical signals into electron flow for an external device, such as a monitor.