The electric response in the wave of second sound: Hardware aspect

A detailed description of the standard measuring techniques and original technical solutions used by the authors while studying the recently discovered phenomenon of electric response in the second sound wave. The most successful amplifier circuits used for precision low-temperature measurements are presented, as well as a sensitivity analysis of the different measuring systems. The main goal of the study is to substantiate the reliability of the electrical activity effect occurring in a resonator with He II when a second sound wave is excited. It is shown that the observed electric response signal is not associated with external interference or internal pick-ups, and is also not the result of either direct acoustoelectric conversion or thermal contact potentials. An analysis and comparison of new experimental data obtained by two scientific groups is also presented.