Conductance detection is especially suited for charged compounds of small size that are otherwise difficult to detect because they do not have good optical absorption, notable examples are inorganic and small organic ions. By revisiting the principles of what was once called oscillometry and more recently somewhat misleadingly called capacitively coupled contactless conductivity detection (C4D), we revisit the theoretical considerations for applications in very high impedance range [1], and use the lessons to develop sensitively detect admittance changes [2].