The present invention relates to a process and apparatus for purifying a molecule of interest from a heterogeneous clarified fluid mixture. Examples include techniques for assessing heart chamber disequilibrium, detecting chamber volumes and pressures, calibrating near-field-based left atrial pressure estimation procedures and for assessing the recovery from injury at the electrode-tissue interface. The controller detects the resistance value of the resistor and reads the ID of the key corresponding to the resistance value from the table. A timing mark is detected and then the adjusted phase of the system clock is held.