The invention is directed to a method of filling a pressurized medium chamber of a level control system which includes a pressurized medium store and a compressor. The method involves the use of non-linear optical techniques, in particular second-harmonic generation to identify conformational changes in kinase proteins obtained from known type I or type II inhibitors. The temperature measured by each of the thermometers is provided to the processor, and the processor establishes ratios using the recovery factors and measured temperatures to determine total temperature and static temperature of the airflow in which the thermometers are placed.