The initial installation of a condition monitoring system (CMS) on a utility scale wind turbine produced a number of unexpected results. The CMS was installed on the TechnoCentre éolien Repower MM92. The installation allowed testing of a MEMS based sensor technology and allowed and in-depth analysis of vibration data and RPM data. A large 3/rev effect, due to tower shadow and wind shear, required the development of an enhanced time synchronous average algorithm. The ability to easily measured changes in main rotor RPM, as a result of tower shadow and wind shear phenomenology, may also facilitate the detection of icing or blade pitch error.