A linear motion guide unit has a track rail of a pair of side walls on which raceway grooves are formed. In at least one embodiment, the controller is capable to control transitions between discontinuous conduction mode and critical conduction mode of the switching power converter using a measured switching time parameter having a value corresponding with an approximately peak voltage of a time-varying supply voltage supplied to the switching power converter. The sunlight analog device is powered by electric supply to generate light which is similar to sunlight. The EMI data is superimposed onto the crash data to provide an indication of how the system performs when exposed to both conditions.