Low concentrations of water vapor within a background of one or more olefin gases may be detected and quantified using a differential absorption spectrometer. The systems and methods may distill oxygen from ambient air by a molecular sieve pressure cycle mechanism, such as a pressure swing absorption, may generate oxygen from water using electricity or may use oxygen enriched air produced by membrane filtration. A bus arbiter is provided for arbitrating between requests to access the bus by a first bus master and one or more other bus masters. A computer programme and a computer programme product. Thus, the number of trace events in the log may be significantly reduced to those trace events that satisfy conditions of interest to an evaluator.