Minimization of the optical smoke detector false alarm probability by optimizing its frequency characteristic

The exclusive use of the time domain analysis in the design tuning to lower the probability of false alarms is caused by the output signal binary nature prevailing in the optical smoke detector designs. However, the characteristic of a standard detector circuit is fairly linear up to the output comparator. On the basis of the generalized functional block scheme, for this linear dependence the Laplace transform is derived in this paper. The transfer function obtained is optimized with respect to false alarm probability minimization, for the second and the fourth order cases. Exploiting the optimization results presented, the improvement of the detector design to obtain lower probability of false alarm reduces to the calculation of element parameters from the coefficients of the optimized transfer function. If the requests for detector time response behavior are different from those adopted here, this paper presents a systematic set of design steps that have to be performed to obtain the optimal performance.