Abstract: An apparatus and method for automatically monitoring dynamic signals, such as from vibration sensors, in an operating industrial or other plant to identify abnormal events, draw conclusions as to their severity, and indicate action to be taken, utilizing a computer to control the scanning of one or two sensor channels at a time through a matrix of analog switches, and to process one or two channel signals through a signal processor for power spectral density (PSD) analysis (two channel signals for cross PSD analysis). The computer compares spectra with predetermined sets of frequency dependent limits and indicates the abnormal condition of apparatus in the plant associated with the spectra as a function of which set of limits is exceeded. The computer also indicates from a stored table the action to be taken for the abnormal condition found.