Internal failure detection of an external failure detection system for industrial plants

An internal failure detection device for an external failure detection system for industrial equipment, said external failure detection system comprising an array of transducers, wherein at least two transducers have an overlapping field of view, the internal failure detection device comprising

• receiving means (2011, 2012, . . . , 201N) to receive a plurality of signals, each signal being measured by a corresponding transducer of the array of transducers,
• processing means (204, 205, 206, 207, 208) arranged to, for each pair of transducers among a number of pairs of transducers, calculate at least one value of a correlation parameter between the received signals corresponding to said pair of transducers, by correlating at least part of said signals or of invertible transforms thereof, and to, for at least one transducer of the number of transducers, estimate from the calculated values of the correlation parameter if this transducer is working properly, and
• transmitting means to transmit a signal generated as a function of the result of the estimating so as to report a possible transducer failure.