A system for monitoring instrumented equipment, comprising: a plurality of sensors (430; 523; 606) capable of being monitored from the instrumented equipment; an information processor (545; 618); a data acquisition input to said information processor (545; 613) for receiving operational values descriptive of physical parameters of the system from said plurality of sensors (430; 523; 606); a memory (551; 620) operable for being coupled with said data acquisition input for storing a set of time-correlated sensor data representative of expected operational states, and signals observed during operation of the instrumented equipment; wherein said information processor (545; 618) is adapted to generate at least one virtual output value descriptive of a parameter of the instrumented equipment, wherein the parameter is not represented by the received operational values, characterised in that said information processor (545; 618) is further adapted to generate the at least one virtual output value based on a similarity operator to obtain a similarity measure between the expected operational states and the received operational values, wherein the similarity operator refers to a calculation that compares at least one of the received operational values with a value that represents an expected state of the system to obtain a similarity measure and wherein the similarity measure is a value within a range where one end of the range means the compared values have no similarity and the other end of the range means the compared values are identical, and wherein said information processor (545; 618) determines a data acquisition failure associated with said data acquisition input from at least one of said plurality of sensors (430; 523; 606) and provides an estimated replacement signal therefor. a plurality of sensors (430; 523; 606) capable of being monitored from the instrumented equipment; an information processor (545; 618); a data acquisition input to said information processor (545; 613) for receiving operational values descriptive of physical parameters of the system from said plurality of sensors (430; 523; 606); a memory (551; 620) operable for being coupled with said data acquisition input for storing a set of time-correlated sensor data representative of expected operational states, and signals observed during operation of the instrumented equipment; wherein said information processor (545; 618) is adapted to generate at least one virtual output value descriptive of a parameter of the instrumented equipment, wherein the parameter is not represented by the received operational values, characterised in that said information processor (545; 618) is further adapted to generate the at least one virtual output value based on a similarity operator to obtain a similarity measure between the expected operational states and the received operational values, wherein the similarity operator refers to a calculation that compares at least one of the received operational values with a value that represents an expected state of the system to obtain a similarity measure and wherein the similarity measure is a value within a range where one end of the range means the compared values have no similarity and the other end of the range means the compared values are identical, and wherein said information processor (545; 618) determines a data acquisition failure associated with said data acquisition input from at least one of said plurality of sensors (430; 523; 606) and provides an estimated replacement signal therefor.