A system for automatically monitoring the viewing activities of television signals, comprising a measurement device, in which the television signals are adapted to be communicated to the measurement device and the TV set, making the measurement device receive the same signals as the TV set; the measurement device is adapted to extract a fingerprint data from the television signals displayed to the viewers, making the measurement device measures the same video signals as those being seen by the viewers; a data center to which the fingerprint data is transferred; and a fingerprint matcher to which the television signals which the viewers are selected to watch are sent to be monitored through the measurement device. The system according to the present invention does not require any change to the other devices already in place before the measurement device is introduced into the connections.