Patent ID: 8854189

Claim:
A method for a secure non-volatile logging in an active RFID tag of a process running in a tagged article in that in subsequent sampling periods a sensor acquires values of a physical parameter, which values determine said process running in the tagged article at the acquisition times, whereat a high limit (h) and a low limit (l) of an interval (l-h) of such values of said physical parameter are determined, which are proper for retaining usability of the tagged article, and the acquired values of said physical parameter and the acquisition times related thereto are converted into less numerous data characterizing said process by a data logger by observing the high limit (h) and the low limit (l) of the interval (l-h) of said values of said physical parameter, which are proper for retaining usability of the tagged article, characterized in that prior to said logging flags for locking at all addresses of a logging area within a non-volatile memory of the tag are set to state 1 by means of an interrogator, and that said data characterizing said process are logged in said logging area within the non-volatile memory of the tag, wherein the data logger has a direct access to the logging area and is able to log regardless of the state of the flag for locking at the particular address within the logging area, and wherein an interrogator is not allowed to write at said address, if the flag for locking is in the state 1.