Patent ID: 8810391

Claim:
A method of sensing exposure to one or more of a plurality of environmental factors, comprising steps of: an exposing step of exposing a code circuit to at least some of the environmental factors, the code circuit disposed over a substrate and including a plurality of sensor patches, each sensor patch having a respective electrical state that changes with exposure to one of the environmental factors, so that the code circuit has an electrical state; a checking step of passing an electrical excitation signal through the code circuit, and detecting a corresponding received electrical signal, using a transceiver formed on a transceiver substrate separate from and disposed over the substrate, wherein the transceiver includes a controller and the received electrical signal depends on the excitation signal and the electrical state of the code circuit; a storing step of using the controller, automatically storing the received electrical signal or a representation thereof in a memory; and a repeating step of using the controller, automatically repeating the checking and storing steps after one or more selected time intervals; and wherein: the exposing step includes contemporaneously exposing a plurality of code circuits to the at least some of the environmental factors, each code circuit disposed over the substrate and including a respective plurality of electrically-connected sensor patches, each sensor patch having an electrical state that changes with exposure to a corresponding one of the one or more environmental factors, so that each code circuit has a respective electrical state; the checking step includes passing a respective electrical excitation signal through each code circuit and detecting a respective received electrical signal; and the storing step includes, using the controller, automatically storing the respective received electrical signals or respective representations thereof in the memory.