초록 ▼

A device for monitoring environmental exposure includes an element whose electrical properties change, in a predetermined way, in response to the environmental exposure. The element may be part of a tuned circuit or of a shield for a tuned circuit. In either case, when the tuned circuit is interroga

A device for monitoring environmental exposure includes an element whose electrical properties change, in a predetermined way, in response to the environmental exposure. The element may be part of a tuned circuit or of a shield for a tuned circuit. In either case, when the tuned circuit is interrogated, preferably by an r.f. or microwave signal, it emits a signal whose intensity depends on the electrical properties of the element. Thus, an incremental environmental exposure can be measured by a change in the signal intensity. The device is particularly useful for monitoring the condition of perishable materials, because it can be located with the perishable inside a packaging material during both storage and interrogation.

대표청구항 ▼

An indicator device comprising a target that has a tuned electrical circuit and that includes an element having an electrical property that, in response to a particular environmental parameter, changes in a predetermined fashion, whereby the response of the target to an electromagnetic interrogation

An indicator device comprising a target that has a tuned electrical circuit and that includes an element having an electrical property that, in response to a particular environmental parameter, changes in a predetermined fashion, whereby the response of the target to an electromagnetic interrogation signal, having a frequency in the microwave range or lower, can be related to the exposure of the target to the parameter.