Patent ID: 7604177

Claim:
A contactless data carrier system comprising a contactless data carrier, a signal source, and an interrogator wherein: the signal source generates an external signal according to an ambient physical quantity; the contactless data carrier includes a measurement port for receiving the external signal, a variable threshold generator for generating different threshold values, a comparator for comparing the external signal received at the measurement port with the different threshold values and for producing comparison results, and a controller for controlling the variable threshold generator according to commands received from the interrogator and for returning the comparison results to the interrogator; and the interrogator exchanges data with the contactless data carrier by wireless communication, commands the controller in the contactless data carrier to have the comparator execute repeated comparisons, supplies the different threshold values to the contactless data carrier, obtains individual comparison results from the contactless data carrier, and obtains information about the ambient physical quantity by finding a boundary value at which the comparison results change.