Importance

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Abstract

A device for measuring physical values, each as pressure changes, includes a sensor transponder section and an interrogator receiver section for transmitting interrogation signals including a power supply from the interrogator receiver section to the sensor transponder section and for transmitting measured signal values in the opposite direction. The sections can be coupled to each other by inductive coils so that electrical connections are avoided. Thus, the pressure in a rotating automobile tire can be measured, for example. The sensor transponder section includes a computer circuit the input of which receives a reference frequency signal and a measured frequency signal. A reference oscillating signal has a frequency determining element that is not influenced by the pressure to be measured, but only by extraneous, e.g. environmental influences. A measuring oscillating circuit has a frequency determining element that is responsive to the changes in the physical value to be measured. Both frequency determining elements are so arranged that they are exposed to the same extraneous conditions, whereby adverse influences of these conditions on the measured values are compensated.

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First Claim