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Remote, inductively coupled, transducer interface

  • US 4,725,839 A
  • Filed: 12/21/1984
  • Issued: 02/16/1988
  • Est. Priority Date: 12/21/1984
  • Status: Expired due to Fees
First Claim
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1. A telemetry system for transmitting information from a remote location, the system including alternating current supply means for applying a square wave voltage signal of a first selected frequency, a current conductor operatively connected with the alternating current supply means for conducting the square wave voltage signal to the remote location, at least one inductive coupler having a primary and a secondary winding in series with the current conductor for inductively transmitting the square wave voltage signal from first to second portions of the current conductor, a transducer at the remote location for generating an output indicative of a remote condition sensed by the transducer, and power converter means adjacent the remote location and operatively connected with the current conductor for converting the square wave voltage signal to electrical power for powering the transducer, the system further comprising:

  • load modulator means for selectively varying the electrical load applied to the current conductor, the load modulator means being operatively connected with the current conductor at the remote location and with the transducer to vary the electrical load in accordance with the output of the transducer;

    load detection and means operatively connected with the primary winding of the at least one inductive coupler for detecting the magnitude of repeatedly varying flyback voltage spikes across the primary winding in response to repeated collapse of the magnetic field within the inductive coupler during transition of the square wave voltage signal, the magnitude of the each flyback voltage spike being related to the magnitude of the varying electrical load applied by the load modulator means; and

    condition detection means responsive to the frequency of an amplitude envelope of the repeatedly varying flyback voltage spikes for generating a signal indicative of the output of the transducer.

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