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Wide dynamic range current measuring apparatus

  • US 4,876,502 A
  • Filed: 05/09/1988
  • Issued: 10/24/1989
  • Est. Priority Date: 05/09/1988
  • Status: Expired due to Term
First Claim
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1. Wide dynamic range current measuring apparatus comprising:

  • a current transformer having a primary winding and a secondary winding in which a secondary current proportional to a current flowing in the primary winding is induced;

    an analog to digital converter having a plurality of discrete selectable reference voltages providing a plurality of resolutions for a digital signal generated thereby;

    an amplifier with programmable gain and with means generating an overrange signal when the amplifier output exceeds a preset limit;

    means applying a signal proportional to said secondary current to said amplifier;

    means applying the output of the amplifier to said analog to digital converter to generate said digital signal; and

    control means responsive to said overrange signal selecting the highest programmable gain of the amplifier which does not produce an overrange signal, selecting in response to the magnitude of the digital signal generated by the analog to digital converter the selectable reference voltage for the analog to digital converter which provides the greatest resolution of said digital signal and providing an output signal including said digital signal and a scale factor which is a function of both the selected gain of said amplifier and the selected reference voltage of the analog to digital converter.

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