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Conversion circuit for process control system

  • US 5,650,777 A
  • Filed: 06/07/1995
  • Issued: 07/22/1997
  • Est. Priority Date: 06/07/1995
  • Status: Expired due to Fees
First Claim
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1. Conversion circuitry for coupling to a field transmitter over a primary process control loop, comprising:

  • digital receiver circuitry coupling to the primary loop for receiving a digital process variable signal from the field transmitter sent over the primary process control loop and providing a digital output;

    control circuitry receiving the digital output and responsively providing a secondary loop control output; and

    secondary loop control circuitry for coupling to a secondary process control loop including a current source for controlling current flowing through the secondary loop in response to the secondary loop control output whereby an analog current in the secondary loop is related to the digital process variable signal provided by the field transmitter.

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