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Process control transmitter having an externally accessible DC circuit common

  • US 6,504,489 B1
  • Filed: 05/15/2000
  • Issued: 01/07/2003
  • Est. Priority Date: 05/15/2000
  • Status: Expired due to Term
First Claim
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1. A process control transmitter having an externally accessible DC common, comprising:

  • first, second and third externally accessible feedthrough terminals, wherein the first and second terminals are couplable to a process control loop and adapted to conduct a loop current IT through the transmitter;

    a series-shunt regulator having an input terminal coupled to the first terminal and a shunt current output terminal coupled to the second terminal, the series-shunt regulator conducting a load current IL and controlling the loop current IT by regulating a shunt current IS out the shunt current output terminal; and

    circuitry energized by the load current IL and adapted to control the loop current IT in response to a sensor signal and provide a digital signal to the third terminal that has a voltage that is regulated relative to a DC common of the circuitry that is coupled to the second terminal, whereby the digital signal is externally accessible between the second and third terminals.

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