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Integrated transmitter and controller

  • US 5,420,578 A
  • Filed: 05/12/1994
  • Issued: 05/30/1995
  • Est. Priority Date: 07/18/1991
  • Status: Expired due to Term
First Claim
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1. A two-wire system for sensing and controlling the values of a process variable, comprising:

  • control means for controlledly varying said process variable in response to analog control signals supplied thereto;

    sensing means for sensing changes in the value of said process variable and for producing first signals representative thereof;

    an integrated transmitter/controller contained within a single system component and spaced from said control means, said integrated transmitter/controller being responsive to said first signals to develop analog controller output signals for supply to said control means as control signals to controlledly vary said process variable;

    a current supply source;

    a two-wire process control loop operatively interconnecting said current supply source, said integrated transmitter/controller and said control means to effect control of said process variable as a function of said first signals from said sensor means;

    wherein said integrated transmitter/controller comprises a digital CPU, supplied with said first signals and operable in a mode such as to produce, operate upon and output signals containing information corresponding to said analog controller output signals, said transmitter/controller also comprising D/A converter means supplied with digital signals from said CPU to produce said analog controller output signals for delivery over said two-wire loop to said control means.

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