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

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Moore Products Co. (Siemens AG)
• Inventors: O'Brien, Christopher J., Moore, James O.
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US08/241,689
• Time in Patent Office: 383 Days
• Field of Search: 340/870.13, 340/870.38, 340/870.39, 340/870.40, 340/870.16, 340/870.18, 340/870.21, 364/139, 364/138
• US Class Current: 340/870.13
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G08C 19/02 in which the signal transmitted is magnitude of current or voltage G08C19/36, G08C19/38 take precedence

Abstract

Integrated transmitters and controllers for use in monitoring process variables. A transmitter and controller for monitoring and controlling a process variable in a process control loop comprises a transmitter for producing a digital signal indicative of the process variable'"'"'s state, and a digital controller supplied with the digital signal from the transmitter responsive to the digital signal, and further interfaced in a process control loop for controlling the process variable in response to the digitally communicated signal from the transmitter. Integrated transmitters and controllers described herein simplify installation and maintenance of industrial process control systems and place the controller functions at the process variable, thereby increasing control system efficiency.

Claims

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.

2. The system of claim 1, wherein said controller output signals are in a range of from 4 to 30 milliamperes.

3. The system of claim 1, further comprising digital bi-directional communication means connected to said integrated transmitter/controller for digitally transmitting process data from said transmitter/controller to said control means superimposed on said analog controller output signals.