Conversion circuit for process control system

Communications: electrical – Continuously variable indicating – Plural transmitters

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C340S870160, C340S315000

Reexamination Certificate

active

06307483

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to process control systems. More specifically, the invention relates to transmission of process variables from field transmitters to control room circuitry in process control systems.
Generally, process variable field transmitters are used in process control systems to measure process variables such as flow, temperature or pressure and transmit these variables to a control room. This information is used at the control room to monitor and control operation of the process.
Traditionally, transmission of process variables has been through the use of two-wire current loops. A 4 mA signal in a typical 4-20 mA current loop represented a minimum reading and a 20 mA signal represented a maximum reading of the process variable. Power for the current loop and field transmitter was supplied from the control room in order to maintain an intrinsically safe and explosion-proof environment in the field. The field transmitter controlled the current flowing through the loop based upon the measured process variable. This, and other types of current loops, have become industry standards.
With the advent of microprocessors, field transmitters have become increasingly automated. One offshoot of this technology is the use of digital signal transmissions from field transmitters. In one design, a digital signal is superimposed on the 4-20 mA process variable current signal. This digital signal can represent a primary process variable typically also represented by the analog loop circuits or secondary process variables. In another configuration, multiple field transmitters are connected to the same process control loop and each transmitter transmits digital process variables over the loop to the control room. Traditional control room circuitry adapted for the analog communication techniques have not been able to fully utilize the transmitters capable of transmitting digital signals.
SUMMARY OF THE INVENTION
Conversion circuitry is provided for coupling a field transmitter transmitting digital information to control room circuitry adapted for receiving analog signals. The field transmitter transmits digital information on a primary process control loop. The conversion circuitry includes a digital receiver for receiving first and second digital signals from the primary loop and providing a digital output representative of the digital signals. A microprocessor receives the digital output and responsively provides a digital secondary loop control output as a function of the first and second digital signals. Secondary loop control circuitry receives the secondary loop control output and responsively controls an analog signal applied to a secondary control loop.
In one embodiment, multiple digital signals are received from the primary loop and separately provided to multiple secondary loops. In one embodiment, the secondary loop is a 4-20 mA loop. A single field transmitter may be used to transmit multiple process variables. Additionally, multiple field transmitters may be used to transmit multiple digital process variables.


REFERENCES:
patent: 3764983 (1973-10-01), Stok
patent: 3872389 (1975-03-01), Willard
patent: 4206443 (1980-06-01), Britton
patent: 4356475 (1982-10-01), Neumann et al.
patent: 4484190 (1984-11-01), Bedard
patent: 4739183 (1988-04-01), Tokura et al.
patent: 4816825 (1989-03-01), Chan et al.
patent: 4818994 (1989-04-01), Orth et al.
patent: 4994788 (1991-02-01), Philippe et al.
patent: 5008662 (1991-04-01), Tokizane et al.
patent: 5223826 (1993-06-01), Amou et al.
patent: 5963147 (1999-10-01), Westfield et al.
patent: 40 21 258 A1 (1991-01-01), None
patent: 42 27 577 C1 (1994-02-01), None
patent: 0 490 864 A1 (1992-06-01), None
patent: 0 589 849 A1 (1994-03-01), None
patent: 0 591 926 A2 (1994-04-01), None
“Remote Terminal Units for Distributing Control and Data Acquisition”, Arcom Control Systems, 1995, (brochure). No Page Nu.
“Field Bus Interface Products for Distributed Control and Data Acquisition”, Arcom Control Systems, 1995 (brochure). No Page Nu.
“Communications Gateway Products for Distributed Control and Data Acquisition”, Arcom Control Systems, 1995 (brochure). No Page Nu.
“Developing Process Systems Using Hart”, Arcom Control Systems, 1992, pp. 3-22.
“Digital Data Communication, Control and Maintenance,” by W. Van Der Bijl,Journal A, vol. 34, No. 1, 1993, pp. 19-23.
“SMV 3000 Smart Multivariable Transmitter; The Four-In-One Transmitter and Flow Computer,” Honeywell Inc., 11/95 (brochure). No Page Nu.
“Multivariable Analog Interface for Smart Transmitters,” by S. Oxenberg et al., Symposium '96, pp. 1-7.
“Fieldbus In TotalPlant Solutions,” by P. Griem et al., Symposium '96, pp. 1-7.
SMV 3000 Multivariable Pressure Transmitter: Release 150 Enhancements, by R. Harvey et al., pp. 1-7.
Materials from www.honeywell.com Internet Site dated Sep. 16, 1996. No Page Nu.
“Multivariable Trip Switch For Smart Transmitters,” Vektron Corporation, Jan. 9, 1997, (Brochure). No Page Nu.
Innovation Awards,FC, Feb. 1997. p. 26.
SMV 3000 Smart Multivariable Transmitter, Honeywell, 1995, pp. 1-11.
“Use of Smart Multivariable Transmitters for Combustion Air Flow Measurement,” by M. Cushing,ISA, 1996, pp. 221-229.
Exhibit and Product Guide to ISA 96,I&CS, Sep. 1996. p. 80.
“The New SMV 3000 Solves the Mystery of Flow,” Honeywell. No Page Nu.

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Conversion circuit for process control system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Conversion circuit for process control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Conversion circuit for process control system will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-2553231

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.