Two-wire field mounted process device

• US 20050080493A1
• Filed: 10/14/2003
• Published: 04/14/2005
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Arntson, Douglas W.
• Granted Patent: US 7,016,741 B2
• Time in Patent Office: Days
• US Class Current: 700/39
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 2219/25006 Interface connected to fieldbus
• CPC Class Codes: G05B 2219/25428 Field device

Abstract

A device for use in a process control system includes a first pair of electrical connections configured to couple to a two-wire process control loop. The loop includes a two-wire process variable transmitter. A second pair of electrical connections is configured to couple to an input channel of a process device having multiple input channels. An electrical component is connected in series in the loop for use in digital communication with the two-wire process variable transmitter.

Claims

2-1. The apparatus of claim 1 wherein the electrical component comprises a resistor.

16. A signal conversion device for use in a process control system, comprising:

a first pair of electrical connections configured to couple to a two-wire process control current loop which includes a two-wire process variable transmitter;

a second pair of electrical connections configured to couple to a voltage input channel of a process device; and

digital communication coupling means for coupling a digital communication signal to the two-wire process control current loop through the first pair of electrical connections.

17. The apparatus of claim 16 wherein the digital communication coupling means comprises a resistor.

18. A method for use in a process control system, comprising:

providing a process control current loop for coupling to a two-wire process variable transmitter;

providing a first pair of electrical connections on the two-wire process control current loop for coupling to a digital communicator; and

providing a second pair of electrical connections for coupling to a voltage input channel of a process device.

19. The method of claim 18 including providing an impedance between the first pair of electrical connections.

20. The method of claim 18 including providing an impedance between the second pair of electrical connections.

21. The method of claim 18 wherein the voltage drop across the second pair of electrical connections is between about 20 mVolts and about 100 mVolts.

22. The method of claim 18 wherein a two-wire process control current loop carries an electrical current between about 4 mA and 20 mA.

23. The method of claim 18 including digitally communicating with the two-wire process variable transmitter.

24. The method of claim 23 wherein the digital communicator comprises communicating in accordance with the HART®

Standard.