Industrial field device with reduced power consumption

• US 8,217,782 B2
• Filed: 05/24/2007
• Issued: 07/10/2012
• Est. Priority Date: 05/24/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Nelson, Richard L., Lovegren, Eric R., Johnson, James A.
• Primary Examiner(s): Lee, Benjamin C
• Assistant Examiner(s): KING, CURTIS J
• Application Number:
  US11/805,728
• Publication Number:
  US 20080291009A1
• Time in Patent Office: 1,874 Days
• Field of Search: 340/3.1
• US Class Current: 340/539.1
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: G05B 2219/25282 Alternative energy for fieldbus devices
• CPC Class Codes: G05B 2219/25286 Switch on power, awake controlled machine from standby if command signal

Abstract

A field device for use in monitoring or controlling an industrial process includes two wire process control loop electrical connections. Digital communications monitoring circuitry coupled to the electrical connections and is configured to control power to the field device electrical circuitry in response to a digital signal on the two wire process control loop.

Claims

1. A field device for use in monitoring or controlling an industrial process, comprising:

an internal power source;

wireless communication circuitry configured to communicate wirelessly with other equipment in the industrial process and powered by the internal power source;

two wire process control loop electrical connections configured to couple to a two wire process control loop;

field device loop communication circuitry having a power-on input configured to communicate on the two wire process control loop when powered in response to the power-on input; and

digital communications monitoring circuitry coupled to the electrical connections and configured to provide a signal to the power-on input of the field device loop communication circuitry in response to a digital signal on the two wire process control loop, whereby the field device loop communication circuitry is powered off when no digital signal on the two wire process control loop is detected and powered on with power from the internal power source when a digital signal on the two wire process control loop is detected wherein power on of the loop communication circuitry is independent of the power on of the wireless communication circuitry.

2. The apparatus of claim 1 including a switch configured to couple electrical power to the power-on input of the field device loop communication circuitry in response to the digital communications monitoring circuitry.

3. The apparatus of claim 1 wherein the power-on input comprises a wakeup input of the field device electrical circuitry responsive to the digital communication monitoring circuitry.

4. The apparatus of claim 1 wherein the digital signal on the two-wire process control loop comprises a digital communication signal in accordance with a communications standard protocol.

5. The apparatus of claim 4 wherein the communication standard protocol comprises the HART®

communication protocol.

6. The apparatus of claim 1 wherein the two wire process control loop comprises a 4-20 mA process control loop.

7. The apparatus of claim 1 including a process variable sensor configured to sense a process variable.

8. The apparatus of claim 1 wherein the digital communications monitoring circuitry includes a filter.

9. The apparatus of claim 1 wherein the digital communications monitoring circuitry includes a comparator arranged to compare a signal with a threshold level and responsibly provide the signal to the power-on input of the field device loop communication circuitry.

10. The apparatus of claim 1 including a band pass filter and a first comparator configured to compare the output of the band pass filter with first threshold, a low pass filter and a second comparator configured to compare an output from a low pass filter with a second threshold.

11. The apparatus of claim 10 wherein the output from the first comparator comprises a square wave.

12. The apparatus of claim 1 wherein the internal power source comprises a battery configured to power the wireless communication circuitry of the field device.

13. The apparatus of claim 1 wherein the two wire process control loop is configured to couple to a portable configuration tool for use in configuring the field device.

14. A method of controlling operation of electrical circuitry in a field device of the type used in monitoring or controlling an industrial process, the method comprising:

wirelessly communicating with another device in the industrial process using power from an internal power source;

monitoring signals carried on a two wire process control loop;

detecting a communications signal from the monitored signals on the two wire process control loop and providing a power on signal to loop communication circuitry; and

powering the loop communication circuitry in response to the power on signal with power from the internal power source when a digital signal on the two wire process control loop is detected wherein power on of the loop communication circuitry is independent of the power on of the wireless communication circuitry.

15. The method of claim 14 including coupling electrical power to a power-on input of the loop communication circuitry in response to the digital communications monitoring circuitry.

16. The method of claim 15 wherein the power-on input comprises a wakeup input of a microprocessor.

17. The method of claim 14 wherein the communications signal on the two-wire process control loop comprises a digital communication signal in accordance with a communications standard protocol.

18. The method of claim 14 wherein the two wire process control loop comprises a 4-20 mA process control loop.

19. The method of claim 14 including sensing a process variable with a process variable sensor.

20. The method of claim 14 including filtering the signals on the two wire process control loop.

21. The method of claim 14 including comparing the monitored signals.