Process field device with radio frequency communication

• US 7,956,738 B2
• Filed: 08/21/2007
• Issued: 06/07/2011
• Est. Priority Date: 06/28/2004
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Karschnia, Robert J., Orth, Kelly M., Westfield, Brian L., Broden, David A., Willcox, Charles R.
• Primary Examiner(s): Crosland; Donnie L
• Application Number:
  US11/842,356
• Publication Number:
  US 20070285224A1
• Time in Patent Office: 1,386 Days
• Field of Search: 340/538, 340/508
• US Class Current: 340/538
• CPC Class Codes: G05B 19/4185 characterised by the network communication
• CPC Class Codes: G05B 2219/33192 Radio link, wireless
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
• CPC Class Codes: Y02P 90/80 Management or planning

Abstract

A field device for use in an industrial process control or monitoring system includes terminals configured to connect to a two-wire process control loop. The loop carries data and provides power to the field device. RF circuitry in the field device is provided for radio frequency communication. A power supply powers the RF circuitry using power received from the two-wire process control loop.

Claims

1. A process control transmitter for monitoring a process variable in an industrial process comprising:

a process variable sensor configured to sense the process variable;

I/O circuitry configured to couple to a two wire process control loop and communicate on the process control loop;

wireless communication circuitry coupled to the two wire process control loop configured to transmit an RF signal; and

power supply circuitry coupled to the two wire process control loop including a voltage regulator, the power supply circuitry electronically connected in series with the process control loop, the voltage regulator configured to receive a voltage drop and responsively provide a regulated voltage output to power the wireless communication circuitry.

2. The apparatus of claim 1 including a terminal block configured to electronically connect to the two wire process control loop and wherein the wireless communication circuitry couples to the terminal block.

3. The apparatus of claim 1 wherein the wireless communication circuitry is completely powered with power from the two wire process control loop.

4. The apparatus of claim 1 wherein the wireless communication circuitry includes a resistor coupled in series with the two wire process control loop.

5. The apparatus of claim 1 including a battery configured to power the wireless communication circuitry.

6. The apparatus of claim 1 wherein the wireless communication circuitry includes two wire loop communication circuitry configured to communicate on the two wire communications loop.

7. The apparatus of claim 1 wherein the wireless communication circuitry includes HART®

communication circuitry.

8. The apparatus of claim 1 wherein the wireless communication circuitry includes intrinsic safety protection circuitry.

9. The apparatus of claim 1 wherein the wireless communication circuitry includes an analog to digital converter configured to provide a digital representation of current flowing through the two wire process control loop.

10. The apparatus of claim 8 wherein the RF signal is based upon the sensed current.

11. The apparatus of claim 1 wherein the wireless communication circuitry includes a microprocessor.

12. The apparatus of claim 1 wherein the wireless communication circuitry includes a memory containing addressing information.

13. The apparatus of claim 1 wherein the wireless communication circuitry includes an antenna.

14. The apparatus of claim 1 wherein the wireless communication circuitry is configured to receive an RF signal and responsively transmit a signal on the two wire process control loop.

15. The apparatus of claim 1 wherein the power supply circuitry includes an electrical element comprises a zener diode configured to couple in series with the two wire process control loop.

16. The apparatus of claim 1 wherein the power supply circuitry includes a wireless communication circuitry is configured to enter a sleep mode during idle periods.

17. The apparatus of claim 1 including:

an energy storage capacitor configured to store an electrical charge using power received from the two-wire process control loop; and

wherein the power supply circuitry is configured to use power from the electrical charge stored on the energy storage capacitor.

18. The apparatus of claim 1 wherein the wireless circuitry is carried on a modular circuit board configured to mount in a housing of the process variable transmitter.

19. The apparatus of claim 1 wherein the wireless communication circuitry includes terminals configured to couple in series with the two-wire process control loop.

20. The apparatus of claim 1 including:

an explosion proof housing configured to enclose the wireless circuitry;

an integral RF transparent region in the housing configured to allow RF transmission therethrough.

21. The apparatus of claim 20 wherein the RF transparent region comprises glass.

22. The apparatus of claim 20 including an end cap configured to mount to a main housing and wherein the end cap includes the RF transparent region.

23. The apparatus of claim 1 including:

a circuit board configured to carry the wireless communication circuitry; and

an RF antenna coupled to the wireless communication circuitry and carried on the wireless communication circuit board.

24. The apparatus of claim 19 wherein the wireless communication circuitry is integral with a terminal block which carries the terminals.

25. The apparatus of claim 1 wherein the wireless communication circuitry is configured to transmit an RF signal related to an analog current level carried through the process loop.

26. The apparatus of claim 1 wherein the wireless communication circuitry is configured to transmit an RF signal related to a digital signal carried by the process control loop.

27. The apparatus of claim 1 including a HART®

module coupled to the wireless communication circuitry configured to operate as a bi-directional HART®

to RF gateway unit.

28. The apparatus of claim 1 wherein the wireless communication circuitry is configured for periodic communication.

29. The apparatus of claim 1 wherein the wireless communication circuitry is configured to transmit an RF signal related to a process variable.

30. The apparatus of claim 1 wherein the voltage regulator comprises a linear regulator.

31. The apparatus of claim 1 wherein the voltage regulator comprises a switch mode regulator.

32. Radio frequency (RF) communication apparatus configured to couple to a field device in a two-wire process control loop, comprising:

first and second electrical connections configured to couple in series with the two-wire process control loop;

a third electrical connection configured to couple to the two-wire process control loop, wherein the second and third electrical connections are configured to couple in parallel with the field device; and

an RF circuit configured to receive power from the two-wire process control loop through the first and second electrical connections and transmit an RF signal which contains information related to data carried on the two-wire process control loop.

33. The apparatus of claim 32 wherein the RF circuit is configured to receive an RF signal which contains incoming data and further including circuitry configured to responsively transmit the incoming data on the two-wire process control loop.

34. The apparatus of claim 32 including a forth electrical connection and wherein the third and forth electrical connections are electrically coupled together.

35. The apparatus of claim 32 including an electrical element coupled between the first and second electrical connections for use in communication on the two-wire process control loop.

36. The apparatus of claim 32 including an electrical element coupled between the first and second electrical connections for use in providing power to the RF circuit.

37. The apparatus of claim 36 including a voltage regulator coupled to the electrical element which provides a regulated voltage output to the RF.

38. The apparatus of claim 32 including HART®

communication circuitry configured to receive information from the two-wire process control loop in accordance with the HART®

communication protocol.

39. The apparatus of claim 38 wherein the information contained in the RF signal comprises information received by the HART®

communication circuitry.

40. The apparatus of claim 32 including a microprocessor coupled to the RF circuit configured to control the RF signal.

41. The apparatus of claim 32 wherein the RF circuit is configured to be added to an existing field device.

42. The apparatus of claim 32 wherein the RF signal carries information related to an analog current level carried on the two-wire process control loop.

43. The apparatus of claim 32 wherein the RF signal carries information related to a digital signal carried on the two-wire process control loop.

44. The apparatus of claim 32 including a filter configured to couple the RF circuit to the two-wire process control loop.

45. The apparatus of claim 32 including a terminal block configured to electronically connect to the two wire process control loop and wherein the RF circuit couples to the terminal block.

46. The apparatus of claim 32 wherein the RF circuit is completely powered with power from the two wire process control loop.

47. The apparatus of claim 32 including a resistor coupled in series with the two wire process control loop.

48. The apparatus of claim 32 including a battery configured to power the RF circuit.

49. The apparatus of claim 32 including two wire loop communication circuitry configured to communicate on the two wire communications loop.

50. The apparatus of claim 32 including intrinsic safety protection circuitry.

51. The apparatus of claim 32 including an analog to digital converter configured to provide a digital representation of current flowing through the two wire process control loop.

52. The apparatus of claim 32 including a microprocessor.

53. The apparatus of claim 32 including a memory containing addressing information.

54. The apparatus of claim 32 including an antenna.

55. The apparatus of claim 32 wherein the RF circuit is configured to receive an RF signal and responsively transmit a signal on the two wire process control loop.

56. The apparatus of claim 36 wherein the electrical element comprises a zener diode configured to couple in series with the two wire process control loop.

57. The apparatus of claim 32 wherein the RF circuit is configured to enter a sleep mode during idle periods.

58. The apparatus of claim 32 including:

an energy storage capacitor configured to store an electrical charge using power received from the two-wire process control loop; and

power supply circuitry configured to use power from the electrical charge stored on the energy storage capacitor to power the RF circuit.

59. The apparatus of claim 32 wherein the RF circuit is carried on a modular circuit board configured to mount to the field device the process variable transmitter.

60. The apparatus of claim 32 including:

an explosion proof housing configured to enclose the RF circuit.

61. The apparatus of claim 60 wherein the explosion proof housing includes:

an integral RF transparent region in the housing configured to allow RF transmission therethrough.

62. The apparatus of claim 61 wherein the RF transparent region comprises glass.

63. The apparatus of claim 61 wherein the RF transparent region comprises plastic.

64. The apparatus of claim 32 including:

a circuit board configured to carry the RF circuit; and

an RF antenna coupled to the RF circuit and carried on the circuit board.

65. The apparatus of claim 32 including a HART®

module coupled to the RF circuit configured to operate as a bi-directional HART®

to RF gateway unit.

66. The apparatus of claim 32 wherein the RF circuit is configured to transmit an RF signal related to a process variable.

67. The apparatus of claim 32 including a directional antenna coupled to the RF circuit.

68. The apparatus of claim 32 wherein the RF signal includes error correction information.

69. The apparatus of claim 32 wherein the RF signal is in accordance with a topology selected from the group of topologies consisting of point to point, spoke and hub, and mesh topologies.

70. The apparatus of claim 32 including a digital chip responsive to a chip select signal.

71. The apparatus of claim 32 including a shunt element configured to shunt electrical current from the two-wire process control loop.

72. The apparatus of claim 32 including loop communication circuitry coupled to the third electrical connection.

73. The apparatus of claim 72 including a microprocessor coupled to the loop communication circuitry.

74. The apparatus of claim 73 wherein the microprocessor is coupled to the RF circuit.

75. The apparatus of claim 32 including power supply circuitry connected in series with the first and second electrical connections.

76. The apparatus of claim 75 wherein the power supply circuitry includes a linear voltage regulator.

77. The apparatus of claim 75 wherein the power supply circuitry includes a switch mode voltage regulator.

78. A method for RF communicating with a two-wire process control loop, comprising:

connecting first and second electrical connections in series to the two-wire process control loop and a field device;

connecting a third electrical connection to the field device;

allowing electrical current from the two-wire process control loop to flow from the first connection through the second connection and through the electrical third connection to the field device;

transmitting an RF signal which contains information related to data carried on the two-wire process control loop.

79. The method of claim 78 wherein the transmitting an RF signal comprises transmitting RF data as a function of information received from the two-wire process control loop in accordance with the HART®

protocol.

80. The method of claim 78 wherein the transmitting comprises digital communicating.

81. The method of claim 78 wherein the transmitting comprises analog communicating.

82. The method of claim 78 including receiving an RF signal which contains incoming data and responsively transmit the incoming data on the two-wire process control loop.

83. The method of claim 78 wherein the first and third electrical connections are electrically coupled together.

84. The method of claim 78 including using an electrical element coupled between the first and second electrical connections for use in communication on the two-wire process control loop.

85. The method of claim 78 including using an electrical element coupled between the first and second electrical connections for use in providing power to the RF circuit.

86. The method of claim 78 including coupling an RF circuit to an existing field device.

87. The method of claim 78 wherein the RF signal carries information related to an analog current level carried on the two-wire process control loop.

88. The method of claim 78 wherein the RF signal carries information related to a digital signal carried on the two-wire process control loop.

89. The method of claim 78 including completely powering RF circuitry with power from the two wire process control loop.

90. The method of claim 78 including storing addressing information in a memory.

91. The method of claim 78 including placing RF circuitry in a sleep mode during idle periods.

92. The method of claim 78 including providing a bi-directional HART®

to RF gateway.

93. The method of claim 78 including transmitting an RF signal related to a process variable.

94. The apparatus of claim 78 wherein the RF signal includes error correction information.

95. The apparatus of claim 78 wherein the RF signal is in accordance with a topology selected from the group of topologies consisting of point to point, spoke and hub, and mesh topologies.

96. The apparatus of claim 78 including providing a shunt element configured to shunt electrical current from the two-wire process control loop.

97. The apparatus of claim 78 including regulating power with a switch mode voltage regulator.