Process field device temperature control

• US 7,679,033 B2
• Filed: 09/29/2005
• Issued: 03/16/2010
• Est. Priority Date: 09/29/2005
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Westfield, Brian L., Orth, Kelly M.
• Primary Examiner(s): PAIK, SANG YEOP
• Application Number:
  US11/238,656
• Publication Number:
  US 20070068922A1
• Time in Patent Office: 1,629 Days
• Field of Search: 2194431-4682, 219490-497, 392485-489, 73700-708, 73717-727
• US Class Current: 219/447.1
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 2219/25428 Field device
• CPC Class Codes: G05B 2219/31121 Fielddevice, field controller, interface connected to fieldbus
• CPC Class Codes: G05D 23/19 characterised by the use of electric means G05D23/1393 takes precedence

Abstract

A field device system for use in an industrial process includes a field device configured to couple to the industrial process and monitor or control the industrial process. The field device provides a temperature control signal output related to a temperature of the field device. A heater coupled to the field device heats the field device in response to the temperature control signal.

Claims

1. A field device system for use in an industrial process configured to couple to a process control loop comprising:

a field device having a housing configured to couple to the industrial process and monitor or control the industrial process, the field device including a temperature control signal output which provides a temperature control signal related to a temperature of the field device, the field device including a process variable sensor configured to sense a process variable of the industrial process and I/O circuitry configured to couple to a process control loop and transmit information related to the process variable; and

a heater mounted to the housing of the field device and externally of the field device, the heater electrically coupled to the temperature control signal output configured to heat the field device in response to the temperature control signal.

2. A field device system of claim 1 wherein the process control loop comprises a two-wire process control loop related to the measured process variable.

3. The field device system of claim 1 wherein the field device includes an internal temperature sensor and the temperature control signal is related to the temperature of the temperature sensor.

4. The field device system of claim 1 wherein the temperature control signal comprises a digital signal.

5. The field device system of claim 2 wherein the temperature control signal is provided on the two-wire process control loop coupled to the field device and to the heater.

6. The field device system of claim 5 wherein the electrical connection provides isolation of DC signals.

7. The field device system of claim 1 wherein the field device is configured to couple to a high purity vacuum process.

8. The field device system of claim 1 wherein the heater couples to an external power supply.

9. The field device system of claim 1 wherein the heater includes a heater element and wherein a relationship between the temperature control signal and heat from the heater element is programmable.

10. The field device system of claim 9 wherein the relationship between the temperature control signal and heat from the heater element is programmed through a local interface.

11. The field device system of claim 9 wherein the relationship between the temperature control signal and heat from the heater element is programmed through digital signals received in accordance with the HART®

communications protocol from the process control loop.

12. The field device system of claim 1 wherein the process variable sensor comprises a pressure sensor configured to sense a pressure of the industrial process.

13. The field device system of claim 12 wherein the pressure sensor includes a temperature sensor and the temperature control signal is related to the temperature of the temperature sensor.

14. The field device system of claim 1 wherein the heater includes a heater element and a controller configured to implement a control algorithm and responsively control heat from the heater element as a function of the temperature control signal.

15. The field device system of claim 1 wherein the heater includes thermal overload protection.

16. The field device system of claim 1 wherein the heater includes a local output configured to provide an indication of heater status.

17. The field device system of claim 1 wherein the heater is configured to diagnose impending failure of a heater element of the heater.

18. A method reducing accumulation of process material on a field device in an industrial process coupled to a process control loop, comprising:

sensing a process variable of the industrial process;

transmitting an output on the process control loop related to the sensed process Variable;

mounting a heater to a housing of the field device, the heater positioned externally to the field device;

sensing an internal temperature of the field device;

providing a temperature control signal output related to the sensed temperature;

coupling the temperature control signal output to a heater which is thermally coupled to the field device; and

responsively heating the field device with the heater as a function upon the temperature control signal output.

19. The method of claim 18 including measuring temperature of the field device with an internal temperature sensor and the temperature control signal output is related to temperature of the temperature sensor.

20. The method of claim 18 wherein the temperature control signal output comprises a digital signal.

21. The method of claim 18 wherein the temperature control signal output is provided on the process control loop coupled to the field device and is further coupled to the heater.

22. The method of claim 18 wherein the heater includes a heater element and wherein a relationship between the temperature control signal output and heat from the heater element is programmable.

23. The method of claim 18 including diagnosing impending failure of a heater element of the heater.

24. The method of claim 18 including controlling heating of the field device to prevent freezing of the device.