Field device and method for transferring the field device's signals

• US 20060092039A1
• Filed: 10/25/2005
• Published: 05/04/2006
• Est. Priority Date: 11/01/2004
• Status: Active Grant

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Saito, Yoji, Nishijima, Takashi
• Granted Patent: US 8,005,514 B2
• Time in Patent Office: Days
• US Class Current: 340/6.1
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 2219/25006 Interface connected to fieldbus
• CPC Class Codes: G05B 2219/25196 Radio link, transponder
• CPC Class Codes: G05B 2219/25428 Field device
• CPC Class Codes: G05B 2219/31251 Redundant access, wireless and hardware access to fielddevices
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

The present invention provides a field device whereby the device'"'"'s additional information can be transmitted wirelessly without the need for battery replacement or external wiring. The present invention also provides a field device whereby the firmware of a wireless module in the field device can be developed at minimum cost and whereby it can be made easy to link the firmware to applications, such as an asset management system, on the host system side. The field device in accordance with the present invention is installed in a plant, factory, or the like, connected to a higher-order distributed control system through a signal line, configured to input or output 4-20 mA signals, and comprised of: an RF unit for transmitting or receiving radio signals; and a power supply block for accumulating extra electric currents when the block is neither transmitting nor receiving radio signals; wherein electric currents accumulated in the power supply block are supplied to the RF unit so as to be used as electric power for transmitting or receiving radio signals.

Claims

1. A field device installed in a plant, factory, or the like, connected to a higher-order distributed control system through a signal line, and configured to receive or transmit analog signals, comprising:

an RF unit for transmitting or receiving radio signals; and

a power supply block for accumulating extra electric currents when said RF unit is neither transmitting nor receiving radio signals;

wherein electric power accumulated in said power supply block are supplied to said RF unit so as to be used as electric power for transmitting or receiving radio signals.

2. The field device of claim 1, wherein said RF unit is configured to operate so as to minimize the current consumption thereof when neither transmitting nor receiving signals.

3. The field device of claim 1 or 2, wherein said RF unit is configured to be able to exchange data with an asset management system.

4. The field device of claim 1 or 2, wherein said RF unit is configured to be able to exchange data with a handheld data terminal.

5. The field device of claim 1 or 2, wherein said RF unit is configured to be able to exchange data with another field device.

6. The field device of claim 1 or 2, wherein said power supply block is configured so as to accumulate extra electric currents received from said 4-20 mA signals in a storage battery or a capacitor.

7. The field device of claim 3, wherein said asset management system monitors and diagnoses field devices according to information sent therefrom.

8. The field device of claim 1 or 2, wherein data transmitted from said RF unit is a major process variable, an auxiliary process variable, diagnostic information or device operation information, or a plurality thereof.

9. The field device of claim 1 or 2, wherein said field device is configured so that additional sensor signals can be externally input thereto.

10. The field device of claim 1 or 2, wherein said RF unit has a modular configuration whereby said RF unit can be removed in part or in whole.

11. The field device of claim 1 or 2, wherein said power supply block has a modular configuration whereby said power supply block can be removed in part or in whole.

12. The field device of claim 1 or 2, wherein said field device is a valve positioner.

13. In a field device installed in a plant, factory, or the like, connected to a higher-order distributed control system through a signal line, configured to receive or transmit 4-20 mA signals, and comprised of an RF unit connected to a signal processing circuit to transmit or receive data using radio signals, a method for transferring signals of said field device wherein data is transmitted wirelessly from said RF unit using part of the frame of a digital communication protocol used for 4-20 mA field devices.

14. The signal transfer method of claim 13, wherein said digital communication protocol frame to be transmitted wirelessly is the data link layer frame or application layer frame of said digital communication protocol used for 4-20 mA field devices, or a combination thereof.

15. The signal transfer method of claim 13 or 14, wherein logical signals not modulated with a modem are used to physically exchange signals between said signal processing circuit and said RF unit.

16. The signal transfer method of claim 13 or 14, wherein said digital communication protocol frame used between said signal processing circuit and said RF unit is the data link layer frame or application layer frame of said digital communication protocol used for 4-20 mA field devices, or a combination thereof.

17. The signal transfer method of claim 13 or 14, wherein said digital communication protocol whose upper layers are used, is HART.

18. A field device configured to input or output analog signals through a signal line, comprising:

a charge control means for calculating a correlation between the electric current value of said signal line and the current consumption of internal circuitry involved in the processing of said analog signals;

a charging circuit for generating a specific electric current or voltage necessary for charging according to signals from said charge control means, using part of the electric current of said signal line;

an electric storage device to be charged by said charging circuit;

a state-of-charge detection means for detecting the degree to which said electric storage device is charged; and

an RF unit which is provided with electric power from said electric storage device and is enabled or disabled according to the output of said state-of-charge detection means.

19. The field device of claim 18, wherein said charge control means and said signal processing circuit involved in the processing of said analog signals are integrally formed into a microprocessor.

20. The field device of claim 18, further comprising:

a first supply voltage generation means which is connected to said signal line and is also connected in parallel with the series circuit of said connected charging circuit and said electric storage device; and

a second supply voltage generation means which is connected in series with said first supply voltage generation means and generates a voltage to be supplied to said internal circuitry.

21. The field device of claim 18, wherein said charge control means controls said charging circuit so that the electric current of said first supply voltage generation means is kept above a given level.