Open wire detection system and method

• US 7,683,796 B2
• Filed: 10/04/2006
• Issued: 03/23/2010
• Est. Priority Date: 10/04/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Stad, Benjamin J., Thalore, Sudhir
• Primary Examiner(s): GOINS, DAVETTA WOODS
• Application Number:
  US11/542,973
• Publication Number:
  US 20080084323A1
• Time in Patent Office: 1,266 Days
• Field of Search: 340/652, 340/635, 340/500, 340/660, 340/661, 340/662, 340/663, 340/664, 324/500, 324/512, 324/522, 324/523, 324/713, 324/718, 361/87, 361/93.1
• US Class Current: 340/652
• CPC Class Codes: G05B 9/02 electric
• CPC Class Codes: H04L 43/022 by sampling

Abstract

An open-wire detection system and method includes a current transmitter that can be connected to one or more wires, wherein the current transmitter provides a minimum current and/or a current that is greater than the minimum current. An anti-aliasing filter is connected to an analog-to-digital converter, such that the anti-aliasing filter receives the minimum current provided by the current transmitter and provides an output signal to the analog-to-digital converter. A noise filter is generally connected to an open-wire threshold detector, wherein the noise filter and the open-wire threshold detector permit detection of input levels below the minimum current provided by the current transmitter. An output from the open-wire threshold detector can be sampled multiple times at intervals that correlate with a frequency of a plurality of digital signals to produce sampled data, such that if the sampled data is below the minimum current, one or more of the wires (e.g., a return field wire and/or a field wire connected to a power supply) is reported as constituting an open-wire.

Claims

1. An open-wire detection system, comprising:

a current transmitter connected to at least one wire, wherein said current transmitter provides a minimum current;

an anti-aliasing filter connected to an analog-to-digital converter, wherein said anti-aliasing filter receives said minimum current provided by said current transmitter and provides an output signal to said analog-to-digital converter; and

a noise filter connected to an open-wire threshold detector, wherein said noise filter and said open-wire threshold detector permit detection of input levels below said minimum current provided by said current transmitter, wherein an output from said open-wire threshold detector is sampled multiple times at intervals that correlate with a frequency of a plurality of digital signals to produce sampled data, such that if said sampled data is below said minimum current, said at least one wire is reported as constituting an open-wire.

2. The system of claim 1 wherein said at least one wire comprises a field wire connected to a voltage supply.

3. The system of claim 1 wherein said at least one wire comprises a return field wire.

4. The system of claim 1 wherein said noise filter reduces high-frequency noise, such that said noise filter contains a time constant selected to be small with respect to a scan rate or a sample rate associated with said analog-to-digital converter.

5. The system of claim 1 wherein said current transmitter comprises a 4-20 mA transmitter.

6. The system of claim 1 further comprising a control system that receives at least one signal from said analog-to-digital converter and at least one signal from said open-wire threshold detector.

7. The system of claim 6 wherein said control system comprises:

a processor;

a module executed by said processor, said module and said processor being operable in combination with one another to monitor and control said open-wire threshold detector, said noise filter, said anti-aliasing filter and/or said analog-to-digital converter.

8. The system of claim 6 further comprising a plurality of screw terminals for connecting said at least one wire to control system.

9. An open-wire detection system, comprising:

a 4-20 mA current transmitter connected to at least one wire, wherein said 4-20 mA current transmitter provides a minimum current;

an anti-aliasing filter connected to an analog-to-digital converter, wherein said anti-aliasing filter receives said minimum current provided by said 4-20 mA current transmitter and provides an output signal to said analog-to-digital converter;

a noise filter connected to an open-wire threshold detector, wherein said noise filter and said open-wire threshold detector permit detection of input levels below said minimum current provided by said 4-20 mA current transmitter, wherein an output from said open-wire threshold detector is sampled multiple times at intervals that correlate with a frequency of a plurality of digital signals to produced sampled data, such that if said sampled data is below said minimum current, said at least one wire is reported as constituting an open-wire; and

a control system that receives at least one signal from said analog-to-digital converter and at least one signal from said open-wire threshold detector.

10. The system of claim 9 wherein said at least one wire comprises a field wire connected to a voltage supply.

11. The system of claim 9 wherein said at least one wire comprises a return field wire.

12. The system of claim 9 wherein said at least one wire comprises at least one field wire connected to a voltage supply and at least one return field wire.

13. The system of claim 9 wherein said noise filter reduces high-frequency noise, such that said noise filter contains a time constant selected to be small with respect to a scan rate or a sample rate associated with said analog-to-digital converter.

14. The system of claim 9 wherein said control system further comprises:

a processor; and

a module executed by said processor, said module and said processor being operable in combination with one another to monitor and control said open-wire threshold detector, said noise filter, said anti-aliasing filter and/or said analog-to-digital converter.

15. An open-wire detection method, comprising:

connecting a current transmitter to at least one wire, wherein said current transmitter provides a minimum current;

connecting an anti-aliasing filter an analog-to-digital converter, wherein said anti-aliasing filter receives said minimum current provided by said current transmitter and provides an output signal to said analog-to-digital converter; and

connecting a noise filter to an open-wire threshold detector, wherein said noise filter and said open-wire threshold detector permit detection of input levels below said minimum current provided by said current transmitter, wherein an output from said open-wire threshold detector is sampled multiple times at intervals that correlate with a frequency of a plurality of digital signals to produced sampled data, such that if said sampled data is below said minimum current, said at least one wire is reported as constituting an open-wire.

16. The system of claim 15 wherein said at least one wire comprises a field wire connected to a voltage supply and a return field wire.

17. The method of claim 15 wherein said noise filter reduces high-frequency noise, such that said noise filter contains a time constant selected to be small with respect to a scan rate or a sample rate associated with said analog-to-digital converter.

18. The method of claim 15 wherein said current transmitter comprises a 4-20 mA transmitter.

19. The system of claim 15 further comprising a control system that receives at least one signal from said analog-to-digital converter and at least one signal from said open-wire threshold detector.

20. The method of claim 19 wherein said control system comprises:

a processor;

a module executed by said processor, said module and said processor being operable in combination with one another to monitor and control said open-wire threshold detector, said noise filter, said anti-aliasing filter and/or said analog-to-digital converter.