Flow disturbance compensation for magnetic flowmeter

• US 20100107776A1
• Filed: 11/03/2008
• Published: 05/06/2010
• Est. Priority Date: 11/03/2008
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Shanahan, Bret A.
• Granted Patent: US 7,779,702 B2
• Time in Patent Office: Days
• US Class Current: 73/861.110
• CPC Class Codes: G01F 1/588 combined constructions of electrodes, coils or magnetic circuits, accessories therefor
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

A transmitter for a magnetic flowmeter comprises a current source, memory and a signal processor. The current source energizes the flowmeter, such that the flowmeter generates an induced electromotive force in response to a process flow. The memory stores a flow configuration that describes a flow pipe disturbance in the process flow. The signal processor determines the flow rate as a function of the induced electromagnetic force, and as a further function of the flow configuration.

Claims

1. A transmitter for a magnetic flowmeter, the transmitter comprising:

a current source for energizing the flowmeter, such that the flowmeter generates an induced electromotive force in response to a process flow;

memory for storing a flow configuration, wherein the flow configuration describes an actual flow pipe disturbance in the process flow, and wherein the flow pipe disturbance is located upstream or downstream of the magnetic flowmeter, as installed in the process flow; and

a signal processor for determining a flow rate as a function of the induced electromotive force and the flow configuration.

2. The transmitter of claim 1, wherein the flow pipe disturbance is located within a region that extends up to five pipe diameters from the magnetic flowmeter.

3. The transmitter of claim 2, wherein the flow pipe disturbance is located within five pipe diameters upstream of the magnetic flowmeter.

4. The transmitter of claim 2, wherein the flow pipe disturbance is located within two pipe diameters downstream of the magnetic flowmeter.

5. The transmitter of claim 2, wherein the signal processor determines the flow rate to an accuracy of one half percent to one-fifth percent.

6. The transmitter of claim 1, wherein the flow pipe disturbance comprises a valve.

7. The transmitter of claim 1, wherein the flow pipe disturbance comprises a reducer or an expander.

8. The transmitter of claim 1, wherein the flow pipe disturbance comprises an elbow.

9. The transmitter of claim 1, wherein the flow pipe disturbance comprises a tee.

10. The transmitter of claim 1, wherein the function of the flow configuration comprises a rotational angle of the flow pipe disturbance.

11. The transmitter of claim 1, further comprising a local user interface for inputting the flow configuration to the memory.

12. The transmitter of claim 1, further comprising a remote interface for inputting the flow configuration to the memory.

13. A magnetic flowmeter comprising:

a pipe section;

a coil proximate a radially outer boundary of the pipe section;

a current source for energizing the coil to generate a magnetic field inside the pipe section;

a probe extending through the pipe section to sense a Faraday voltage induced by process flow through magnetic field;

a storage device for storing a flow configuration representing an actual flow pipe disturbance in the process flow, wherein the flow pipe disturbance is located upstream or downstream of the magnetic flowmeter, as installed in the process flow; and

a processor to determine a rate of the process flow as a function of the Faraday voltage and to correct the rate of the process flow based on the flow pipe disturbance.

14. The flowmeter of claim 13, wherein the flow pipe disturbance is within five pipe diameters of the flowmeter.

15. The flowmeter of claim 14, wherein the flow pipe disturbance comprises a change in cross-sectional flow area.

16. The flowmeter of claim 14, wherein the flow pipe disturbance comprises a change in flow direction.

17. The flowmeter of claim 13, wherein the signal processor corrects the process flow rate to an accuracy of one half percent to one-fifth percent.

18. The flowmeter of claim 13, further comprising an interface for inputting the configuration representing the flow pipe disturbance to the storage device.

19. A method for measuring a flow rate, the method comprising:

storing a flow configuration describing an actual flow pipe disturbance in a process flow, wherein the flow pipe disturbance is located upstream or downstream of the magnetic flowmeter, as installed in the process flow;

generating a magnetic field across the process flow;

sensing an electromotive force induced across the process flow by the magnetic field; and

determining the flow rate as a function of the electromotive force and as a further function of the flow configuration.

20. The method of claim 19, wherein storing the flow configuration comprises storing an upstream or downstream position of the flow pipe disturbance in the process flow.

21. The method of claim 20, wherein storing the flow configuration comprises storing a type of the flow pipe disturbance in the process flow.

22. The method of claim 21, wherein storing the flow configuration comprises storing a rotational angle of the flow pipe disturbance in the process flow.

23. The method of claim 19, wherein the further function of the flow configuration comprises a k-factor based on a calibration of the flow rate when subject to the flow pipe disturbance in the process flow.