Magnetic flowmeter with verification

• US 7,750,642 B2
• Filed: 09/28/2007
• Issued: 07/06/2010
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Graber, William F., Foss, Scot R., Schulz, Robert K.
• Primary Examiner(s): Nguyen; Vincent Q
• Application Number:
  US11/863,566
• Publication Number:
  US 20080078252A1
• Time in Patent Office: 1,012 Days
• Field of Search: 324/439, 738/610.8, 738/611.2, 731/521.8, 702/76
• US Class Current: 324/439
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

A magnetic flowmeter is provided including a magnetic flowtube arranged to receive a flow of process fluid. The magnetic flowtube includes a drive coil and at least one sense electrode. Measurement circuitry is coupled to the flowtube and is configured to provide a drive signal to the drive coil and measure flow of process fluid through the flow tube based upon an output from the sense electrode. A memory contains a stored value related to a nominal parameter of the flowtube. Verification circuitry is arranged to measure a parameter of the magnetic flowtube and responsively provide a verification output related to operation of the magnetic flowmeter based upon a comparison of the measured parameter and the stored value.

Claims

1. A magnetic flowmeter, comprising:

a magnetic flowtube arranged to receive a flow of process fluid, the magnetic flowtube including a drive coil and at least one sense electrode;

measurement circuitry coupled to the flowtube configured to provide a drive signal to the drive coil and measure flow of process fluid through the flow tube based upon an output from the at least one sense electrode;

a non-volatile memory configured to contain a plurality of stored values related to nominal parameters of the flowtube placed in the memory during manufacture of the flowmeter; and

verification circuitry arranged to measure a plurality of parameters of the magnetic flowtube and responsively provide a verification output related to operation of the magnetic flowmeter based upon a comparison of the plurality of measured parameters and the plurality of stored values.

2. The apparatus of claim 1 wherein the measurement circuitry is configured to measure flow during operation of the verification circuitry.

3. The apparatus of claim 1 wherein the verification circuitry is configured to measure resistance of a coil of the flowtube.

4. The apparatus of claim 1 wherein the verification circuitry is configured to measure inductance of a coil of the flowtube.

5. The apparatus of claim 1 wherein the verification circuitry is configured to measure resistance of electrodes of the flowtube to process ground.

6. The apparatus of claim 1 wherein the verification circuitry is further configured to measure an output placed on a two-wire process control loop.

7. The apparatus of claim 1 wherein the verification circuitry is configured to measure a current level of current of the drive signal applied to the drive coil by the measurement circuitry.

8. The apparatus of claim 1 wherein the nominal parameter values are stored in the memory by the verification circuitry.

9. The apparatus of claim 1 wherein the nominal parameter values are selected from the group of values consisting of pulse output, digital inputs and digital outputs.

10. A method for verifying operation of a magnetic flowmeter, comprising:

electrically coupling to a magnetic flowtube arranged to receive a flow of process fluid, the flowtube coupled to a flow of process fluid, the magnetic flowtube including a drive coil and at least one sense electrode;

storing a plurality of nominal parameter values in a non-volatile memory during manufacture of the flowmeter;

measuring a plurality of parameters of the magnetic flowtube;

retrieving the stored nominal parameter values from non-volatile memory of the flowtube; and

providing a verification output based upon a comparison of the measured parameters of the magnetic flowtube and the stored nominal parameter values.

11. The method of claim 10 wherein measuring parameters comprises measuring resistance of a coil of the flowtube.

12. The method of claim 10 wherein measuring parameters comprises measuring inductance of a coil of the flowtube.

13. The method of claim 10 wherein measuring parameters comprises measuring resistance of electrodes of the flowtube.

14. The method of claim 10 wherein measuring parameters comprises further measuring an output placed on a two-wire process control loop.

15. The method of claim 10 including measuring a current level of current of the drive signal applied to the drive coil by the measurement circuitry.