Flow measurement diagnostics

• US 8,290,721 B2
• Filed: 08/14/2006
• Issued: 10/16/2012
• Est. Priority Date: 03/28/1996
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Wehrs, David L., Eryurek, Evren
• Primary Examiner(s): Huynh, Phuong
• Application Number:
  US11/503,878
• Publication Number:
  US 20060277000A1
• Time in Patent Office: 2,255 Days
• Field of Search: 702 45- 54, 702179-189
• US Class Current: 702/45
• CPC Class Codes: G01F 15/00 Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

A flow meter for measuring flow of a process fluid includes a sensor configured to provide a sensor output signal. The sensor output signal is related to flow of the process fluid. Circuitry in the flow meter is configured to determine a statistical parameter related to sensor output signal. Diagnostic circuitry provides a diagnostic output based upon the determined statistical parameter and the sensor output signal.

Claims

1. A flow meter for measuring flow of a process fluid, comprising:

a sensor configured to provide a sensor output related to flow of the process fluid;

measurement circuitry configured to determine flow rate of the process fluid based upon the sensor output; and

diagnostic circuitry configured to receive the sensor output, and determine standard deviation of the sensor output from the sensor and identify a diagnostic condition by performing diagnostics by comparing a nominal relationship to a current relationship, wherein the diagnostic circuitry determines standard deviation during substantially steady state flow conditions,

the nominal relationship comprising;

a relationship between the flow rate of the process fluid and the standard deviation of the sensor output from the sensor during normal operation, and

the current relationship comprising;

a relationship between a current flow rate of the process fluid and a current standard deviation of the sensor output from the sensor.

2. The apparatus of claim 1 wherein the sensor comprises a differential pressure sensor.

3. The apparatus of claim 1 wherein the sensor comprises a magnetic sensor of a magnetic flowmeter.

4. The apparatus of claim 1 wherein the sensor comprises a vibration sensor of a vortex or corioles flowmeter.

5. The apparatus of claim 1 including a memory configured to store the nominal relationship.

6. The apparatus of claim 1 including output circuit that transmits the sensor output over a process control loop.

7. The apparatus of claim 1 wherein the diagnostic condition is related to a condition of an orifice plate.

8. The apparatus of claim 1 wherein the diagnostic condition is related to a composition of the process fluid.

9. The apparatus of claim 1 wherein the diagnostic circuitry includes a band pass filter.

10. The apparatus of claim 1 wherein the diagnostic circuitry includes a high pass filter.

11. The apparatus of claim 1 wherein the nominal relationship is determined during manufacture of the flow meter.

12. The apparatus of claim 1 wherein the nominal relationship is determined during operation of the flow meter.

13. A method of diagnosing operation of a flow meter of the type used to measure flow of process fluid, the method comprising:

coupling a sensor to a process fluid flowing through a conduit;

measuring flow of the process fluid using the sensor;

determining using a diagnostic circuitry, standard deviation of an output from the sensor during substantially steady state flow conditions; and

performing diagnostics by comparing a current relationship with a nominal relationship and responsively providing a diagnostic, output wherein;

the current relationship comprises;

a relationship between current standard deviation of the sensor output and current flow rate, and

the nominal relationship comprises;

a previously determined relationship between standard deviation of the sensor output and flow rate during normal operation.

14. The method of claim 13 wherein the sensor comprises a differential pressure sensor.

15. The method of claim 13 wherein the diagnostic output is indicative of plugging of a conduit which couples the sensor to the process fluid.

16. The method of claim 13 wherein the diagnostic output is indicative of a condition of a restrictive element in the conduit.