Magnetic flowmeter with automatic operating setpoint selection

• US 10,641,627 B2
• Filed: 12/20/2013
• Issued: 05/05/2020
• Est. Priority Date: 12/20/2013
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Rovner, Bruce D., Foss, Scot Ronald, Rogers, Steven B.
• Primary Examiner(s): Peters, Lisa E
• Application Number:
  US14/136,955
• Publication Number:
  US 20150177035A1
• Time in Patent Office: 2,328 Days
• Field of Search: None
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01F 1/58 by electromagnetic flowmeters
• CPC Class Codes: G01F 1/584 constructions of electrodes, accessories therefor
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 25/10 of flowmeters
• CPC Class Codes: G05B 13/00 Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion G05B19/00 takes precedence
• CPC Class Codes: G06F 17/40 Data acquisition and logging for input to computer G06F3/00
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A magnetic flowmeter includes a flowtube with electrodes and field coil and a transmitter that automatically determines an operating setpoint for the magnetic flowmeter based upon sensed coil inductance, sensed coil resistance, a power rating for the transmitter, the flowtube, or both, and selected performance criteria.

Claims

1. A magnetic flowmeter comprising:

a flowtube that includes;

a pipe through which fluid flows;

a field coil mounted on the pipe, the field coil characterized by a coil resistance and a coil inductance; and

electrodes for sensing voltage induced by a magnetic field generated by the field coil in the fluid that flows through the pipe; and

a transmitter configured to measure the coil resistance and the coil inductance of the field coil, the transmitter including;

a coil driver for exciting the field coil using a pulsed DC current waveform characterized by an excitation frequency, a coil drive current, and a coil drive duty cycle so as to produce the magnetic field; and

a processor for producing a flow measurement value as a function of the voltage sensed by the electrodes, and for determining an operating setpoint that defines the excitation frequency, the coil drive current, and the coil drive duty cycle, the processor determining the operating setpoint based on the measured coil resistance, and the measured coil inductance.

2. The magnetic flowmeter of claim 1, wherein the transmitter is further configured to measure magnetic flux density of the magnetic field, the processor determining the operating setpoint further based on the measured magnetic flux density.

3. The magnetic flowmeter of claim 1, wherein the transmitter is further configured to measure flowtube gain, the processor determining the operating setpoint further based on the measured flowtube gain.

4. The magnetic flowmeter of claim 1, wherein the transmitter is further configured to determine the operating setpoint by tailoring the drive current, drive frequency, and/or duty cycle setpoint to best achieve performance criteria including at least one of the group consisting of electrode noise, signal-to-noise ratio, and electrode voltage zero shift characteristics.

5. The magnetic flowmeter of claim 1, wherein the processor determines the operating setpoint further based on a power rating that comprises at least one of the group consisting of a flowtube power rating and a transmitter power rating.

6. The magnetic flowmeter of claim 1, wherein the processor determines the operating setpoint further based on performance criteria that comprise at least one of the group consisting of fastest response, highest signal-to-noise ratio for a particular excitation frequency, highest-signal-to-noise ratio for a particular accuracy, and power efficiency.

7. The magnetic flowmeter of claim 1, wherein the processor continuously adjusts the operating setpoint.

8. A magnetic flowmeter comprising:

a flowtube having a coil for producing an alternating magnetic field and electrodes for sensing voltage induced by the alternating magnetic field in fluid flowing through the flowtube, the coil characterized by a coil resistance and a coil inductance;

a coil driver connected to the coil to produce the alternating magnetic field using a pulsed DC current waveform characterized by a coil drive frequency and a current setpoint, the coil driver including circuitry for sensing the pulsed DC current waveform; and

a processor that generates a flow output as a function of a sensed voltage between the electrodes, wherein the processor determines an operating setpoint that defines the coil drive frequency and the current setpoint, the processor determining the operating setpoint based on the coil resistance and the coil inductance as measured by the processor.

9. The magnetic flowmeter of claim 8, wherein the processor determines the operating setpoint further based on magnetic flux density as measured by the processor.

10. The magnetic flowmeter of claim 8, wherein the operating setpoint further includes a coil drive duty cycle.

11. The magnetic flowmeter of claim 8, wherein the processor further determines the operating setpoint based upon at least one of the group consisting of flowtube gain, coil current, electrode noise and electrode voltage zero shift characteristics.

12. The magnetic flowmeter of claim 8, wherein the processor determines the operating setpoint further based on a power rating that comprises at least one of the group consisting of a flowtube power rating and a transmitter power rating.

13. The magnetic flowmeter of claim 8, wherein the processor determines the operating setpoint further based on performance criteria that comprises at least one of the group consisting of fastest response, highest signal-to-noise ratio for a particular excitation frequency, highest-signal-to-noise ratio for a particular accuracy, and power efficiency.

14. A transmitter for use with a magnetic flowtube, the transmitter comprising:

a coil driver for supplying a pulsed DC current waveform to a coil of the magnetic flowtube, the coil characterized by a coil resistance and a coil inductance, the pulsed DC current waveform characterized by an excitation frequency, and a coil drive current; and

a processor for measuring the coil resistance and the coil inductance, the processor further configured to determine an operating setpoint based on the measured coil resistance, and the measured coil inductance, and to control operation of the coil driver based on the operating setpoint.

15. The transmitter of claim 14, wherein the operating setpoint is further characterized by a coil drive duty cycle.

16. The transmitter of claim 14, wherein the processor determines the operating setpoint further based on at least one of the group consisting of flowtube gain, coil current, electrode noise, signal-to-noise ratio, and electrode voltage zero shift characteristics.

17. The transmitter of claim 14, wherein the processor determines the operating setpoint further based on a power rating that comprises at least one of the group consisting of flowtube power rating and transmitter power rating.

18. The transmitter of claim 14, wherein the processor determines the operating setpoint further based on performance criteria that comprise at least one of the group consisting of fastest response, highest signal-to-noise ratio for a particular excitation frequency, highest-signal-to-noise ratio for a particular accuracy, and power efficiency.

19. The transmitter of claim 14, wherein the processor continuously adjusts the operating setpoint.

20. A method of controlling operation of a magnetic flowmeter, the method comprising:

obtaining flowmeter parameters that include coil resistance, coil inductance, and a power rating;

inputting a performance criteria selection;

determining an operating setpoint that includes current and frequency setpoint values based upon the measured flowmeter parameters and the inputted performance criteria selection; and

controlling field coil excitation of the magnetic flowmeter based on the determined operating setpoint.

21. The magnetic flowmeter of claim 20, wherein the determined operating setpoint further includes a coil drive duty cycle setpoint value.

22. The method of claim 20, wherein the flowmeter parameters further include at least one of the group consisting of flowtube gain, coil current, electrode noise, signal-to-noise ratio, and electrode voltage zero shift characteristics.

23. The method of claim 20, wherein the power rating comprises at least one of the group consisting of flowtube power rating and transmitter power rating.

24. The method of claim 20, wherein the performance criteria selection comprises at least one of the group consisting of fastest response, highest signal-to-noise ratio for a particular excitation frequency, highest-signal-to-noise ratio for a particular accuracy, and power efficiency.

25. The method of claim 20 and further comprising:

adjusting the operating setpoint to account for changes in the flowmeter parameters during operation of the magnetic flowmeter.