Electromagnetic flowmeter and zero point measurement method thereof

• US 20080282766A1
• Filed: 03/10/2008
• Published: 11/20/2008
• Est. Priority Date: 03/13/2007
• Status: Active Grant

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Ishikawa, Ikuhiko, Shimura, Toru, Koike, Yasumi
• Granted Patent: US 8,047,080 B2
• Time in Patent Office: Days
• US Class Current: 73/1.88
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 25/10 of flowmeters
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence

Abstract

An electromagnetic flowmeter for giving a magnetic field to a measurement fluid, detecting an electric signal occurring in the measurement fluid according to the magnetic field, and computing a flow quantity value based on the electric signal includes a zero point measurement section for measuring a zero point of the measurement fluid; a storage section for storing the measured zero point measurement value; a determination section for determining whether or not the difference between the preceding zero point measurement value stored in the storage section and the present zero point measurement value is beyond a predetermined value range; and at least either a transmission section for transmitting the determination result or a display section for displaying the determination result when the determination section determines that the difference is beyond the predetermined value range.

Claims

1. An electromagnetic flowmeter for supplying an excitation current to an exciting coil for giving a magnetic field to a measurement fluid, detecting an electric signal occurring in the measurement fluid according to the magnetic field, and computing a flow quantity value based on the electric signal, said electromagnetic flowmeter comprising:

a zero point measurement section for measuring a zero point of the measurement fluid;

a storage section for storing the measured zero point measurement value;

a determination section for determining whether or not the difference between the preceding zero point measurement value stored in said storage section and the present zero point measurement value stored in said storage section is beyond a predetermined value range; and

at least either a transmission section for transmitting the determination result or a display section for displaying the determination result when said determination section determines that the difference is beyond the predetermined value range.

2. The electromagnetic flowmeter as claimed in claim 1 further comprising:

an acquisition section for acquiring a request signal for further measuring a zero point of the measurement fluid based on at least either the transmitted or displayed determination result, wherein

an output current, the excitation current, and an excitation method of said electromagnetic flowmeter are changed based on the acquired signal and then a zero point is measured by said zero point measurement section and the zero point measurement value is stored in said storage section.

3. The electromagnetic flowmeter as claimed in claim 1 wherein when said determination section determines that the difference is beyond the predetermined value range, an output current, the excitation current, and an excitation method of said electromagnetic flowmeter are changed and then a zero point is measured by said zero point measurement section and the zero point measurement value is stored in said storage section.

4. The electromagnetic flowmeter as claimed in claim 1 wherein said electromagnetic flowmeter is a two-wire electromagnetic flowmeter for receiving power supply from a transmission line for transmitting an output current.

5. A zero point measurement method of an electromagnetic flowmeter for supplying an excitation current to an exciting coil for giving a magnetic field to a measurement fluid, detecting an electric signal occurring in the measurement fluid according to the magnetic field, and computing a flow quantity value based on the electric signal, said zero point measurement method comprising the steps of:

measuring a zero point of the measurement fluid;

storing the measured zero point measurement value;

determining whether or not the difference between the stored preceding zero point measurement value and the stored present zero point measurement value is beyond a predetermined value range; and

at least either transmitting the determination result or displaying the determination result when it is determined in said determining step that the difference is beyond the predetermined value range.

6. An electromagnetic flowmeter comprising:

an excitation circuit for supplying an excitation current to an exciting coil for giving a magnetic field to a measurement fluid;

a detecting section for detecting an electric signal occurring in the measurement fluid according to the magnetic field;

a flow quantity computation section for computing a flow quantity value based on the electric signal;

a zero point measurement section for measuring a zero point of the measurement fluid;

a storage section for storing the measured zero point measurement value;

a determination section for determining whether or not the difference between the preceding zero point measurement value stored in said storage section and the present zero point measurement value stored in said storage section is beyond a predetermined value range; and

a zero point correction section for subtracting the zero point measurement value stored in the storage section from the flow quantity value computed in the flow quantity computation section to compute a flow quantity value subjected to zero point correction,

wherein when said determination section determines that the difference is within the predetermined value range, said zero point correction section subtracts the present zero point measurement value stored in said storage section from the flow quantity value computed in the flow quantity computation section.