Magnetic-inductive flowmeter and method of operating the same

Patent metadata

Field	Value
Publication number	US-12123754-B2
Application number	US-202217933688-A
Country	US
Kind code	B2
Filing date	Sep 20, 2022
Priority date	Oct 20, 2021
Publication date	Oct 22, 2024
Grant date	Oct 22, 2024

Abstract

A magnetic-inductive flowmeter includes a tube, electrodes in contact with a medium in the tube, a magnetic field generator, an impedance signal generator, and a control device. A first signal path interconnects the impedance signal generator and a first electrode, and a second signal path interconnects the impedance signal generator and a second electrode. A first switch and first and third capacitors are connected such that, in a first state, only the first capacitor and, in a second state, only the third capacitor is in the first signal path. A second switch and second and fourth capacitors are connected such that, in a first state, only the second capacitor and, in a second state, only the fourth capacitor is in the second signal path. The control device sets the switches to the first state during a positive magnetic phase and to the second state during a negative magnetic phase.

First claim

The invention claimed is:

1. A magnetic-inductive flowmeter, comprising:
a measuring tube;
a first electrode;
a second electrode
a magnetic field generator;
an impedance signal generator;
a coupling device; and
a control device;
wherein the first electrode and the second electrode are arranged on the measuring tube for direct contact with a medium in the measuring tube;
wherein the magnetic field generator is designed to generate an alternating magnetic field with a positive magnetic field phase and a negative magnetic field phase in the medium in the measuring tube;
wherein the impedance signal generator is designed to generate excitation signals;
wherein the coupling device comprises a first capacitor, a second capacitor, a first signal path and a second signal path;
wherein the first signal path interconnects the impedance signal generator and the first electrode and the second signal path interconnects the impedance signal generator and the second electrode for transmitting the excitation signals;
wherein the control device is designed for determining a flow rate of a medium through the measuring tube using flow rate measurement signals caused by the alternating magnetic field in the medium and measurable at the first electrode and the second electrode;
wherein the control device is designed to determine an impedance of the medium in the measuring tube using impedance measurement signals induced by the excitation signals and measurable at the first electrode and the second electrode;
wherein the coupling device has a third capacitor, a fourth capacitor, a first switch and a second switch;
wherein the first switch, the first capacitor and the third capacitor are connected to one another in such a way and the first switch is designed in such a way that, in a first switching state, only the first capacitor and, in a second switching state, only the third capacitor are connected in the first signal path;
wherein the second switch, the second capacitor and the fourth capacitor are connected to one another in such a way and the second switch is designed in such a way that, in a first switching state, only the second capacitor and, in a second switching state, only the fourth capacitor is connected into the second signal path; and
wherein the control device is designed to set the first switch and the second switch to the first switching state for a duration of the positive magnetic field phase and to set them to the second switching state for a duration of the negative magnetic field phase.

2. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch and the second switch are each two single pole single throw switches.

3. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch and the second switch are each a single-pole changeover switch.

4. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch and the second switch are implemented with a multiplexer.

5. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch and the second switch are semiconductor switches implemented on the same die.

6. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch and the second switch are arranged in the same housing.

7. The magnetic-inductive flowmeter according to claim 1 , wherein the first switch is located between, on the one hand, the first capacitor and the third capacitor and, on the other hand, the impedance signal generator; and
wherein the second switch is located between, on the one hand, the second capacitor and the fourth capacitor and, on the other hand, the impedance signal generator.

8. The magnetic-inductive flowmeter according to claim 1 , wherein the control device is designed to measure the flowmeter signals and/or the impedance measurement signals as voltages between the first electrode and the second electrode.

9. The magnetic-inductive flowmeter according to claim 1 , wherein the alternating magnetic field is a pulsating DC magnetic field.

10. A method for operating a magnetic-inductive flowmeter including a measuring tube, a first electrode, a second electrode, a magnetic field generator, an impedance signal generator, a coupling device and a control device, wherein the first electrode and the second electrode are arranged on the measuring tube for direct contact with a medium in the measuring tube, wherein the coupling device comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first switch, a second switch, a first signal path and a second signal path, wherein the first signal path interconnects the impedance signal generator and the first electrode and the second signal path interconnects the impedance signal generator and the second electrode, the method comprising:
generating, by the magnetic field generator, an alternating magnetic field with a positive magnetic field phase and a negative magnetic field phase in the medium in the measuring tube;
determining, by the control device, a flow rate of the medium through the measuring tube using flow rate measurement signals induced by the alternating magnetic field in the medium and measured at the first electrode and the second electrode;
generating, by the impedance signal generator, excitation signals;
transmitting the excitation signals from the impedance signal generator via the first signal path to the first electrode and via the second signal path to the second electrode;
setting, by the control device, the first switch and the second switch to a first state for a duration of the positive magnetic field phase, so that only the first capacitor is switched into the first signal path and only the second capacitor is switched into the second signal path;
setting, by the control device, the first switch and the second switch set to a second state for a duration of the negative magnetic field phase, so that only the third capacitor is connected in the first signal path and only the fourth capacitor is connected in the second signal path; and
determining, by the control device, an impedance of the medium in the measuring tube using impedance measurement signals caused by the excitation signals and measured at the first electrode and the second electrode.

11. The method according to claim 10 , wherein the magnetic-inductive flowmeter is configured such that at least one of:
the first switch and the second switch are each two single pole single throw switches;
the first switch and the second switch are each a single-pole changeover switch;
the first switch and the second switch are implemented with a multiplexer;
the first switch and the second switch are semiconductor switches implemented on the same die;
the first switch and the second switch are arranged in the same housing;
the first switch is located between, on the one hand, the first capacitator and the third capacitator and, on the other hand, the impedance signal generator, and the second switch is located between, on the one hand, the second capacitor and the fourth capacitor and, on the other hand, the impedance signal generator;
the control device is designed to measure the flowmeter signals and/or the impedance measurement signals as voltages between the first electrode and the second electrode; and
the alternating magnetic field is a pulsating DO magnetic field.

Assignees

• Krohne Messtechnik Gmbh

Inventors

• Brockhaus Helmut
• Dabrowski Markus
• Schwenger Ulrike

Classifications

• G01F1/588

  combined constructions of electrodes, coils or magnetic circuits, accessories therefor · CPC title

• G01F1/60 Primary

  Circuits therefor · CPC title

• G01F1/586

  constructions of coils, magnetic circuits, accessories therefor (G01F1/582 takes precedence; magnet; inductances; transformers; selection of materials for their magnetic properties per se H01F) · CPC title

• G01N27/02

  by investigating impedance · CPC title

• G01F1/584 Primary

  constructions of electrodes, accessories therefor · CPC title