A nuclear magnetic measuring device (1) is illustrated with a measuring device (4), wherein the measuring device (4) has a control unit (6), a generator unit (7), an antenna unit (10), a receiving unit (15) and a measuring signal path (16), wherein the measuring signal path (16) comprises an excitation signal path (17) and a reaction signal path (18), and wherein the antenna unit (10) has an antenna signal path.

The object of the invention is to provide a nuclear magnetic measuring device (1) that determines at least one unstable property of the measuring signal path (16).

The object is achieved in that the measuring device (4) has a bypass signal path (20) and a transmission unit (12), that are connected to one another for transmission of signals between the bypass signal path (20) and the antenna signal path (19), that a first changeover switch (8) is arranged such that, in a first switching state, the generator unit (7) is connected to the excitation signal path (17) and, in a second switching state, it is connected to the bypass signal path (20), that a second changeover switch (14) is arranged such that, in a first switching state, the receiving unit (15) is connected to the reaction signal path (18) and, in a second switching state, it is connected to the bypass signal path (20), that the control unit (6) is designed to control the changeover switches (8, 14) such that a part of the measuring signal path (16) is bypassed by the bypass signal path (20) and then to generate a test excitation signal with the generator unit (7), to receive a test reaction signal caused by the test excitation signal with the receiving unit (15), and to determine a property of the measuring signal path (16) using the test excitation signal and the test reaction signal.

A flowmeter for determining the flow of a multi-phase medium through a measuring tube has a first and a second measuring device, one of which operates on a tomographic measuring principle and one of uses a measuring principle based on nuclear magnetic resonance. The first measuring device operates in a different manner from the second measuring device, e.g., using a measuring device operating on the measuring principle of pre-magnetization contrast measurement and having a pre-magnetization section with a constant magnetic field. The magnetic field has at least one component perpendicular to the direction of flow of the multi-phase medium and is generated by using magnetic field generating elements, which are arranged around the measuring tube. Additionally, an assembly for exciting nuclear spin by a RF excitation pulse or a RF excitation pulse sequence is part of the measuring device.

A method for operating a flowmeter for determining the flow of a multiphase medium flowing through a measuring tube using a first and a second measuring device, one of which operates on a tomographic measuring principle and one of which uses a measuring principle based on nuclear magnetic resonance. The first measuring device operates in a different manner from the second measuring device, e.g., using a measuring device operating on the measuring principle of pre-magnetization contrast measurement and having a pre-magnetization section with a constant magnetic field. The magnetic field has at least one component perpendicular to the direction of flow of the multi-phase medium and is generated by using magnetic field generating elements, which are arranged around the measuring tube. Additionally, an assembly for exciting nuclear spin by a RF excitation pulse or a RF excitation pulse sequence is part of the measuring device.

A method for determining a liquid portion of a flowing medium with a nuclear magnetic flowmeter includes: generating a gradient magnetic field in a measuring tube volume of the flowmeter; exposing the medium to the gradient magnetic field and a magnetic field generated by a magnetizing device of the flowmeter; generating and irradiating an excitation signal into the magnetized medium for exciting nuclear magnetic resonances therein; measuring nuclear magnetic resonances excited by the excitation signal in the magnetized medium as a measuring signal; determining frequencies of the nuclear magnetic resonances in the measuring signal; assigning the determined frequencies to positions along a first gradient direction in the measuring tube volume; assigning the nuclear magnetic resonances at the positions to liquid and gaseous portions of the medium; and determining a liquid portion of the medium in the measuring tube volume from the positions of the nuclear magnetic resonances.

A method for determining a liquid portion of a flowing medium with a nuclear magnetic flowmeter includes: generating a gradient magnetic field in a measuring tube volume of the flowmeter; exposing the medium to the gradient magnetic field and a magnetic field generated by a magnetizing device of the flowmeter; generating and irradiating an excitation signal into the magnetized medium for exciting nuclear magnetic resonances therein; measuring nuclear magnetic resonances excited by the excitation signal in the magnetized medium as a measuring signal; determining frequencies of the nuclear magnetic resonances in the measuring signal; assigning the determined frequencies to positions along a first gradient direction in the measuring tube volume; assigning the nuclear magnetic resonances at the positions to liquid and gaseous portions of the medium; and determining a liquid portion of the medium in the measuring tube volume from the positions of the nuclear magnetic resonances.

A nuclear magnetic resonance flowmeter comprising at least one coil (40) of electrically conductive material through which an electrical current flows when the apparatus is in use. This generates a magnetic field in a region through which flows a fluid the flow of which is to be measured and throughout which there is a uniform weak magnetic field such as the Earth's magnetic field. Electrical circuitry (46 to 52) is connected to the said at least one coil (40) to switch on and abruptly switch off such an electrical current. There is an NMR sensor (42) connected to the electrical circuitry (46 to 52) to provide a measure of the decay in the NMR signal from nuclei within such fluid following the abrupt switching off of such an electrical current. A processor (52) of the electrical circuitry (46 to 52) is formed and/or programmed to provide a measure of the flow of such fluid from the said measure of the decay. Also, a method of measuring the flow of a fluid using such a flowmeter.

A nuclear magnetic resonance flowmeter comprising at least one coil (40) of electrically conductive material through which an electrical current flows when the apparatus is in use. This generates a magnetic field in a region through which flows a fluid the flow of which is to be measured and throughout which there is a uniform weak magnetic field such as the Earth's magnetic field. Electrical circuitry (46 to 52) is connected to the said at least one coil (40) to switch on and abruptly switch off such an electrical current. There is an NMR sensor (42) connected to the electrical circuitry (46 to 52) to provide a measure of the decay in the NMR signal from nuclei within such fluid following the abrupt switching off of such an electrical current. A processor (52) of the electrical circuitry (46 to 52) is formed and/or programmed to provide a measure of the flow of such fluid from the said measure of the decay. Also, a method of measuring the flow of a fluid using such a flowmeter.

A method for assessing a gas phase in a flowing multi-phase fluid comprises flowing the fluid through magnetic resonance and pre-polarization modules and applying to the fluid a radio-frequency pulse sequence at least once with and at least once without a magnetic field gradient. The method further includes measuring an NMR signal. The method also includes using a calibration between the ratio of slope and intercept of the NMR signal and flow velocity for at least one non-gas phase with the gradient applied to determine that phase's velocity. A calibration between the signal intensity of the liquid phases as function of flow velocity is used, with and without gradient, to correct the gradient-induced attenuation of the liquid signals and to calculate a gradient-corrected signal intensity of the liquid phases without a magnetic field gradient. Additionally, the method includes subtracting the gradient-corrected signal intensity from the NMR signal to calculate the volumetric fraction of the liquid phase.

A method for assessing a gas phase in a flowing multi-phase fluid comprises flowing the fluid through magnetic resonance and pre-polarization modules and applying to the fluid a radio-frequency pulse sequence at least once with and at least once without a magnetic field gradient. The method further includes measuring an NMR signal. The method also includes using a calibration between the ratio of slope and intercept of the NMR signal and flow velocity for at least one non-gas phase with the gradient applied to determine that phase's velocity. A calibration between the signal intensity of the liquid phases as function of flow velocity is used, with and without gradient, to correct the gradient-induced attenuation of the liquid signals and to calculate a gradient-corrected signal intensity of the liquid phases without a magnetic field gradient. Additionally, the method includes subtracting the gradient-corrected signal intensity from the NMR signal to calculate the volumetric fraction of the liquid phase.

A method for operating a nuclear magnetic flowmeter having a measuring device for determining the flow of the medium through the measuring tube, the measuring device having a magnetic field generator for generating a magnetic field permeating the medium and the measuring tube and for carrying out nuclear magnetic measurements of measuring volumes that are adjustable in position and size in the magnetic field. The nuclear magnetic measurements involve adjusting the size of the measuring volume, positioning the measuring volume, generating excitation signals for exciting the medium, transmitting excitation signals into the measuring volume and measuring echo signals caused by the excitation signals. Deposits on the inner wall of the measuring tube are determined from echo signals of all nuclear magnetic measurements assigned to the position of the measuring volume of the respective nuclear magnetic measurement and at least one abrupt change in the echo signals detected.