Patent Description:
The international patent application <CIT> discloses an electromagnetic flowmeter that comprises two primary electrodes and two secondary electrodes. Both the primary electrodes and the secondary electrodes are arranged in an opposing manner in a single plane in the tube to which the flowmeter is attached. Furthermore, the flowmeter comprises hall sensors which are accommodated near the primary or secondary electrodes respectively.

The current disclosure relates to electromagnetic flowmeters. As mentioned previously, electromagnetic flowmeters measure volumetric flow of fluid by applying a magnetic field perpendicular to the flow of the fluid. Accordingly, to generate the magnetic field, the electromagnetic flowmeter includes a plurality of electromagnetic coils which when excited (by applying a current to them), generate the magnetic field. Electromagnetic flowmeters can be used along with pipes of various sizes including large diameter pipes. For large diameter electromagnetic flowmeters, coils have to be of special construction, to ensure the generated magnetic field is spread across the diameter of a measuring section of the electromagnetic flowmeter.

Often such flowmeters utilize a pair of diamond shaped or rhombus shaped of coils, where each coil covers half of the circumference of a measuring section. Through the rhombus shape, the resultant magnetic field is distributed across the cross section of the flowmeter. However, this requires large coils which are difficult to construct and often involve substantial costs. Additionally, special care has to be during the construction of the flowmeter to ensure that the large coils are installed properly. Accordingly, there is a need for an electromagnetic flowmeter which addresses the issues mentioned above.

Accordingly, the current disclosure describes an electromagnetic flowmeter comprising a measuring section configured to permit a flow of the fluid through the electromagnetic flowmeter, and a plurality of pairs of coils installed on the circumference of the measuring section. The plurality of pair of coils comprises one or more primary pairs of coils and one or more secondary pairs of coils. The one or more primary pairs of coils generate one or more magnetic fields within the measuring section, for measuring the volumetric flow of fluid. The one or more secondary pairs of coils are capable of being excited independently in relation the one or more primary pairs of coils. Additionally, the electromagnetic flowmeter comprises a transmitter for exciting the plurality of pairs of coils by providing one or more driving currents. Upon the detection of a predefined event, the transmitter is configured to excite the secondary pairs of coils. In an example, upon excitation, the one or more secondary pairs of coils generate at least one secondary magnetic field. The generated least one secondary magnetic field interacts with at least one magnetic field from the one or more magnetic fields generated by the one or more primary pairs of coils, for improving at least one of a magnetic field homogeneity of the one or more magnetic fields and a magnetic gain of the at least one magnetic field.

Accordingly, the current disclosure describes an electromagnetic flowmeter having a plurality of coils which are used to generate a plurality of magnetic fields within the measuring section of the electromagnetic flowmeter. Through the usage of the plurality of coils, the electromagnetic flowmeter is able to ensure that resultant magnetic fields are spread evenly across the cross section of the measuring section of the electromagnetic flowmeter.

Additionally, since each coil from the pair of coils is required to generate a magnetic field covering only a part of the cross section of the measuring section, the size of the coil is relatively small and therefore the construction effort and the cost of the electromagnetic flowmeter is relatively low. Moreover, through the usage of the secondary pairs of coils, the electromagnetic flowmeter is able to better regulate the magnetic fields generated by the primary pairs of coils. Accordingly, via the interaction between the magnetic fields generated by the secondary fields and the magnetic fields by the primary fields, even distribution of the magnetic fields is ensured in the cross section of the measuring section of the electromagnetic flowmeter.

In an example, the one or more secondary coils are capable of measuring the one or more magnetic fields generated by the one or more primary coils. The one or more secondary coils are capable of forming an electromagnetic circuit with the one or more primary coils and accordingly, due to the magnetic fields generated by the primary coils, a voltage may be generated in the one or more secondary pairs of coils. Accordingly, based on the magnitude of voltage generated across the secondary pairs of coils, the strength of the magnetic fields generated by the one or more primary coils can be measured. Accordingly, this allows for measurement of magnetic fields generated by primary pairs of coils, without additional elements.

Additionally, through the usage of the secondary pairs of coils, measurement inaccuracies due gradual degradation or due to improper installation/assembly of the electromagnetic flowmeter, may be addressed. Since the secondary pairs of coils are capable of measuring the magnetic fields generated by the primary pairs of coils, and when an issue with the magnetic fields (such as degradation) the secondary pairs of coils can generate additional magnetic fields to compensate for the issue. Accordingly, this reduces the number of calibration and maintenance required for the electromagnetic flowmeter.

In an example, the predefined event is associated with a measurement parameter of the electromagnetic flowmeter, wherein the measurement parameter is indicative of a measurement effectiveness of the electromagnetic flowmeter. For example, the measurement parameter is associated with flow profile. In another example, the measurement parameter is indicative of the strength of the magnetic field within the measuring section. In another example, the predefined event is a periodic event with a frequency set during one of the calibration of the electromagnetic flowmeter and installation of the electromagnetic flowmeter. Accordingly, the secondary pairs of coils may be switched on regularly to enable the electromagnetic flowmeter to take measurements at higher magnetic field strength to ensure better measurement accuracy.

In yet another example, the predefined event is associated with a condition of a process equipment. The electromagnetic flowmeter is installed on a fluid carrying channel for measuring the volumetric flow of a fluid flowing within the fluid carrying channel, and the fluid carrying channel is connected to at least one of an input and output valves of the process equipment. Accordingly, the secondary pair of coils are activated only when required based on the condition of the process equipment. Accordingly, the activation of the secondary pairs of coils can be configured based on the application where the electromagnetic flowmeter is deployed.

In an example, a diameter of the measuring section is within a range of <NUM> millimeters to <NUM> millimeters. Accordingly, the electromagnetic flowmeter is for use with pipes of large diameter. In an example, the magnetic field strength at the center of the measuring section is between. <NUM> milli Tesla and <NUM> milli Tesla. In an example, wherein the one or more primary pairs of coils and the one or more secondary pairs of coils are installed along a first plane of the measuring section, the first plane perpendicular to the flow of the fluid in the measuring section. Accordingly, the magnetic fields generated by the plurality of pairs of coils are all generated along the same plane.

In another aspect, the current disclosure describes a method of operating an electromagnetic flowmeter for measuring a volumetric flow of a fluid. The electromagnetic flowmeter comprises a plurality of pairs of coils installed on a circumference of a measuring section of the electromagnetic flowmeter. the plurality of pair of coils includes one or more primary pairs of coils for generating one or more magnetic fields within the measuring section, for measuring the volumetric flow of fluid and one or more secondary pairs of coils capable of being excited independently in relation the one or more primary pairs of coils. The method comprises detecting an occurrence of a predefined event, wherein the predefined event is associated with one of process equipment, the one or more magnetic fields generated by the primary pairs of coils, and a predefined frequency set during one of the calibration of the electromagnetic flowmeter and installation of the electromagnetic flowmeter and determining at least one pair of coils from the secondary pairs of coils and one or more parameters of a driving current associated with the at least one pair of coils from the secondary pairs of coils, for generating an secondary magnetic field. The secondary magnetic field is capable of interacting with at least one magnetic field from the one or more magnetic field s generated by the primary coils, for improving at least one of a magnetic field homogeneity of the one or more magnetic fields and a magnetic gain of the at least one magnetic field. The advantages of the device apply to the method described herein. These aspects are further described in relation <FIG>.

<FIG> illustrates an example electromagnetic flowmeter <NUM> in accordance to the current disclosure. The electromagnetic flowmeter <NUM> is installed on a pipe (also referred to as fluid carrying channel) in an industrial facility for measuring volumetric flow of a conducting fluid through the pipe. The electromagnetic flowmeter comprises flanges <NUM> and <NUM> for connecting to the flowmeter <NUM> to the ends of two pipes in the industrial facility. Additionally, the electromagnetic flowmeter <NUM> includes a measuring section <NUM> which forms the main channel of the electromagnetic flowmeter <NUM> through which the conducting fluid flows through. Additionally, the electromagnetic flowmeter <NUM> includes a transmitter and an HMI (human machine interface) module <NUM>. The transmitter and HMI module <NUM> allows for display of values associated with the electromagnetic flowmeter <NUM> and configuration of the electromagnetic flowmeter <NUM>. Additionally, the transmitter and HMI module <NUM> is capable of exciting a plurality of coils (also known as electromagnetic coils) for measurement of the volumetric flow of the fluid through the flowmeter. The measuring section and the coils are further illustrated in <FIG> and explained in the description associated with <FIG>.

<FIG> shows a perspective internal view of an example measuring section <NUM>. The measuring section <NUM> includes an insulating liner within the inner diameter of the measuring section in order to insulate the fluid from the rest of the measuring section <NUM>. On the outer diameter of the measuring section <NUM>, a plurality of pairs of electromagnetic coils (shown as coils <NUM>, <NUM>, <NUM>, and <NUM>) are installed. The plurality of pairs of coils are installed along a first plane <NUM> of the measuring section <NUM>, wherein the first plane <NUM> is perpendicular to the flow of the fluid in the measuring section <NUM>. In an example a diameter of the measuring section (<NUM>) is within a range of <NUM> millimeters to <NUM> millimeters.

The plurality of pairs of electromagnetic coils (also referred to as coils) includes one or more primary pairs of coils and one or more secondary pairs of coils. As mentioned previously, the transmitter <NUM> is capable of exciting the plurality of pairs of coils by providing one or more driving currents. The one or more primary pairs of coils, upon excitation, generate one or more magnetic fields within the measuring section, for measuring the volumetric flow of fluid. The magnetic field strength at the center of the measuring section <NUM> is between. <NUM> milli Tesla and <NUM> milli Tesla.

The interaction of the magnetic fields and the conducting fluid flowing through the measuring section <NUM>, generates a voltage which is then measured by one or more measuring electrodes. The generated voltage is proportional to the magnetic field and the velocity of the fluid and accordingly, based on the generated voltage, the velocity of the fluid can be determined. Relative to diamond coils as known in the state of the art, the relative size of each coil from each pair of coils is small and accordingly each coil does not produce a magnetic field which covers the entire cross section of the measuring section <NUM>. However, this issue is addressed by having a plurality of pairs of coils which generate a plurality of magnetic fields. Accordingly, the plurality of magnetic fields cover the majority of the cross section of the measuring section <NUM>. Therefore, through the usage of the small coils (where each magnetic field generated by a corresponding pair of coils covers only a part of measuring section), the ease of construction of the electromagnetic flowmeter is improved and the overall cost of the electromagnetic flowmeter.

The one or more secondary pairs of coils are capable of being excited independently in relation the one or more primary pairs of coils, and accordingly, during normal operation, the one or more secondary pairs of coils are not excited. The secondary pairs of coils are excited upon the detection of a predefined event, in order to improve magnetic field within the measuring section <NUM>. This is further explained in relation to <FIG>.

<FIG> shows front cross-sectional view of an example measuring section <NUM> with a plurality of pairs of coils (shown as coils <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>). As mentioned previously, the plurality of pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) are mounted on the measuring section <NUM>. While in the figure, four pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) are shown, there may be other combinations involving at least two pairs of coils. As mentioned previously, the plurality of pairs of coils includes one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) and one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>). For example, the primary pairs of coils include coils <NUM> and <NUM>, and coils <NUM> and <NUM>. Each pair of coils from the primary pairs of coils generates a corresponding magnetic field upon being excited by a driving current from a transmitter (not shown in the figure). For example, as shown in the figure, the primary pair of coils <NUM> and <NUM> when excited, generate the magnetic field <NUM>.

Similarly, the pairs of coils <NUM> and <NUM> when excited, generate the magnetic field <NUM>. As mentioned above, during normal operation, only the primary pair of coils are active and accordingly, only the magnetic fields (<NUM> and <NUM>) are generated within the measuring section <NUM>. Accordingly, measurement is performed using the magnetic fields (<NUM> and <NUM>) generated by the primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>). Additionally, during the normal operation, the secondary pairs of coils are not excited as such. The transmitter <NUM>, during the normal operation, provides the driving current (or driving currents) to the primary pairs of coils to generate the magnetic fields (<NUM> and <NUM>). Additionally, the transmitter <NUM> is configured to detect a predefined event (or a plurality of predefined events). The predefined event (s) is indicative of a need for improving the magnetic fields within the measuring section <NUM>. Accordingly, based on the occurrence of the predefined event (s), the transmitter <NUM> is configured to excite one or more secondary pairs of coils which then generate one or more additional magnetic fields (also referred to as secondary magnetic fields), shown in the figure as secondary magnetic fields <NUM> and <NUM>.

In an example, the one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) are capable of measuring the one or more magnetic fields (<NUM> and <NUM>) generated by the one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), when not excited. The one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) are capable of forming an electromagnetic circuit with the one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) and accordingly, due to the magnetic fields (<NUM>, <NUM>) generated by the primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), a voltage may be generated in the one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>). Accordingly, based on the magnitude of voltage generated across the secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), the strength of the magnetic fields generated by the one or more primary coils (<NUM> and <NUM>, <NUM> and <NUM>) can be measured.

The one or more secondary magnetic fields (<NUM>, <NUM>) are capable of interacting with at least one magnetic field (<NUM>, <NUM>) from the one or more magnetic fields (<NUM>, <NUM>) generated by the one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), for improving at least one of a magnetic field homogeneity of the one or more magnetic fields (<NUM>, <NUM>) and a magnetic gain of the at least one magnetic field (<NUM>, <NUM>). For example, when the magnetic homogeneity is not even within the measuring section <NUM> and is biased on the right side of the electromagnetic flowmeter, the secondary pairs of coils (<NUM> and <NUM>, and <NUM> and <NUM>) can generate additional magnetic fields (<NUM> and <NUM>) to tune the existing magnetic fields (<NUM> and <NUM>) to eliminate the bias and improve magnetic homogeneity. Accordingly, the magnetic fields within the measuring section <NUM> are improved and this enables better accuracy in measurement. Further examples in relation to the predefined event are provided below.

In an example, the predefined event is associated with a measurement parameter of the electromagnetic flowmeter, wherein the measurement parameter is indicative of a measurement effectiveness of the electromagnetic flowmeter (<NUM>). This is explained in relation to <FIG>.

<FIG> illustrates excitation voltage applied across the primary pairs of coils, over a period of time. The magnitude of the voltage is shown along the vertical axis (i.e. Y-axis) and time is shown along the horizontal axis (i.e. X-axis). As shown in the figure, the excitation voltage (also referred to as coil voltage) is a pulsed DC voltage provided by the transmitter <NUM>, to excite the primary pairs of coils. Accordingly, based on the excitation of the primary pairs of coils and the movement of the conducting fluid within the measuring section <NUM>, a voltage (also referred to measured voltage) is generated across the measurement electrodes (not shown in figures). The measured voltage is proportional to the magnetic field and the flow velocity, and accordingly, similar to the excitation voltage, has alternating cycles and resembles the excitation voltage waveform <NUM>. This is shown in <FIG>, where the measured voltage is shown as waveform <NUM> (which is similar to the waveform <NUM>). The magnitude of the measured voltage is measured after the waveform has stabilized. Additionally, the magnitude is measured in both positive and negative phases of a cycle. For example, as shown in the <FIG>, the magnitudes are measured during time periods <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>. During normal operation, after stabilization and removal of noise etc., the magnitude of the measured voltage during the positive phase (referred to as Uee+) and negative phase (Uee- ), is same. Accordingly, the transmitter <NUM> checks the values of the measured voltage, during both phases of the measurement. However, when the values of the measured voltage don't match (i.e. the magnitude Uee+ is not equal to the magnitude of Uee-), the transmitter detects a potential abnormality. Sometimes, this may occur due to assembling or installing issues, dirt/wear of the coils, etc., while the flow velocity is constant. This may lead to accuracy problems. Accordingly, the predefined event is when the values of the measured voltage don't match (i.e. the magnitude Uee+ is not equal to the magnitude of Uee-).

When the transmitter <NUM> detects the above mentioned event, the transmitter utilizes the secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) to check the magnetic fields (<NUM> and <NUM>) generated by the primary pair of coils (<NUM> and <NUM>, <NUM> and <NUM>) to evaluate if the deviation in the magnitudes of voltages (Uee+ and Uee-) come from a issue with the electromagnetic flowmeter or from a change in the flow profile of the fluid. If the magnetic fields (<NUM> and <NUM>) are inequal, the transmitter determines that the issue originates due to improper installation or due to degradation of the coils. Accordingly, to address this, the transmitter excites the secondary pairs of coils and/or adapts the driving current of the primary pairs of coils to adjust the magnetic fields and stabilize the measured voltage signal. For example, by exciting the secondary pairs of coils, secondary magnetic fields (<NUM>, <NUM>) are generated. The secondary magnetic fields are capable of interacting with at least one magnetic field (<NUM>, <NUM>) from the one or more magnetic fields (<NUM>, <NUM>) generated by the one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), for improving at least one of a magnetic field homogeneity of the one or more magnetic fields (<NUM>, <NUM>) and a magnetic gain of the at least one magnetic field (<NUM>, <NUM>).

In an example, the predefined event is a periodic event with a frequency set during one of the calibration of the electromagnetic flowmeter and installation of the electromagnetic flowmeter. For example, the electromagnetic flowmeter is power by a local power source (such as batteries) and accordingly, in order to conserve power, the secondary pairs of coils are inactive usually and only excited at certain intervals to ensure that the measurements performed using the magnetic fields generated by the primary pairs of coils are accurate. For example, once every hour, the secondary pair of coils are excited, and the measurements made with during this instance are compared with the measurements made when the secondary pairs of coils are unexcited. For example, this is referred to as `High accuracy' mode, the overall magnetic field homogeneity and magnetic field strength is increased substantially and this allows for precise measurement If the measurements are equivalent or if no measurement issues (such as difference in Uee+ and Uee-) are detected, then the secondary pairs of coils are no longer excited and only the primary pair of coils remain excited, This is referred to as 'stand-by and control' mode.

In an example, the electromagnetic flowmeter is installed on a fluid carrying channel for measuring the volumetric flow of a fluid flowing within the fluid carrying channel and the predefined event is associated with a condition of a process equipment. The fluid carrying channel is connected to at least one of an input and output valves of the process equipment. Accordingly, the secondary pairs of coils are excited based on the condition of the process equipment. For example, the process equipment is a pump, and the secondary pairs of coils are excited only when the pump is at a certain load threshold.

Accordingly, through the usage of the secondary pairs of coils, the electromagnetic flowmeter is able to fine tune the magnetic fields generated by the primary pairs of coils and thereby enables improved accuracy. Additionally, through the dynamic activation of the secondary pairs of coils, the electromagnetic flowmeter is more resilient to perturbations in flow profile of the fluid. Additionally, through the measurements of the magnetic fields generated by the primary pairs of coils using the secondary pairs of coils and through the dynamic excitation of the secondary pairs of coils, the electromagnetic flowmeter is able to adapt to the installation & operating conditions of the industrial facility. Additionally, this reduces the need for additional calibration. Accordingly, the current disclosure discloses an electromagnetic flowmeter which is capable of adapting the magnetic field within the measuring section of the electromagnetic flowmeter, and this improves the accuracy of the electromagnetic flowmeter since this enables the flowmeter to adapt to the conditions of the industrial facility. For example, this allows the flowmeter to be used in proximity to turns in the pipes and accordingly, the flowmeter does not need long inlet/outlet pipes (which is usually required for conventional flowmeters).

Claim 1:
An electromagnetic flowmeter (<NUM>) comprising:
a. a measuring section (<NUM>) configured to permit a flow of the fluid through the electromagnetic flowmeter (<NUM>);
b. a plurality of pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) installed on the circumference of the measuring section (<NUM>), wherein plurality of pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) comprises:
i. one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>), for generating one or more magnetic fields (<NUM> and <NUM>) within the measuring section (<NUM>), for measuring the volumetric flow of fluid; and
ii. one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) capable of being excited independently in relation the one or more primary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) ;
c. a transmitter (<NUM>) for exciting the plurality of pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) by providing one or more driving currents, wherein the transmitter (<NUM>) is configured to excite the secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) upon the detection of a predefined event associated with a measurement parameter of the electromagnetic flowmeter (<NUM>), characterized in that the one or more secondary pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) are not excited during normal operation of the electromagnetic flowmeter and that the measurement parameter is indicative of a measurement effectiveness of the electromagnetic flowmeter (<NUM>) and is associated with one of flow profile, strength of magnetic field within a measuring section of the electromagnetic flowmeter, and a condition of a process equipment.