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.

Document <CIT> teaches an electromagnetic flowmeter which comprises four electrodes which are arranged with a right angle between them. The four electrodes form two pairs with each electrode positioned opposite the other electrode of the respective pair. Furthermore, the four electrodes are arranged in a single plane perpendicular to the flow to be measured.

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 taken during the construction of the flowmeter to ensure that the large coils are installed properly on the measuring section of the electromagnetic flowmeter. Accordingly, there is a need for an electromagnetic flowmeter which addresses the issues mentioned above.

Accordingly, the current disclosure describes an electromagnetic flowmeter capable of being installed on a fluid carrying channel for measuring a volumetric flow of a fluid flowing within the fluid carrying channel. The electromagnetic flowmeter comprises a measuring section configured for flow of the fluid through the electromagnetic flowmeter, a plurality of pairs of coils installed on the circumference of the measuring section, and a transmitter for exciting the plurality pairs of coils by providing one or more driving currents. The plurality of pairs of coils comprises a first pair of coils capable of generating a first magnetic field within the measuring section, and a second pair of coils capable of generating a second magnetic field within the measuring section. The first and second pairs of coils from the plurality of 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, this ensures that most of generated magnetic fields are all along the same plane and ensure proper measurement of the volumetric flow.

Accordingly, by using a plurality of pairs 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 pair of coils is capable of being excited by the transmitter by a corresponding driving current, the interaction between the resultant magnetic fields can be controlled to ensure even distribution in 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. The first magnetic field is distinct from the second magnetic field. In an example, a value of at least one parameter associated with a driving current of the first magnetic field is distinct from a corresponding value of the corresponding at least one parameter associated with a driving current of the second magnetic field. For example, the driving current of the first magnetic field may have a different amplitude or frequency compared to the driving current of the second magnetic field. Accordingly, the first magnetic field is different from the second magnetic field.

Additionally, a first coil from the first pair of coils acts as one pole of the first magnetic field and a second coil from the first pair of coils acts as the second pole of the first magnetic field. Similarly, first coil from the second pair of coils acts as one pole of the second magnetic field and a second coil from the second pair of coils acts as the second pole of the second magnetic field. Accordingly, a magnetic circuit associated with the first magnetic field is distinct is from a magnetic circuit associated with the second magnetic field. Accordingly, while each magnetic field is distinct from the other magnetic fields, by having a plurality of magnetic fields spread across the majority of the measuring section using smaller coils, the need for large and expensive coils is eliminated.

According to the invention, the plurality of coils includes a third pair of coils capable of generating a third magnetic field. The third magnetic field is capable of interacting with at least one of the first and the second magnetic field for tuning at least one of the first magnetic field and the second magnetic field. Accordingly, the third pair of coils allow for adjusting the magnetic fields to ensure operation of the electromagnetic flowmeter.

In an example, the first pair of coils and the second pair of coils are connected in a series connection to each other. In another example, the first pair of coils are connected to the transmitter via a first electrical connection and wherein the second pair of coils are connected to the transmitter via a second electrical connection. In yet another example, the first pair of coils and the second pair of coils are connected in a parallel connection to each other.

In another aspect, the current disclosure describes a method for measuring a volumetric flow fluid carrying channel for measuring a volumetric flow of a fluid flowing within the fluid carrying channel using an electromagnetic flowmeter. The electromagnetic flowmeter comprises a measuring section configured for flow of the fluid through the electromagnetic flowmeter, a plurality of pairs of coils installed on the circumference of the measuring section, and a transmitter for exciting the plurality of coils by providing a plurality of driving currents. The method comprises providing a first driving current to a first pair of coils for generating a first magnetic field and providing a second driving current to a second pair of coils for generating a second magnetic field. The magnetic circuit associated with the first magnetic field is distinct is from the magnetic circuit associated with the second magnetic field. The method further comprises measuring a voltage generated on a pair of measuring electrodes and determining the volumetric flow rate based on the measured voltage.

According to the invention, the method further comprises determining a parameter associated with the first magnetic field and providing a third driving current to a third pair of coils based on the determined parameter associated with the first magnetic field, wherein the third pair of coils generate a third magnetic field for tuning the first 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 with 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> which forms the main channel of the electromagnetic flowmeter <NUM> through which the conducting fluid flows through. The measuring section <NUM> includes an insulating liner <NUM> 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>, <NUM>) are installed for generating a plurality of magnetic fields within the inner diameter of the measuring section <NUM>. The plurality of pairs of coils (<NUM>, <NUM>, <NUM>, <NUM>) are installed along a first plane <NUM> of the measuring section <NUM>. The first plane <NUM> is perpendicular to the flow of the fluid in the measuring section <NUM>. 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 <NUM> is improved and the overall cost of the electromagnetic flowmeter <NUM>. The electromagnetic coils and the magnetic fields are further explained in relation to in <FIG>.

<FIG> shows front cross-sectional view of the example measuring section <NUM> illustrating the 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> & <NUM>, <NUM> & <NUM>, <NUM> & <NUM>, <NUM> & <NUM>) are mounted on the measuring section <NUM>. While in the figure, four pairs of coils (<NUM> & <NUM>, <NUM> & <NUM>, <NUM> & <NUM>, <NUM> & <NUM>) are shown, there may be other combinations involving at least two pairs of coils (such as six pairs of coils, eight pairs of coils, etc.). Each pair of coils generates a corresponding magnetic field upon being excited by a driving current from a transmitter. For example, as shown in the figure, the pair of coils <NUM> and <NUM> when excited, generate the magnetic field <NUM>. Similarly, the 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>. Similarly, the pairs of coils <NUM> and <NUM> when excited, generate the magnetic field <NUM>. While all the pairs of coils can be excited to generate the corresponding magnetic fields, in an example, a selected number of pairs of coils are excited for generating the corresponding magnetic fields during normal operating condition. For example, during normal operation, only the pairs <NUM> and <NUM> (also referred to as first pair of coils), and <NUM> and <NUM> (also referred to as second pair of coils) are excited by the transmitter for generating the magnetic fields <NUM> (also referred to as first magnetic field) and <NUM> (also referred to as second magnetic field). A first coil from the first pair of coils acts as one pole of the first magnetic field and a second coil from the first pair of coils acts as the second pole of the first magnetic field. Similarly, a first coil from the second pair of coils acts as one pole of the second magnetic field and a second coil from the second pair of coils acts as the second pole of the second magnetic field. The first and the second magnetic fields <NUM> and <NUM> interact with the conducting fluid flowing through the measuring section <NUM> and generate a voltage across two or more measuring electrodes (not shown in the figure) mounted on the measuring section <NUM>. The first and second pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) are connected to and excited by the transmitter.

<FIG> illustrates a plurality of options in which the first and second pair of coils are connected. In an example, as shown in section A of <FIG>, the first and the second pairs of coils (<NUM>, <NUM>) are connected in series to each other and to a current source <NUM> associated with the transmitter. Accordingly, the same driving current is provided to the first and second pairs of coils. In another example, the first and second pairs of coils (<NUM>, <NUM>) are connected in parallel to each other, as shown in section B of the <FIG>, while being connected to the same current source <NUM> associated with the transmitter. Accordingly, the driving current is divided between the first pair of coils <NUM> and the second pair of coils <NUM>. Accordingly, while the magnetic circuits and magnetic poles of the first magnetic field and the second magnetic field are different, the magnitude and characteristics of the first and second magnetic fields may be similar (when connected in series or in parallel). In yet another example, the first and the second pair of coils (<NUM>, <NUM>) may be connected to two different current sources (<NUM>, <NUM>) associated with the transmitter as shown in section c of the <FIG>. For example, the first pair of coils <NUM> are connected to the current source <NUM> and the second pair of the coils <NUM> are connected to the current source <NUM>. Accordingly, the driving current used to excite the first pair of coils <NUM> may be different from the driving current used to excite the second pairs of coils <NUM>. For example, the frequency or magnitude of the driving current for exciting the first pair of coils <NUM> may be different from the frequency or magnitude of the driving current for exciting the second pairs of coils <NUM>. Accordingly, the first magnetic field may be different from the second magnetic field.

As mentioned above, during normal operation, only the first and second pair of coils are active and accordingly, only the first and second magnetic fields are generated within the measuring section. However, when abnormal operation is detected or based on a predefined criterion, one or more additional pairs of coils are excited (in addition to the first and second pairs of coils). For example, when the volume of fluid flowing in the measuring section is too small, additional magnetic fields may be required to ensure accurate measurement. Accordingly, the coils <NUM> and <NUM> and coils <NUM> and <NUM>, may be excited to generate a third and fourth magnetic fields (<NUM> and <NUM>). As mentioned previously, the driving current provided to the coils <NUM> and <NUM>, and coils <NUM> and <NUM> may be similar or different from the currents provided to the first and second pair of coils (<NUM> & <NUM>, <NUM> & <NUM>). In another example, the additional pairs of coils are excited to interact with the first and the second magnetic fields. For example, the coils <NUM> and <NUM> generate the magnetic field <NUM> which is capable of interacting with the magnetic field <NUM> (generated by the coils <NUM> and <NUM>). For example, the magnetic field <NUM> can tune the magnetic field <NUM> or amplify the magnetic field <NUM>. Similarly, the coils <NUM> and <NUM> generate the magnetic field <NUM> which is capable of interacting with the magnetic field <NUM> (generated by the coils <NUM> and <NUM>). For example, the magnetic field <NUM> can tune the magnetic field <NUM> or amplify the magnetic field <NUM>.

Claim 1:
An electromagnetic flowmeter (<NUM>) capable of being installed on a fluid carrying channel for measuring a volumetric flow of a fluid flowing within the fluid carrying channel, the electromagnetic flowmeter (<NUM>) comprising:
a. a measuring section (<NUM>) configured for flow of the fluid through the electromagnetic flowmeter;
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. a first pair of coils (<NUM> and <NUM>) capable of generating a first magnetic field (<NUM>) within the measuring section (<NUM>), and
ii. a second pair of coils (<NUM> and <NUM>) capable of generating a second magnetic field (<NUM>) within the measuring section (<NUM>); and
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 first and second pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>) from the plurality of pairs of coils (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) are installed along a first plane (<NUM>) of the measuring section (<NUM>), the first plane (<NUM>) perpendicular to the flow of the fluid in the measuring section (<NUM>) , characterized in that
the plurality of pairs (<NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>) of coils includes a third pair of coils (<NUM> and <NUM>) capable of generating a third magnetic field (<NUM>), wherein the third pair of coils (<NUM> and <NUM>) is excited upon detection of an abnormal operation and wherein the third magnetic field (<NUM>) is for tuning at least one of the first magnetic field (<NUM>) and the second magnetic field (<NUM>).