JP7740071B2 - electromagnetic flow meter - Google Patents

Description

This disclosure relates to an electromagnetic flowmeter.

Electromagnetic flowmeters that use electromagnetic induction to measure the flow rate of conductive fluids are known. Patent Document 1 describes an electromagnetic flowmeter that can measure the flow rate and resistance of the fluid being measured and detect abnormalities related to the fluid being measured.

JP 2016-176785 A

However, conventional electromagnetic flowmeters have complex circuit configurations and there is room for improvement in circuit size.

The objective of this disclosure is to provide an electromagnetic flowmeter that can detect abnormalities in the fluid being measured using a simpler circuit configuration.

According to some embodiments, the electromagnetic flowmeter applies a magnetic field generated by an excitation current to a fluid to be measured flowing inside a measuring tube, and measures the flow rate of the fluid to be measured based on a detection signal generated at electrodes installed inside the measuring tube. The electromagnetic flowmeter includes a control unit that extracts frequency components above a predetermined frequency from the detection signal as high-frequency components, and detects the presence or absence of an abnormality in the fluid to be measured based on the extracted high-frequency components. In this way, the electromagnetic flowmeter detects the presence or absence of an abnormality in the fluid to be measured based on the detection signal generated at the electrodes inside the measuring tube, making it possible to detect an abnormality in the fluid to be measured with a simpler circuit configuration, without the need for a configuration to measure the resistance of the fluid to be measured.

In one embodiment of the electromagnetic flowmeter, the control unit may compare the extracted high-frequency component with a preset reference high-frequency component, and if the difference between the two exceeds a predetermined threshold, detect an abnormality related to the fluid being measured. In this way, the electromagnetic flowmeter detects an abnormality by comparing the high-frequency component extracted from the detection signal with the reference high-frequency component, making it possible to properly detect an abnormality.

In one embodiment of the electromagnetic flowmeter, the control unit may output an alarm when an abnormality related to the fluid being measured is detected. In this way, the electromagnetic flowmeter outputs an alarm when an abnormality is detected, allowing the user to easily recognize the occurrence of an abnormality.

In one embodiment of the electromagnetic flowmeter, when an abnormality is detected in the fluid being measured, the control unit may identify the cause of the abnormality in the fluid being measured based on the frequency characteristics of the extracted high-frequency components. In this way, the electromagnetic flowmeter identifies the cause of the abnormality in the fluid being measured, allowing the user to perform appropriate maintenance depending on the cause of the abnormality.

In one embodiment of the electromagnetic flowmeter, the control unit may extract, as the high-frequency components, frequency components above a predetermined frequency from a signal that is thinned out from the detection signal at a predetermined timing, and obtain the frequency characteristics of the extracted high-frequency components based on the high-frequency components extracted from the thinned signal. In this way, the electromagnetic flowmeter obtains the frequency characteristics of the high-frequency components based on the high-frequency components extracted from the thinned signal, making it possible to identify the cause of the abnormality with high accuracy.

In one embodiment of the electromagnetic flowmeter, the control unit may acquire a signal that has been thinned out from the extracted high-frequency components at a predetermined timing, and acquire the frequency characteristics of the extracted high-frequency components based on the thinned signal. In this way, the electromagnetic flowmeter acquires the frequency characteristics of the high-frequency components based on a signal acquired by thinning out the high-frequency components of the detection signal, making it possible to identify the cause of the abnormality with high accuracy.

According to one embodiment of the present disclosure, it is possible to detect abnormalities in the fluid being measured using a simpler circuit configuration.

FIG. 1 is a diagram illustrating an example of the configuration of an electromagnetic flowmeter according to an embodiment. FIG. 2 is a diagram illustrating a configuration example of an excitation circuit in FIG. 1 . 2 is a timing chart showing an example of sampling in the electromagnetic flowmeter of FIG. 1 . 10 is a graph showing an example of a change over time in a flow rate signal of a fluid to be measured that contains bubbles. 10 is a graph showing an example of a spectrum distribution of noise levels of a fluid to be measured that contains bubbles. 2 is a flowchart showing an example of a processing procedure executed by the electromagnetic flowmeter of FIG. 1 .

<Comparative Example>
An electromagnetic flowmeter measures the electromotive force generated by passing a conductive fluid through a measuring tube in which a magnetic field is applied in a direction perpendicular to the direction of the fluid flow. Because this electromotive force is proportional to the flow velocity of the fluid, the electromagnetic flowmeter can obtain the volumetric flow rate of the fluid based on the measured electromotive force.

The electromagnetic flowmeter according to the comparative example measures the resistance (conductivity) of the fluid being measured in addition to its flow rate, and analyzes the measured flow rate and resistance to detect abnormalities related to the fluid being measured. Detectable abnormalities include the adhesion of insulating foreign matter to the electrodes, electrode corrosion, the generation of bubbles in the fluid being measured, a decrease in the conductivity of the fluid being measured, and the generation of a slurry (sludge) fluid.

However, in order to detect such abnormalities, the electromagnetic flowmeter in the comparative example required a circuit to measure and sample the resistance of the fluid being measured, which resulted in a complex circuit configuration and room for improvement in circuit size.

<Embodiment>
The electromagnetic flowmeter according to the present disclosure detects an abnormality in the fluid to be measured based on the high-frequency component of the electromotive force of the fluid to be measured, which is generated by electromagnetic induction. Therefore, the electromagnetic flowmeter according to the present disclosure does not require a circuit for measuring and sampling the resistance of the fluid to be measured, and can detect an abnormality in the fluid to be measured with a simpler circuit configuration.

One embodiment of the present disclosure will be described below with reference to the drawings. In each drawing, parts having the same configuration or function are designated by the same reference numerals. In describing this embodiment, duplicate descriptions of identical parts may be omitted or simplified as appropriate.

(Configuration of an electromagnetic flowmeter)
1 is a diagram showing an example of the configuration of an electromagnetic flowmeter 1 according to an embodiment. The electromagnetic flowmeter 1 includes a detector 30 and a converter 40.

The detector 30 detects an electromotive force proportional to the flow rate of the fluid being measured. The detector 30 includes a magnetic circuit 11, a tube 13, a pair of measurement electrodes 14 (14a, 14b), and an earth electrode 15.

The magnetic circuit 11 is a circuit that applies a magnetic field in a direction perpendicular to the direction of flow of the fluid to be measured. In this embodiment, the magnetic circuit 11 has a pair of coils 12 (12a, 12b) that are provided facing each other outside the tube 13. A magnetic field can be generated between the coils 12a, 12b by passing an excitation current _Iex from the excitation circuit 18 of the converter 40. The number of coils 12 may be one or three or more. The magnetic circuit 11 forms a feedback magnetic path and may have a magnetic body such as an iron core.

Tube 13 is a measurement tube that forms a flow path for the fluid to be measured. The liquid-contacting portion of tube 13 (e.g., inner wall, etc.) may be made of an electrically insulating material.

The pair of measurement electrodes 14 (14a, 14b) are electrodes for detecting an electromotive force signal (detection signal, e.g., a voltage signal) proportional to the magnetic field formed between the coils 12a, 12b and the flow rate of the fluid to be measured flowing through the tube 13. The pair of measurement electrodes 14 (14a, 14b) outputs the detected electromotive force signal, for example, as a voltage signal, to the buffer 16 of the converter 40.

The earth electrode 15 grounds the detector 30. The earth electrodes 15 may be provided, for example, at both ends of the tube 13.

The converter 40 converts the electromotive force signal detected by the detector 30, which is proportional to the flow rate of the fluid being measured, and outputs it to the outside. The converter 40 includes a buffer 16, a differential amplifier 17, an excitation circuit 18, A/D (Analog-to-Digital) converters 19 and 20, a control unit 21, an HMI (Human Machine Interface) 22, a current output unit 23, a pulse output unit 24, a status output unit 25, and a communication unit 26.

The buffer 16 converts the impedance of the electromotive force signal measured by the measurement electrode 14 and detects it. The buffer 16 may include two comparators 16a and 16b corresponding to the pair of measurement electrodes 14a and 14b. The buffer 16 outputs the impedance-converted electromotive force signal to the differential amplifier 17.

The differential amplifier 17 removes external noise that occurs commonly between the pair of measurement electrodes 14 (14a, 14b) from the electromotive force signal input from the buffer 16 and amplifies the signal to the desired amplitude level. The differential amplifier 17 may also input the outputs from the two comparators 16a, 16b and amplify the difference between these outputs. The differential amplifier 17 outputs the amplified electromotive force signal to the A/D converter 19.

The A/D conversion unit 19 A/D converts the electromotive force signal input from the differential amplifier 17, converting the analog signal format electromotive force signal so that it can be read as a digital value. The A/D conversion unit 19 A/D converts the analog format electromotive force signal using the sampling rate input from the control unit 21. The A/D conversion unit 19 outputs the electromotive force signal converted into a digital signal to the control unit 21.

The control unit 21 is a control device connected to each circuit of the electromagnetic flowmeter 1 and controls the operation of the electromagnetic flowmeter 1. The control unit 21 includes one or more processors and memory. In one embodiment, the "processor" may be, for example, a general-purpose processor such as a CPU (Central Processing Unit), or a dedicated processor specialized for specific processing, but is not limited to these.

The control unit 21 uses the electromotive force signal (detection signal) input from the A/D conversion unit 19 to calculate the flow rate and integrated value of the fluid being measured, as well as to perform calculations such as diagnosing abnormalities related to the fluid being measured. The control unit 21 transmits the results of these calculations to output circuits such as the HMI 22, current output unit 23, pulse output unit 24, status output unit 25, and communication unit 26, and issues instructions regarding the output of information. The control unit 21 accepts various instructions from the user via the HMI 22. The control unit 21 communicates with external devices via the communication unit 26.

The excitation circuit 18 flows an excitation current _Iex through the coils 12 (12a, 12b) under the control of the control unit 21, generating a magnetic field between the coils 12a, 12b. The excitation circuit 18 outputs a signal indicating the value of the excitation current _Iex to the A/D conversion unit 20.

The A/D converter 20 A/D converts a signal (voltage V _iex described later) indicating the value of the excitation current I _ex input from the excitation circuit 18. The A/D converter 20 outputs the signal indicating the value of the excitation current I _ex converted into a digital signal to the control unit 21.

The HMI 22 presents to the user the results of calculations performed by the electromagnetic flowmeter 1, such as measured values such as the flow rate of the fluid being measured and abnormality diagnosis results, and accepts operations from the user. To present information to the user, the HMI 22 may be equipped with, for example, a display such as an LCD display or an OLED (Organic Light-Emitting Diode) panel, a lamp, a speaker, etc. To accept operations from the user, the HMI 22 may be equipped with, for example, multiple keys, a touch screen integrated with the display, a pointing device, etc.

The current output unit 23 scales information such as measurement values and abnormality diagnosis results to current values within a predetermined range, such as 4-20 mA, and outputs the scaled values. The pulse output unit 24 scales information such as measurement values and abnormality diagnosis results to frequency pulses within a predetermined range and outputs the scaled values. The status output unit 25 outputs information about the internal state of the electromagnetic flowmeter 1 to the outside by turning a contact on/off. The communication unit 26 is a device that communicates various information such as measurement values and abnormality diagnosis results with external devices. The communication protocol used by the communication unit 26 may be, for example, HART (Highway Addressable Remote Transducer), FOUNDATION Fieldbus, PROFIBUS (Process Field Bus), or Modbus. Note that the output units shown here are merely examples and are not limited to these examples.

2 is a diagram showing an example configuration of the excitation circuit 18 of FIG. 1. The excitation circuit 18 includes a DC power supply E1, a constant current source CCS, and switching elements Q1, Q2, Q3, and Q4. The constant current source CCS controls the current flowing through the circuit to a constant current value _Iex . The switching elements Q1, Q2, Q3, and Q4 may be configured with transistors such as FETs (Field Effect Transistors).

Timing signals T1, T2, T3, and T4 from the control unit 21 control the on/off of the switching elements Q1, Q2, Q3, and Q4. The timing signals T1, T2, T3, and T4 determine the direction of current flowing through the coil 12. For example, when the switching elements Q1 and Q3 are on and the switching elements Q2 and Q4 are off, the current flows from left to right through the coil 12 in FIG. 2. When the switching elements Q1 and Q3 are off and the switching elements Q2 and Q4 are on, the current flows from right to left through the coil 12 in FIG. 2. Hereinafter, the excitation state generated in the magnetic circuit 11 when the current flows from left to right through the coil 12 in FIG. 2 is referred to as a positive excitation state, and the excitation state generated in the magnetic circuit 11 when the current flows from right to left through the coil 12 is referred to as a negative excitation state. Specific examples of the timing signals T1, T2, T3, and T4 will be described later with reference to FIG. 3. The voltage V _iex generated across the resistor R connected in series to the coil 12 indicates a value corresponding to the excitation current I _ex , and is sampled by the A/D converter 20 and input to the control unit 21 .

(Operation of electromagnetic flowmeter)
Fig. 3 is a timing chart showing an example of sampling in the electromagnetic flowmeter 1 of Fig. 1. Fig. 3 shows the progression of time from the left to the right of the drawing.

In FIG. 3, _Iex is the excitation current flowing into the coil 12. As shown in FIG. 3, the control unit 21 divides one excitation cycle into two periods: a first half and a second half. The control unit 21 outputs timing signals T1 and T3 so that the switching elements Q1 and Q3 are on only in the first half period, and outputs signals T2 and T4 so that the switching elements Q2 and Q4 are on only in the second half period. As a result, the excitation current _Iex repeats a cycle consisting of a positive excitation period of current +I and a negative excitation period of current -I. In other words, the excitation current _Iex alternates between +I and -I at a constant cycle.

It is known that differential noise is mixed into the measured value of the excitation current _Iex immediately after switching from a positive excitation period to a negative excitation period, and immediately after switching from a negative excitation period to a positive excitation period. Therefore, the electromagnetic flowmeter 1 measures the flow rate of the fluid to be measured and diagnoses an abnormality based on the value of the excitation current _Iex in the latter half of the positive excitation period or the latter half of the negative excitation period, which are periods when the differential noise is small enough to be ignored. Hereinafter, the latter half of the positive excitation period will be referred to as the positive excitation stable period, and the latter half of the negative excitation period will be referred to as the negative excitation stable period.

The flow rate signal ES is obtained by A/D conversion of the positive excitation stable period (+I) or negative excitation stable period (-I). This flow rate signal ES contains noise caused by the fluid being measured. Such noise is generated by fluctuations in the electrode potential of the measurement electrode 14 due to factors such as air bubbles, low conductivity, slurry fluids, electrode corrosion, or changes in fluid conductivity.

For example, Figures 4A and 4B show noise spectra at the measuring electrode 14 when bubbles are generated in the tube 13. Figure 4A is a graph showing an example of a change over time in the flow rate signal of a fluid to be measured that contains bubbles. Figure 4B is a graph showing an example of a spectral distribution of the noise level of a fluid to be measured that contains bubbles. In Figure 4A, the horizontal axis represents time, and the vertical axis represents the value of the flow rate signal corresponding to the value of the excitation current _Iex . In Figure 4B, the horizontal axis represents the time frequency, and the vertical axis represents the value of the noise level corresponding to the value of the excitation current _Iex .

When bubbles are generated in the tube 13, the noise spectrum at the measuring electrode 14 is known to have a characteristic of decreasing at 1/f, with a corner frequency of 10 to several tens of Hz. It is also known that the measured value of the excitation current I _ex exhibits a similar 1/f noise spectrum due to the aforementioned low conductivity, slurry fluid, electrode corrosion, and changes in fluid conductivity. Therefore, the electromagnetic flowmeter 1 extracts high-frequency components from the measured value of the excitation current I _ex during the positive excitation stable period or negative excitation stable period, and detects abnormalities in the measured fluid, such as noise, based on the spectral distribution. Therefore, the electromagnetic flowmeter 1 can detect abnormalities in the measured fluid without providing a configuration for measuring and sampling the resistance of the measured fluid.

In Figure 3, the flow signal sampling points indicate the timing at which data is sampled from the flow signal ES to detect the flow rate of the fluid being measured. Because the absolute value of the flow signal ES is proportional to the flow velocity of the fluid being measured, the electromagnetic flowmeter 1 measures the flow velocity of the fluid being measured from the average value of the absolute values of the sampled flow signal ES, etc.

In Figure 3, the diagnostic signal sampling points indicate the timing at which data is sampled from the flow signal ES to detect abnormalities related to the fluid being measured. As shown in Figure 3, the electromagnetic flowmeter 1 acquires the sampling data (diagnostic signal) required for diagnosis from the acquired flow signal sampling points at a period suitable for diagnosing the noise level (diagnostic signal sampling points EN). The electromagnetic flowmeter 1 may diagnose abnormalities such as noise using data sampled from either the positive excitation period or the negative excitation period. Figure 3 shows an example of acquiring a diagnostic signal during the positive excitation period.

The diagnostic signal EN contains low-frequency components that are proportional to the flow rate of the fluid being measured, and high-frequency components due to fluid noise. Therefore, the electromagnetic flowmeter 1 applies a high-pass filter (HPF) to the diagnostic signal EN to extract the high-frequency components, and detects noise based on the high-frequency components of the diagnostic signal EN. This allows the electromagnetic flowmeter 1 to measure the noise level without being affected by the signal proportional to the flow rate.

Furthermore, the electromagnetic flowmeter 1 may perform sampling to appropriately thin out the acquired data (frequency characteristic analysis points EF). In this way, the electromagnetic flowmeter 1 can observe the amount of noise related to the calculation interval. FIG. 3 shows an example in which the electromagnetic flowmeter 1 thins out the flow signal ES during the positive excitation stable period at 2 ⁿ period intervals to acquire frequency characteristic analysis points EFn (n = 1, 2, 3, ...). When calculations are performed with different calculation periods, such as EF1, EF2, EF3, ..., the reciprocal of the calculation period (1/calculation period) reflects the frequency component characteristics of the sampled signal. Therefore, by providing multiple variations in the calculation period, the frequency characteristics of the noise can be known from the amount of noise corresponding to the calculation period.

The electromagnetic flowmeter 1 may store in advance in the memory of the control unit 21 the noise frequency characteristics measured in advance for each noise cause, such as low conductivity, slurry fluid, electrode corrosion, and changes in fluid conductivity. By comparing the frequency characteristics of signals sampled from the flow signal ES at various calculation intervals with the noise frequency characteristics measured in advance for each noise cause, the electromagnetic flowmeter 1 can identify the noise in the fluid being measured and the type of abnormality causing it.

Details of the operation of the electromagnetic flowmeter 1 will be described with reference to FIG. 5. FIG. 5 is a flowchart showing an example of a processing procedure executed by the electromagnetic flowmeter 1 of FIG. 1. The operation of the electromagnetic flowmeter 1 described with reference to FIG. 5 corresponds to a control method for the electromagnetic flowmeter 1 according to this embodiment. Each step in FIG. 5 is executed under the control of the control unit 21 of the electromagnetic flowmeter 1. The processing in FIG. 5 may be executed in parallel with the processing for measuring the flow velocity of the fluid to be measured.

In step S1, the control unit 21 starts measurement. That is, the control unit 21 controls the excitation circuit 18 to apply a magnetic field from the magnetic circuit 11 to the fluid to be measured in the tube 13. Furthermore, the control unit 21 starts measuring the electromotive force using the measurement electrode 14.

In step S2, the control unit 21 acquires data on the positive and negative excitation stable periods. For example, the control unit 21 acquires data at the flow signal sampling points (ES) in Figure 3.

In step S3, the control unit 21 extracts either a positive or negative excitation signal (one-sided excitation signal) from the data acquired in FIG. 3. For example, the control unit 21 may extract data from the flow rate signal ES during the positive excitation stable period. Here, the control unit 21 may appropriately thin out and sample the data.

In step S4, the control unit 21 applies an HPF to the single-sided excitation signal extracted in step S3 to extract high-frequency components. For example, the control unit 21 may extract frequency components above a predetermined frequency from the single-sided excitation signal as high-frequency components.

In step S5, the control unit 21 performs noise diagnosis based on the high-frequency components of the single-sided excitation signal extracted in step S4. For example, the control unit 21 may compare the high-frequency components extracted in step S4 with predetermined high-frequency components extracted from a reference fluid to be measured that is known to be noise-free, and obtain the difference between the two as the noise level of the high-frequency components. If the frequency corresponding to the noise spans a certain frequency range, the control unit 21 may obtain the integral value of the difference corresponding to that range as the noise level. Furthermore, the control unit 21 may identify the noise in the fluid to be measured and the type of abnormality that caused it by comparing the frequency characteristics of signals sampled from the flow rate signal ES at various calculation intervals with the frequency characteristics of noise measured in advance for each noise cause.

In step S6, the control unit 21 compares the noise level obtained in step S5 with a predetermined threshold. The predetermined threshold may be, for example, a value that is a certain number of times (e.g., 2, 5, 10, etc.) the integral value (noise level) of the fluctuation amplitude of the high-frequency component extracted from the signal of the measured fluid that is known to be normal. If the noise level exceeds the threshold (YES in step S6), the control unit 21 proceeds to step S7; if not (NO in step S6), the control unit 21 returns to step S2.

In step S7, the control unit 21 outputs an alarm via the HMI 22. For example, the control unit 21 may display an image indicating that an abnormality has occurred on the display of the HMI 22. Depending on the type of noise, the control unit 21 may output a specific sound from the speaker of the HMI 22. This allows the user to recognize that an abnormality has occurred in the fluid being measured and to perform maintenance. When outputting the alarm, the control unit 21 may also display information such as the intensity of the noise and the type of abnormality that caused it. This allows the user to recognize the intensity of the noise and the type of abnormality, etc., and select and perform appropriate maintenance. In addition to or instead of outputting information via the HMI 22, the control unit 21 may communicate information indicating the occurrence of an abnormality, as well as information about the noise and the type of abnormality that caused it, to an external device via the communication unit 26. This makes it possible to communicate the occurrence of an abnormality and the type of noise (or abnormality) to a user in a remote location. Furthermore, the control unit 21 outputs information about the electromotive force signal from the current output unit 23, pulse output unit 24, and status output unit 25, allowing the user to use this information to analyze the electromotive force signal in detail and perform appropriate maintenance. After completing step S7, the control unit 21 ends the processing of the flowchart.

As described above, the electromagnetic flowmeter 1 applies a magnetic field generated by an excitation current to the fluid to be measured flowing inside the tube 13, and measures the flow rate of the fluid to be measured based on the detection signal generated at the measurement electrode 14 provided inside the tube 13. The control unit 21 of the electromagnetic flowmeter 1 extracts frequency components above a predetermined frequency from the detection signal as high-frequency components, and detects the presence or absence of an abnormality in the fluid to be measured based on the extracted high-frequency components. In this way, the electromagnetic flowmeter 1 detects the presence or absence of an abnormality in the fluid to be measured based on the detection signal generated at the measurement electrode 14 inside the tube 13, making it possible to detect an abnormality in the fluid to be measured with a simpler circuit configuration without the need for a configuration to measure the resistance of the fluid to be measured.

The control unit 21 may compare the extracted high-frequency component with a preset reference high-frequency component, and if the difference between the two exceeds a predetermined threshold, detect an abnormality related to the fluid being measured. In this way, the electromagnetic flowmeter 1 detects abnormalities by comparing the high-frequency component extracted from the detection signal with the reference high-frequency component, making it possible to properly detect abnormalities.

The control unit 21 may output an alarm when an abnormality related to the fluid being measured is detected. For example, the control unit 21 may output the alarm by displaying the alarm on the display of the HMI 22, outputting information from the current output unit 23, pulse output unit 24, and status output unit 25, and communicating with an external device via the communication unit 26. In this way, the electromagnetic flowmeter 1 outputs an alarm when an abnormality is detected, allowing the user to easily recognize the occurrence of an abnormality.

When an abnormality is detected in the fluid being measured, the control unit 21 may identify the cause of the abnormality in the fluid being measured based on the frequency characteristics of the extracted high-frequency components. Causes of such abnormalities may include, for example, process changes such as bubble generation, low conductivity, slurry fluid, electrode corrosion, and changes in fluid conductivity. In this way, the electromagnetic flowmeter 1 identifies the cause of the abnormality in the fluid being measured, allowing the user to perform appropriate maintenance depending on the cause of the abnormality.

The control unit 21 may extract frequency components exceeding a predetermined frequency as high-frequency components from the signal that is thinned out from the detection signal at a predetermined timing, and obtain the frequency characteristics of the extracted high-frequency components based on the high-frequency components extracted from the thinned out signal. In this way, the electromagnetic flowmeter 1 obtains the frequency characteristics of the high-frequency components based on the high-frequency components extracted from the thinned out signal, making it possible to identify the cause of the abnormality with high accuracy.

Instead of extracting high-frequency components from the thinned detection signal and acquiring their frequency characteristics, the control unit 21 may extract high-frequency components from the detection signal and then acquire a signal that has been thinned from the extracted high-frequency components at a predetermined timing. The control unit 21 may then acquire the frequency characteristics of the extracted high-frequency components based on the signal that has been thinned from the high-frequency components. In this way, the electromagnetic flowmeter 1 acquires the frequency characteristics of the high-frequency components based on a signal acquired by thinning out the high-frequency components of the detection signal, making it possible to identify the cause of the abnormality with high accuracy.

The electromagnetic flowmeter 1 may also generate an excitation current having a positive excitation period and a negative excitation period, and extract high-frequency components of the detection signal from either the positive excitation period or the negative excitation period to detect an abnormality. The electromagnetic flowmeter 1 can appropriately detect an abnormality by detecting the abnormality using the high-frequency components extracted from either the positive excitation period or the negative excitation period.

In addition, the electromagnetic flowmeter 1 can properly detect abnormalities without being affected by differential noise by extracting and analyzing high-frequency components from the positive excitation stable period or negative excitation stable period, when differential noise is small enough to be ignored.

The present disclosure is not limited to the above-described embodiments. For example, multiple blocks shown in the block diagrams may be integrated, or one block may be divided. Multiple steps shown in the flowcharts may be executed in parallel or in a different order, depending on the processing capabilities of the device executing each step, or as needed, instead of being executed chronologically as described. Other modifications are possible without departing from the spirit of the present disclosure.

1 Electromagnetic flowmeter 11 Magnetic circuit 12a, 12b Coil 13 Tube 14a, 14b Pair of measurement electrodes 15 Earth electrode 16 Buffer 17 Differential amplifier 18 Excitation circuit 19 A/D conversion unit 20 A/D conversion unit 21 Control unit 22 HMI
23 Current output section 24 Pulse output section 25 Status output section 26 Communication section

Claims (5)

An electromagnetic flowmeter that applies a magnetic field generated by an excitation current to a fluid to be measured flowing through a measuring pipe, and measures a flow rate of the fluid to be measured based on a detection signal generated at an electrode provided in the measuring pipe,
extracting, as high frequency components, frequency components exceeding a predetermined frequency from the detection signal in the latter half of the positive excitation period or the latter half of the negative excitation period;
detecting whether or not there is an abnormality in the fluid to be measured based on the extracted high frequency components;
A control unit is provided ,
The control unit
extracting, as the high frequency components, frequency components exceeding the predetermined frequency from a signal obtained by thinning out the detection signal at a plurality of predetermined periodic intervals;
acquiring frequency characteristics of the extracted high-frequency components based on the high-frequency components extracted from the signal thinned out at the plurality of periodic intervals;
Electromagnetic flowmeter. An electromagnetic flowmeter that applies a magnetic field generated by an excitation current to a fluid to be measured flowing through a measuring pipe, and measures a flow rate of the fluid to be measured based on a detection signal generated at an electrode provided in the measuring pipe,
extracting, as high frequency components, frequency components exceeding a predetermined frequency from the detection signal in the latter half of the positive excitation period or the latter half of the negative excitation period;
detecting whether or not there is an abnormality in the fluid to be measured based on the extracted high frequency components;
A control unit is provided,
The control unit
obtaining a signal decimated at a plurality of predetermined periodic intervals from the extracted high frequency components;
acquiring frequency characteristics of the extracted high-frequency components based on the signals thinned out at the plurality of periodic intervals;
Electromagnetic flowmeter. 3. The electromagnetic flowmeter according to claim 1, wherein the control unit compares the extracted high-frequency component with a predetermined reference high-frequency component, and detects an abnormality related to the fluid to be measured if a difference between the extracted high-frequency component and a reference high-frequency component exceeds a predetermined threshold. The electromagnetic flowmeter according to claim 1 , wherein the control unit outputs an alarm when an abnormality related to the fluid to be measured is detected. 5. The electromagnetic flowmeter according to claim 1, wherein, when an abnormality related to the fluid to be measured is detected, the control unit identifies a cause of the abnormality related to the fluid to be measured based on the frequency characteristics of the extracted high-frequency components.