JP2016205936A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost electromagnetic flowmeter by connecting a detector unit and a converter unit with one circuit of cable.SOLUTION: In an electromagnetic flowmeter of an embodiment of the invention, a transmission path is configured by a single transmission line for transmitting an excitation current and a flow rate signal, a converter unit has a first switching circuit for switching between the supply of the excitation current from an excitation circuit to the transmission path and the supply of the flow rate signal from the transmission path to a control unit with a prescribed timing, and a detector unit is provided with a second switching circuit which is switched in synchronization with the first switching circuit, and supplies the excitation current from the transmission path to a coil unit when the first switching circuit is supplying the excitation current to the transmission path and supplies the flow rate signal from a signal generation unit to the transmission path when the first switching circuit is supplying the flow rate signal from the transmission path to the control unit.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to an electromagnetic flow meter.

  The electromagnetic flowmeter includes a measuring tube, a coil portion for generating a magnetic field in the measuring tube, an electrode portion for detecting an induced electromotive force generated when a fluid flows in the magnetic field, and a coil. It comprises a converter part composed of an excitation circuit for controlling the excitation current flowing through the part and a signal processing circuit for calculating the flow rate of the fluid from the induced electromotive force detected by the electrode part.

  Conventionally, an electromagnetic flow meter has two systems: a cable that connects the excitation circuit of the converter unit and the coil unit of the detector unit, and a cable that connects the electrode unit of the detector unit and the signal processing circuit of the converter unit. There was a problem that a cable was required and cost was increased. In particular, in the separate type in which the detector unit and the converter unit are connected to each other in order to install the detector unit and the converter unit apart from each other, the cable cost increases depending on the distance between the detector unit and the converter unit. There was a problem.

Japanese Patent No. 5635907

  The problem to be solved by the present invention is to provide a low-cost electromagnetic flow meter by connecting the detector unit and the converter unit with one system cable.

  In order to solve the above problems, an electromagnetic flow meter according to an embodiment includes a measurement tube through which a measurement object flows, a coil unit that is disposed in the measurement tube and generates a magnetic field in the measurement tube, and the magnetic field provided in the measurement tube. A detector unit comprising: an electrode unit that detects an induced electromotive force generated by the measurement object flowing in the inside; and a signal generation unit that generates a flow signal from the induced electromotive force detected by the electrode unit; An excitation circuit that is provided separately from the detector unit and generates an excitation current to be applied to the coil unit, and a control that calculates a flow rate value of the measurement object from a flow rate signal generated by the signal generation unit of the detector unit A converter unit, and an excitation current generated by an excitation circuit of the converter unit is transmitted to the detector unit, and a flow rate signal generated by the detector unit is transmitted to the signal of the converter unit. Transmission to the processing circuit And the transmission path is constituted by a single transmission line that transmits the excitation current and the flow rate signal, and the converter unit supplies the excitation current from the excitation circuit to the transmission path. A first switching circuit that switches the flow rate signal from the transmission path to the control unit at a predetermined timing, and the detector unit is synchronized with the first switching circuit. When the first switching circuit is supplying the excitation current to the transmission path, the excitation current from the transmission path is supplied to the coil section, and the first switching circuit is supplied to the transmission path. A second switching circuit that supplies the flow rate signal from the signal generation unit to the transmission line when the flow rate signal from the signal generation unit is being supplied to the control unit.

The schematic of the electromagnetic flowmeter which is 1st Embodiment. The block diagram of the electromagnetic flowmeter which is 1st Embodiment. The block diagram of the signal processing circuit 15. FIG. The block diagram of the timing adjustment circuit 31 and the 2nd switching circuit 24. FIG. The timing chart of the electromagnetic flowmeter which is 1st Embodiment. The block diagram of the electromagnetic flowmeter which is 2nd Embodiment. The block diagram of a delay circuit. The block diagram of the electromagnetic flowmeter which is 3rd Embodiment. The block diagram of the electromagnetic flowmeter which is 4th Embodiment. The block diagram of the signal processing circuit 25 in 4th Embodiment.

  Hereinafter, an embodiment of an electromagnetic flow meter will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic view of an electromagnetic flow meter according to the first embodiment. The electromagnetic flowmeter includes a detector unit 20, a converter unit 10 provided apart from the detector unit 20, and a transmission path 30 that electrically connects the detector unit 20 and the converter unit 10. Become.

  The converter unit 10 generates an excitation current and transmits the excitation current to the detector unit 20 via the transmission path 30. A detector tube 21 is provided inside the detector unit 20. Pipings 40, 40 are connected to both sides of the measurement pipe 21, and a measurement object flowing through one pipe 40 flows to the other pipe 40 via the measurement pipe 21.

  The excitation current transmitted to the detector unit 20 is supplied to a coil unit 23 (see FIG. 2 described later) disposed in the measurement tube 21. The coil section 23 generates a magnetic field in the measurement tube 21 by flowing an exciting current. When a measurement object flows through this magnetic field, an induced electromotive force is generated. The detector unit 20 transmits a flow rate signal based on the induced electromotive force to the converter unit 10 via the transmission line 30.

  The converter unit 10 calculates the flow value of the measurement object flowing through the measurement tube 21 from the flow signal based on the induced electromotive force transmitted from the detector unit 20. The converter unit 10 has a display unit 16 for displaying the calculated flow rate value.

  FIG. 2 is a block diagram of the electromagnetic flow meter according to the first embodiment. The converter unit 10 includes a central processing unit (hereinafter referred to as a CPU 11) that is a control unit, an excitation circuit 12, a timing control circuit 13, a first switching circuit 14, a signal processing circuit 15, and a display unit 16. It has.

  The CPU 11 is electrically connected to the excitation circuit 12, the timing control circuit 13, and the signal processing circuit 15. The CPU 11 outputs a signal related to generation of an excitation current to the excitation circuit 12 and outputs a control signal to the timing control circuit 13. This control signal includes excitation current supply and stop switching timing in the excitation circuit 12, switching timing of the first switching circuit 14, and timing used when the signal processing circuit 15 converts the flow rate signal into a digital signal. It becomes information of. Further, the CPU 11 calculates the flow rate value of the measurement object from the digital signal converted by the signal processing circuit 15 and causes the display unit 16 to display the calculated flow rate value.

  The excitation circuit 12 is a circuit that generates an excitation current that flows through the coil unit 23 for generating a magnetic field in the measurement tube 21 of the detector unit 20. The excitation circuit 12 is electrically connected to the first switching circuit 14 and supplies an excitation current to the first switching circuit 14.

  The first switching circuit 14 is electrically connected to the excitation circuit 12, the timing control circuit 13, and the signal processing circuit 15. The first switching circuit 14 is electrically connected to a transmission line in the transmission path 30. The first switching circuit 14 supplies the excitation current generated by the excitation circuit 12 to the transmission path 30, and supplies the flow rate signal transmitted from the transmission path 30 to the signal processing circuit 15. The first switching circuit 14 periodically switches the supply of the excitation current and the supply of the flow signal. When supplying the excitation current to the transmission line 30, the first switching circuit 14 is switched to the excitation circuit 12 side, and after the supply of the excitation current is cut off, the first switching circuit 14 is switched to the signal processing circuit 15 side. That is, the first switching circuit 14 performs time division switching so that the excitation current and the flow rate signal are not transmitted to the transmission line 30 at the same time.

  The timing control circuit 13 is electrically connected to the CPU 11, the excitation circuit 12, the first switching circuit 14, and the signal processing circuit 15. When the timing control circuit 13 receives the control signal from the CPU 11, the timing control circuit 13 controls the excitation circuit 12 to generate positive and negative excitation currents based on the control signal.

  The signal processing circuit 15 is electrically connected to the CPU 11, the first switching circuit 14, and the timing control circuit 13. The signal processing circuit 15 converts the analog flow rate signal supplied from the first switching circuit 14 into a digital signal so that the CPU 11 calculates the flow rate value of the measurement object.

  FIG. 3 is an example of a block diagram of the signal processing circuit 15. The signal processing circuit 15 includes an A / D converter 50 and a signal output circuit 51. The A / D converter 50 converts an analog flow signal into a digital signal. The signal output circuit 51 receives a signal related to sampling control from the timing control circuit 13 and performs sampling processing. The signal output circuit 51 outputs a digital signal of a flow rate signal to the CPU 11 from the digital signal and a signal related to sampling control.

  However, the signal processing circuit 15 is not limited to the configuration of FIG. The signal processing circuit 15 may be configured such that the flow rate signal is amplified by an amplifier or the like and then input to the A / D converter 50. Further, the signal output circuit 51 may be omitted, and the CPU 11 may perform sampling processing.

  As shown in FIG. 2, the detector unit 20 includes a measurement tube 21, electrode units 22 and 22, coil units 23 and 23, a second switching circuit 24, a signal generation unit 25, and a timing adjustment circuit 31. I have.

  The second switching circuit 24 is connected to the transmission path 30, the timing adjustment circuit 31, the coil units 23 and 23, and the signal generation unit 25. The second switching circuit 24 switches the connection destination of the transmission path 30 between the coil units 23 and 23 and the signal generation unit 25 by a signal generated from the timing adjustment circuit 31.

  When an excitation current is applied to the coil parts 23, 23, a magnetic field is generated from one coil part 23 toward the other coil part 23 inside the measurement tube 21. When a measurement object flows through the measurement tube 21, an induced electromotive force is generated. This induced electromotive force is generated in a direction substantially orthogonal to the direction of the magnetic field and the direction in which the measurement object flows. The induced electromotive force is detected by the electrode portions 22 and 22.

  An example of the signal generation unit 25 is a differential amplifier. Since the induced electromotive force is very small, the signal generator 25 amplifies it. In this embodiment and the following embodiments, the signal output by the signal generation unit 25 is referred to as a flow rate signal. This flow rate signal is supplied to the second switching circuit 24.

  The switching timing of the second switching circuit 24 is synchronized with the switching timing of the first switching circuit 14. When the first switching circuit 14 supplies the excitation current to the transmission path 30 and the excitation current is transmitted from the transmission path 30 to the second switching circuit 24, the second switching circuit 24 sends the excitation current to the coil unit 23. Supply.

  FIG. 4 is a block diagram of the timing adjustment circuit 31 and the second switching circuit 24. The timing adjustment circuit 31 and the second switching circuit 24 are connected to the transmission line 30. The timing adjustment circuit 31 includes a potential detection unit 32 and a switching timing adjustment unit 33. The potential detector 32 detects the potential of the connection portion between the timing adjustment circuit 31 and the transmission path 30. When the potential detection unit 32 detects a zero potential, the switching timing adjustment unit 33 issues a signal for switching connection to the second switching circuit 24 after a predetermined time has elapsed since the detection.

  Actually, the potential detector 32 detects a high potential when an excitation current is flowing through the transmission line 30, and zeros when no excitation current is flowing through the transmission line 30 and when a flow rate signal is flowing. Detects potential. In general, the voltage applied to flow the excitation current is about 10 (V) to 20 (V), which is higher than the voltage when the flow rate signal is flowing. However, the value of the applied voltage is not limited to the above value.

  FIG. 5 is a timing chart through which the excitation current and the flow signal of this embodiment flow. FIG. 5A is a waveform diagram of the excitation current generated by the excitation circuit 12. The timing control circuit 13 controls the excitation circuit 12 to determine the excitation current generation state in the positive direction, the generation direction in the negative direction, and the non-generation state between them based on the control signal. Generate periodically. The exciting current is generated as a rectangular wave as shown in FIG.

  In FIG. 5A, when the excitation current is generated in the positive direction and the negative direction, the timing control circuit 13 causes the first switching circuit 14 to electrically connect the excitation circuit 12 and the transmission path 30. The excitation current is transmitted to the detector unit 20. The timing control circuit 13 switches the first switching circuit 14 at a period of T.

  When a positive rectangular wave current of excitation current is supplied from the excitation circuit 12 to the transmission line 30 via the first switching circuit 14, the potential of the potential detector 32 in FIG. Hereinafter, it transits to simply a positive potential). When the potential detection unit 32 detects a positive potential, the second switching circuit 24 supplies the exciting current from the transmission path 30 to the coil unit 23.

  After the excitation current is transmitted to the detector unit 20, that is, after the positive excitation current is transmitted for the time T, the timing control circuit 13 transmits the flow rate signal generated by the detector unit 20 to the transmission line 30 and the first channel. The switching of the first switching circuit 14 is controlled so as to be supplied to the signal processing circuit 15 via the switching circuit 14. That is, when the excitation current is generated as shown in FIG. 5A and supplied to the coil unit 23, the coil unit 23 is intermittently driven. A flow rate signal is transmitted from the detector unit 20 to the converter unit 10 when the coil unit 23 is not driven.

  FIG. 5B is a timing chart of the flow rate signal generated by the signal generation unit 25. The second switching circuit 24 is switched in synchronization with the first switching circuit 14.

  When the transmission of the positive rectangular wave current of the excitation current is completed and the first switching circuit 14 is switched from the supply of the excitation current to the stop, the potential detection unit 32 detects the zero potential from the positive potential. When the first predetermined time (0.1T in FIG. 5) elapses after the potential detector 32 detects the zero potential, the second switching circuit 24 switches to supply the flow rate signal to the transmission line 30. do.

  At this time, the switching timing adjustment unit 33 in FIG. 4 transmits a switching signal to the second switching circuit 24 from the block (0.1 T has elapsed). When receiving the switching signal, the second switching circuit 24 performs switching for connecting the signal generation unit 25 and the transmission path 30. Thereby, supply of the flow signal to the converter unit 10 is started.

  Further, the second switching circuit 24 switches the second switching circuit 24 after the second predetermined time (0.9 T in FIG. 5) has elapsed after the potential detecting unit 32 detects the zero potential, thereby switching the transmission line 30. Shut off the flow signal supply. Performs switching to shut off the supply of the flow signal.

  At this time, the switching timing adjustment unit 33 in FIG. 4 transmits a switching signal to the second switching circuit 24 from the block (0.9 T has elapsed). When receiving the switching signal, the second switching circuit 24 performs switching for connecting the coil unit 23 and the transmission path 30. Thereby, supply of the flow signal to the converter unit 10 is interrupted.

  As described above, the second switching circuit 24 performs switching in synchronization with the switching of the first switching circuit 14 that stops the supply of the excitation current. That is, switching is performed so that the flow rate signal is supplied to the transmission line 30 only between 0.1T and 0.9T after the first switching circuit 14 stops supplying the exciting current. However, the above-mentioned 0.1T and 0.9T are merely examples in the present embodiment and the following embodiments, and are not limited to these values. Even if the first switching circuit 14 is switched at the same time. Good.

  The switching timing of the first switching circuit 14 is detected by the detector unit 20 based on the potential of the transmission line 30 and the second switching circuit 24 is switched based on a predetermined delay time after detecting the zero potential. The means for performing is referred to as switching timing adjusting means.

  By this switching timing adjustment means, the exciting current and the flow rate signal can be transmitted through the same transmission line in the transmission line 30 without being mixed.

  With this configuration, the transmission line 30 transmits the excitation current generated by the converter unit 10 to the detector unit 20 and converts the flow signal based on the induced electromotive force detected by the detector unit 20. Transmission to the instrument unit 10 can be performed by a single transmission line.

  The signal processing circuit 15 converts the analog flow signal in FIG. 5B into a digital signal. As an example of this digital signal, the maximum amplitude value of each rectangle in FIG. FIG. 5C shows an example of a digital signal. When the flow rate of the measurement object is 1.00 (l / min), the flow rate is 100, and when the flow rate of the measurement object is 0.75 (l / min), the flow rate is 011. However, in the present embodiment and the following embodiments, the digital signal of the flow rate signal is not limited to FIG.

(Second Embodiment)
A schematic diagram of an electromagnetic flow meter according to the second embodiment is the same as that shown in FIG. FIG. 6 is a block diagram of the electromagnetic flow meter of the second embodiment. In this embodiment, a delay circuit 26 is inserted between the signal generator 25 and the second switching circuit 24 of the detector unit 20 of the first embodiment. By inserting the delay circuit 26, it is possible to adjust the timing at which the flow rate signal supplied from the signal generation unit 25 is supplied to the second switching circuit 24.

  FIG. 7 shows an example of the delay circuit 26. The delay circuit 26 includes a plurality of buffer circuits 26a and a switch 26b. The buffer circuit 26a is a feedback of the output of the OP amplifier. The plurality of buffer circuits 26 a are connected in series, and their input terminals are electrically connected to the output of the signal generation unit 25. A node 26c is provided at the output end of each buffer circuit 26a, and a switch 26b is connected thereto. The switch 26b is electrically connected to the second switching circuit 24. By changing the node 26c to which the switch 26b is connected, the delay amount of the flow rate signal by the delay circuit 26 can be adjusted.

  FIG. 7 shows an example of the delay circuit 26. For example, a CR delay circuit combining a resistance element (R) and a capacitance (C) may be used. The form of the delay circuit 26 is not limited to the form of FIG. 7 or the CR delay circuit.

  As described above, also in the present embodiment, the excitation current and the flow rate signal are not mixed in the transmission line 30 and can be transmitted through the same transmission line.

(Third embodiment)
A schematic diagram of an electromagnetic flow meter according to the third embodiment is the same as that shown in FIG. FIG. 8 is a configuration diagram of the electromagnetic flow meter of the third embodiment. In the present embodiment, a holding circuit 27 is inserted between the signal generation unit 25 and the second switching circuit 24 of the detector unit 20 of the first embodiment. As an example, the holding circuit 27 includes a capacitor and may be a variable capacitor having a variable capacitance.

  In the present embodiment, the excitation current shown in FIG. 5A is generated, and the flow rate signal generated by the signal generation unit 25 is temporarily generated by the holding circuit 27 while the excitation current is transmitted through the transmission path 30. Hold on. The second switching circuit 24 switches in synchronization with the first switching circuit 14. When the first switching circuit 14 is switched and the transmission line 30 is electrically connected to the signal processing circuit 15 side, the second switching circuit 24 is switched to electrically connect the holding circuit 27 and the transmission line 30. . At this time, the flow rate signal held in the holding circuit 27 is supplied to the transmission path 30 and transmitted to the converter unit 10. In other words, the flow rate signal is stored in the holding circuit 27 even after the transmission of the excitation current through the transmission path 30 is completed.

  As described above, also in the present embodiment, the excitation current and the flow rate signal are not mixed in the transmission line 30 and can be transmitted through the same transmission line.

(Fourth embodiment)
A schematic diagram of an electromagnetic flow meter according to the fourth embodiment is the same as that shown in FIG. FIG. 9 is a configuration diagram of the electromagnetic flow meter of the fourth embodiment. In the present embodiment, the signal processing circuit 15 is omitted from the converter unit 10 of the first embodiment. The signal generation unit 25 of the detector unit 20 includes an A / D converter 53 and outputs a digital flow rate signal to the transmission line 30.

  FIG. 10 is an example of a configuration diagram of the signal generation unit 25 of the detector unit 20. The signal generation unit 25 includes an amplifier 52, an A / D converter 53, and a signal output circuit 54. The amplifier 52 is a circuit that amplifies the induced electromotive force detected by the electrode unit 22. The A / D converter 53 is a circuit that converts the analog induced electromotive force amplified by the amplifier 52 into a digital value. The signal output circuit 54 is a circuit for sampling the A / D converted digital value so as to be supplied to the transmission line 30. That is, the signal generation unit 25 converts the induced electromotive force output from the electrode unit 22 into a digital signal and supplies the digital signal to the transmission line 30 via the second switching circuit 24. However, the signal generator 25 is not limited to the configuration of FIG.

  The converter unit 10 is supplied with a digital signal of a flow rate signal from the transmission line 30 by the first switching circuit 14. Therefore, the signal processing circuit 15 for A / D conversion in the first embodiment can be omitted, and the first switching circuit 14 can output a digital flow rate signal to the CPU 11.

  In this embodiment, a delay circuit 26, a holding circuit 27, or a combination of these circuits is connected between the electrode unit 22 and the signal generation unit 25 so that the digital signal of the flow rate signal is the second switching circuit 24. It is also possible to adjust the timing supplied to the. In addition, the signal generation unit 25 may include a delay circuit 26, a holding circuit 27, or a combination of these.

  Thereby, since the transmission path 30 transmits the flow rate signal as a digital signal, the flow rate signal is not attenuated even if the distance of the transmission path 30 is increased.

  As described above, also in the present embodiment, the excitation current and the flow rate signal are not mixed in the transmission line 30 and can be transmitted through the same transmission line.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 ... Converter part,
11 ... CPU,
12 ... Excitation circuit,
13. Timing control circuit,
14... First switching circuit,
15. Signal processing circuit,
16 ... Display section,
20 ... Detector part,
21 ... Measurement tube,
22 ... Electrode part,
23 ... coil part,
24 ... the second switching circuit,
25 ... Signal generator,
26 ... Delay circuit,
26a ... buffer circuit,
26b ... switch,
26c node,
27 ... Holding circuit,
30 ... Transmission path,
31 ... Timing adjustment circuit,
32 ... Potential detector,
33 ... Switching timing adjustment unit,
40 ... piping,
50 ... A / D converter,
51... Signal output circuit,
52 ... Amplifier,
53 A / D converter,
54 Signal output circuit.

Claims (7)

A measurement tube through which a measurement object flows, a coil unit that is arranged in the measurement tube and generates a magnetic field in the measurement tube, and an induced electromotive force that is provided in the measurement tube and that is generated when the measurement object flows in the magnetic field A detector unit comprising: an electrode unit for detecting the flow rate; and a signal generation unit for generating a flow rate signal from the induced electromotive force detected by the electrode unit;
A flow rate value of the measurement object is calculated from an excitation circuit that is provided separately from the detector unit and generates an excitation current to be applied to the coil unit, and a flow rate signal generated by the signal generation unit of the detector unit. A converter unit having a control unit;
A transmission path for transmitting the excitation current generated by the excitation circuit of the converter unit to the detector unit, and for transmitting the flow rate signal generated by the detector unit to the control unit of the converter unit,
An electromagnetic flow meter comprising:
The transmission path is constituted by a single transmission line that transmits the excitation current and the flow rate signal,
The converter part is
A first switching circuit that switches the supply of the excitation current from the excitation circuit to the transmission path and the supply of the flow rate signal from the transmission path to the control unit at a predetermined timing;
Have
The detector section is
Switched in synchronization with the first switching circuit, and when the first switching circuit is supplying the excitation current to the transmission path, supplying the excitation current from the transmission path to the coil unit, A second switching circuit for supplying the flow rate signal from the signal generation unit to the transmission path when the first switching circuit is supplying the flow rate signal from the transmission path to the control unit; ,
Electromagnetic flow meter. The detector unit detects the state of the potential of the transmission path, and the second switching circuit is switched based on the detection result of the potential detection unit, and the flow rate signal of the signal generation unit is sent to the detector unit. Switching timing adjustment means for supplying to the transmission line,
The electromagnetic flowmeter according to claim 1. The switching timing adjusting means switches the second switching circuit after the first predetermined time has elapsed after the potential detecting unit detects that the potential of the transmission line becomes zero potential, and switches the second switching circuit. Supplying the flow signal of the generator to the transmission line;
The electromagnetic flow meter according to claim 2. The switching timing adjustment unit is configured to change the excitation current from the transmission path after the second predetermined time has elapsed after the potential detection unit detects that the potential of the transmission path has become zero. Switching the second switching circuit to supply to the
The electromagnetic flowmeter according to claim 2 or claim 3.   The said signal generation part has a delay circuit or a holding circuit for supplying the said flow rate signal to the said transmission line from the 1st predetermined time by the said switching timing adjustment means to the 2nd predetermined time. Electromagnetic flow meter. A signal processing circuit including an A / D converter that converts a flow rate signal supplied from the transmission path from an analog signal to a digital signal, between the first switching circuit and the control unit; Obtains a flow rate value from the signal converted into a digital signal by the A / D converter,
The electromagnetic flowmeter according to any one of claims 1 to 5.   The signal generation unit includes an A / D converter that converts a flow rate signal from an analog signal to a digital signal, and transmits the flow rate signal as a digital value from the detector unit to the converter unit via the transmission path. The electromagnetic flow meter according to any one of claims 1 to 5.

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