JP2016169964A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an ultrasonic flowmeter with which it is possible to reduce the effect of a cyclic noise such as the ripple noise of a power supply unit occurring in a switching regulator, etc., relatively easily.SOLUTION: Provided is an ultrasonic flowmeter comprising a detection unit in which a sensor including an ultrasonic conversion element for transmitting/receiving an ultrasonic signal to/from a measurement tube in which a fluid to be measured flows, a control unit for performing transmission/reception of an ultrasonic signal in the sensor and calculating the flow of the fluid to be measured on the basis of the detection signal of the sensor, and a power supply unit consisting of a switching regulator for supplying prescribed drive power to each unit, wherein the control unit exerts control so that the sensor transmits/receives an ultrasonic signal in synchronism with the switching of the power supply unit on the basis of a sync control signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic flow meter, and more particularly to reducing the influence of periodic noise generated from a power supply unit.

As a flow measurement method of the ultrasonic flowmeter,
a) Propagation time difference method Ultrasound is radiated to the fluid flowing in the pipe, and the flow rate is obtained by the propagation time difference of the received signals of the upstream and downstream transducers when passing through the fluid. b) Doppler method and reflection correlation method In the fluid There is a method of calculating a flow rate by obtaining a flow velocity distribution on a survey line through which ultrasonic waves propagate from reflected signals from contained bubbles and impurities.

  FIG. 4 is a configuration explanatory view showing an example of an ultrasonic flowmeter conventionally used. In FIG. 4, an ultrasonic flowmeter includes a detection unit 10 that transmits and receives an ultrasonic signal, a control unit 20 that performs overall control and signal processing of each unit, and a power source that supplies predetermined driving power to each unit. The unit 30 is configured.

  The detection unit 10 includes a measurement tube 11 through which a fluid to be measured flows, and the propagation path of each ultrasonic signal on the outer wall of the measurement tube 11 so as to sandwich the measurement tube 11 at a predetermined angle with respect to the tube axis of the measurement tube 11. It is composed of sensors 12, 13 and the like including ultrasonic transducers that transmit and receive ultrasonic signals that are disposed opposite to each other upstream and downstream in a positional relationship that intersects the direction.

  The control unit 20 includes a transmission / reception switching unit 21, a transmission unit 22, a reception unit 23, a signal processing unit 24, a display unit 25, and the like.

  The transmission / reception switching unit 21 is configured such that when one sensor 12 is connected to the transmission unit 22, the other sensor 13 is connected to the reception unit 23, and when one sensor 12 is connected to the reception unit 23, Transmission and reception of the sensors 12 and 13 are complementarily switched so that the sensor 13 is connected to the transmission unit 22.

  The signal processing unit 24 generates a transmission / reception timing signal for driving the sensors 12 and 13 at a predetermined timing and performs a flow rate calculation based on the detection signals of the sensors 12 and 13 according to a predetermined program. Output to the display unit 25.

  The display unit 25 displays not only the calculation result of the signal processing unit 24 but also parameters and the like unique to each device preset in advance according to the operation of the operator.

  By the way, in the flow measurement method using the reflection correlation type ultrasonic flowmeter, as described above, the flow velocity on the ultrasonic propagation path is measured based on the reflection signal from the bubbles and impurities contained in the fluid, and the measurement is performed. The flow rate is measured from the flow velocity distribution in the tube 11.

  Here, since the reflected signal from the bubbles / contaminants is much smaller than the reverberation vibration, a wall for removing the reverberation vibration described in JP 2011-122914 A in the signal processing unit 24. Filter (hereinafter referred to as WF) processing is performed.

  FIG. 5 is a waveform example illustrating the operation of the reflection correlation type ultrasonic flowmeter. FIG. 5A shows a received waveform before WF processing, which includes reverberation vibration generated when the sensor 12 or 13 transmits ultrasonic waves, in addition to the reflected signal from the bubbles.

  FIG. 5B shows a reverberation vibration waveform removed from the received waveform of FIG. 5A as a standing wave by WF processing. By removing the reverberation vibration waveform shown in FIG. 5B from the received waveform shown in FIG. 5A, a reflected signal from a bubble / contamination as shown in FIG. 5C is obtained.

  The signal processing unit 24 performs arithmetic processing such as a flow rate and a flow rate using the received signal from which the reverberation vibration has been removed in this manner.

  Patent Document 1 describes a technique for reducing the processing load of WF for removing standing waves in an ultrasonic flowmeter.

  Non-Patent Document 1 describes the measurement principle and configuration of an ultrasonic flowmeter of the propagation time difference method similar to the present invention.

JP 2011-122914 A

Satoshi Fukuhara, 3 others, “Ultrasonic Flowmeter US350”, Yokogawa Technical Report, Yokogawa Electric Corporation, January 20, 2004, Vol. 48 No. 1 (2004) p. 29-32

  In order to reduce the size and increase the efficiency of the ultrasonic flowmeter, it is conceivable to use a switching regulator as the power supply unit 30.

  However, when a switching regulator is used, ripple noise synchronized with the switching period as shown in FIG. 6 is generated as the switching regulator is driven, and may be superimposed on the received waveform.

  FIG. 7 is a waveform example diagram for explaining the operation of the reflection correlation type ultrasonic flowmeter using a switching regulator as the power supply unit 30. FIG. 7A shows a reception waveform before WF processing. In addition to a reception signal including a reflection signal from a bubble, reverberation vibration generated when the sensor 12 or 13 transmits an ultrasonic wave, and driving of a switching regulator. Ripple noise as shown in FIG. This ripple noise is asynchronous to the received signal.

  FIG. 7B shows a reverberation vibration waveform that is removed from the received waveform of FIG. 7A as a standing wave by WF processing. By removing the reverberation vibration waveform shown in FIG. 7B from the received waveform shown in FIG. 7A, a reflected signal from a bubble / contamination as shown in FIG. 7C is obtained.

  However, since the ripple noise generated with the driving of the switching regulator is asynchronous to the received signal, it is difficult to remove the ripple noise only by removing the reverberation vibration waveform shown in FIG. As shown in FIG. 7C, the influence of ripple noise remains.

  When calculating the flow velocity based on a waveform that remains affected by ripple noise, if the received signal from bubbles or other contaminants is smaller than the noise, the flow velocity cannot be obtained or an incorrect value is output. May occur.

  Possible measures to avoid this effect include configuring the power supply unit with a series regulator with low ripple noise and electrically isolating the power supply unit and the control unit, but this reduces efficiency and makes it difficult to reduce the size. New problems occur.

  In addition, the influence of ripple noise can be reduced by devising the circuit configuration or optimizing the circuit arrangement. However, when the device shape is restricted, it is very difficult to realize these.

  The present invention solves these problems, and an object of the present invention is to realize an ultrasonic flowmeter that can relatively easily reduce the influence of periodic noise such as ripple noise of a power supply section generated by a switching regulator or the like. There is to do.

In order to achieve such an object, the invention described in claim 1 of the present invention is
A detection unit including a sensor including an ultrasonic transducer that transmits and receives an ultrasonic signal to a measurement tube through which the fluid to be measured flows, and the ultrasonic signal is transmitted and received by the sensor and the target is detected based on the detection signal of the sensor. In an ultrasonic flowmeter composed of a control unit that performs flow calculation of a measured fluid and a power supply unit that includes a switching regulator that supplies predetermined driving power to each unit,
The control unit controls the sensor to transmit and receive an ultrasonic signal in synchronization with switching of the power supply unit based on a synchronization control signal.

The invention according to claim 2 is the ultrasonic flowmeter according to claim 1,
The synchronization control signal is supplied from the control unit to the power supply unit.

The invention according to claim 3 is the ultrasonic flowmeter according to claim 1,
The synchronization control signal is supplied from the outside to the control unit and the power supply unit.

The invention according to claim 4 is the ultrasonic flowmeter according to any one of claims 1 to 3,
The power supply unit includes a plurality of switching regulators.

The invention according to claim 5 is the ultrasonic flowmeter according to any one of claims 1 to 4,
The control unit performs wall filter processing for removing reverberation vibration on the detection signal of the sensor.

  Accordingly, it is possible to realize an ultrasonic flowmeter that can relatively easily reduce the influence of periodic noise such as ripple noise of a power supply unit generated by a switching regulator or the like.

It is a configuration explanatory view showing an embodiment of the present invention. It is explanatory drawing which shows the structural example of the specific power supply part based on this invention. 2 is a timing chart illustrating the operation of FIG. 1. It is composition explanatory drawing which shows an example of the ultrasonic flowmeter based on the reflection correlation method used conventionally. It is an example of a waveform explaining operation of a reflection correlation type ultrasonic flowmeter. It is explanatory drawing of the ripple noise which generate | occur | produces periodically with the drive of a switching regulator. FIG. 6 is a waveform example diagram illustrating the operation of a reflection correlation type ultrasonic flowmeter using a switching regulator as the power supply unit 30.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of an embodiment of the present invention, and the same reference numerals are given to portions common to FIG. 1 is different from FIG. 4 in that a synchronization control signal is supplied from the signal processing unit 24 of the control unit 20 to the power supply unit 30, and the sensors 12 and 13 output ultrasonic signals in synchronization with the switching of the power supply unit 30. It is to send and receive.

  The synchronization control signal supplied from the signal processing unit 24 of the control unit 20 to the power supply unit 30 can be set to any desired value by configuring the signal processing unit 24 of the control unit 20 with, for example, an FPGA (Fielded Programmable Gate Array). Can be set.

  FIG. 2 is an explanatory diagram showing a specific configuration example of the power supply unit according to the present invention. In FIG. 2, the power supply unit 30 includes a plurality of n level shifters 31, a plurality of n pull-down circuits 32, and a plurality of n switching regulators 33 integrated into an integrated circuit.

  As the switching regulator 33, a switching regulator configured to arbitrarily set the switching frequency from the outside by using a synchronization control signal or the like is used, for example. For example, a clock signal generated by the signal processing unit 24 is input to the synchronous input terminal, and when the clock signal is not input, the synchronous input terminal is pulled down (or pulled up) so as to operate at a frequency specified by the integrated circuit. . The clock signal is connected to the synchronous input terminal of each regulator 33 via the level shifter 31 for level conversion to the operating voltage of the integrated circuit.

  In the embodiment of FIG. 2, those having different output voltages are used as the plurality of switching regulators 33, but those having the same output voltage may be used depending on the application.

  3A and 3B are timing charts for explaining the operation of FIG. 1, wherein FIG. 3A shows a switching waveform in the power supply unit 30, FIG. 3B shows switching noise in the power supply unit 30, and FIG. An example of an ultrasound transmission sequence is shown, and (d) shows an example of an ultrasound transmission sequence in the configuration based on the present invention.

  As shown in FIG. 3C, the ultrasonic transmission sequence in the conventional configuration is executed at an independent arbitrary timing without being synchronized with the switching operation in the power supply unit 30.

  As a result, as shown in FIG. 7C, the influence of ripple noise that is not synchronized with the switching operation remains, and there is a problem in that a highly accurate calculation result cannot be obtained.

  On the other hand, according to the present invention, the ultrasonic transmission sequence is executed at a timing synchronized with the waveform of the switching operation in the power supply unit 30 as shown in FIG.

  By synchronizing the timing of ultrasonic transmission and the switching timing of the power supply unit 30 in this way, the noise generated by the switching of the power supply unit 30 is synchronized with the switching of the power supply unit 30. Therefore, noise during transmission and reception always occurs at the same timing.

  The ripple noise as shown in FIG. 7C generated by switching based on the timing control apparently becomes a standing wave like the reverberation vibration, and is removed as shown in FIG. 5C by the WF process described above. be able to.

  That is, the power supply unit 30 includes a synchronization input terminal and is configured to be able to arbitrarily set a switching frequency, and operates as a switching power supply at a frequency N times that of the synchronization control signal in synchronization with the synchronization control signal.

  The signal processing unit 24 transmits the ultrasonic signal in synchronization with the synchronization control signal, so that the ultrasonic transmission signal and the switching of the power supply unit 30 are synchronized.

  And, since the flow velocity profile inside the pipe is determined by the time from transmission to reception, the reception signal is always acquired from the transmission at the same timing as long as the internal parameters are not changed. . Therefore, if the transmission of the ultrasonic signal and the switching of the power supply unit 30 are synchronized, the reception is also synchronized with the switching of the power supply unit 30.

  It is also possible to provide a function of inputting a clock signal having the same cycle as a noise source outside the device and synchronizing the transmission timing of the ultrasonic wave with the clock signal, and to reduce the influence of external noise by WF.

  In the above-described embodiments, the transmission type ultrasonic flowmeter has been described. However, the present invention is not limited to the transmission type, and can be applied to a reflection type ultrasonic flowmeter.

  As described above, according to the present invention, it is possible to realize an ultrasonic flowmeter that can relatively easily reduce the influence of periodic noise such as ripple noise of a power supply unit generated by a switching regulator or the like.

DESCRIPTION OF SYMBOLS 10 Detection part 11 Measuring tube 12, 13 Sensor 20 Control part 20
DESCRIPTION OF SYMBOLS 21 Transmission / reception switching part 22 Transmission part 23 Reception part 24 Signal processing part 25 Display part 30 Power supply part 31 Level shifter 32 Pull-down circuit 33 Switching regulator

Claims (5)

A detection unit including a sensor including an ultrasonic transducer that transmits and receives an ultrasonic signal to a measurement tube through which the fluid to be measured flows, and the ultrasonic signal is transmitted and received by the sensor and the target is detected based on the detection signal of the sensor. In an ultrasonic flowmeter composed of a control unit that performs flow calculation of a measured fluid and a power supply unit that includes a switching regulator that supplies predetermined driving power to each unit,
The ultrasonic flowmeter, wherein the control unit controls the sensor to transmit and receive an ultrasonic signal in synchronization with switching of the power supply unit based on a synchronization control signal.   The ultrasonic flowmeter according to claim 1, wherein the synchronization control signal is supplied from the control unit to the power supply unit.   The ultrasonic flowmeter according to claim 1, wherein the synchronization control signal is supplied to the control unit and the power supply unit from outside.   The ultrasonic flowmeter according to claim 1, wherein the power supply unit includes a plurality of switching regulators.   The ultrasonic flowmeter according to any one of claims 1 to 4, wherein the control unit performs wall filter processing for removing reverberation vibration on a detection signal of the sensor.

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