KR102010184B1 - Vortex flowmeter - Google Patents

Abstract

Vortex flowmeters are provided to quickly select the appropriate bandpass filter. It is a vortex flowmeter provided with the sensor which detects the Karman vortex which generate | occur | produces in a vortex generator, and the converter which outputs the flow volume of the fluid under measurement based on the signal output from the sensor. The transducer calculates the vortex frequency based on the band pass filter 30 for removing the unnecessary frequency band signal included in the signal output from the sensor, and the interval of the pulse signal pulsing the signal output from the sensor, and vortex And a signal processing section 34 for obtaining a vortex frequency detected at the highest frequency among the frequencies, and a filter selecting section 31 for selecting a band pass filter based on the vortex frequency detected at the highest frequency. The signal output from the sensor is passed through the selected band pass filter to remove the signal of unnecessary frequency band.

Description

Vortex Flowmeter {VORTEX FLOWMETER}

The present invention relates to a vortex flowmeter, and more particularly, a sensor for detecting a Karman vortex generated in the vortex generator, and a transducer for outputting a flow rate of the fluid under measurement based on a signal output from the sensor. It relates to a vortex flow meter having a.

The vortex flowmeter is composed of a vortex generator (also referred to as a bluff body) for generating a Karman vortex, a sensor for detecting the Karman vortex, and a transducer for processing the signal detected by the sensor. The vortex generator is formed, for example, in the shape of a triangular column and placed at right angles to the flow of the fluid in the measuring tube. In the sensor, the fluctuation pressure (for example, the differential pressure generated by the Karman vortex) generated in the vortex generator can be detected.

The frequency (also called the vortex frequency) occurring in the Karman vortex is proportional to the flow rate. In the transducer, the flow velocity in the measuring tube is determined from the detected vortex frequency, and the flow rate (volume flow rate) is obtained by multiplying the flow rate by the cross-sectional area of the measuring tube.

In the converter, when detecting the vortex frequency, the signal output from the sensor is passed through a band-pass filter to remove noise. For example, Patent Literature 1 discloses a technique for selecting a band pass filter to pass.

Japanese Unexamined Patent Publication No. 2001-153698

By the way, in a converter, after the pulsed signal output from a sensor is pulsed, the method of calculating the average value of vortex frequency from the interval and the number of pulse signals measured within predetermined time, for example, and selecting the bandpass filter which let it pass is known. have.

However, if a band pass filter corresponding to the average value of the vortex frequency is selected, there is a problem that an appropriate band pass filter cannot be selected under the influence of an outlier value such as a signal that has not reached the trigger level. In addition, in order to obtain the average value of the vortex frequency, a large number of samples of the signal are required, and there is also a problem that a band pass filter cannot be selected quickly.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a vortex flowmeter capable of quickly selecting an appropriate bandpass filter.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the 1st technical means of this invention is equipped with the sensor which detects the Karman vortex which generate | occur | produces in a vortex generator, and the transducer which outputs the flow volume of the fluid under measurement based on the signal output from the said sensor. As a vortex flow meter, the transducer includes a band pass filter for removing an unnecessary frequency band signal included in a signal output from the sensor, and a vortex frequency based on an interval of a pulse signal pulsed by the signal output from the sensor. And a signal processing unit for obtaining a vortex frequency detected at the highest frequency among the vortex frequencies, and a filter selector for selecting the band pass filter based on the vortex frequency detected at the highest frequency, and outputting from the sensor. Passes the selected signal through the selected band pass filter to remove an unnecessary frequency band signal. Is one wherein dwell.

The second technical means is that the band pass filter is a digital filter.

According to the present invention, the band pass filter is selected based on the vortex frequency of the highest frequency, not the average value of the vortex frequency, and is not affected by the deviated value as it is selected based on the average value of the vortex frequency. Band pass filter can be selected. Further, when the band pass filter is selected from the vortex frequency of the highest frequency, the band pass filter can be selected quickly because the number of samples of the signal is smaller than in the case of the selection based on the average value of the vortex frequency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the vortex flowmeter which concerns on one Embodiment of this invention.
It is a figure which shows the eddy current detection sensor which concerns on one Embodiment of this invention.
3 is a configuration diagram of the vortex flow meter of FIG. 1.
4 is a configuration diagram of the variable BPF of FIG. 3.
It is a figure explaining the measurement of a vortex frequency.
It is a figure explaining the analysis of a vortex frequency.
7 is a diagram illustrating waveform data such as a comparative example.
8 is a diagram for explaining waveform data of the present embodiment.
9 is a configuration diagram of a variable BPF according to another embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of the vortex flowmeter of this invention is described, referring an accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the vortex flowmeter which concerns on one Embodiment of this invention, and has shown the flange-shaped detector 1, for example. It is a figure which shows the eddy current detection sensor which concerns on one Embodiment of this invention.

The detector 1 has, for example, a vortex generator 3 formed in a triangular column shape, and a cylinder such that the side surface of the vortex generator 3 is perpendicular to the flow of the fluid to be measured (in the direction of the arrow in FIG. 2). It is provided in the measuring tube 2 of a shape. The mounting cylinder 5 is provided in the upper surface of the measuring tube 2, and is fixed to the measuring tube 2 by fastening members, such as a bolt, for example. The converter 10 is provided above the mounting cylinder 5. Moreover, although the converter integrated type is demonstrated as an example, the converter separated type which isolate | separated the transducer from the detector may be sufficient.

In the measurement tube 2, the vortex detection sensor 7 is provided behind the vortex generator 3. In addition, the eddy current detection sensor 7 corresponds to the sensor of this invention.

When the fluid flows in the measuring tube 2, Karman vortices in proportion to the flow velocity are generated downstream of the vortex generator 3, and alternating pressures of the vortex generator 3 are caused by carman vortices. Fluctuations occur. As a result, in the vortex detection sensor 7, a signal (also referred to as a vortex signal) corresponding to the fluctuation pressure generated in the vortex generator 3 is detected and output to the transducer 10. The transducer 10 has a flow rate indicator 16, and the flow rate indicator 16 digitally displays the flow rate and the like of the fluid to be measured obtained by the transducer 10. FIG.

3 is a block diagram of a vortex flowmeter.

The converter 10 includes a control unit 15, a communication I / F 17, an amplifier unit 18, a filter unit 19, and the like in addition to the flow rate indicator 16 described above, which are connected by a bus.

The control unit 15 can communicate with the detector 1 or an external device through the communication I / F 17. In addition, the control unit 15 includes, for example, one or a plurality of CPUs (Central Processing Units) and the like, and loads various programs and data stored in a ROM into a RAM, for example, in the loaded RAM. Run the program. Thereby, operation | movement of a vortex flowmeter can be controlled.

The amplifier unit 18 includes, for example, a constant current circuit 20, an amplifier 21, an output circuit 22, and the like. The constant current circuit 20 supplies a current to the eddy current detection sensor 7 of the detector 1. The amplifier 21 amplifies the eddy current signal output from the eddy current detection sensor 7. The amplified eddy current signal is output to the filter unit 19.

The filter unit 19 has a variable BPF 26 and a comparator 27. The variable BPF 26 passes the eddy current signal amplified by the amplifier 21 and removes an unnecessary frequency band signal included in the eddy current signal. The comparator 27 pulses the waveform after the filter which has passed through the variable BPF 26. The pulsed trigger waveform is output to the output circuit 22 of the amplifier unit 18.

When a pulse output proportional to the flow rate is obtained, the frequency (also called the vortex frequency) occurring in the Karman vortex can be detected. The vortex frequency is proportional to the flow velocity, and the relationship is as follows.

f = StV / d

f is the vortex frequency, V is the average flow velocity of the fluid, d is the width of the vortex generator, and St is the Strouhal number (constant). The number of throwholes varies with the Reynolds number (the value that determines the state of flow), but becomes nearly constant over a wide range of Reynolds numbers.

Therefore, it can be seen that the vortex frequency f is proportional to the average flow rate V in a range where the number of straw holes is constant. In addition, since the width d of the vortex generator is known, the average flow velocity V in the measurement tube can be obtained by detecting the vortex frequency f. Here, the output circuit 22 calculates the flow rate (volume flow rate) by multiplying the average flow rate V by the cross-sectional area of the measuring tube, and outputs it to the flow rate indicator 16 or the like.

Here, in the transducer 10 as described above, when the eddy current frequency is detected, the eddy current output from the eddy current detection sensor 7 is amplified by the amplifier 21 and then passed through the variable BPF 26 to unnecessary frequency bands. Eliminating the signal.

FIG. 4 is a configuration diagram of the variable BPF of FIG. 3. The variable BPF 26 includes a first BPF 30, a selection processor 31, a second BPF 32, a comparator 33, and a signal processor 34. Consists of. In addition, the 1st BPF 30 is corresponded to the bandpass filter of this invention, and the selection processing part 31 is corresponded to the filter selection part of this invention.

The second BPF 32 has a wider passband than the first BPF 30, and passes the eddy current signal amplified by the amplifier 21 described with reference to FIG. 3. The comparator 33 pulses the eddy current signal passing through the second BPF 32. This pulse signal is output to the signal processor 34.

The signal processing unit 34 includes, for example, a frequency measuring unit 34a and a frequency analyzing unit 34b, and the frequency measuring unit 34a measures the vortex frequency from the pulse signal obtained by the comparator 33 within a predetermined time. In addition, you may count the number of pulse signals instead of the measurement of predetermined time.

5 is a diagram for explaining measurement of the eddy current frequency. In the comparator 33 of FIG. 4, the eddy current signal S which passed the 2nd BPF 32 and the predetermined amplitude value (trigger level) T are compared and pulsed, and this trigger level T is exceeded. One eddy current signal S is counted as a pulse.

As shown in FIG. 5, when the eddy current S continuously exceeds the trigger level T, the comparator 33 of FIG. 4 obtains a continuous pulse that does not miss (drop) the peak. Therefore, in the frequency measuring part 34a, the vortex frequency f1, f2, etc. corresponding to the space | interval (period) of the adjacent peak are measured. In addition, when the vortex signal S exceeds the trigger level T in the state in which one peak is missing, a slightly longer pulse is obtained, so that the vortex frequency f3 or the like is measured. In addition, when the vortex signal S exceeds the trigger level T in a state in which two peaks are omitted, a longer pulse is obtained and measured as the vortex frequency f4.

Next, this measurement result is output to the frequency analysis part 34b of FIG. The frequency analyzer 34b calculates the vortex frequency of the highest frequency among the vortex frequencies measured by the frequency measuring unit 34a.

It is a figure explaining the analysis of a vortex frequency. The frequency measurement part 34a of FIG. 4 shows the vortex frequency and the number thereof, for example, 10 50 Hz, 4 90 Hz, 20 100 Hz, 5 110 Hz, 1 120 Hz, When it is measured that 200 Hz is one, the frequency analyzer 34b creates a histogram, for example, and calculates the vortex frequency of the highest frequency detected at the highest frequency among the vortex frequencies within a predetermined time. That is, in the case of FIG. 6, since 20 are the most, the frequency analyzer 34b determines 100 Hz as the vortex frequency of the highest frequency.

In addition, when the flow rate of the fluid under measurement is small, eddy current signals (also referred to as missing pulses) that do not reach the trigger level increase. By this effect, the average value of the Kalman vortex frequency similar to the conventional one becomes small. Specifically, as described above, the vortex frequency and the number thereof are 10 at 50 Hz, 4 at 90 Hz, 20 at 100 Hz, 5 at 110 Hz, 1 at 120 Hz, and 1 at 200 Hz. In the case of measurement, the average value of the vortex frequency is 90.98 Hz.

Subsequently, as shown in FIG. 4, the calculation result of the frequency analyzer 34b is output to the selection processor 31. The selection processing unit 31 selects a signal passing through the filter corresponding to the vortex frequency of the highest frequency among the plurality of band pass filters set in the first BPF 30. As a result, the eddy current signal output from the eddy current detection sensor and amplified by the amplifier passes through only the filter selected by the selection processor 31 to remove noise, and then outputs toward the comparator 27 described with reference to FIG. 3.

FIG. 7 is a view for explaining waveform data (flow signal, for example 400 Hz) of the comparative example, FIG. 7 (A) is a waveform after filter passing through the variable BPF of FIG. 3, and FIG. 7 (B) is shown in FIG. The trigger waveform of the comparator.

For example, when the ambient temperature of the vortex detection sensor or the temperature of the fluid under measurement is low, the sensitivity of the vortex detection sensor is lowered and the amplitude of the vortex signal is reduced. In this case, since the filter selected from the average value of the conventional Karman vortex frequency is influenced by the deviation value such as 50 Hz or 200 Hz in the flow rate example of FIG. 6, the waveform after the filter is shown in FIG. If the peak interval or amplitude becomes uneven and the waveform is pulsed, the pulse is not pulsed as the signal or the signal is not pulsed as the noise. Therefore, as shown in FIG. This is uneven.

In this case, in order to increase the sensitivity of the vortex detection sensor, the worker goes out to the installation site of the vortex flowmeter and manually increases the drive voltage of the vortex detection sensor. However, since the noise of the electric signal increases and the vortex signal which reaches the trigger level increases, the average value of the Karman vortex frequency tends to increase.

On the other hand, even when the ambient temperature of the vortex detection sensor or the like is low, an appropriate band pass filter can be selected by using the vortex frequency of the highest frequency.

In detail, FIG. 8 is a diagram illustrating waveform data (flow signal, for example 400 Hz) of the present embodiment, and the filter corresponding to the vortex frequency (400 Hz) of the highest frequency from the vortex frequency and the number as described above is shown. When the selection is made, it is not affected by the deviation value as in the case of the selection based on the average value of the vortex frequency, so that the post-filter waveform has an even peak interval and amplitude as shown in Fig. 8A. When the waveform is pulsed, it becomes difficult to pulse the signal and, conversely, to pulse the noise, so that the trigger waveform has an even interval and amplitude as shown in Fig. 8B. As a result, as shown in Fig. 8C in which a filter corresponding to the vortex frequency of the highest frequency is selected, it can be seen that each frequency of the output pulses gathers around about 400 Hz, so that the effect of missing pulses is not seen.

In this way, by using the most frequent vortex frequency, an appropriate band pass filter can be selected, and noise is not mixed in the output pulse.

When the filter is selected from the vortex frequency of the highest frequency, the number of samples of the signal is at least as compared with the case of selecting from the average value of the vortex frequency, so that the filter can be selected quickly. In detail, in the case of selecting from the average value as in the related art, since the selection of the filter requires about 300 ms, in the present embodiment, the selection can be made in 50 ms, so that the response speed of the filter selection is improved.

9 is a configuration diagram of a variable BPF according to another embodiment. In the said embodiment, it demonstrated and gave the example which mechanically switches the said filter. However, as shown in Fig. 9, the first BPF 40 may be a digital filter using software or the like. In this case, when the selection processor 41 selects a filter corresponding to the vortex frequency of the highest frequency, the first BPF 40 sets a parameter for changing the frequency characteristic, and the filter corresponding to the vortex frequency of the highest frequency is provided. Is selected. This makes it possible to reliably remove an unnecessary frequency band signal.

1: detector
2: measuring tube
3: vortex generator
5: mounting bin
7: vortex detection sensor
10: converter
15: control unit
16: flow indicator
17: Communication I / F
18: amplifier section
19: filter part
20: constant current circuit
21: amplifier
22: output circuit
26: variable BPF
27, 33: comparator
30, 40: first BPF
31, 41: selection processing unit
32: second BPF
34: signal processor
34a: frequency measurement unit
34b: frequency analyzer

Claims (2)

A vortex flowmeter having a sensor for detecting Karman vortex generated in the vortex generator and a transducer for outputting a flow rate of the fluid under measurement based on a signal output from the sensor,
The transducer calculates a vortex frequency based on a band pass filter for removing an unnecessary frequency band signal included in a signal output from the sensor, and an interval of a pulse signal that pulses the signal output from the sensor. A signal processing unit for obtaining a vortex frequency detected at the highest frequency among the vortex frequencies, and a filter selection unit for selecting the band pass filter based on the vortex frequency detected at the highest frequency, and selecting the signal output from the sensor. A vortex flow meter which passes through a band pass filter to remove an unnecessary frequency signal. The method of claim 1,
Vortex flowmeter, characterized in that the band pass filter is a digital filter.

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