JPH10239123A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter that can be corrected in temperature and can be improved in measuring accuracy. SOLUTION: The ultrasonic flowmeter is provided with an arithmetic device 11, which finds the temperature of an ultrasonic sensor 5 by collating the measured data of an impedance measuring instrument 9 and a gain measuring instrument 12 with the data stored in a gain/frequency data storing circuit 13 and adjusts the frequency of a pulse impressed upon an ultrasonic transmitter 3 based on the temperature data. Since the sensor 5 fulfills the function of the conventional temperature sensor, no separate temperature sensor is required. Therefore, the measuring accuracy of the flowmeter can be improved, because the change in the flow of a fluid, which may occur when a temperature sensor is provided in a pipe 1 does not occur. Since the number of parts becomes smaller and no temperature sensor is required in the pipe 1, the structure of the flowmeter is simplified and, in its turn, the cost of the flowmeter can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring a flow rate of a fluid.

[0002]

2. Description of the Related Art An example of a conventional ultrasonic flowmeter is shown in FIG. In the figure, a vortex generating column 2 is provided in a pipe 1 through which a fluid flows.
Are provided to alternately generate Karman vortices on both sides. The tube 1 is provided with an ultrasonic sensor 5 composed of ultrasonic transmitters / receivers 3 and 4. The ultrasonic transmitters / receivers 3 and 4 are attached to the wall of the tube 1 so as to face each other with a vortex generating region in the tube 1 therebetween.

The ultrasonic transmitter 3 includes the ultrasonic transmitter 3
Is connected to a pulse generator 6 for applying a pulse of a predetermined frequency to transmit ultrasonic waves. A flow detection circuit (not shown) is provided so as to be connected to the pulse signal output side of the pulse generator 6 and the ultrasonic receiver 4. The flow rate detection circuit obtains the generation cycle of the Karman vortex, and thus the flow rate of the fluid, based on the change in the ultrasonic wave propagation characteristics between the ultrasonic wave transmitter / receivers 3 and 4.

[0004] When the temperature of the fluid changes, the volume of the fluid, the ultrasonic wave propagation speed, and the like change. Therefore, in order to perform accurate flow rate measurement, it is necessary to perform correction in consideration of a change in the volume of the fluid due to a temperature change and a change in the ultrasonic wave propagation velocity.

The ultrasonic flowmeter shown in FIG. 7 is provided with a temperature sensor 7 on the inner peripheral side of the pipe 1 and connected to the temperature sensor 7 and the pulse generator 6 in order to achieve the above-mentioned correction in consideration of the temperature change. Thus, a temperature correction circuit 8 is provided. The output signal of the temperature sensor 7 is supplied to a temperature compensating circuit 8,
Calculates fluid temperature data from the supplied signal. The temperature correction circuit 8 obtains a correction signal based on the temperature data, outputs the correction signal to the pulse generator 6, adjusts the frequency of the pulse applied to the ultrasonic transmitter 3, and adjusts the reception level of the ultrasonic receiver 4 to a desired value. In this way, good measurement data is obtained.

[0006]

In the above-mentioned prior art, since the temperature sensor 7 is provided on the inner peripheral side of the pipe 1, the flow of the fluid is disturbed by the temperature sensor 7, so that the Karman vortex is generated. Affecting the occurrence of
There was a risk of an error in flow measurement.

The present invention has been made in view of the above circumstances, and has as its object to provide an ultrasonic flowmeter capable of performing temperature correction and improving measurement accuracy.

[0008]

According to the present invention, there is provided an ultrasonic sensor comprising an ultrasonic transmitter / receiver disposed in a pipe through which a fluid to be measured flows and transmitting and receiving ultrasonic waves via the fluid to be measured, and the ultrasonic sensor. Pulse generation means for exciting the ultrasonic transmitter to generate ultrasonic waves by applying a pulse of a predetermined frequency set in advance to the transmitter, and the propagation characteristics of the ultrasonic waves received by the ultrasonic receiver A flow rate detecting means for detecting a flow rate of the fluid to be measured based on the measured value; an impedance measuring means for measuring an impedance of the ultrasonic sensor; a transmission gain measuring means for measuring a transmission gain of the ultrasonic sensor; and a temperature parameter. Impedance-frequency data storage means for storing impedance-frequency data of the ultrasonic sensor, and the ultrasonic sensor using temperature as a parameter. Gain-frequency data storage means for storing transmission gain-frequency data of the sensor; first temperature calculating means for obtaining a temperature from the impedance-frequency data based on the impedance measured by the impedance measuring means; A second temperature calculation unit that obtains a temperature from the calculation result of the first temperature calculation unit and the transmission gain-frequency data based on the transmission gain measured by the transmission gain measurement unit; and the first or the second,
Pulse adjusting means for adjusting the frequency of the pulse generated by the pulse generating means based on the temperature obtained by the second temperature calculating means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic flow meter according to an embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, inside a pipe 1 through which a fluid flows,
A vortex generating column 2 is provided to alternately generate Karman vortices on both sides. The tube 1 is provided with an ultrasonic sensor 5 composed of ultrasonic transmitters / receivers 3 and 4. The ultrasonic transmitters / receivers 3 and 4 are attached to the tube 1 so as to face each other with a vortex generating region in the tube 1 therebetween.

The ultrasonic transmitter 3 includes the ultrasonic transmitter 3
Is connected to a pulse generator 6 for applying a pulse of a predetermined frequency to transmit ultrasonic waves. A flow detection circuit (not shown) as flow detection means is connected to the pulse signal output side of the pulse generator 6 and the ultrasonic receiver 4. The flow rate detection circuit obtains the generation cycle of the Karman vortex, and thus the flow rate of the fluid, based on the change in the ultrasonic wave propagation characteristics between the ultrasonic wave transmitter / receivers 3 and 4. Pulse generator 6 (pulse generation means)
An impedance measuring device 9 (impedance measuring means) is provided between the ultrasonic transmitter 3 and the ultrasonic transmitter 3 so that a pulse signal from the pulse generator 6 can be supplied to the ultrasonic transmitter 3. The impedance measuring device 9 calculates the voltage value and the current value of the pulse signal from the pulse generator 6 and measures the impedance of the ultrasonic sensor 5.

The pulse generator 6 excites the ultrasonic transmitter 3 by applying a pulse of a predetermined frequency to the ultrasonic transmitter 3 to emit ultrasonic waves. Impedance measuring instrument 9
A gain measuring device (transmission gain measuring means) 10 is provided so as to be connected to the pulse output side and the ultrasonic receiver 4. The gain measuring device 10 compares the amplitude of the pulse applied to the ultrasonic transmitter 3 with the amplitude of the ultrasonic wave (pulse) received by the ultrasonic receiver 4, and determines the transmission gain of the ultrasonic wave transmitted through the fluid. Is measured.

A pulse generator 6, an impedance measuring device 9
And an arithmetic unit 11 connected to the gain measuring device 10. The arithmetic unit 11 is connected to the ultrasonic transmitters / receivers 3 and 4, and generates a Karman vortex generation cycle based on a change in the ultrasonic wave propagation characteristics between the ultrasonic transmitters / receivers 3 and 4, and furthermore, the flow rate of the fluid. Is obtained, and constitutes a flow rate detecting means. The arithmetic unit 11 further includes an impedance-frequency data storage circuit (impedance-frequency data storage circuit).
A frequency data storage means) 12, a gain-frequency data storage circuit (gain-frequency data storage means) 13, a corresponding data storage circuit 14, and an output circuit 15 are connected.

Impedance-frequency data storage circuit 1
2 is a plurality of impedances using temperature as a parameter.
Curve K ₁₀ to frequency data (described _{later, K 20, K 22, K} 29
... etc.) are stored. Gain-frequency data storage circuit 1
Reference numeral 3 stores a plurality of transmission gain-frequency data using temperature as a parameter (curves J ₁₅ , J ₂₀ , J ₂₄ ... Described later). The output circuit 15 obtains the temperature of the fluid from the input measured temperature t, and outputs the temperature data of the fluid to a display or a printer (not shown).

Here, the impedance-frequency data and the transmission gain-frequency data of the ultrasonic sensor 5 will be described. First, impedance-frequency data of the ultrasonic sensor 5 will be described with reference to FIGS.
For example the relationship between the impedance and the frequency of the ultrasonic sensor 5 at a temperature t _20, the horizontal axis frequency f, expressed by the impedance Z on the vertical axis, a curve K ₂₀ as shown in FIG. The curve K ₂₀ becomes maximum at minimum at the portion corresponding to the resonance frequency f ₂₀ (resonance point) (impedance Z _r), and the portion of the frequency of large value than the resonance frequency f ₂₀ (anti-resonance point) .

[0016] The resonance frequency f ₂₀ the following portion of the frequency of the curve K ₂₀ (below,. Hereinafter referred to as partial resonance frequency) K ₂₀ a is,
Impedance (hereinafter referred to as saturation impedance.) With a decrease in frequency increasing returns to saturate the Z _S. Part from the resonance point of the curve K ₂₀ to the anti-resonance point (resonance point - anti-resonance point between the portions) K ₂₀ b is increased rapidly with increasing frequency, the impedance of the anti-resonance point impedance Z
_The value greatly exceeds _S. In addition, the portion K ₂₀ c above the frequency of the anti-resonance point gradually decreases as the frequency increases so as to converge to a predetermined value that greatly exceeds the impedance Z _S. A difference (hereinafter referred to as an impedance reference change amount) ΔZ _H obtained by subtracting the impedance Z _r at the resonance point from the saturation impedance Z _S is a constant value (for example, 5
00 Ω).

The shape of the curve of the impedance-frequency data of the ultrasonic sensor 5 is constant irrespective of the temperature change, drifts (transitions) with respect to the frequency according to the temperature change, and the drift rate is constant ([ It is known that (frequency change amount) / [temperature change amount] = constant). For example, as shown in FIG. 5, the impedance at compared to low temperature _{t 10 (t 10 <t 20} ) to a temperature t ₂₀ - curve K ₁₀ frequency data, the curve K ₂₀ to the right (frequency increase direction ) Drifted. That is,
The portion K ₂₀ a below the resonance frequency of the curve K _20, the portion K ₂₀ b between the resonance point and the anti-resonance point, the portion K ₁₀ a below the resonance frequency of the curve K ₁₀ corresponding to the portion K ₂₀ c above the frequency of the anti-resonance point, The portion K ₁₀ b between the resonance point and the anti-resonance point, and the portion K ₁₀ c at or above the frequency of the anti-resonance point are drifted toward the higher frequency. Similarly, drift minimum point (resonance point), the resonance frequency f ₁₀ of the ultrasonic sensor 5 (curve K ₁₀₎ at a temperature t _10, the resonance frequency of the ultrasonic sensor 5 (curve K ₂₀₎ at a temperature t ₂₀ It is larger than the _{f 20 (f 10> f 20} ). By curve K ₁₀ is obtained by drifting the curve K ₂₀ to the right, the value of the impedance of the minimum point of the curve K ₁₀ (resonance point) is adapted to the impedance Z _r.
The curve K ₂₉ in the curve K ₂₂ or t ₂₉ at high temperatures t ₂₂ than the temperature _{t 20 (t 22> t 20} ) (t 29> t 22) is obtained by drifting the temperature curve K ₂₀ to the left Becomes

As described above, when the temperatures are t ₂₉ , t ₂₂ ,
As the temperature decreases as t ₂₀ and t ₁₀ , the corresponding curves K ₂₉ , K ₂₂ , K ₂₀ and K ₁₀ will be shown drifting to the right as shown in FIG. As indicated by a rightward arrow. Further, when the temperatures are t ₁₀ , t ₂₀ , t
₂₂ and t ₂₉ , the corresponding curve K ₁₀ ,
K ₂₀ , K ₂₂ , and K ₂₉ are shown drifting to the left as shown in FIG. 5 and are indicated by leftward arrows as “temperature increasing directions”.

The curve of the impedance-frequency data is
It is shown as drifting rightward or leftward as shown in FIG. 5 with the temperature change, but the drift ratio ([frequency change amount] / [temperature change amount]) is constant. For example, the resonance frequency _{f 29, f 22, f 20} , f 10 corresponding to the common value Z _r on each curve _{K 29, K 22, K 20} , K 10 as an example, [f ₂₉ -f _22] / [ t ₂₉ −t ₂₂ ] = [f ₂₂ −
f _20] / [t ₂₂ -t _20] = [f ₂₀ -f _10] / [t ₂₀ -t
₁₀ ] = constant. Impedance Z Similarly drift rate to that also described above for frequencies corresponding to another impedance value other than _r ([frequency variation) / (temperature change amount]) = is constant.

Since the impedance Z and the frequency f are in a correspondence relationship as shown in FIG. 5 using the temperature as a parameter, the impedance change ΔZ and the temperature change Δt
Has a certain correspondence. Then, ΔZ-Δt correspondence data indicating this correspondence relationship is stored in the correspondence data storage circuit 14. Here, the impedance variation ΔZ is measured this time when the impedance Z _n and the difference between the impedance Z _n-1 of the previous measurement _{(Z n -Z n-1)} . As will be described later, a pulse is transmitted at the resonance frequency at the temperature determined by the previous measurement to determine the impedance at that time. When the impedance Z is less than the saturation impedance Z _S , the corresponding curve is the temperature rising direction side. On the other hand, two curves on the temperature decreasing side [one curve corresponds to a portion below the resonance frequency, and the other curve corresponds to a portion between the resonance point and the anti-resonance point. ], It is not possible to specify the curve corresponding to the resonance frequency only with FIG. To deal with this, the impedance change Δ
[Delta] Z-Delta] t indicated Z and temperature variation Delta] t _d of the temperature lowering direction, the correspondence between the amount of temperature change Delta] t _u each temperature rise direction
_u and Δt _d corresponding data are obtained in advance, and the corresponding data is stored in the corresponding data storage circuit 14.

Note that Δt used in step S15 described later
_{u, Δt d -ΔG u, ΔG} d corresponding data, the temperature drop direction of temperature change Delta] t _d, the gain variation .DELTA.G of temperature decrease direction is determined in advance in correspondence with the temperature variation Delta] t _u temperature rise direction _d , the gain change amount ΔG _{u in the} temperature rising direction
, And the the corresponding data [Delta] Z-Delta] t corresponding data and [Delta] Z-Delta] t _u described above, with Delta] t _d corresponding data are stored in the corresponding data storage circuit 14.

Next, transmission gain-frequency data of the ultrasonic sensor 5 will be described with reference to FIG. For example the correspondence between the transmission gain and the frequency of the ultrasonic sensor 5 at a temperature t _20, the horizontal axis frequency f, expressed by the gain G (dB) on the vertical axis, the convex upward as shown in FIG. 6 a curve J _20. The curve J ₂₀ becomes maximum (maximum gain) at the portion corresponding to the resonance frequency f ₂₀ (resonance point). The curve J ₂₀
Vary greatly in the way of change with the resonance point as a boundary.

[0023] That is, part of the resonance frequency f ₂₀ is smaller than the frequency (hereinafter, referred to as a small frequency portion.) In J ₂₀ a,
The gain G tends to sharply decrease as the frequency decreases. The portion of the resonance frequency f ₂₀ is larger than the frequency (hereinafter, the large frequency portion of.) J ₂₀ b, at a portion close to the resonance point, and the gain G is diminishing with increasing frequency, further partial frequency is large, The gain G tends to sharply decrease as the frequency increases.

The shape of the curve of the transmission gain-frequency data of the ultrasonic sensor 5 is constant irrespective of the temperature change, and drifts (transitions) with respect to the frequency according to the temperature change.
And the drift ratio is constant ([frequency change amount]
/ [Temperature change amount] = constant).

For example, as shown in FIG. 6, the curve J ₁₅ of the transfer gain-frequency data at the temperature t ₁₅ (t ₁₅ <t ₂₀ ) lower than the temperature t ₂₀ has the curve J ₂₀ on the right side (frequency (In the direction in which becomes larger). That is, a small frequency portion J ₂₀ a curve J _20, a large frequency portion J ₂₀
Small frequency portion J ₁₅ a curve J ₁₅ corresponding to b, a large frequency portion J ₁₅ b drifts towards frequency is large (Fig. 6 right side), the ultrasonic sensor 5 at a temperature t ₁₅ (curve J ₁₅₎ The resonance frequency f ₁₅ is determined by the ultrasonic sensor 5 at the temperature t ₂₀ .
(F ₂₀ ) which is larger than the resonance frequency f ₂₀ (curve J ₂₀ ).
_15> f _20). Similarly, the resonance point of the curve J _20, drift in Figure 6 the right direction, the curve J _20, the gain of each curve J ₁₅ is in the same gain value G _r.

The temperature t ₂₄ (t is higher than the temperature t ₂₀ )
₂₄ > t ₂₀ ) Transfer gain-frequency data curve J ₂₄
Is a curve J ₂₀ (in the direction in which the frequency is decreased) on the left side those drift. That is, a small frequency portion J ₂₀ a curve J _20, a small frequency portion J ₂₄ a curve J ₂₄ corresponding to the large frequency portion J ₂₀ b, a large frequency portion J ₂₄ b has better frequency is small (Fig. 6 right side) drift to the resonance frequency f ₂₄ of the ultrasonic sensor 5 (curve J ₂₄₎ at a temperature t ₂₄ is smaller than the resonance frequency f ₂₀ of the ultrasonic sensor 5 (curve J ₂₀₎ at a temperature t ₂₀ (f ₂₄ <f _20). Similarly, the resonance point of the curve J ₂₄ also drifts 6 leftward, the gain of the curves J ₂₄ is curve J _20, has a curved J ₁₅ gain value G _r equivalent to the respective gains.

As mentioned above, the temperatures t ₂₄ , t ₂₀ , t ₁₅
, The corresponding curves J ₂₄ , J ₂₀ , J
₁₅ is drifted to the right side as shown in FIG. 6 and is indicated by a rightward arrow as the “temperature decreasing direction”. In addition, as the temperature increases as t ₁₅ , t ₂₀ , and t ₂₄ , the corresponding curves J ₁₅ , J ₂₀ , and J ₂₄ drift to the left as shown in FIG. This is indicated by a leftward arrow as the "temperature increasing direction".

The curve of the transmission gain-frequency data is shown as drifting rightward or leftward as shown in FIG. 6 with the temperature change. The drift ratio ([frequency change amount] / [temperature change] Amount)) is constant.
For example, the resonance frequency f _24, f _20, f ₁₅ corresponding to the common values G _r in each curve J _24, J _20, J ₁₅ as an example, [f ₂₄ -
f _20] / [t ₂₄ -t _20] = [f ₂₀ -f _15] / [t ₂₀ -t
₁₅ ] = constant. Similarly drift rate to that also described above for the frequency corresponding to the other transmission gain values other than transmission gain G _r ([frequency variation) / (amount of temperature change]) is constant.

The arithmetic unit 11 uses the measurement data of the impedance measurement device 9, the measurement data of the gain measurement device 10, the data stored in the corresponding data storage circuit 14, and the data of FIGS. 2 and 3) to determine the temperature of the ultrasonic sensor 5 affected by the temperature of the fluid. Further, the arithmetic unit 11 adjusts the frequency of the pulse applied to the ultrasonic transmitter 3 based on the temperature data (step S13). In this case, the frequency of the pulse is set to the same magnitude as the resonance frequency of the ultrasonic sensor 5 at the determined temperature, so that the ultrasonic transmitter 3 is surely resonated and emits ultrasonic waves well. I have to.

Next, the contents of the arithmetic processing of the arithmetic unit 11 are shown in FIG.
And the flowchart of FIG. First,
In step S1, the number of measurements N is set to "0", and in the next step S2
Add “1” to the number of measurements N. In the following step S3, it is determined whether or not the number of measurements N is 1 (N = 1?).

If YES is determined in the step S3, the step
Proceeding to S4, if it is determined to be NO (it is determined to be NO in the second and subsequent measurements), the process proceeds to step S5 to perform processing. In step S4, the temperature t _(n-1) at the previous measurement is set to 20 ° C., and the temperature t _(n) (hereinafter, referred to as “step S11” ₎ in step S11 described below.
Compared to the temperature t _(n-1) at the previous measurement, for convenience,
It is referred to as the temperature t _(n) at the time of the current measurement at the time of the previous measurement. )
In addition to coping with the calculation, the resonance frequency f
Set _(n-1) = f _20, the resonance frequency f at step S12 with the pulses originating at the next step S6 _(n) (hereinafter, in contrast to the resonance frequency f of the previous measurement _(n-1) For convenience, the current resonance frequency f _(n) at the previous measurement
That. ) I am trying to deal with the calculation.

In step S5, the temperature t _(n-1) at the previous measurement at the current measurement and the resonance frequency at the previous measurement are set so that the "current" at the previous measurement becomes the "previous" at the current measurement. f _(n-1) is set, and the processing in steps S11 and S6 described later is dealt with. Step S4 or Step S5
After the processing of ₍₁₎ , a pulse is transmitted at the resonance frequency f _(n-1) at the time of the previous ((N-1) times) measurement (step S6). In step S6 after step S4 processing, the resonance frequency f _(n-1) in the previous measurement is f _20, as described above.

Next, the impedance Z _(n) of the ultrasonic sensor 5 measured by the impedance measuring device 9 is input (step S7). In step S8 following step S7, the amount of change in impedance ΔZ is determined by the following equation (1). ΔZ = Z _(n) -Z _(n-1) ... (1) Z _(n) ; impedance at the time of this measurement Z _(n-1) ; impedance at the time of the previous measurement

In the next step S9, it is determined whether or not the impedance Z _(n) at the time of the current measurement is _{equal to} or higher than the saturation impedance Z _S. If YES is determined in the step S9, the step
On the other hand, if NO is determined while performing the processing of S10 to step S13, the process proceeds to step S14 to perform the processing. Step S10
In step S8, the impedance change amount ΔZ obtained in step S8 is compared with the ΔZ-Δt corresponding data in the corresponding data storage circuit 14, and the corresponding temperature change amount Δt is read.

Then, in step S11 (first temperature calculating means), the temperature change amount Δt is calculated based on the temperature t at the time of the previous measurement.
_{(n-1) In} addition to (Step S4 or Step S5), the temperature t _(n) at the time of the current measurement is obtained. In the next step S12, the resonance frequency f _(n) corresponding to the temperature t _(n) at the time of the current measurement (FIG.
) From the impedance-frequency storage circuit 12. In step S13 following step S11, the pulse generation frequency of the pulse generator 6 is corrected to f _(n) , and the corrected f
_{In (n)} , an ultrasonic pulse is transmitted so that the flow rate can be measured. When step S13 ends, the process returns to step S2 so that a new temperature change can be dealt with.

If the determination in step S9 is NO, the process proceeds to step S14 as described above. However, the determination in step NO is as follows. That is, when the impedance Z _(n) is less than the saturation impedance Z _S is the impedance - of the frequency curve, the resonance point - between antiresonance point portion (e.g. K ₁₀ b) not only the resonant frequency following moieties (e.g. K ₁₀ a) is a target, and the temperature change Δt in step S10 cannot be obtained only from the characteristic (impedance-frequency characteristic) in FIG. And step
In order to obtain the temperature change Δt of S10, the following step S14
Alternatively, the processing of step S22 is performed. As shown in FIG.
In step S14, the impedance change amount ΔZ obtained in step S8 is stored in the corresponding data storage circuit
-Δt _u and Δt _d are matched with corresponding data, and the corresponding Δt
_u and Δt _d are read.

Subsequently, Δt read in step S14
_u and Δt _d in the corresponding data storage circuit 14 as Δt _u and Δt _d
-DerutaG _u, by collating the .DELTA.G _d corresponding data, reads the gain variation .DELTA.G _u of the corresponding gain variation in the temperature lowering direction .DELTA.G _d and temperature rise direction. In the next step S16, the gain G measured by the gain measuring device 10 is input. Subsequently, the gain change amount ΔG is obtained by the following equation (2) (step S17).

ΔG = G _(n) −G _(n-1) (2) G _(n) ; gain at the time of this measurement G _(n-1) ; gain at the time of the previous measurement

In step S18 following step S17, it is determined whether or not the gain change ΔG is equal to the gain change ΔG _u in the temperature increasing direction. A determination is made as to whether or not the gain variation ΔG _d in the decreasing direction matches (step S19). If YES is determined in the step S18, the temperature change amount Δt _d in the temperature decreasing direction is set to the temperature change amount Δt in a step S20, and the process returns to the step S11 in FIG. Also step
If it is determined YES in S19, performs the process returns to step S11 in FIG. 2 the process by setting the temperature variation Delta] t _u temperature rise direction variation in temperature Delta] t at step S21. Step S19
If NO is determined in step S22, it is notified that an error has occurred due to an alarm (not shown) (step S22).
). In the present embodiment, steps S14 to S21 and step S11 constitute a second temperature calculating means, and step S13 constitutes a pulse adjusting means.

In the ultrasonic flowmeter configured as described above, the measurement data of the impedance measuring device 9 and the gain measuring device 10 are compared with the impedance-frequency data of FIG. 5 and the gain-frequency data of FIG. and obtains the temperature change amount Δt corresponding to a difference between the temperature that was last measured, the temperature change amount Δt temperature t of the previous measurement _(n-1) in addition to this at the time of measurement temperature t _(n) Is obtained (step S11), and the pulse generation frequency of the pulse generator 6 is corrected to f _(n) so that a pulse is generated at a frequency equal to the resonance frequency corresponding to the temperature t _(n) at the time of the current measurement (step S13). . For this reason, it is possible to reliably resonate the ultrasonic transmitter 3 and transmit a good ultrasonic wave. Further, in the above embodiment, the fact that an error state has occurred in step S22 is notified, so that the ultrasonic transmitter / receiver 3,
Since it can be determined that normal transmission / reception of ultrasonic waves is not performed between the four, it can be understood that there is an abnormality such as a failure of the ultrasonic sensor 5 or mixing of air bubbles into the tube 1.

As described above, since the ultrasonic sensor 5 fulfills the function of the temperature sensor used in the prior art, it is not necessary to separately provide the temperature sensor. For this reason, tube 1
The measurement accuracy can be improved without causing a change in the flow of the fluid which may occur by providing the temperature sensor in the inside. In addition, since the number of components is reduced and the temperature sensor is not provided in the pipe 1, the structure of the device can be simplified, and the cost of the device can be reduced.

In the above embodiment, an ultrasonic flowmeter for measuring the flow rate of a fluid by providing a vortex generator has been described as an example. However, the present invention is not limited to this, and the propagation speed of the ultrasonic wave may vary from upstream to downstream. An ultrasonic flowmeter configured to measure the flow rate of a fluid without providing a vortex generator may be used by utilizing a difference between the case of going to the upstream and the case of going from the downstream to the upstream.

[0043]

According to the present invention, since the ultrasonic sensor performs the function of the temperature sensor used in the prior art, it is not necessary to separately provide the temperature sensor. For this reason, it is possible to improve the measurement accuracy without causing a change in the flow of the fluid that may occur when the temperature sensor is provided in the pipe. Further, since the number of parts is reduced and the temperature sensor is not provided in the pipe, the structure of the apparatus is simplified, and the apparatus can be reduced in cost.

It is possible to measure the temperature of the ultrasonic sensor, which changes with the change of the fluid temperature, and obtain the resonance frequency corresponding to the temperature of the ultrasonic sensor.
The pulse generation frequency of the pulse generation means can be optimized with respect to the change in the resonance frequency due to the temperature change, and the reception level can be increased to improve the flow rate measurement accuracy.

It is possible to determine the fluid temperature from the temperature measurement value of the ultrasonic sensor and display the temperature of the fluid on a display or to print out the fluid temperature. Can be quickly dealt with when there is a large change in

Further, since the ultrasonic flowmeter is a volume flowmeter, it is necessary to convert the flow rate in accordance with the fluid temperature. For this flow rate conversion, the fluid temperature obtained from the measured temperature of the ultrasonic sensor is used. Therefore, it is not necessary to newly provide a means for measuring the fluid temperature for flow rate conversion.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an ultrasonic flowmeter according to one embodiment of the present invention.

FIG. 2 is a part of a flowchart showing processing contents of an arithmetic unit of the ultrasonic flowmeter.

FIG. 3 is a flowchart that follows step S9 of the flowchart in FIG. 2;

FIG. 4 is a diagram showing impedance-frequency characteristics of an ultrasonic sensor of the ultrasonic flow meter.

FIG. 5 is a diagram showing a plurality of impedance-frequency characteristics using temperature as a parameter.

FIG. 6 is a diagram showing a transmission gain-frequency characteristic of an ultrasonic sensor of the ultrasonic flowmeter.

FIG. 7 is a diagram schematically showing an example of a conventional ultrasonic flowmeter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 tube 3 ultrasonic transmitter 4 ultrasonic receiver 5 ultrasonic sensor 9 impedance measuring device 10 gain measuring device 11 arithmetic unit 12 impedance-frequency data storage circuit 13 gain-frequency data storage circuit

Claims (1)

[Claims] 1. An ultrasonic sensor comprising an ultrasonic transmitter / receiver disposed in a pipe through which a fluid to be measured flows and transmitting and receiving ultrasonic waves via the fluid to be measured, and a predetermined sensor set in the ultrasonic transmitter A pulse generating means for exciting the ultrasonic transmitter by applying a pulse of a frequency to generate ultrasonic waves, and a flow rate of the fluid to be measured based on propagation characteristics of the ultrasonic waves received by the ultrasonic receiver. Flow rate detecting means for detecting the ultrasonic sensor; impedance measuring means for measuring the impedance of the ultrasonic sensor; transmission gain measuring means for measuring the transmission gain of the ultrasonic sensor; impedance of the ultrasonic sensor using temperature as a parameter. Impedance storing frequency data-frequency data storage means, transmission gain of the ultrasonic sensor using temperature as a parameter-
Gain-frequency data storage means for storing frequency data; first temperature calculation means for obtaining a temperature from the impedance-frequency data based on the impedance measured by the impedance measurement means; and transmission gain measurement means A second temperature calculating means for obtaining a temperature from the calculation result of the first temperature calculating means and the transmission gain-frequency data based on the transfer gain measured by the first and second temperature calculating means; An ultrasonic flowmeter, comprising: pulse adjusting means for adjusting the frequency of a pulse generated by the pulse generating means based on the temperature obtained by the means.