JP2002107195A - Flow measurement device - Google Patents

Abstract

(57) [Problem] To provide a delay means having a delay time with higher precision than immediately after the operation since the accuracy of the delay time in repeated measurement directly affects the measurement accuracy. SOLUTION: A delay means 17 operates for a predetermined period of time before a control means 15 sends a measurement start signal prompting a drive signal to a first vibrator 12. This avoids an unstable state in the initial operation of the delay unit 17 at an early stage of operation and starts the measurement after the state is stabilized, so that accurate flow rate measurement can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring the flow rate of a gas or liquid by ultrasonic waves.

[0002]

2. Description of the Related Art As a conventional flow measuring device, a device as shown in FIG. 9 is generally used. The apparatus includes an ultrasonic sensor 2 installed on a measurement path 1 through which a fluid flows, a driving circuit 3 for driving the ultrasonic sensor 2, a control unit 4 for outputting a start signal to the driving circuit 3, and A timer 5 for measuring, an arithmetic unit 6 for receiving measurement data from the timer 5,
An ultrasonic sensor 7 for receiving the ultrasonic wave transmitted from the ultrasonic sensor 2, a variable gain amplifier 9 for amplifying the output of the ultrasonic sensor 7 with an amplification factor according to the output of the gain control circuit 8, and an output of the variable gain amplifier 9 Detection circuit 1 for comparing timer and reference voltage and stopping timer 5 when the magnitude relationship is reversed
0, and a level detection circuit 11 for detecting the output level of the variable gain amplifier 9 and outputting it to the gain control circuit 8.

[0003] In the above ultrasonic current meter, the driving circuit 3 which receives a start signal from the control unit 4 drives the ultrasonic sensor 2 in a pulsed manner for a predetermined time, and at the same time, the timer 5 controls the control unit 4.
Start time measurement by the signal from. Ultrasonic waves are transmitted from the pulse-driven ultrasonic sensor 2. The ultrasonic wave transmitted from the ultrasonic sensor 2 propagates in the fluid to be measured and is received by the ultrasonic sensor 6. The reception output of the ultrasonic sensor 7 is amplified by the variable gain amplifier 9 according to the amplification factor set by the control unit 4. Then, the timing detection circuit 10 receiving the output of the variable gain amplifier 9 determines the reception of the ultrasonic wave and stops the timer 5. Then, the control unit 4 controls the timer 5
Is obtained from the time information t obtained from Equation (1) (the measurement time obtained from the timer 5 is t, the effective distance in the flow direction between the ultrasonic sensors is L, the sound velocity is c, and the flow velocity of the fluid to be measured is v And).

V = (L / t) -c (Equation 1) The timing detection circuit 10 compares a reference voltage with a received signal by a comparator.

[0005] The reception signal has a waveform that rises gently, and the level of the reception signal changes depending on the temperature characteristics and the flow velocity of the ultrasonic sensor. If the reference voltage and the level of the received signal are not appropriate, the operation of the timing detection circuit 10 will not be stable and the measurement accuracy will be poor. Therefore, the level detection circuit 11 receiving the output of the variable gain amplifier 9 monitors the peak level of the input signal, and outputs to the gain control unit 8 when the peak value is small or large. The gain control unit 8 determines the gain of the variable gain amplifier 9 with the level detection circuit 1.
The output of the variable gain amplifier 9 is set so as to be substantially constant in accordance with the signal from No. 1. Then, the next received signal is amplified to a target signal level by the variable gain amplifier 9 and supplied to the timing detection circuit 10. By making the peak of the signal applied to the timing detection circuit 10 substantially constant as described above, the timing for determining the reception time has been stabilized.

As another measurement method, the result of the judgment by the timing detection circuit 10 may be returned to the drive circuit 3 after being delayed by a predetermined time by the delay circuit instead of the timer 5, and then transmitted again. There is also a method of measuring the time by performing such a repetitive operation a predetermined number of times and measuring the time, and calculating the flow velocity by calculation of (Equation 2) based on the measured time (the delay time of the delay circuit is Td, and the number of repetitions is n. , The measurement time is ts,
The effective distance in the flow direction between the ultrasonic sensors is L, the sound speed is c,
Let the flow rate of the fluid to be measured be v).

V = L / (ts / n−Td) −c (Equation 2) According to this method, measurement can be performed with higher accuracy than the method of (Equation 1).

Further, the ultrasonic sensor 2 and the ultrasonic sensor 7 are switched to measure the respective propagation times of the fluid to be measured from upstream to downstream and from downstream to upstream.
(Measurement time from upstream to downstream is t1, and measurement time from downstream to upstream is t2).

V = L / 2 ((1 / t1) − (1 / t2)) (Equation 3) According to this method, the flow rate can be measured without being affected by the change in the speed of sound. Therefore, it is widely used for measuring flow velocity, flow rate, distance, etc.

[0010]

However, the accuracy of the delay time of the delay circuit in the above-mentioned conventional ultrasonic flowmeter directly affects the measurement accuracy. Therefore, the realization of a delay circuit having a highly accurate delay time is an issue. there were.

[0011]

In order to solve the above-mentioned conventional problems, a delay means in a flow rate measuring device according to the present invention delays an output of a timing detection means for determining a reception timing by a predetermined time and outputs a trigger signal of a drive circuit. When the control means outputs a measurement start signal, the control means operates for a predetermined period of time.

In this way, the delay means performs an operation before sending the measurement start signal to perform an unstable operation at the beginning of the operation in advance to be in a stable state, and then measures the delay time. It is possible to improve the measurement with high accuracy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a pair of vibrators arranged in a flow path of a fluid to be measured for transmitting and receiving ultrasonic waves, and driving means for driving one of the vibrators. Control means for outputting a measurement start signal for operating the driving means; timing detecting means for receiving the other transducer output to determine a reception timing; and driving the output of the timing detecting means with a predetermined time delay. Delay means for outputting as a trigger signal of the means, transmission and reception of ultrasonic waves, and repetition means for measuring the number of operations of repeating transmission and reception of ultrasonic waves after the delay operation by the delay means and stopping the operation at a predetermined number of times, A timer for measuring the propagation time of the ultrasonic wave from the driving of the transducer by the driving unit to the stop of the operation of the repetition unit; and And an arithmetic means for calculating the flow velocity of the fluid to be measured between the vibrator by calculation, wherein the delay means is a flow rate measuring device to be operated a predetermined time before the measurement start signal.

Since the delay means performs an operation before sending the measurement start signal and performs an unstable operation at the beginning of the operation in advance to be in a stable state, the measurement is performed, so that the degree of stability of the delay time is good. Therefore, highly accurate measurement can be performed.

The invention described in claim 2 is particularly advantageous in claim 1.
By operating the described delay means for a predetermined time before the measurement start signal according to the number of repetitions set in the repetition means, it is possible to adjust the operation time of the delay means and reduce the change in measurement accuracy with respect to the number of repetitions, Stable and accurate flow measurement can be performed.

[0016] The invention described in claim 3 is particularly advantageous in claim 1.
By operating the delay means described in the above for a predetermined time before the measurement start signal in accordance with the value of the timer means, even if the total repetition time obtained by the timer means changes, the initial operation taking into account the characteristics of the delay means By performing the above, it is possible to realize accurate measurement because the delay means performs a stable operation.

The invention described in claim 4 is particularly advantageous in claim 1.
The delay means described in 1) is operated for a predetermined time before the measurement start signal is output according to the time when the reception timing is detected by the timing detection means after outputting the measurement start signal, and the time per repetition number is determined according to the time per one repetition. By adjusting the operation time of the delay means in advance, it is possible to reduce the dispersion of the delay time due to the heat radiation of the delay means itself and to realize stable measurement.

According to a fifth aspect of the present invention, there is provided switching means for switching and setting the transmission function and the reception function of the two transducers for transmitting and receiving ultrasonic waves. By operating the delay means according to item 1 for a predetermined time before the measurement start signal in accordance with the number of repetitions set in the repetition means, the respective propagation times from upstream to downstream and from downstream to upstream are measured and propagated. When obtaining the flow rate from the time difference, the difference in the initial operation characteristics of the delay means can be reduced, so that the flow rate can be obtained accurately.

According to a sixth aspect of the present invention, there is provided a switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving an ultrasonic wave. By operating the delay means according to claim 1 or 3 for a predetermined time before the measurement start signal in accordance with the value of the timer means, the respective propagation times from upstream to downstream and from downstream to upstream are measured, and the propagation time difference is measured. When obtaining the flow rate, the difference in the initial operation of the delay means can be reduced, and the measurement accuracy can be improved.

According to a seventh aspect of the present invention, there is provided switching means for switching and setting the transmission function and the reception function of the two transducers for transmitting and receiving ultrasonic waves. The switching means is operated by operating the delay means according to claim 1 or 4 for a predetermined time before outputting the measurement start signal and before the measurement start signal in accordance with the time when the reception timing is detected by the timing detection means. In consideration of whether it is before or after, the delay means is operated for a predetermined time immediately before the measurement taking into account the time per repetition and the time before the measurement, so that the difference in the operation of the delay means when calculating the flow rate from the propagation time difference is reduced. And the measurement accuracy can be improved.

The invention according to claim 8 has switching means for switching and setting the transmission function and the reception function of the two transducers for transmitting and receiving ultrasonic waves, and in particular, the switching means for switching the delay means according to claim 1 By operating for a predetermined time before the measurement start signal according to the operation time of the means, it is possible to make the state of the measurement system almost the same when measuring the propagation time difference,
The flow measurement accuracy can be improved.

According to a ninth aspect of the present invention, there is provided switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving ultrasonic waves, and in particular, the switching means for switching the delay means according to the first aspect. After switching a pair of transmission and reception by means,
By performing the operation for a predetermined time before the measurement start signal in accordance with the time until the next measurement start signal, it is possible to realize an optimal measurement system when measuring the propagation time difference and improve the accuracy.

According to a tenth aspect of the present invention, there is provided a temperature detecting means, and in particular, by operating the delaying means of the first aspect for a predetermined time before a measurement start signal in response to a signal from the temperature detecting means. By changing the initial stabilization method of the delay means depending on the ambient temperature, it is possible to quickly bring the delay means to an optimum state.

The eleventh aspect of the present invention is particularly applicable to the first aspect.
By operating the delay means described in (1) for a predetermined time before the measurement start signal according to the flow rate of the fluid to be measured, stable time accuracy can be maintained even at a low flow rate, and as a result, the accuracy of the flow rate is also improved. Becomes possible.

According to a twelfth aspect of the present invention, there is provided a voltage detecting means for detecting a power supply voltage supplied for performing the measurement, and in particular, the delay means according to the first aspect is changed in accordance with an output of the voltage detecting means. By performing the operation for a predetermined time before the measurement start signal, the initial stabilization method before the measurement is changed. This makes it possible to set the optimal initial operation of the delay means from the state of the measurement system.

According to a thirteenth aspect of the present invention, there is provided a first storage means for storing at least one of the number of times that the stability of the delay means is saturated and an operation time, and in particular, the first storage means.
By operating the delay means described in the above for a predetermined time before the measurement start signal according to the value of the first storage means,
Since the operation is performed based on the information unique to the delay means, it is possible to easily set a stable state, and the variation of the flow rate measuring device can be reduced.

According to a fourteenth aspect of the present invention, the ambient temperature, the number of repetitions, the repetition time, the time when the reception timing is detected by the timing detecting means after outputting the trigger signal, the operating time of the switching means, the flow rate, and the power supply voltage to be supplied And a second storage means for storing an optimum delay time by a combination of at least two of the above.
By operating the delay means described in the above for a predetermined time before the measurement start signal according to the value of the second storage means,
Since the operation is performed in consideration of the information unique to the delay means and the surrounding state, a stable state can be easily set, and the variation of the flow rate measuring device can be reduced.

The invention described in claim 15 is particularly advantageous in claim 1.
By making the first storage means described in (3) rewritable, if the optimum operating point of the delay means is shifted depending on the place or time when the flow rate measuring device is installed, the contents can be corrected. Also, when an aging or the like occurs, it is possible to rewrite similarly to cope with it. Then, a stable state can be maintained for a long time.

The invention described in claim 16 is particularly advantageous in claim 1.
By rewriting the second storage means described in 4 according to the condition during measurement, even if the battery voltage is aged or the components are aged, the rewriting is performed in the same manner. Is possible. Then, a stable state can be maintained for a long time.

The invention described in claim 17 is particularly advantageous in claim 1.
By rewriting the first storage means according to claim 3 or according to the condition during measurement, it is easy to change the initial operation of the delay means according to the measurement state and to establish an optimum state as a measurement system. Can be realized.

The invention described in claim 18 is particularly advantageous in claim 1.
By rewriting the second storage means according to claim 4 or according to the condition during measurement, it is easy to change the initial operation of the delay means depending on the measurement state and to establish an optimum state as a measurement system. Can be realized. Further, long-term operation can be made possible by considering the correlation with the power supply voltage.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of an ultrasonic flow meter according to Embodiment 1 of the present invention. FIG. 2A is a diagram showing the operation timing of the delay means. In FIG. 1, an ultrasonic flowmeter according to the present invention includes a flow path 1 through which a fluid to be measured flows, and a first transmitting and receiving ultrasonic wave disposed in the flow path 1.
Oscillator 12, a second oscillator 13, a driving unit 14 for driving the first oscillator 12, a control unit 15 for outputting a measurement start signal for operating the driving unit 14, and the second A timing detecting means for receiving a received signal from the vibrator and determining a receiving timing; and a driving means for delaying an output of the timing detecting means by a predetermined delay time.
A delay means 17 for outputting as a trigger signal, an ultrasonic wave transmission / reception means, and a repetition means 18 for measuring the number of operations of repeating transmission / reception of ultrasonic waves after a delay time by the delay means 17 and stopping the operation at a predetermined number of times; A timer 19 for measuring the propagation time of the ultrasonic wave at least from the start of driving of the first transducer 12 by the driving means 14 to the stop of the operation of the repetition means 18; And a calculating means 20 for calculating the flow velocity and calculating the flow rate therefrom.

The delay means 17 operates for a predetermined period of time before the control means 15 sends a measurement start signal for prompting a drive signal to the first vibrator 12. In this way, an unstable state in the initial operation of the delay means is avoided, and measurement is started after a stable state.

For example, the result of the determination by the timing detecting means 16 shown in the conventional example is delayed for a predetermined time by the delay means 17 and then returned to the driving means 14 to be transmitted again. A method will be described in which the flow rate is determined by calculating (Equation 2) based on the measurement time and the measurement time is used, and the flow rate is determined using the cross-sectional area of the flow channel known in advance from the flow rate. Here, the delay means 17 is operated for a predetermined time immediately before the measurement in accordance with the number of repetitions set in the repetition means 18.

In this case, if the number of repetitions is set to several hundred, the operation of the delay means 17 may be different between the first time and the last time. Normally, an LC distributed constant circuit or the like is used as the delay means 17, but these elements also include a resistance component.

If there is a resistance component in the delay means 17, there is no problem in the first repetition as long as a current flows, but as the number of times increases, heat is generated by the current, and as a result, the delay time changes. However, since this heat also has an equilibrium point, the delay time can be considered to be constant at a certain number of repetitions or more. FIG. 2A shows a conceptual diagram of the number of repetitions and the delay time per one time of the delay unit 17.

If the number of repetitions is smaller than this, the difference in delay time is large, so that the long time delay means 17 is operated before measurement. When the number of repetitions is large, the difference in delay time is small and the initial time difference may be within the error range when averaged by the number of times. In such a case, the delay means 17 may be operated for a short time before the measurement start signal to be measured.

The operation of the delay means 17 before the measurement start signal for starting the measurement may be changed in proportion to the number of repetitions, or may be a fixed time after the specified number of times. In actual use, the time is determined based on the capacity of the power supply and the limitation of the measurement time. In order to further improve the measurement accuracy, the following is considered. If the number of repetitions at the time of measurement is not sufficiently large with respect to the number of times that the delay time becomes stable (x in FIG. 2), the delay means 17 is operated at least for the time required for the x times. As a result, the operation of the delay unit 17 becomes sufficiently stable, and it becomes possible to realize a delay time with higher accuracy than in the initial stage of measurement.

As described above, since the unstable operation at the initial stage of the operation of the delay means 17 is performed in advance, and the operation at the time of measurement can be stabilized, stable time measurement can be performed and accurate flow rate measurement can be performed. Can be. And especially, the delay means 17
By adjusting the operation time, the change in measurement accuracy with respect to the number of repetitions can be reduced, and stable and accurate flow measurement can be performed.

A series of flows is as shown in the timing chart of FIG.

If the distance between the transducers changes or the delay time unique to the delay means 17 changes, the total time measured by the timer 19 changes even if the number of repetitions is the same.
The thermal equilibrium point when the delay means 17 has a resistance component as described above may be related to the total time of repetition, not the number of repetitions.

In this case, in order to improve the measurement accuracy, the delay means 17 is operated before the measurement with reference to the point y in FIG. 2B where the delay time becomes stable. For example, if the total time is long, the difference between the delay times also falls within the error range when averaged, so that the delay means may be operated for a short time before the measurement.

Thus, even if the total time changes repeatedly,
By performing the initial operation in consideration of the characteristics of the delay unit 17, the delay unit 17 can perform a stable operation, thereby realizing accurate measurement.

Similarly, if the distance between the transducers changes or the delay time inherent to the delay means 17 changes, or if the delay time changes, the ratio of the delay time of the delay means 17 to one repetition time also changes. . When the ratio of the delay time is large, the thermal equilibrium is reached in a short time. On the other hand, when the ratio of the delay time is small, the thermal equilibrium is delayed due to heat radiation or the like. In this case, in order to improve the measurement accuracy, the delay means 17 is operated before the measurement according to the time when the reception timing is detected by the timing detection means 16 after outputting the measurement start signal. For example, since the time in the delay unit 17 is roughly known from the time measured by the clock unit 19 in FIG. 1 for one repetition operation, the delay time of the delay unit 17 in the repetition time is known. The delay unit 17 is operated before the measurement with reference to the point z in FIG.

By adjusting the operation time of the delay means 17 before the measurement start signal for starting the measurement in accordance with the time per one repetition, the dispersion of the delay time due to the heat radiation of the delay means itself can be reduced. Stable measurement can be realized with less.

(Embodiment 2) A flow rate measuring apparatus according to the present invention according to a second embodiment according to claims 5, 6, 7, 8 and 9 will be described. FIG. 4 is a block diagram showing the configuration of this embodiment. The difference from the first embodiment is that the switching means 2 is provided between the driving means 14 and the first vibrator 12 and between the second vibrator 13 and the timing detecting means 16.
1 is provided so that transmission and reception of ultrasonic waves are alternately performed between the first vibrator 12 and the second vibrator 13. When the switching means 21 performs transmission and reception alternately in this manner, the operation of the delay means 17 differs when transmitting first with the first transducer 12 and then transmitting with the second transducer 13. May come.

For example, in the case of the method of measuring the propagation times of the fluid to be measured from upstream to downstream and from downstream to upstream, obtaining the velocity v from (Equation 3), and obtaining the flow rate from the flow velocity as shown in the conventional example. And so on. According to this method, the flow rate can be measured without being affected by a change in the speed of sound, so that the method is widely used. However, an accurate value cannot be obtained if a time measurement error by the delay means 17 is included in the measurement. A method for preventing this phenomenon will be described below.

When the number of repetitions is set to several hundreds as described in the first embodiment, the delay means 17 is used for the first and last times.
However, there are other factors. For example, when the switching unit 21 is operated after performing the repetition operation a predetermined number of times to invert the transmission and reception of the vibrator and perform the same repetition operation,
Since the delay means 17 has already been operated before performing the switching operation, there is a possibility that the delay point 17 has sufficiently reached the equilibrium point. FIG. 5 (a)
Is an example showing a change in delay time when the first repetitive operation is performed. FIG. 5B shows the delay time after the switching means 21 is operated to change the transmission / reception direction.

Due to such characteristics, the switching means 21 is not operated simply before the measurement start signal which is measured according to the number of operations of the repetition means.
Considering whether the operation is before or after the operation, the delay means is operated for a predetermined time immediately before the measurement, taking into account the operation and the number of repetitions set by the repetition means.

In this way, when the respective propagation times from the upstream to the downstream and from the downstream to the upstream are measured and the flow rate is determined from the difference in the propagation time, the difference between FIGS. 5 (a) and 5 (b) can be reduced. be able to.

In addition, the total time measured by the timer 19 changes before and after the operation of the switching means 21 even if the number of repetitions is the same depending on the flow rate and the like. In this case, in order to improve the measurement accuracy, the delay means 17 is not operated simply before the measurement start signal to be measured according to the repetition time.
Considering whether the switching means 21 is operating before or after, the predetermined time delay means 17 is operated before the measurement start signal to be measured in consideration of the time required for the number of repetitions set by the repeating means.

This makes it possible to reduce the difference in operation of the delay means 25 when measuring the respective propagation times from upstream to downstream and from downstream to upstream and obtaining the flow rate from the difference in propagation time, thereby improving the measurement accuracy. be able to.

Similarly, the ratio of the delay time of the delay means 17 to one repetition time differs before and after the operation of the switching means 21 depending on the flow rate and the like. In this case, in order to improve the measurement accuracy, the delay means 17 is simply provided before the measurement start signal to be measured according to the time per one repetition.
Is not operated, the predetermined time delay means is operated before the measurement start signal for measuring taking into account whether the switching means 21 is operating before or after the operation and considering the time per one repetition.

As a result, it is possible to reduce the difference in the operation of the delay means 17 when obtaining the flow rate from the propagation time difference, and to improve the measurement accuracy.

Also, when the switching means 21 is operated to switch the transmission / reception direction, and then the measurement start signal is transmitted from the control means 15 to meet the driving means 14 to drive the vibrator.
During the switching operation, the delay means 17 may deviate from the operation equilibrium point due to heat radiation or the like. As a specific example, the difference between the delay times shown in FIGS. 5A and 5B changes from the thermal equilibrium point. If the series of operations is fast, there is not much time to deviate from the equilibrium point.
Although the difference between (a) and (b) is large, if the switching operation is slow, the deviation from the equilibrium point becomes large, the warmed delay means 17 cools down, and the difference becomes small. Therefore, when obtaining the flow rate from the propagation time difference, the predetermined time delay means 17 is operated before the measurement start signal to be measured according to the time required for this switching. Specifically, when the switching time is long, the delay means is extremely cold, so that there is not much difference in the delay time before and after the switching. In such a case, there is a possibility that sufficient accuracy can be obtained without performing the operation of the delay means 17 before the measurement. Conversely, if the switching operation is performed sufficiently early, there is a large difference in the delay time before and after the switching. For this reason, when the measurement start signal to be measured first is transmitted, it is necessary to operate the delay means 17 for a long time before the measurement in order to sufficiently warm the delay means 17.

As described above, the delay means 17 is switched according to the switching time.
By operating before the measurement start signal for measuring the propagation time difference, the state of the measurement system can be made almost the same when measuring the propagation time difference, and the accuracy can be improved.

After measuring the propagation time difference between a pair of transmission / reception signals, the flow rate measuring device which repeats the same operation after a certain period of time and continues the measurement continues the pair of transmission / reception signal switching operations and performs the next measurement. To perform the measurement, the delay unit 17 is operated for a predetermined time before the measurement start signal measured according to the time until the measurement start signal is transmitted. In FIG. 6, first at t0, the first vibrator 12 is transmitting and the second vibrator 13 is operating on the receiving side. After a predetermined number of repetitions, the switching means operates at time tx, and then the second vibrator 13 transmits and the first vibrator 12 operates on the receiving side. The propagation time difference is obtained by this pair of operations, and the same transmission and reception are performed at the next time t2.

In this case, the predetermined time delay means is operated immediately after the measurement start signal to be measured according to the time from t0 to t2 or the time from t1 to t2 (hereinafter, the sampling interval time).

If the sampling time is sufficiently long, the delay means is extremely cooled. Therefore, it is necessary to operate the delay means for a long time before measurement. Conversely, when the sampling time is short, the delay means 17 does not deviate much from the equilibrium point. Therefore, when the measurement is first performed after the elapse of the sampling time, the delay means 17 is operated before the measurement start signal for measuring the short time. Alone, the delay means 17 can sufficiently reach the equilibrium point. As described above, by operating before the measurement start signal for measuring the delay unit 17 according to the sampling time, it is possible to realize an optimal measurement system when measuring the propagation time difference and improve the accuracy.

In this case, after the elapse of the sampling time, the first vibrator always starts the operation of measuring the propagation time difference on the transmitting side, but it does not matter if the second vibrator starts measuring on the transmitting side. There is no.

(Embodiment 3) A flow rate measuring apparatus according to the present invention according to a third embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the present embodiment. The difference from the first embodiment is that a temperature detecting unit and a voltage detecting unit are provided.

The delay means 17 has an equilibrium point depending on the temperature.
Therefore, the stabilization time varies depending on the ambient temperature. For this purpose, a temperature detecting means 22 is provided, and the measuring means is operated for a predetermined time before a measurement start signal for measuring the delay means 17 in accordance with the signal from the temperature detecting means 22, and the measurement is started after a stable state. For example, it takes a long time to reach a stable state at low temperatures such as winter, and conversely, when it is installed in summer or in a place where direct sunlight shines, a stable temperature is short or already in a stable state There are cases.

As described above, by changing the initial stabilization method depending on the ambient temperature, it is possible to quickly bring the delay means 17 to an optimum state.

The flow rate calculating means 20 obtains the flow rate from the measured time difference. A large flow rate means that the measured fluid flows through the flow path at a high speed, so that the propagation time difference obtained by switching the transmission and reception of the ultrasonic wave becomes large. If the propagation time difference is large, the measurement error is not so noticeable, but if the flow rate is small, the propagation time difference becomes small. If the operation of the delay means 17 is not stable, the measurement error becomes large. Therefore, before the measurement start signal for measuring the delay means 17 in accordance with the flow rate obtained by the flow rate calculation means 20, the operation is performed for a predetermined time and the measurement is started after the operation is stabilized.

By performing such an operation, stable time accuracy can be maintained even at a low flow rate, and as a result, the accuracy of the flow rate can be improved.

The delay means 17 has an equilibrium point depending on the temperature. However, when this measuring system is operated electrically, the amount of heat generated differs depending on the voltage. Therefore, a voltage detecting means 23 for monitoring the power supply voltage supplied to the measuring system is provided, and in response to a signal from the voltage detecting means 23, the delay means 17 is operated for a predetermined time immediately before the measurement to make the state stable. Start measurement. For example, when a battery is used, the voltage is high at the beginning of operation, but the voltage gradually decreases as the battery is used. In the case of a high voltage, there is a high possibility that a large amount of current flows, and a large amount of heat is generated. In this case, the thermal equilibrium point is reached quickly, and when the voltage is low, the current does not flow so much and it takes time to reach the thermal equilibrium point. In consideration of these states, the initial stabilization method is changed before the measurement start signal for measuring according to the voltage.

This makes it possible to set the optimum initial operation of the delay means from the state of the measurement system.

The power saving operation can be performed by monitoring the voltage. In the figure, the temperature detecting means and the voltage detecting means are combined, but if one is provided, the operation can be sufficiently satisfied.

Although the switching means is not shown in the drawings shown in the present embodiment, the same effect can be obtained with the configuration having the switching means as shown in the second embodiment.

(Embodiment 4) A flow rate measuring apparatus according to a fourth embodiment of the present invention according to claim 13, claim 14, claim 15, claim 16, claim 17, and claim 18 will be described. FIG. 8 is a block diagram showing the configuration of this embodiment. The difference from the first embodiment is that the first storage unit and the second storage unit
Is provided.

Although the stability of the delay means 17 is not good at the beginning of the operation, the operation of the delay means 17 gradually becomes more stable. A stable state is often determined by the number of operations or the operation time. Therefore, at least one of the number of operations or the operation time until the delay unit 17 is substantially stabilized is previously obtained by an experiment or the like, and this is stored in the first storage unit 24. If there is a variation between the objects of the delay means 17, a value obtained by the inspection is stored.
When actually operating, the delay unit 17 is operated before the measurement start signal for measuring only the number of operations or the operation time stored in the first storage unit 24, and the measurement is started after the operation is stabilized.

As a result, since the operation is performed based on the information unique to the delay means 17, a stable state can be easily set, and the variation of the flow rate measuring device can be reduced.

In order to improve the stability of the delay means 17, the optimum value may change depending on the ambient temperature, the number of repetitions, the flow rate and the power supply voltage. In order to improve the accuracy of the low flow rate, it is necessary to provide a measurement system incorporating these changing factors sufficiently. Accordingly, the ambient temperature, the number of repetitions, the repetition time, and the time when the trigger signal is output until the delay means 17 is approximately stabilized, the time when the reception timing is detected by the timing detection means, the operation time and the flow rate of the switching means, and the power supply voltage to be supplied The optimum delay time due to at least two or more combinations of
To memorize it.

If there is a variation between the objects of the delay means 17, a value obtained by the inspection is stored. In the case of actual operation, the delay unit 17 is operated before the measurement start signal for measuring only the delay time stored in the second storage unit 25 and the measurement is started, and then the measurement is started.
Accordingly, since the operation is performed in consideration of the information unique to the delay unit 17 and the surrounding state, a stable state can be easily set, and the variation of the flow rate measurement device can be reduced.

The first storage means 24 has a state in which rewriting is possible. For example, rewriting is performed from a microcomputer, or an external signal is input to rewrite. In the semiconductor storage means, the semiconductor itself can be replaced.

Thus, if the optimum operating point of the delay means is shifted depending on the place or time when the flow rate measuring device is installed, the contents can be corrected. Also, when an aging or the like occurs, it is possible to rewrite similarly to cope with it. Then, a stable state can be maintained for a long time.

The second storage means 25 has a state in which rewriting is possible. Accordingly, if the optimum operating point of the delay unit 17 is shifted depending on the place or time when the flow rate measuring device is installed, the content is corrected. Even when the battery voltage deteriorates over time or the components change over time, it is possible to rewrite similarly and cope with the case.
This makes it possible to maintain a stable state for a long time.

The first storage means 24 performs rewriting according to the conditions during the measurement operation. For example, when the low flow rate state continues for a long time or the like, in order to further improve the accuracy, the control unit 15 or the like stops the actual measurement operation (for example, between t1 and t2 in FIGS. 6A and 6B). ) Is rewritten so as to further increase the stability of the delay means 17. Conversely, when the flow rate is large and the operation of the delay means can be ignored as an error, the stability of the delay means 17 can be reduced to a certain level or less. In this way, it is easy to change the initial operation of the delay means depending on the measurement state and to establish an optimum state as a measurement system.

Further, the second storage means 25 is adapted to rewrite according to conditions during the measurement operation. For example, the temperature may fluctuate rapidly depending on the installation location. In such a case, control means 1 is used to maintain the accuracy.
The conditions are rewritten so that the stability of the delay means 17 is maintained during the time period when the actual measurement operation is completed from 5 and the like (for example, between t1 and t2 in FIGS. 6A and 6B). In this way, it is easy to change the initial operation of the delay means depending on the measurement state and to establish an optimum state as a measurement system. Further, long-term operation can be made possible by considering the correlation with the power supply voltage.

In the figure, the first storage means 24 and the second storage means 25 are combined, but if one is provided, the operation can be sufficiently satisfied.

In the above description, the thermal equilibrium of the delay means 17 has been described. However, the stability of the delay means 17 is not limited to heat, but can be similarly operated for a fixed time to avoid an initial unstable state. Similar effects can be obtained.

In the above description, the delay means 17 is operated before the measurement start signal output from the control means 15. However, if the operation is sufficiently stabilized before the reception signal is inputted by the prior operation, The operation of the delay means 17 is not limited to before the measurement start signal, but may be any time that does not hinder the start of the measurement.

[0084]

As is apparent from the above description, the flow rate measuring device according to the present invention has the following effects.

(1) By operating the delay means before the measurement start signal for starting the measurement, an unstable state in the initial operation of the delay means can be avoided, the degree of stability of the delay time is improved, and highly accurate measurement is performed. Will be able to

(2) By adjusting the operation time of the delay means according to the number of repetitions, a change in measurement accuracy with respect to the number of repetitions can be reduced, and stable and accurate flow measurement can be performed.

(3) Even if the total time changes repeatedly, by performing the initial operation in consideration of the characteristics of the delay means, the delay means performs a stable operation, so that accurate measurement can be realized. .

(4) By adjusting the operation time of the delay means in advance according to the time per one repetition, the dispersion of the delay time due to the heat radiation of the delay means itself can be reduced to realize a stable measurement. it can.

(5) Considering before and after the operation of the switching means, the delay means is operated for a predetermined time before the measurement start signal measured according to the number of repetitions set in the repetition means, so that the upstream and the downstream and the downstream are operated. Since the difference in the initial operation characteristics of the delay means can be reduced when measuring the propagation time from the upstream to the upstream and determining the flow rate from the difference in the propagation time, the flow rate can be determined accurately.

(6) Considering before and after the operation of the switching means, the delay means is operated for a predetermined time before the measurement start signal measured in accordance with the repetition time obtained by the time measurement means, so that the upstream to downstream and the downstream to upstream It is possible to reduce the difference in the initial operation of the delay means when measuring the respective propagation times and calculating the flow rate from the difference in the propagation times, thereby improving the measurement accuracy.

(7) Considering before and after the operation of the switching means, the delay means outputs a measurement start signal and then operates for a predetermined time before the measurement start signal which measures according to the time when the reception timing is detected by the timing detection means. By taking into account whether the switching means is operating before or after, the predetermined time delay means is operated before the measurement start signal to be measured in consideration of the time and the time per one repetition,
When the flow rate is determined from the propagation time difference, the difference in the operation of the delay means can be reduced, and the measurement accuracy can be improved.

(8) By operating the delay means for a predetermined time before the measurement start signal to be measured in accordance with the operation time of the switching means, it is possible to make the state of the measurement system substantially the same when measuring the propagation time difference. The flow rate measurement accuracy can be improved.

(9) After a pair of transmission and reception are switched by the switching means, the propagation time difference is measured by operating for a predetermined time before the measurement start signal measured according to the time until the next measurement start signal. In this case, an optimal measurement system can be realized and the accuracy can be improved.

(10) By operating the delay means for a predetermined time before the measurement start signal for measuring according to the signal of the temperature detection means, the delay means is changed to the initial stabilization method depending on the ambient temperature to obtain an optimum state. Can be brought quickly.

(11) By operating the delay means for a predetermined time before the measurement start signal for measuring according to the flow rate of the fluid to be measured, stable time accuracy can be maintained even at a low flow rate. Accuracy can also be improved.

(12) The delay means is operated for a predetermined time before the measurement start signal to be measured in accordance with the output of the voltage detection means for detecting the power supply voltage supplied for performing the measurement, thereby stabilizing the initial state before the measurement. By changing the method, it is possible to set the optimal initial operation of the delay means from the state of the measurement system.

(13) The first storage means for storing at least one of the number of times or the operation time at which the stability of the delay means is saturated is used, and the delay means is set in accordance with the value of the first storage means. By operating for a predetermined time before the measurement start signal to be measured, it is possible to easily set a stable state because it operates based on information unique to the delay means,
Variations in the flow measurement device can also be reduced.

(14) At least two of the following: the ambient temperature, the number of repetitions, the repetition time, the time when the reception timing is detected by the timing detection means after outputting the trigger signal, the operation time of the switching means, the flow rate, and the power supply voltage to be supplied. By using the second storage unit that stores the optimal delay time based on the above combination, and operating the delay unit for a predetermined time before the measurement start signal that is measured according to the value of the second storage unit, Since the operation is performed in consideration of the information unique to the delay means and the surrounding state, a stable state can be easily set, and the variation of the flow rate measuring device can be reduced.

(15) By making the first storage means rewritable, if the optimum operating point of the delay means is shifted depending on the place or time when the flow rate measuring device is installed, the contents can be corrected. Also, when an aging or the like occurs, it is possible to rewrite similarly to cope with it. Then, a stable state can be maintained for a long time.

(16) By rewriting the second storage means according to the conditions during measurement, even if the battery voltage decreases over time or the components change over time, the rewriting is performed similarly. It is possible to Then, a stable state can be maintained for a long time.

(17) By rewriting the first storage means according to conditions during measurement, it is easy to change the initial operation of the delay means depending on the measurement state and to establish an optimum state as a measurement system. it can.

(18) By rewriting the second storage means according to conditions during measurement, it is easy to change the initial operation of the delay means depending on the measurement state and to establish an optimum state as a measurement system. it can. Further, long-term operation can be made possible by considering the correlation with the power supply voltage.

[Brief description of the drawings]

FIG. 1 is an overall block diagram of a flow measurement device according to a first embodiment of the present invention.

2A is a diagram showing the relationship between the number of repetitions and the delay time in the flow rate measuring device. FIG. 2B is a diagram showing the relationship between the repetition time and the delay time in the flow rate measuring device. Diagram showing the relationship between repetition time and delay time

FIG. 3A is a timing chart showing an operation of an oscillating wave of the flow rate measuring device; FIG. 3B is a timing chart showing an operation of a received wave of the flow rate measuring device; FIG. Timing chart

FIG. 4 is an overall block diagram of a flow measurement device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a state of a delay time in the operation of the switching means of the flow rate measuring device.

6A is a timing chart showing an operation of a first oscillator of the flow rate measuring device. FIG. 6B is a timing chart showing an operation of a second oscillator of the flow rate measuring device.

FIG. 7 is an overall block diagram of a flow rate measuring device according to a third embodiment of the present invention.

FIG. 8 is a block diagram of an entire flow rate measuring device of an ultrasonic anemometer according to a fourth embodiment of the present invention.

FIG. 9 is an overall block diagram of a conventional flow measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow path 12 1st vibrator 13 2nd vibrator 14 Driving means 15 Control means 16 Timing detection means 17 Delay means 18 Repetition means 19 Clocking means 20 Flow rate calculation means 21 Switching means 22 Temperature detection means 23 Voltage detection means 24 First storage means 25 Second storage means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Nagaoka 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Shuji Abe 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 2F035 DA16 DA23

Claims (18)

[Claims] 1. A pair of vibrators arranged in a flow path of a fluid to be measured for transmitting and receiving ultrasonic waves, driving means for driving one of the vibrators, and outputting a measurement start signal for operating the driving means. Control means; timing detection means for receiving an output from the other transducer to determine a reception timing; delay means for outputting an output of the timing detection means as a trigger signal of the driving means with a predetermined delay; A repetition means for measuring the number of operations of repeating transmission and reception of ultrasonic waves after the transmission / reception and the delay operation by the delay means and stopping the operation at a predetermined number of times, and at least the driving of the vibrator by the driving means to the repetition means Time measuring means for measuring the propagation time of the ultrasonic wave until the operation is stopped, and the flow rate of the fluid to be measured between the pair of transducers from the value of the time measuring means. A flow rate measuring device comprising: calculating means for obtaining by calculation, wherein the delay means is operated for a predetermined time before a measurement start signal. 2. A flow rate measuring apparatus wherein a delay means is operated for a predetermined time before a measurement start signal in accordance with the number of repetitions set in the repetition means. 3. The flow measuring device according to claim 1, wherein the delay means is operated for a predetermined time immediately before the measurement in accordance with the value of the time measuring means. 4. The flow rate measuring apparatus according to claim 1, wherein the delay means outputs a measurement start signal and operates for a predetermined time before the measurement start signal in accordance with a time when the reception timing is detected by the timing detection means. 5. A switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving ultrasonic waves, and a delay means is set in the repetition means in consideration of before and after the operation of the switching means. 3. The flow measurement device according to claim 1, wherein the flow measurement device is operated for a predetermined time before the measurement start signal according to the number of times. 6. A switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving an ultrasonic wave, and a delay means measures in accordance with a value of a timer means in consideration of before and after operation of the switching means. 4. The flow measuring device according to claim 1, wherein the flow measuring device is operated for a predetermined time before the start signal. 7. A switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving an ultrasonic wave, and a delay means outputs a measurement start signal in consideration of before and after the operation of the switching means. 5. The flow measuring device according to claim 1, wherein the flow measuring device is operated for a predetermined time before the measurement start signal according to the time when the reception timing is detected by the timing detecting means. 8. A switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving an ultrasonic wave, wherein the delay means is provided with a predetermined time before a measurement start signal in accordance with an operation time of the switching means. The flow measurement device according to claim 1, which is operated. 9. A switching means for switching and setting a transmission function and a reception function of two transducers for transmitting and receiving an ultrasonic wave, wherein the delay means switches a pair of transmission and reception by the switching means and then sets a next measurement start signal. 2. The flow measurement device according to claim 1, wherein the flow measurement device is operated for a predetermined time before the measurement start signal according to the time until the measurement. 10. The flow rate measuring device according to claim 1, further comprising a temperature detecting means, wherein the delay means is operated for a predetermined time before a measurement start signal in response to a signal from the temperature detecting means. 11. The flow rate measuring device according to claim 1, wherein the delay means is operated for a predetermined time before the measurement start signal according to the flow rate of the fluid to be measured. 12. The apparatus according to claim 1, further comprising voltage detection means for detecting a power supply voltage supplied for performing the measurement, wherein the delay means is operated for a predetermined time before a measurement start signal in accordance with an output of the voltage detection means. Flow measuring device. 13. A first storage means for storing at least one of the number of operations or the operation time at which the stability of the delay means is saturated, wherein the delay means is adapted to store the value of the first storage means. 2. The flow measurement device according to claim 1, wherein the flow measurement device is operated for a predetermined time before the measurement start signal. 14. At least two or more of an ambient temperature, the number of repetitions, a repetition time, a time when a reception timing is detected by a timing detection means after outputting a trigger signal, an operation time of a switching means, a flow rate, and a power supply voltage to be supplied. 2. The apparatus according to claim 1, further comprising a second storage unit for storing an optimum delay time based on a combination of the above, and the delay unit being operated for a predetermined time before the measurement start signal in accordance with the value of the second storage unit. Flow measurement device. 15. The flow rate measuring device according to claim 13, wherein the first storage means is rewritable. 16. The flow rate measuring device according to claim 14, wherein the second storage means is rewritable. 17. The flow rate measuring device according to claim 13, wherein the first storage means rewrites according to a condition during the measurement. 18. The flow rate measuring device according to claim 14, wherein the second storage means rewrites according to a condition during the measurement.