JP4830191B2 - Flow measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device that measures the flow rate of a gas or a liquid by ultrasonic waves.
[0002]
[Prior art]
A conventional flow rate measuring apparatus is generally as shown in FIG. This apparatus includes an ultrasonic sensor 2 installed in a measurement path 1 through which a fluid flows, a drive circuit 3 that drives the ultrasonic sensor 2, a control unit 4 that outputs a start signal to the drive circuit 3, and an ultrasonic propagation time. A timer 5 for measurement, a calculation unit 6 for receiving measurement data from the timer 5, an ultrasonic sensor 7 for receiving ultrasonic waves transmitted from the ultrasonic sensor 2, and an output of the ultrasonic sensor 7 according to the output of the gain control circuit 8 The variable gain amplifier 9 that amplifies at the amplification factor, the timing detection circuit 10 that compares the output of the variable gain amplifier 9 with the reference voltage and stops the timer 5 when the magnitude relationship is inverted, and the output level of the variable gain amplifier 9 And a level detection circuit 11 that outputs to the gain control circuit 8.
[0003]
In the ultrasonic current meter, when the drive circuit 3 receiving the start signal from the control unit 4 performs pulse driving of the ultrasonic sensor 2 for a certain period of time, the timer 5 starts measuring time according to the signal from the control unit 4. An ultrasonic wave is transmitted from the pulse-driven ultrasonic sensor 2. The ultrasonic wave transmitted from the ultrasonic sensor 2 propagates through 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 gain set by the control unit 4 in the variable gain amplifier 9. The timing detection circuit 10 receiving the output of the variable gain amplifier 9 determines reception of the ultrasonic wave and stops the timer 5. Then, the control unit 4 obtains the flow velocity from the time information t obtained from the timer 5 by (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, The flow velocity of the fluid to be measured is v).
[0004]
v = (L / t) -c (Formula 1)
The timing detection circuit 10 compares the reference voltage and the received signal by a comparator.
[0005]
The received signal has a waveform that rises gently, and the level of the received signal changes depending on the temperature characteristics of the ultrasonic sensor and the flow velocity. If the reference voltage and the level of the received signal are not appropriate, the operation of the timing detection circuit 10 is not stable and the measurement accuracy is deteriorated. 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 sets the amplification factor of the variable gain amplifier 9 so as to correspond to the signal from the level detection circuit 11 so that the output of the variable gain amplifier 9 becomes substantially constant. Then, the next received signal is amplified to a target signal level by the variable gain amplifier 9 and given to the timing detection circuit 10. Thus, by making the peak of the signal applied to the timing detection circuit 10 substantially constant, the timing for determining the reception time is stabilized.
[0006]
As another measurement method, the determination result of the timing detection circuit 10 may be returned to the drive circuit 3 after being delayed by a 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 obtaining the flow velocity by the calculation of (Equation 2) based on the measurement 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 speed of sound is c, and the flow velocity of the fluid to be measured is v).
[0007]
v = L / (ts / n−Td) −c (Expression 2)
According to this method, it is possible to measure with higher accuracy than the method of (Equation 1).
[0008]
In addition, there is a method in which the ultrasonic sensor 2 and the ultrasonic sensor 7 are switched, the propagation times of the fluid under measurement from upstream to downstream and from downstream to upstream are measured, and the velocity v is obtained from (Equation 3) (upstream Measurement downstream time T1, measurement from downstream to upstream time T2).
[0009]
v = L / 2 ((1 / t1)-(1 / t2)) (Formula 3)
According to this method, the flow rate can be measured without being affected by the change in the sound speed, and thus it is widely used for measuring the flow velocity, the flow rate, the distance, and the like.
[0010]
[Problems to be solved by the invention]
However, since the accuracy of the delay time of the delay circuit in the conventional ultrasonic flowmeter directly affects the measurement accuracy, the realization of a delay circuit having a highly accurate delay time has been a problem.
[0011]
[Means for Solving the Problems]
In order to solve the conventional problem, the delay means in the flow rate measuring device of the present invention is: , Consisting of LC distributed constant circuit including resistance component, The output of the timing detection means for determining the reception timing is output as a trigger signal for the drive circuit with a predetermined time delay. Before, the operation is performed before the measurement start signal for a predetermined time required for the temperature of the resistance component to reach the equilibrium point, and the time measuring means is from when the measurement start signal is output until when the operation of the repetitive means is stopped. The time of Is.
[0012]
As a result, the delay means operates before sending the measurement start signal, so that the unstable operation at the initial stage of the operation is performed in advance and becomes stable. Accurate measurement is possible.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
First The invention includes a pair of transducers arranged in a flow path through which a fluid to be measured flows and transmits / receives ultrasonic waves, and a driving unit that drives one of the transducers , Timing detection means for receiving the output from the other transducer and determining the reception timing; It consists of LC distributed constant circuit including resistance component, A delay unit that outputs the output of the timing detection unit as a trigger signal of the drive unit with a delay of a predetermined time, an ultrasonic wave transmission and reception, and the number of operations of repeating the ultrasonic wave transmission and reception again after a delay operation are measured and predetermined. Repetitive means for stopping the operation at the number of times, Control means for outputting a measurement start signal for causing the drive means to perform the first drive; Measuring means for measuring the propagation time of the ultrasonic wave from at least the driving of the vibrator by the driving means to stopping the operation of the repeating means; and the flow rate of the fluid to be measured between the pair of vibrators from the value of the timing means. Calculation means obtained by calculation and , Comprising the delay means Is Before the measurement start signal , The operation is performed before the measurement start signal for a predetermined time necessary for the temperature of the resistance component to reach the equilibrium point, and the time measuring means determines the time from the output of the measurement start signal to the stop of the operation of the repetitive means. Time This is a flow rate measuring device.
[0014]
The delay means operates before sending the measurement start signal so that the unstable operation at the initial stage of the operation is performed in advance and becomes stable. Measurement is possible.
[0015]
Second The invention is particularly In the first invention, By operating the delay means for a predetermined time before the measurement start signal according to the number of repetitions set in the repetition means, the operation time of the delay means can be adjusted, and the change in measurement accuracy with respect to the number of repetitions can be reduced and stable. Accurate flow measurement can be performed.
[0016]
Third The invention is particularly In the first invention, By operating the delay means for a predetermined time before the measurement start signal according to the value of the time measurement means, even if the total repetition time obtained by the time measurement means changes, the initial operation is performed in consideration of the characteristics of the delay means. Thus, since the delay means performs a stable operation, it is possible to realize accurate measurement.
[0017]
4th The invention A pair of transducers arranged in the flow path through which the measurement fluid flows, transmitting and receiving ultrasonic waves, a driving unit that drives one transducer, a timing detection unit that receives an output from the other transducer and determines a reception timing; It consists of an LC distributed constant circuit including a resistance component, delay means for delaying the output of the timing detection means for a predetermined time and outputting it as a trigger signal of the drive means, transmission / reception of ultrasonic waves, and transmission / reception of ultrasonic waves again after a delay operation by the delay means Repeating means for measuring the number of times of repeating the operation and stopping the operation at a predetermined number of times, control means for outputting a measurement start signal for causing the driving means to perform the first drive, and timing means for measuring the propagation time of the ultrasonic wave, A calculating means for calculating the flow velocity of the fluid under measurement between the pair of vibrators from the value of the time measuring means, By operating the delay means for a predetermined time before the measurement start signal in accordance with the time when the reception timing is detected by the timing detection means after outputting the measurement start signal, the delay means is set according to the time per one repetition. Adjust the working time in advance Can In addition, stable measurement can be realized by reducing variation in delay time due to heat radiation of the delay means itself.
[0018]
5th The invention Especially in the first or second invention, A switching means for switching and setting a transmission function and a reception function of two vibrators for transmitting and receiving ultrasonic waves; Presence of Considering , The delay means is operated for a predetermined time before the measurement start signal according to the number of repetitions set in the repetition means, thereby measuring the propagation time from upstream to downstream and from downstream to upstream, and obtaining the flow rate from the propagation time difference. At this time, since the difference in the initial operating characteristics of the delay means can be reduced, the flow rate can be obtained with high accuracy.
[0019]
6th The invention Especially in the first or third invention, A switching means for switching and setting a transmission function and a reception function of two vibrators for transmitting and receiving ultrasonic waves; Presence of Considering , By operating the delay means for a predetermined time before the measurement start signal according to the value of the time measurement means, the propagation time of the delay means is determined when measuring the propagation time from upstream to downstream and from downstream to upstream and determining the flow rate from the propagation time difference. The difference in the initial operation can be reduced, and the measurement accuracy can be improved.
[0020]
7th The invention Especially in the first invention, A switching means for switching and setting a transmission function and a reception function of two vibrators for transmitting and receiving ultrasonic waves; Presence of Considering , The delay means is operated for a predetermined time before the measurement start signal according to the time when the reception timing is detected by the timing detection means after the measurement start signal is output, so that the switching means is considered before or after the operation. In addition, since the delay means is operated for a predetermined time immediately before the measurement, taking into account the time per repetition, the difference in operation of the delay means can be reduced when determining the flow rate from the propagation time difference, Accuracy can be improved.
[0021]
8th The invention Especially in the first invention, Has switching means to switch and set the transmission function and reception function of two transducers that transmit and receive ultrasonic waves , By operating the delay means for a predetermined time before the measurement start signal according to the operation time of the switching means, the state of the measurement system can be made substantially the same when measuring the propagation time difference, and the flow measurement accuracy is improved. Can be achieved.
[0022]
9th The invention Especially in the first invention, Has switching means to switch and set the transmission function and reception function of two transducers that transmit and receive ultrasonic waves , After switching the pair of transmission and reception by the switching means, the delay means is operated for a predetermined time before the measurement start signal according to the time until the next measurement start signal, so that it is an optimal measurement system for measuring the propagation time difference. To improve accuracy.
[0023]
10th The invention Especially in the first invention, Has temperature detection means , By operating the delay means for a predetermined time before the measurement start signal according to the signal from the temperature detection means, it is possible to quickly bring the delay means to an optimum state by changing the initial stabilization method according to the ambient temperature. become.
[0024]
Eleventh The invention Especially in the first invention, By operating the delay means 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 low flow rates, and as a result, the flow rate accuracy can be improved. Become.
[0025]
12th The invention Especially in the first invention, It has voltage detection means to detect the power supply voltage to be supplied for measurement , By operating the delay means for a predetermined time before the measurement start signal in accordance with the output of the voltage detection means, the initial stabilization method before measurement is changed. This makes it possible to set the optimum initial operation of the delay means from the state of the measurement system.
[0026]
Thirteenth The invention Especially in the first invention, First storage means for storing in advance at least one of the number of times the stability of the delay means is saturated or the operation time; , By operating the delay means for a predetermined time before the measurement start signal according to the value of the first storage means, it becomes possible to easily set a stable state because it operates according to information unique to the delay means, Variations in the flow rate measuring device can also be reduced.
[0027]
14th The invention Especially in the first invention, Optimum by a combination of at least two or more of the ambient temperature, the number of repetitions, the repetition time, the time when the reception timing is detected by the timing detection means, the operation time of the switching means, the flow rate, and the power supply voltage to be supplied Second storage means for storing the delay time; , By operating the delay means for a predetermined time before the measurement start signal in accordance with the value of the second storage means, it is possible to easily set a stable state in order to operate considering the information unique to the delay means and the surrounding state. Therefore, the variation in the flow rate measuring device can be reduced.
[0028]
15th The invention Particularly in the thirteenth invention, By making the first storage means rewritable, the contents can be corrected if the optimum operating point of the delay means is deviated depending on the location and time of installation of the flow rate measuring device. In addition, when an aging change or the like occurs, it can be similarly rewritten and dealt with. And it becomes possible to maintain a stable state for a long time.
[0029]
16th The invention Particularly in the fourteenth invention, By rewriting the second storage means according to conditions during measurement, even if a battery voltage aging or a secular change of each component occurs, it can be rewritten and dealt with similarly. . And it becomes possible to maintain a stable state for a long time.
[0030]
17th The invention Especially in the thirteenth or fifteenth invention, By rewriting the first storage means according to conditions during measurement, it is possible to easily realize the optimum state as the measurement system by changing the initial operation of the delay means according to the measurement state.
[0031]
18th The invention Especially in the fourteenth or sixteenth invention, By rewriting the second storage means according to conditions during measurement, it is possible to easily realize the optimum state as a measurement system by changing the initial operation of the delay means according to the measurement state. In addition, it is possible to operate for a long time by considering the correlation with the power supply voltage.
[0032]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0033]
Example 1
FIG. Is 1 is a block diagram of an ultrasonic flow meter related to Example 1. FIG. FIG. 2A shows the operation timing of the delay means. 1, the ultrasonic flowmeter of the present invention includes a flow path 1 through which a fluid to be measured flows, a first vibrator 12 and a second vibrator 13 that transmit and receive ultrasonic waves disposed in the flow path 1. The receiving means 14 for driving the first vibrator 12, the control means 15 for outputting a measurement start signal for operating the driving means 14, and the reception signal of the second vibrator 13 are received to determine the reception timing. The timing detection means 16 for performing the output, the delay means 17 for outputting the output of the timing detection means 16 as a trigger signal for the drive means 14 with a delay of a predetermined delay time, the transmission / reception of ultrasonic waves, and the delay means 17 again after the delay time. Repeating means 18 for measuring the number of operations of repeating transmission and reception of sound waves and stopping the operation at a predetermined number of times, and said repeating means from the start of driving of the first vibrator 12 by at least the driving means 14 8 includes a time measuring means 19 for measuring the propagation time of the ultrasonic wave until the operation is stopped, and a calculating means 20 for calculating the flow velocity between the pair of vibrators from the value of the time measuring means 19 and obtaining the flow rate therefrom. is there.
[0034]
The delay means 17 operates for a predetermined time before sending a measurement start signal for urging the drive signal from the control means 15 to the first vibrator 12. As a result, an unstable state in the initial stage of operation unique to the delay means is avoided, and measurement is started after the state is stabilized.
[0035]
For example, the determination result of the timing detection unit 16 also shown in the conventional example is delayed by a delay unit 17 for a predetermined time, and then returned to the drive unit 14 to transmit again and repeat the operation a predetermined number of times to measure the time. Based on the measurement time, a method of obtaining the flow rate by calculation of (Equation 2) and obtaining the flow rate using the cross-sectional area of the flow path previously known from the flow rate will be described. Here, the delay means 17 is operated for a predetermined time immediately before measurement according to the number of repetitions set in the repetition means 18.
[0036]
In this case, when the number of repetitions is several hundred, the operation of the delay means 17 may differ between the first time and the last time. Usually, an LC distributed constant circuit or the like is used as the delay means 17, but these elements also include a resistance component.
[0037]
If there is a resistance component in the delay means 17, there is no problem in the first repetition if a current is passed. However, as the number of times is increased, heat is generated by the current, and as a result, the delay time changes. However, since this heat generation also has an equilibrium point, the delay time may be regarded as constant at a certain number of repetitions. FIG. 2A shows a conceptual diagram of the number of repetitions and the delay time per delay of the delay means 17.
[0038]
If the number of repetitions is less than this, the difference in delay time is large, so the long 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 averaged by the number of times and may enter the error range. In such a case, the delay means 17 may be operated for a short time before the measurement start signal to be measured.
[0039]
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 longer than the specified number. In actual use, the time is determined based on the capacity of the power source and 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 x times. Thus, the operation of the delay means 17 becomes sufficiently stable, and it becomes possible to realize a delay time with higher accuracy than the initial measurement.
[0040]
As described above, the unstable operation at the initial stage of the operation of the delay means 17 can be performed in advance, and the operation at the time of measurement can be stabilized. Therefore, stable time measurement can be performed and accurate flow rate measurement can be performed. In particular, by adjusting the operating time of the delay means 17, the change in measurement accuracy with respect to the number of repetitions can be reduced, and stable and accurate flow rate measurement can be performed.
[0041]
The series of flows is as shown in the timing diagram of FIG.
[0042]
Further, if the distance between the vibrators changes or the delay time unique to the delay means 17 changes, the total time measured by the time measuring means 19 changes even if the number of repetitions is the same. When the delay means 17 has a resistance component as described above, the thermal equilibrium point may be related not to the number of repetitions but to the total time of repetition.
[0043]
In this case, in order to improve the measurement accuracy, the delay means 17 is operated before the measurement with reference to the y point in FIG. 2B where the delay time becomes stable. For example, if the total time is long, the difference in the delay time averages into the error range, so the delay means may be operated for a short time before the measurement.
[0044]
As a result, even if the total time is repeatedly changed, by performing the initial operation in consideration of the characteristics of the delay means 17, the delay means 17 performs a stable operation, so that it is possible to realize accurate measurement.
[0045]
Similarly, when the distance between the transducers changes, the delay time unique to the delay means 17 changes, or 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 contrary, when the ratio of the delay time is small, the thermal equilibrium is delayed due to heat dissipation. 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 timing detection means 16 detects the reception timing after outputting the measurement start signal. For example, since the time in the delay means 17 is roughly known from the time measured by the time measuring means 19 in FIG. 1 for one repetitive operation, the delay time of the delay means 17 occupying the repeat time is known. The delay means 17 is operated before the measurement with reference to the z point in FIG.
[0046]
As a result, by adjusting the operation time before the measurement start signal for starting the measurement of the delay means 17 according to the time per repetition, the variation in the delay time due to heat dissipation of the delay means itself is reduced. Stable measurement can be realized.
[0047]
(Example 2)
In Example 2 A flow rate measuring apparatus according to the present invention will be described. FIG. 4 is a block diagram showing the configuration of this embodiment. A difference from the first embodiment is that a switching means 21 is provided between the driving means 14 and the first vibrator 12 and between the second vibrator 13 and the timing detecting means 16 to transmit / receive ultrasonic waves to the first vibrator. 12 and the second vibrator 13 are alternately performed. When the transmission / reception is alternately performed by the switching means 21 in this way, the operation of the delay means 17 is different in the case where transmission is first performed by the first vibrator 12 and then transmission is performed by the second vibrator 13. May come.
[0048]
For example, the method of measuring the propagation time from upstream to downstream and from downstream to upstream of the fluid to be measured, which is also shown in the conventional example, obtaining the velocity v from (Equation 3), and obtaining the flow rate from the flow velocity. . This method is widely used because the flow rate can be measured without being affected by the change in sound speed, but an accurate value cannot be obtained if there is a timing error due to the delay means 17 at the time of measurement. A method for preventing this phenomenon will be described below.
[0049]
As described in the first embodiment, when the number of repetitions is several hundred, the operation of the delay means 17 differs between the first time and the last time, but there are other factors. For example, when the switching means 21 is operated after performing the repetitive operation a predetermined number of times, and the same repetitive operation is performed by reversing the transmission / reception of the vibrator, the delay means 17 is already operating before the switching operation, so that the sufficiently balanced point is reached. It may be reached. FIG. 5A 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 and the transmission / reception direction is changed.
[0050]
Because of such characteristics, the delay means 17 is not operated before the measurement start signal to be measured according to the number of operations of the repeat means, but before or after the switching means 21 is operated. Considering this and the number of repetitions set by the repetition means, the delay means is operated for a predetermined time immediately before the measurement.
[0051]
Accordingly, when measuring the propagation time from upstream to downstream and from downstream to upstream and obtaining the flow rate from the difference in propagation time, the difference between FIGS. 5A and 5B can be reduced, so that the flow rate can be obtained with high accuracy. .
[0052]
Further, even if the number of repetitions is the same before and after the operation of the switching means 21, the total time measured by the time measuring means 19 varies. In this case, in order to improve the measurement accuracy, the delay means 17 is not operated before the measurement start signal that is measured according to the repetition time, but before or after the switching means 21 is operated. The predetermined time delay means 17 is operated before the measurement start signal to be measured in consideration of the time taken for the number of repetitions set by the repetition means.
[0053]
This makes it possible to reduce the difference in operation of the delay means 25 when measuring the propagation time from upstream to downstream and from downstream to upstream and obtaining the flow rate from the propagation time difference, thereby improving the measurement accuracy. .
[0054]
Similarly, the ratio of the delay time of the delay means 17 occupying one repetition time before and after the operation of the switching means 21 varies depending on the flow velocity or the like. In this case, in order to improve the measurement accuracy, the delay means 17 is not operated before the measurement start signal that is measured according to the time per repetition, but before or after the switching means 21 is operated. Considering this, the predetermined time delay means is operated before the measurement start signal to be measured in consideration of this and the time per repetition.
[0055]
This makes it possible to reduce the difference in operation of the delay means 17 when determining the flow rate from the propagation time difference, and improve the measurement accuracy.
[0056]
In addition, when the transmission / reception direction is switched by operating the switching means 21 and then the measurement start signal is transmitted from the control means 15 to meet the driving means 14 to drive the vibrator, the delay is made during the switching operation. The means 17 may deviate from the operation equilibrium point due to heat dissipation or the like. As a specific example, the difference in delay time shown in FIGS. 5A and 5B is changed from the thermal equilibrium point. When the series of operations is fast, there is not much time to deviate from the equilibrium point. Therefore, the difference between FIGS. 5A and 5B is large. On the contrary, when the switching operation is slow, the delay means has become warm due to a large deviation from the equilibrium point. 17 gets cold and the difference is not so much. 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 cooled, so there is not much difference in the delay time before and after switching. In such a case, there is a possibility that sufficient accuracy can be obtained without operating the delay means 17 before the measurement. On the other hand, when the switching operation is performed quickly enough, the difference in delay time before and after switching is large. Therefore, when sending the measurement start signal to be measured first, 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.
[0057]
Thus, by operating before the measurement start signal for measuring the delay means 17 in accordance with the switching time, the state of the measurement system can be made substantially the same when measuring the propagation time difference, thereby improving the accuracy. Can do.
[0058]
In a flow rate measurement device that measures the propagation time difference between a pair of transmission / reception signals and then repeats the same operation after a certain period of time to continue the measurement, the pair of transmission / reception signal switching operations are terminated and the next measurement is performed. The delay means 17 is operated for a predetermined time before the measurement start signal to be measured according to the time until the measurement start signal is sent. In FIG. 6, at first t0, the first vibrator 12 is transmitting and the second vibrator 13 is operating on the receiving side. After the operation has been repeated a predetermined number of times, the switching means operates at time tx, and then the second vibrator 13 is transmitting and the first vibrator 12 is operating on the receiving side. Although the propagation time difference is obtained by this pair of operations, the same transmission / reception is performed at the next time t2.
[0059]
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, sampling interval time).
[0060]
This means that if the sampling time is sufficiently long, the delay means is also cooled down. Therefore, it is necessary to operate the delay means for a long time before measurement. On the contrary, when the sampling time is short, the delay means 17 is not so deviated from the equilibrium point. Therefore, when the measurement is performed for the first time after the sampling time elapses, the delay means 17 is operated before the measurement start signal for measuring only a short time. It is possible to reach the equilibrium point of the delay means 17 sufficiently. Thus, by operating before the measurement start signal for measuring the delay means 17 in accordance with the sampling time, it is possible to realize an optimum measurement system when measuring the propagation time difference and improve the accuracy.
[0061]
In this case, after the sampling time elapses, the first vibrator always starts the operation of measuring the propagation time difference on the transmission side, but there is no problem even if the second vibrator starts measurement on the transmission side.
[0062]
(Example 3)
In Example 3 A flow rate measuring apparatus according to the present invention will be described. FIG. 7 is a block diagram showing the configuration of this embodiment. The difference from the first embodiment is that a temperature detection unit and a voltage detection unit are provided.
[0063]
The delay means 17 has an equilibrium point due to temperature. Therefore, the stabilization time varies depending on the ambient temperature. For this reason, the temperature detection means 22 is provided, and the measurement is started after the signal from the temperature detection means 22 is operated for a predetermined time before the measurement start signal for measuring the delay means 17 in accordance with the signal and is brought into a stable state. For example, it takes a long time to reach a stable state at low temperatures, such as in winter. There is a case.
[0064]
In this way, by changing the initial stabilization method according to the ambient temperature, the delay means 17 can be quickly brought to an optimum state.
[0065]
Further, the flow rate calculation means 20 obtains the flow rate from the measured time difference. A large flow rate means that the difference in propagation time obtained by switching transmission / reception of ultrasonic waves increases because the fluid to be measured flows through the flow path at high speed. If the propagation time difference is large, the measurement error is not so conspicuous, but if the flow rate is small, the propagation time difference is small. If the operation of the delay means 17 is not stable, the measurement error becomes large. Therefore, the measurement is started after being operated for a predetermined time 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 to be in a stable state.
[0066]
By performing such an operation, it is possible to maintain a stable time accuracy even at a low flow rate, and as a result, it is possible to improve the accuracy of the flow rate.
[0067]
The delay means 17 has an equilibrium point due to temperature. When this measuring system is operated electrically, the amount of heat generated varies depending on the voltage. Accordingly, the voltage detection means 23 for monitoring the power supply voltage supplied to the measurement system is provided, and the delay means 17 is operated for a predetermined time immediately before the measurement in accordance with a signal from the voltage detection means 23 to be in a stable state. Start measurement. For example, when a battery is used, the voltage is high at the beginning of operation, but the voltage gradually decreases as it 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. On the other hand, when the voltage is low, not much current flows and it takes time to reach the thermal equilibrium point. Considering these states, the initial stabilization method is changed before the measurement start signal to be measured according to the voltage.
[0068]
This makes it possible to set the optimum initial operation of the delay means from the state of the measurement system.
[0069]
Further, it is possible to perform a power saving operation by monitoring the voltage. In the figure, the temperature detecting means and the voltage detecting means are combined, but if one of them is present, the operation can be sufficiently satisfied.
[0070]
Although the switching means is not described in the drawing shown in the present embodiment, the same effect can be obtained with the configuration having the switching means as shown in the second embodiment.
[0071]
(Example 4)
In Example 4 A flow rate measuring apparatus according to the present invention will be described. FIG. 8 is a block diagram showing the configuration of this embodiment. The difference from the first embodiment is that a first storage unit and a second storage unit are provided.
[0072]
The delay means 17 is not stable in the initial stage of operation, but becomes gradually more stable as it operates. The stable state often depends on the number of times of operation 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 determined by experiments or the like and stored in the first storage unit 24. Further, when there is an inter-object variation of the delay means 17, a value obtained by inspection is stored. In the actual operation, the delay means 17 is operated before the measurement start signal for measuring only the number of operations or the operation time stored in the first storage means 24, and measurement is started.
[0073]
As a result, since the operation is based on the information unique to the delay means 17, it is possible to easily set a stable state and to reduce the variation of the flow rate measuring device.
[0074]
In order to improve the stability of the delay means 17, the optimum value may vary depending on the ambient temperature, the number of repetitions, the flow rate, and the power supply voltage. In order to improve the accuracy of low flow rate, it is necessary to have a measurement system that fully incorporates these factors of change. Accordingly, the ambient temperature until the delay means 17 is substantially stabilized, the number of repetitions, the repetition time, the trigger signal, and the time when the reception timing is detected by the timing detection means, the operating time of the switching means, the flow rate, and the power supply voltage to be supplied The optimum delay time due to the combination of at least two or more is previously examined and stored in the second storage means 25.
[0075]
Further, when there is an inter-object variation of the delay means 17, a value obtained by inspection is stored. In the actual operation, the delay means 17 is operated before the measurement start signal for measuring only the time corresponding to the delay time stored in the second storage means 25, and the measurement is started after it is stabilized. As a result, since the operation is performed in consideration of the information unique to the delay means 17 and the surrounding state, a stable state can be easily set, and variations in the flow rate measuring device can be reduced.
[0076]
The first storage means 24 is in a state where it can be rewritten. For example, rewriting is performed from a microcomputer or by inputting a signal from the outside. In the semiconductor memory means, the semiconductor itself can be replaced.
[0077]
As a result, when the optimum operating point of the delay means is deviated depending on the location and time of installation of the flow rate measuring device, the contents can be corrected. In addition, when an aging change or the like occurs, it can be similarly rewritten and dealt with. And it becomes possible to maintain a stable state for a long time.
[0078]
The second storage means 25 has a state in which rewriting is possible. As a result, when the optimum operating point of the delay means 17 is deviated depending on the place and time of installation of the flow rate measuring device, the contents are corrected. Even when the battery voltage ages or the aging of each constituent element occurs, it can be similarly rewritten and dealt with. This makes it possible to maintain a stable state for a long time.
[0079]
The first storage means 24 performs rewriting according to conditions during the measurement operation. For example, when the low flow rate state continues for a long time, in order to further improve the accuracy, the time period during which the actual measurement operation is finished from the control means 15 or the like (for example, between t1 and t2 in FIGS. 6A and 6B). Etc.), the conditions are rewritten to further increase the stability of the delay means 17. On the contrary, when the flow rate is large and the operation of the delay means can be sufficiently ignored as an error, the stability of the delay means 17 can be lowered to a certain level or less. In this way, it is possible to easily realize the optimum state as the measurement system by changing the initial operation of the delay means according to the measurement state.
[0080]
The second storage means 25 performs rewriting according to conditions during the measurement operation. For example, this is a case where the temperature fluctuates rapidly depending on the installation location. In such a case, in order to maintain accuracy, the delay means 17 in the time zone during which the actual measurement operation is finished from the control means 15 or the like (for example, between t1 and t2 in FIGS. 6A and 6B). Rewrite the conditions to maintain the stability of. In this way, it is possible to easily realize the optimum state as the measurement system by changing the initial operation of the delay means according to the measurement state. In addition, it is possible to operate for a long time by considering the correlation with the power supply voltage.
[0081]
In the figure, the first storage means 24 and the second storage means 25 are combined. However, if there is one, the operation can be sufficiently satisfied.
[0082]
In the above description, the thermal balance of the delay means 17 has been described. However, the stability of the delay means 17 is not limited to heat. Can be obtained.
[0083]
In the above description, the delay means 17 is operated before the measurement start signal output from the control means 15. However, if the received signal is sufficiently stabilized by the prior operation, this delay means. The operation 17 is not limited to the time before the measurement start signal, and may be a time that does not hinder the start of measurement.
[0084]
【The invention's effect】
As is apparent from the above description, the flow measurement device of the present invention provides the following effects.
[0085]
(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 can be performed. become.
[0086]
(2) By adjusting the operating time of the delay means according to the number of repetitions, the change in measurement accuracy with respect to the number of repetitions can be reduced, and stable and accurate flow rate measurement can be performed.
[0087]
(3) Even if the total time is changed 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.
[0088]
(4) By adjusting the operating time of the delay means in advance according to the time per repetition, stable measurement can be realized with less delay time variation due to heat dissipation of the delay means itself.
[0089]
(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 to be measured according to the number of repetitions set in the repetition means, and from upstream to downstream and from downstream to upstream. Since the difference in the initial operating characteristics of the delay means can be reduced when the respective propagation times are measured and the flow rate is obtained from the propagation time difference, the flow rate can be obtained with high accuracy.
[0090]
(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 that is measured according to the repetition time obtained by the time measuring means, so that the upstream to the downstream and the downstream to the upstream respectively When the propagation time is measured and the flow rate is obtained from the propagation time difference, the difference in the initial operation of the delay means can be reduced, and the measurement accuracy can be improved.
[0091]
(7) By considering the operation before and after the switching means, by operating the delay means for a predetermined time before outputting the measurement start signal and measuring the signal according to the time when the reception timing is detected by the timing detection means. Considering whether it is before or after the switching means is operated, the flow rate is obtained from the propagation time difference in order to operate the delay means for a predetermined time before the measurement start signal to be measured in consideration of the time per repetition count In this case, the difference in operation of the delay means can be reduced, and the measurement accuracy can be improved.
[0092]
(8) By operating the delay means for a predetermined time before the measurement start signal that is measured according to the operation time of the switching means, the state of the measurement system can be made substantially the same when measuring the propagation time difference. Measurement accuracy can be improved.
[0093]
(9) When measuring the propagation time difference by operating the delay means for a predetermined time before the measurement start signal measured according to the time until the next measurement start signal after switching the pair of transmission and reception by the switching means. An optimal measurement system can be realized and accuracy can be improved.
[0094]
(10) By operating the delay means for a predetermined time before the measurement start signal that is measured according to the signal of the temperature detection means, the delay means can be quickly brought into an optimum state by changing the initial stabilization method according to the ambient temperature. It becomes possible to go.
[0095]
(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, and as a result, the flow rate accuracy is also improved. It becomes possible to do.
[0096]
(12) The initial stabilization method before the measurement is changed by operating for a predetermined time before the measurement start signal to be measured according to the output of the voltage detection means for detecting the power supply voltage supplied for performing the measurement of the delay means. This makes it possible to set the optimum initial operation of the delay means from the state of the measurement system.
[0097]
(13) Measurement using a first storage unit that stores in advance at least one of the number of times that the stability of the delay unit is saturated or the operation time, and measuring the delay unit according to the value of the first storage unit By operating for a predetermined time before the start signal, the operation is based on information unique to the delay means, so that a stable state can be easily set, and variations in the flow rate measuring device can be reduced.
[0098]
(14) A combination of at least two or more of 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 means for storing the optimum delay time according to the above, and by operating the delay means for a predetermined time before the measurement start signal that is measured according to the value of the second storage means, Therefore, it is possible to easily set a stable state and to reduce variations in the flow rate measuring device.
[0099]
(15) By making the first storage means rewritable, the contents can be corrected if the optimum operating point of the delay means is deviated depending on the location and time of installation of the flow rate measuring device. In addition, when an aging change or the like occurs, it can be similarly rewritten and dealt with. And it becomes possible to maintain a stable state for a long time.
[0100]
(16) By rewriting the second storage unit according to conditions during measurement, even if a battery voltage aging or a secular change of each component occurs, the case can be similarly rewritten and dealt with. Is possible. And it becomes possible to maintain a stable state for a long time.
[0101]
(17) By rewriting the first storage means according to conditions during measurement, it is possible to easily realize the optimum state as the measurement system by changing the initial operation of the delay means according to the measurement state.
[0102]
(18) By rewriting the second storage means according to conditions during measurement, it is possible to easily realize the optimum state as the measurement system by changing the initial operation of the delay means according to the measurement state. In addition, it is possible to operate for a long time by considering the correlation with the power supply voltage.
[Brief description of the drawings]
FIG. 1 is an overall block diagram of a flow rate measuring apparatus according to a first embodiment of the present invention.
FIG. 2A is a diagram showing the relationship between the number of repetitions and the delay time in the same flow rate measuring device.
(B) The figure which shows the relationship between the repetition time and delay time in the same flow measuring device
(C) The figure which shows the relationship between one repetition time and delay time in the same flow measuring device.
FIG. 3A is a timing chart showing the operation of an oscillation wave of the flow rate measuring device.
(B) Timing chart showing received wave operation of the flow rate measuring device
(C) Timing chart showing the operation of the delay means of the flow rate measuring device
FIG. 4 is an overall block diagram of a flow rate measuring device according to Embodiment 2 of the present invention.
FIG. 5 is a diagram showing the state of delay time in the operation of the switching means of the flow rate measuring device
FIG. 6A is a timing chart showing the first vibrator operation of the flow rate measuring device.
(B) Timing chart showing the second vibrator operation of the flow rate measuring device
FIG. 7 is an overall block diagram of a flow rate measuring apparatus according to Embodiment 3 of the present invention.
FIG. 8 is a block diagram of the entire flow rate measuring device for an ultrasonic current meter in Embodiment 4 of the present invention
FIG. 9 is an overall block diagram of a conventional flow rate measuring device.
[Explanation of symbols]
1 channel
12 First vibrator
13 Second vibrator
14 Drive means
15 Control means
16 Timing detection means
17 Delay means
18 Repeating means
19 Timekeeping
20 Flow rate calculation means
21 Switching means
22 Temperature detection means
23 Voltage detection means
24 first storage means
25 Second storage means

Claims (18)

A pair of transducers arranged in the flow path of the fluid to be measured and transmitting and receiving ultrasound;
Driving means for driving one of the vibrators ;
Timing detection means for receiving the output from the other transducer and determining the reception timing;
A delay means that comprises an LC distributed constant circuit including a resistance component, delays the output of the timing detection means for a predetermined time, and outputs it as a trigger signal of the drive means;
Repeating means for measuring the number of operations of repeating the transmission and reception of ultrasonic waves again after the transmission and reception of ultrasonic waves and the delaying operation, and stopping the operation at a predetermined number of times,
Control means for outputting a measurement start signal for causing the driving means to perform initial driving;
Timing means for measuring the propagation time of the ultrasonic waves,
And a calculating means for obtaining by calculating the flow velocity of the fluid to be measured between the pair of transducers from the value of the clock means,
The delay means operates before the measurement start signal for a predetermined time required for the temperature of the resistance component to reach an equilibrium point,
The said time measuring means is a flow measuring device which time-measures the time from the time of the output of the said measurement start signal to the time of the operation stop of the said repeating means . The flow rate measuring device according to claim 1 , wherein the delay unit changes the length of the predetermined time according to the number of repetitions set in the repetition unit. The flow rate measuring apparatus according to claim 1 , wherein the delay unit changes the length of the predetermined time according to a value of the time measuring unit. A pair of transducers arranged in a flow path through which the measurement fluid flows and transmitting / receiving ultrasonic waves, and a driving means for driving one of the transducers;
Timing detection means for receiving the output from the other transducer and determining the reception timing;
A delay means that comprises an LC distributed constant circuit including a resistance component, delays the output of the timing detection means for a predetermined time, and outputs it as a trigger signal of the drive means;
Repeating means for measuring the number of operations of repeating the transmission and reception of ultrasonic waves again after the transmission and reception of ultrasonic waves and the delay operation by the delay means, and stopping the operation at a predetermined number of times,
Control means for outputting a measurement start signal for causing the driving means to perform initial driving;
Time measuring means for measuring the propagation time of the ultrasonic wave;
Calculating means for calculating the flow velocity of the fluid under measurement between the pair of vibrators from the value of the time measuring means,
A predetermined time required for the temperature of the resistance component to reach the equilibrium point is determined according to the time when the reception timing is detected by the timing detection means after the measurement start signal is output, and the next measurement is performed for the operation time. It works before the start signal
The time measuring means is a flow rate measuring device that measures the time from when the next measurement start signal is output to when the operation of the repeating means is stopped . A switching unit configured to switch between a transmission function and a reception function of two transducers that transmit and receive ultrasonic waves, the delay unit depending on the presence or absence of the operation of the switching unit and the number of repetitions set in the repetition unit The flow rate measuring device according to claim 1, wherein the length of the predetermined time is changed . Has a switching means for setting switching the receiving function and the transmission function of the two transducers for transmitting and receiving ultrasonic waves, said delay means, the predetermined time according to the value of the presence and timing means operation of said switching means The flow rate measuring device according to claim 1 or 3, wherein the length is changed . Has a switching means for setting switching the receiving function and the transmission function of the two transducers for transmitting and receiving ultrasonic waves, said delay means, the timing detecting means from the output whether the measurement start signal of the operation of said switching means flow rate measuring apparatus according to claim 1, wherein changing the length of the predetermined time according to the time of detecting the reception timing. Has a switching means for setting switching the receiving function and the transmission function of the two transducers for transmitting and receiving ultrasonic waves, said delay means, claim to change the length of the predetermined time according to the operation time of the switching means 1. The flow rate measuring device according to 1. Has a switching means for setting switching the receiving function and the transmission function of the two transducers for transmitting and receiving ultrasonic waves, said delay means, after switching the pair of transmitted and received by the switching means, the time until the next measurement start signal The flow rate measuring apparatus according to claim 1, wherein the length of the predetermined time is changed according to the condition. The flow rate measuring apparatus according to claim 1 , further comprising a temperature detection unit, wherein the delay unit changes the length of the predetermined time in accordance with a signal from the temperature detection unit. The flow rate measuring apparatus according to claim 1 , wherein the delay unit changes the length of the predetermined time according to the flow rate of the fluid to be measured. Has a voltage detecting means for detecting a power supply voltage supplied to perform measurement, the delay means, the flow rate measuring apparatus according to claim 1, wherein changing the length of the predetermined time in accordance with the output of said voltage detecting means . Having a first storage means for stability of the pre-delay means stores at least one of the operating time or the operating time is saturated, the delay means, the predetermined in accordance with a value of said first storage means The flow rate measuring apparatus according to claim 1, wherein the time length is changed . Optimum by a combination of at least two or more of the ambient temperature, the number of repetitions, the repetition time, the time when the reception timing is detected by the timing detection means, the operation time of the switching means, the flow rate, and the power supply voltage to be supplied The flow rate measuring apparatus according to claim 1 , further comprising a second storage unit configured to store a delay time, wherein the delay unit changes the length of the predetermined time according to a value stored in the second storage unit.   The flow rate measuring apparatus according to claim 13, wherein the first storage means can be rewritten.   15. The flow rate measuring device according to claim 14, wherein the second storage means can be rewritten.   The flow rate measuring device according to claim 13 or 15, wherein the first storage means performs rewriting according to conditions during measurement.   17. The flow rate measuring device according to claim 14, wherein the second storage means rewrites according to conditions during measurement.

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