JP3945530B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures a flow rate of gas or the like using ultrasonic waves.

For example, as shown in FIG. 11, a conventional flow measuring device of this type is provided with ultrasonic transducers 2 and 3 in a part of a fluid conduit 1 so as to be opposed to the flow direction. When an ultrasonic wave is generated and the ultrasonic wave is detected by the vibrator 2, the ultrasonic wave is again generated from the vibrator 1, and this time is repeated to measure the time. The same repetition time was measured, and the fluid velocity was calculated from the difference in time (see, for example, Patent Document 1).
JP-A-4-328424

  However, in the conventional flow rate measuring device, the measurement start signal is determined to be a certain frequency or a function including a random function, and measurement is performed at the determined sampling frequency even when no fluid is flowing. It was broken. For this reason, the frequency of using electric power is high, and in the case of battery driving, battery replacement is required within a short period of time, and reduction of power consumption has been an issue.

  The present invention solves the above-described problems, and aims to reduce power consumption.

In order to achieve the above object, a flow rate measuring apparatus according to the present invention includes a first vibrator provided in a fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, A measurement circuit for measuring a signal propagation time between the transducers, a flow rate calculation unit for calculating a flow rate based on a signal of the measurement circuit, a measurement start unit for starting measurement by the transducer, and a flow rate calculation unit An average period variable means for changing an average value of the period of the measurement start means based on a value, an irregular value generation means for generating a random value, and a signal of the irregular value generation means as a signal of the average period variable means And a period variable means to which is added.

  The flow rate measuring device of the present invention can accurately measure even if the flow rate varies.

The flow rate measuring device of the present invention includes a first vibrator provided in a fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a signal transmission between the vibrators. a measuring circuit for measuring time, and flow rate calculation means for calculating a flow rate based on the signal of the measuring circuit, a measurement starting means for starting the measurement by the transducer, the measurement start based on the value of the flow rate computing means An average period variable means for changing the average value of the period of the means , an irregular value generating means for generating a random value, and a period variable means for adding a signal of the irregular value generating means to a signal of the average period variable means; It is equipped with .

  Before describing embodiments of the present invention, reference embodiments will be described.

(Reference Example 1)
In FIG. 1, a first vibrator 5 that transmits ultrasonic waves and a second vibrator 6 that receives ultrasonic waves are disposed in the flow direction in the middle of a fluid conduit 4. 7 is a transmission circuit to the first vibrator 5, and 8 is an amplification circuit for the signal received by the second vibrator 6. This amplified signal is compared with the reference signal by the comparison circuit 9, and the time from transmission to reception is shown. Is measured by the time measuring means 10 such as a timer counter, and the measuring circuit 11 is formed from the transmitting circuit 7 to the time measuring means 10.

  The flow rate calculation unit 12 obtains a flow rate value in consideration of the size of the pipe line and the flow state according to the ultrasonic propagation time by the time measuring unit 10, and the cycle variable unit 13 determines the measurement cycle based on the value of the flow rate calculation unit 12. And the timing of signal transmission to the transmission circuit 7 is adjusted by the measurement start means 14 in accordance with the value of the period variable means 13. The calculation end of the flow rate calculation means 12 is sent to the measurement end means 15, and the voltage of the measurement circuit 11 is lowered by the voltage control means 16 in synchronization with the measurement end means 15. Further, the voltage of the measurement circuit 14 is restored in synchronization with the start of measurement by the measurement start means 14.

  Next, the operation will be described. The ultrasonic signal transmitted from the measurement starting means 14 from the transmission circuit 7 and transmitted by the first vibrator 5 is transmitted through the flow and received by the second vibrator 6 and received by the amplification circuit 8 and the comparison circuit 9. The time from the transmission to the reception is measured by the time measuring means 10.

If the sound in the static fluid is c and the velocity of the fluid flow is v, the propagation speed of the ultrasonic wave in the forward direction of the flow is (c + v). When the distance between the transducers 5 and 6 is L, and the angle between the ultrasonic transmission axis and the central axis of the pipe is φ, the time t when the ultrasonic wave reaches is
t = L / (c + vCOSφ) (1)
From the equation (1), v = (L / tc) / COSφ (2)
If L and φ are known, the flow velocity v can be obtained by measuring t.

From this flow velocity, if the flow rate Q is S and the correction count is K,
Q = KSv (3)
It becomes.

  For example, when the integrated value is accurately obtained as in a gas meter, the measurement needs to be performed in a complicated manner. In particular, when the flow rate is large, it is necessary to shorten the measurement sampling time to reduce the error, but when the flow rate is relatively small or 0, even if the measurement sampling time is delayed, there is almost no error.

  Therefore, the measurement interval can be changed according to the flow rate calculation means 12. FIG. 2 shows the state of measurement when the flow rate changes with time. When the value of the flow rate calculation means 12 is small, the interval of the measurement time is increased by the period variable means 13 and the value of the flow rate calculation means 12 is changed. The measurement time interval is reduced as the value increases.

  In this way, the measurement cycle is changed according to the flow rate value, but the voltage of the measurement circuit 11 is reduced between the measurements. That is, when the flow rate calculation means 12 finishes measuring the flow rate, a signal is sent to the measurement end means 15 and the voltage control means 16 lowers the voltage or makes it zero. Before the measurement is started by the measurement start means 14, the voltage control means 16 restores the voltage of the measurement circuit 11 to the original.

(Reference Example 2)
FIG. 4 shows a second embodiment. When the value of the flow rate calculation means 12 is zero, the measurement cycle is changed by the cycle variable means 13 by the zero count detection means 19, and the number of times of zero flow is continuously increased. Accordingly, the measurement cycle of the measurement start means 14 is increased.

  FIG. 5 shows a state in which the measurement time interval changes as the flow rate changes with time. At this time, even if the flow rate is zero for a long period of time, a large flow rate may suddenly flow out, so an upper limit is set to avoid an extremely long measurement cycle.

(Reference Example 3)
  FIG. 6 shows a third embodiment, in which the value of the flow rate calculation means 12 is integrated by the integration calculation means 20 to obtain an integrated value for one day, one month, or one year, and is used for a gas meter or the like. FIG. 7 shows a case where a large flow rate suddenly starts to flow after the flow rate zero continues several times and the measurement cycle becomes large.

In FIG. 7, when the flow rate zero continues several times, and it is actually assumed that there is a flow rate as shown in a to b, the measurement is zero at time T9 and the flow rate at the next measurement time period T10. b will be measured. At this time, there are three types of methods for integrating the integration calculation means 20. As a first method, a value obtained by multiplying the value of the flow rate b by a time difference of time T10-T9 (hereinafter referred to as Δt9) is added, and at this time, the integrated value is always calculated more than the actual value. As a second method, a value obtained by multiplying the value (zero) of the flow rate a by the time difference Δt9 is added, that is, 0 is added. At this time, the integrated value is always smaller than the actual value. As a third method, a value obtained by multiplying a constant value (0.1 to 0.9) in the value of the flow rate b by a time difference Δt9 is added. When the constant is 0.5, the value is half of the flow rate b in FIG. A value obtained by multiplying the value by Δt9 is added. That is, a line connecting the flow rate c and the flow rate b is added.

( Reference Example 4)
FIG. 8 shows a fourth embodiment, in which ultrasonic transmission from the transmission means 7 to the comparison means 9 is repeated by the repetition means 21 for the number of times set by the number setting means 22, and the accumulated time is measured by the timing means 10. When the value of the flow rate calculation means 12 continuously measures a zero value, the value of the measurement period is changed by the period variable means 13 together with the number of times, and the number of repetitions is reduced, that is, the number of times of transmission of the vibrator is reduced. The measurement is performed to obtain an outline of the flow value by the search and measurement means 23 that shortens the measurement time and reduces power consumption.

The interval between the flow rate and the measurement time at this time is shown in FIG. Search measurement is performed at times T3 ', T4', T5 ', and T6' during measurement of T3, T4, T5, and T6 for obtaining an accurate flow rate. As shown in FIG. 8, when a flow rate of a predetermined value or more is detected in the search measurement of T6 ', the next measurement is performed with a measurement cycle reduced as in T7 and T8.

(Reference Example 5)
  FIG. 10 shows a fifth embodiment, in which the cycle of the measurement is changed by the cycle variable means 13 according to the value of the flow rate calculation means 12 and the flow coefficient of the flow rate calculation means 12 is changed by the coefficient setting means 24. The flow coefficient is corrected in consideration of changes in the operating time of the electronic circuit and the ultrasonic transducer due to the change in the measurement period, and changes in response and sensitivity.

  Based on the above reference embodiment, an embodiment of the present invention will be described below with reference to the accompanying drawings.

Example 1
In FIG. 3, the average value of the measurement period is changed by the period variable means 17 according to the value of the flow rate calculation means 12, and a signal for generating a random value is generated by the irregular value generation means 18. The value is added by the period variable means 13 to change the signal transmission period to the measurement start means 14. At this time, even if the flow rate value is constant, the measurement cycle changes irregularly within a predetermined range by the signal of the irregular value generating means 18. The value of the irregular value generating means 18 is set to be zero when averaged.

  The above reference embodiment and the technical significance of the embodiment are summarized as follows.

(1) a first vibrator provided in a fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators , A flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit, a measurement start means for starting measurement by the vibrator, a measurement end means for notifying completion of flow rate measurement by the flow rate calculation means, and a measurement end means or measurement Since the voltage control means for controlling the supply voltage of the measurement circuit by the start means and the cycle variable means for changing the cycle of the measurement start means based on the value of the flow rate calculation means, the measurement cycle is shortened when the flow value is large. Therefore, when the flow rate value is small, the power consumption can be reduced by extending the measurement cycle, and the power consumption can be reduced by making the circuit voltage small or zero during intermittent measurement. Measure Bets can be, it is possible to increase the battery life.

  (2) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. The flow rate calculation means for calculating the flow rate based on the signal of the measurement circuit, the measurement start means for starting measurement by the vibrator, and the average cycle variable for changing the average value of the cycle of the measurement circuit based on the value of the flow rate calculation means Means, a random value generating means for generating a random value, and a period variable means in which the signal of the irregular value generating means is added to the signal of the average period variable means. However, high accuracy can be maintained even if the measurement period is long.

  (3) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. , A flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit, a measurement start means for starting measurement by the vibrator, and a period for increasing the cycle of the measurement start means in accordance with the number of zero values detected by the flow rate calculation means Since it has a variable means, the measurement cycle can be extended when the flow rate is zero, that is, when no fluid is used, so the power consumption is greatly reduced when the daily usage time is short, such as a household gas meter. it can.

  (4) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. A flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit, a measurement start means for starting measurement by the vibrator, and a cycle variable means for increasing the cycle of the measurement start means when a zero value is detected by the flow rate calculation means, In addition to integrating the flow rate value of the flow rate calculation means, and equipped with an integration calculation means for adding a value obtained by multiplying the flow rate value by the elapsed time from the previous measurement when a flow rate of a predetermined value or more is detected after the zero value is detected. When the measurement cycle becomes long, the flow rate value that has unexpectedly started to flow is measured to a large extent, and this acts on the safe side when the amount of dangerous fluid leakage is calculated.

  (5) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. A flow rate calculating means for calculating a flow rate based on the signal of the measuring circuit, a measurement starting means for starting measurement by the vibrator, and a variable variable for increasing the period of the measurement starting means when a zero value of the flow rate calculating means is detected. And the integration calculation means for adding the flow rate value when the flow rate value greater than or equal to the predetermined value is detected after continuous zero value detection, and the measurement cycle becomes longer. Sometimes the flow rate value that has unexpectedly started to flow is measured to be small, and this acts on the safe side when the flow rate integrated value is always supplied in excess of the required amount.

  (6) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. A flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit, a measurement start means for starting measurement by the vibrator, and a cycle variable means for increasing the cycle of the measurement start means when a zero value of the flow rate calculation means is detected. And an integration calculation means for adding and multiplying the flow rate value by a predetermined coefficient when a flow rate greater than or equal to a predetermined value is detected after continuous zero value detection. Depending on the situation, it is possible to integrate more or less flow rate values that have unexpectedly started to flow when the time becomes longer, and if the average value is taken, a substantially accurate integrated value can be obtained in the long term.

(7) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a repeating unit that performs ultrasonic transmission between the vibrators a plurality of times. , A number setting means for setting the number of repetition means, a measurement circuit for measuring the accumulated time of the signal transmission time, a flow rate calculation means for calculating a flow rate based on a signal of the measurement circuit, and a measurement by the vibrator is started Since the measurement start means, the cycle variable means for increasing the period of the measurement start means after detection of the zero value of the flow rate calculation means, and the search measurement means for decreasing the value of the number setting means during the measurement period are provided. Even when a large flow rate flows unexpectedly when the cycle is long, the fact that the fluid has started to flow can be performed with little power consumption.

  (8) a first vibrator provided in the fluid conduit, a second vibrator that receives an ultrasonic signal transmitted from the first vibrator, and a measurement circuit that measures a signal propagation time between the vibrators. A flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit, a measurement start means for starting measurement by the vibrator, a cycle variable means for changing the cycle of the measurement start means based on a value of the flow rate calculation means, Since the coefficient setting means for changing the coefficient of the flow rate calculation means according to the value of the period variable means is provided, the state of the ultrasonic transducer and the circuit changes compared to when the measurement period is long and continuous measurement is performed. The error due to this can be corrected by the flow coefficient.

Control block diagram of flow rate measuring apparatus of Reference Example 1 of the present invention Characteristic diagram showing the change in flow rate of the equipment over time FIG. 1 is a control block diagram of the flow rate measuring device according to the first embodiment of the present invention. Control block diagram of flow rate measuring apparatus of Reference Example 2 of the present invention Characteristic diagram showing the change in flow rate of the equipment over time Control block diagram of flow rate measuring device of Reference Example 3 of the present invention Characteristic diagram showing the change in flow rate of the equipment over time Control block diagram of flow rate measuring device of Reference Example 4 of the present invention Characteristic diagram showing the change in flow rate of the equipment over time Control block diagram of flow rate measuring apparatus of Reference Example 5 of the present invention Control block diagram of a conventional flow measurement device

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Fluid pipe line 5 1st vibrator 6 2nd vibrator 10 Time measuring means 11 Measurement circuit 12 Flow rate calculating means 13 Period variable means 14 Measurement start means 15 Measurement end means 16 Voltage control means 17 Average period variable means 18 Irregular value generation Means 19 Zero count detection means 20 Accumulation calculation means 21 Repetition means 22 Number of times setting means 23 Search measurement means 24 Coefficient setting means

Claims (1)

A first vibrator provided in a fluid conduit, a second vibrator for receiving an ultrasonic signal transmitted from the first vibrator, a measurement circuit for measuring a signal propagation time between the vibrators, A flow rate calculation unit that calculates a flow rate based on a signal from the measurement circuit, a measurement start unit that starts measurement by the vibrator, and an average value of the period of the measurement start unit is changed based on a value of the flow rate calculation unit. A flow rate measuring device comprising: an average period varying means for generating; an irregular value generating means for generating a random value; and a period varying means for adding a signal of the irregular value generating means to a signal of the average period varying means.

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