JP4292620B2 - 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 fluid such as a gas.
[0002]
[Prior art]
A conventional flow measuring device of this type is disclosed in JP-A-10-318811. That is, as shown in FIG. 8, the signal propagation time is measured by the propagation time difference detection means 3 at the time of flow rate measurement from the reception means 2 connected by the flow velocity detection means 1, and compared with the stored value of the propagation time storage means 4, and stored. When the measurement by the receiving means is longer than the value, it is detected that a different medium is mixed and a warning is displayed.
[0003]
[Problems to be solved by the invention]
However, in the above conventional flow rate measuring device, although it can be detected that a different medium is mixed, the flow rate cannot be accurately measured in the mixed state, and it is a problem to maintain the flow rate accuracy in a state where the gas component changes. It was.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a transceiver for transmitting and receiving ultrasonic waves in a fluid, a measurement circuit for measuring a propagation time of transmission from upstream to downstream of a flow or transmission from downstream to upstream, and ultrasonic waves Flow rate calculating means for calculating a flow rate according to propagation time, fluid discrimination means for determining the type of fluid in the flow path from the transceiver, and circuit constant correction means for changing the constant of the measurement circuit according to the value of the fluid discrimination means The flow rate is measured with high accuracy while maintaining the state of the measuring device appropriately with the change of the gas component.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a transmitter / receiver for transmitting / receiving ultrasonic waves in a fluid, a measurement circuit for measuring a propagation time of transmission from upstream to downstream of a flow or transmission from downstream to upstream, and a flow rate for calculating a flow rate by the ultrasonic propagation time. It comprises a calculation means, a fluid discrimination means for determining the type of fluid in the flow path from the transceiver, and a circuit constant correction means for changing the constant of the measurement circuit according to the value of the fluid discrimination means.
[0006]
Also, a transmitter / receiver that transmits / receives ultrasonic waves in the fluid, a measurement circuit that measures the propagation time of transmission from upstream to downstream or downstream to upstream, and a flow coefficient determined by the flow state in the flow path Setting means; flow rate calculation means for calculating a flow rate by ultrasonic propagation time and the flow coefficient setting means; fluid discrimination means for determining the type of fluid in the flow path from the transceiver; and the flow coefficient setting means. Is provided with coefficient correction means for changing the value according to the value of the fluid discrimination means.
[0007]
Further, the fluid discriminating means is determined by the magnitude of the reception voltage of the transceiver.
[0008]
Further, the fluid discriminating means judges based on the propagation time.
[0009]
Further, the received voltage or the propagation time is corrected by the temperature detecting means for measuring the temperature of the flow path.
[0010]
The circuit constant correcting means changes the amplification level of the received signal of the transceiver or the reference signal value compared with the amplified signal by the comparator.
[0011]
The circuit constant correcting means changes the magnitude of the transmission signal of the transceiver or the drive wave number of the transmission signal.
[0012]
In addition, a repetition means for retransmitting after receiving the ultrasonic wave and a repetitive flow rate calculation means for calculating a flow rate from the accumulated transmission / reception time are provided, and the setting of the repetitive means is changed by the fluid discrimination means.
[0013]
In addition, the apparatus includes a repeating unit that transmits again through the delay unit after receiving the ultrasonic wave, and a repeated flow rate calculating unit that calculates a flow rate from the accumulated time of the repeated transmission and reception, and the setting of the delay unit is changed by the fluid discrimination unit. It is.
[0014]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
Example 1
A first embodiment of the present invention will be described. In FIG. 1, transmitters / receivers 5 and 6 for transmitting / receiving ultrasonic waves in a fluid are provided upstream and downstream of a flow path 7, respectively, and the propagation time of transmission from upstream to downstream or transmission from downstream to upstream is measured. The ultrasonic propagation time is obtained as a result of the measurement circuit 8, and the flow rate is calculated by the flow rate calculation means 9. Further, there is a fluid discriminating means 10 for judging the type of fluid in the flow path from the signal magnitudes and propagation times of the transceivers 5 and 6, and a circuit constant for changing the constant of the measuring circuit 8 according to the value of the fluid discriminating means 10. And correction means 11.
[0016]
Next, the operation will be described. An ultrasonic drive signal is transmitted from the transmission means 13 of the measurement circuit 8 by the signal of the start 12, and ultrasonic waves are transmitted from the transceivers 5 to 6 through the switching means 14, that is, along the flow, and propagate through the flow path 7. The ultrasonic wave reaches the transmitter / receiver 6 after being accelerated by the flow velocity. The signal in the transmitter / receiver 6 is amplified by the amplifying means 15 and further sent to the comparing means 16 to detect reception of ultrasonic waves. The ultrasonic transmission time from the transceivers 5 to 6 is measured by the time measuring means 17 and stored as the forward propagation time. Next, the switching means 14 is switched to transmit ultrasonic waves against the flow from the transmitter / receiver 6 to 5, and the transmission time from the transmitter / receiver 6 to 5 is stored as the backward propagation time in the same manner as described above. The flow rate calculation means 9 calculates the flow rate from the time difference between the time and the forward propagation time, and the flow rate coefficient calculated in advance according to the cross-sectional area of the flow path 7 and the flow state. In the actual calculation, the flow rate is calculated based on the reciprocal difference of the propagation time so that the influence of the sound speed is theoretically eliminated.
[0017]
Next, the case where the type of fluid flowing through the flow path 7 is changed will be described. The components of natural gas and LP gas as fuel supplied to the home are not always constant, and vary considerably depending on the season and place of supply. When the fluid component changes, the signal of the transceiver 6 also changes. For example, when hydrogen gas is mixed in propane gas, which is the main component of LP gas, the ultrasonic reception voltage is reduced and the propagation time is also reduced. The fluid discriminating means 10 detects the received voltage and the propagation time, discriminates the type of gas from the values, and the circuit constant of the measuring circuit 8 is corrected, for example, by the circuit constant correcting means 11 to correct the amplification degree and the transmission voltage, thereby maintaining the flow rate accuracy. Acts like
[0018]
(Example 2)
FIG. 2 shows a second embodiment in which the fluid is discriminated based on the value of 17 of the time measuring means, that is, the propagation time of the ultrasonic wave. The flow rate coefficient used in the flow rate calculation unit 9 is corrected by the coefficient correction unit 18 in accordance with the type of fluid determined by the fluid determination unit 10, and the flow rate is accurately calculated. If the type of fluid changes, the state of the flow changes, and the flow velocity distribution in the flow path 7 changes, which affects the flow coefficient and causes a flow rate error. Since the value of the flow coefficient depends on the Reynolds number of the fluid, the Reynolds number may be estimated by the fluid discrimination means. If the type of gas mixed, such as propane gas and hydrogen gas described above, is clear, the relationship between the propagation time and the Reynolds number may be obtained in advance by experiments and stored in a microcomputer or the like. Since the propagation time changes as the fluid temperature changes, the temperature is detected by the temperature detection means 19 when the fluid temperature changes, and the type of fluid is determined based on the propagation time converted to, for example, 20 ° C. Since the Reynolds number also changes depending on the temperature, it can be corrected simultaneously.
[0019]
(Example 3)
FIG. 3 shows a third embodiment, in which the type of fluid is determined based on the magnitude of the received signal level. When hydrogen gas is mixed into the propane gas shown in the first embodiment, the propane gas is received. Compared with the level of fluid A, when hydrogen gas is mixed, the reception level is reduced as in fluid B. It can be estimated how much hydrogen gas is mixed by the magnitude of the reception level.
[0020]
(Example 4)
FIG. 4 shows a fourth embodiment in which the amplification factor of the received signal is increased by the preamplifier 19 by the circuit constant correction means 11. As described in the fourth embodiment, when the hydrogen gas is mixed, the reception level becomes small, so that the lack of ultrasonic reception sensitivity is corrected. If the reception level is high, the pre-amplification means 19 is not necessary, so it may be set to sleep. As another means for adjusting the reception sensitivity, the circuit constant correction means 11 switches the comparator comparison signal of the comparison means 16 to correct the circuit. As shown in FIG. 3, when the fluid is expected to have a large received signal, the fluid is operated at the comparison level C, and when the fluid is expected to be small, the fluid is operated at the comparison level D.
[0021]
(Example 5)
FIG. 5 shows a fifth embodiment, in which the transmission means 13 is controlled by the circuit constant correction means 11. As described in the fourth embodiment, when a fluid with low reception sensitivity is expected, for example, the wave number of burst transmission is increased or the transmission voltage is set high to obtain an appropriate ultrasonic signal.
[0022]
(Example 6)
FIG. 6 shows a sixth embodiment, which is an embodiment in the sing-around method in which an ultrasonic wave is received and then transmitted again, and the flow rate is calculated from the total time obtained by repeating this transmission and reception a plurality of times. In the third embodiment, when hydrogen gas is mixed, the received voltage is reduced, so that the ratio of noise to the received signal is increased and the S / N is decreased, so that the variation in measurement time is increased. Therefore, in the sixth embodiment, the flow rate accuracy is maintained by discriminating the type of fluid due to the decrease in the received voltage and increasing the number of repetitions by the repetition means 20.
[0023]
(Example 7)
FIG. 7 shows a seventh embodiment, in which the delay time from reception to transmission is changed by the delay means 21 in accordance with the kind of fluid in the above-described sing-around method. In the sing-around method, since ultrasonic waves are repeatedly transmitted, the ultrasonic waves are reflected between the transmitter / receivers 5 and 6 and become noise, so that accurate ultrasonic detection cannot be performed. Therefore, a delay time is provided between reception and transmission of the next ultrasonic wave to reduce the influence of reflection. The optimum delay time varies depending on the properties of the fluid. Therefore, a delay time is set in advance according to the type of fluid, and a delay time corresponding to the determined type of fluid is set. If the delay time is obtained by dividing a delay element of 1 microsecond or less a plurality of times, the delay time can be set by changing the setting value of the counter.
[0024]
In this embodiment, the gas type is described as a mixed gas of propane gas and hydrogen gas. However, in the natural gas, a flammable fluid such as methane gas and propane gas or hydrogen gas, or a mixed fluid of flammable fluid and air is used. Is also applicable.
[0025]
Further, the mixing ratio and fluid properties can be set from the outside via a communication means by a non-volatile memory or the like in addition to being stored by a microcomputer.
[0026]
【The invention's effect】
As is apparent from the above description, the flow measurement device of the present invention provides the following effects.
[0027]
(1) The present invention relates to a transmitter / receiver that transmits / receives ultrasonic waves in a fluid, a measurement circuit that measures the propagation time of transmission from upstream to downstream or downstream to upstream, and the flow rate by ultrasonic propagation time. Since the flow rate calculating means for calculating, the fluid discriminating means for judging the type of fluid in the flow path from the transmitter / receiver, and the circuit constant correcting means for changing the constant of the measurement circuit according to the value of the fluid discriminating means, The most suitable measurement circuit is selected according to the component, and the ultrasonic wave can be made an appropriate signal, and the flow accuracy is high.
[0028]
(2) A transmitter / receiver that transmits / receives ultrasonic waves in a fluid, a measurement circuit that measures the propagation time of transmission from upstream to downstream or transmission from downstream to upstream, and a flow rate determined by the flow state in the flow path A coefficient setting means, a flow rate calculation means for calculating a flow rate by means of ultrasonic propagation time and flow rate coefficient setting means, a fluid discrimination means for determining the type of fluid in the flow path from the transceiver, and a flow coefficient setting means for fluid discrimination Since the coefficient correction means that changes according to the value of the means is provided, the flow rate coefficient that changes depending on the type of fluid is automatically corrected, so that the flow rate accuracy is high.
[0029]
(3) Since the fluid discriminating means determines based on the magnitude of the reception voltage of the transceiver, the fluid type can be easily determined from the relationship between the fluid type and the ultrasonic transmission / reception sensitivity.
[0030]
(4) Since the fluid discrimination means determines based on the propagation time, the fluid type can be easily determined from the relationship between the fluid type and the ultrasonic propagation time (sound speed).
[0031]
(5) Since the received voltage or propagation time is corrected by the temperature detecting means for measuring the temperature of the flow path, the type of fluid can be accurately determined even if the temperature changes.
[0032]
(6) Since the circuit constant correction means changes the amplification level of the received signal of the transmitter / receiver or the reference signal value compared with the amplified signal by the comparator, even if the ultrasonic signal changes depending on the type of fluid, It can be corrected and detected accurately.
[0033]
(7) The circuit constant correction means changes the magnitude of the transmission signal of the transmitter / receiver or the drive wave number of the transmission signal, so that the reception signal can be stabilized by adjusting the transmission according to the type of fluid.
[0034]
(8) Since the repetition means for transmitting again after receiving the ultrasonic wave and the repetition flow rate calculation means for calculating the flow rate from the accumulated transmission / reception time, the setting of the repetition means is changed by the fluid discrimination means. Even with gas, the number of repetitions can be increased to ensure flow rate accuracy.
[0035]
(9) It is provided with a repetitive means for retransmitting through the delay means after reception of the ultrasonic wave, and a repetitive flow rate calculating means for calculating the flow rate from the cumulative transmission / reception time, and the setting of the delay means is changed by the fluid discrimination means. Therefore, it is possible to improve the flow rate accuracy by preventing the reflection of the ultrasonic wave that differs depending on the gas type.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow rate measuring apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram of a flow rate measuring apparatus according to a second embodiment of the present invention. Fig. 4 is a block diagram of a flow rate measuring device according to a fourth embodiment of the present invention. Fig. 5 is a block diagram of a flow rate measuring device according to a fifth embodiment of the present invention. Fig. 6 is a flow rate measuring device according to the sixth embodiment of the present invention. FIG. 7 is a block diagram of a flow rate measuring device according to a seventh embodiment of the present invention. FIG. 8 is a block diagram of a conventional flow rate measuring device.
5, 6 Transceiver 8 Measuring circuit 9 Flow rate calculating means 10 Fluid discriminating means 11 Circuit constant correcting means 13 Transmitting means 16 Comparing means 18 Coefficient correcting means 19 Preamplifying means 20 Repeating means 21 Delay means

Claims (1)

A transmitter / receiver for transmitting / receiving ultrasonic waves in the fluid, a measurement circuit for measuring a propagation time of transmission from upstream to downstream of the flow or transmission from downstream to upstream, and a flow rate calculation means for calculating a flow rate by the ultrasonic propagation time; In the flow rate measuring device, comprising: a fluid discriminating unit that determines the type of fluid in the flow path from the transceiver; and a circuit constant correcting unit that changes a constant of the measuring circuit according to a value of the fluid discriminating unit. The fluid discriminating means is determined by the magnitude of the received voltage of the transceiver ,
And the circuit constant correction means changes the reference signal value compared with the amplification degree of the reception signal of the transceiver or the amplified signal and the comparator,
And a repeater for retransmitting via the delay means after receiving the ultrasonic wave, and a repeat flow rate calculating means for calculating the flow rate from the accumulated time of the repeat transmission / reception, and changing the setting of the delay means by the fluid discriminating means. To
Flow measurement device.

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