Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2002-02-25
2004-01-06
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S048000, C702S050000, C073S861280, C073S861270
Reexamination Certificate
active
06675111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for measuring flow velocity of a fluid and a method and apparatus for measuring flow rate of a fluid by using a signal sound, mainly, ultrasound.
2. Description of the Related Art
In recent years, there is a current meter for measuring flow velocity of a fluid by using ultrasound.
The ultrasound flow velocity meter is constructed by disposing two oscillators with a spacing in the longitudinal direction in a tube member through which a fluid flows. Ultrasound is transmitted from one of the oscillators and received by the other oscillator, and ultrasound is transmitted from the other oscillator and received by the one of the oscillators. From the difference between the propagation time of the ultrasounds, the flow velocity of the fluid in the tube member is obtained. The flow rate is derived by multiplying the flow velocity with the internal diameter of the tube member.
Although the conventional ultrasound flow velocity meter uses a measuring method such as a time difference method or a phase difference method, if the spacing between the two oscillators is short, the time difference or phase difference is minute. Naturally, an error becomes big.
The propagation speed of ultrasound changes according to the temperature, pressure, and kind of a fluid. The changes may be ignored as errors, but they become a problem in the case of measuring flow velocity with high precision.
Similarly, they become a problem in the case of measuring the flow rate with high precision.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of the circumstances as described above and its object is to provide a method and apparatus for measuring flow velocity and a method and apparatus for measuring flow rate, capable of measuring flow velocity and flow rate with high precision.
According to a first aspect of the present invention, there is provided a flow velocity measuring method for measuring flow velocity of a fluid that flows, comprising: a step of allowing a signal sound to propagate to the upstream or downstream side in a fluid and detecting a phase difference between the signal sound and an original signal; a step of eliminating a phase difference detected in the step and synchronizing the phases; a step of detecting time or oscillation frequency required to complete the phase synchronization in the step; and a step of calculating flow velocity of the fluid with reference to the flow velocity preset in correspondence with the time or oscillation frequency on the basis of the time or oscillation frequency required to complete the phase synchronization in the step.
According to the first aspect, the higher the flow velocity of a fluid is, the larger the phase difference is. When the phase difference becomes large, in proportion to the phase difference, the time required to synchronize phases becomes long and the change in oscillation frequency becomes large. When the relation between the flow velocity of a fluid and time or oscillation frequency required to synchronize phases is preset, by referring to the preset flow velocity on the basis of the detected time or oscillation frequency, the flow velocity of a fluid can be calculated. As a result, the phase difference as a minute numerical value can be accurately replaced with time or oscillation frequency required to synchronize phases as a relatively large numerical value, and the flow velocity can be measured with high precision.
According to a second aspect of the present invention, there is provided the flow velocity measuring method in the first aspect, wherein flow velocities are preset in correspondence with not only the time or oscillation frequency but also changes in temperature, pressure, and kind of a fluid.
According to the second aspect, correction can be made in correspondence with a change in temperature, pressure, and kind of a fluid. Since the phase difference changes according to the temperature, pressure, and kind of a fluid, the flow velocities are preset in association with changes in temperature and the like. Thus, even when the temperature, pressure, or kind of a fluid changes, the flow velocity can be obtained with high precision.
According to a third aspect of the present invention, there is provided the flow velocity measuring method in the first or second aspect, wherein phase difference detection performed by making signal sound propagate to the upstream side in the fluid and phase difference detection performed by making signal sound propagate to the downstream side in the fluid are alternately switched, and a calibration signal is output at the time of switching to prevent a fluctuation at the time of switching.
According to the third aspect, signals are propagated to both the upstream and downstream sides and a phase difference between the signals is detected. Flow velocities are obtained with respect to two phases deviated to the opposite directions and averaged, thereby improving the reliability of a measured value. At the time of switching the propagation direction of a signal sound, a calibration signal is output. The propagation of a signal sound may be fluctuated at the time of switching the direction of propagation of the signal sound between the upstream side and the downstream side. There is a case such that the propagating signal sound becomes extremely large or small and a measurement value largely fluctuates. To solve the problem, a calibration signal is output to prevent a fluctuation at the time of switching, that is, a large fluctuation in the measurement value. With the configuration, the flow velocity can be measured with high precision.
According to a fourth aspect of the present invention, there is provided the low velocity measuring method in the third aspect, wherein the frequency of the calibration signal output at the time of switching is modulated in correspondence with a change in temperature, pressure, and kind of the fluid.
According to the fourth aspect, the calibration signal whose frequency is modulated in correspondence with a change in temperature or the like of a fluid is output at the time of switching. Consequently, even if a change in the temperature or the like of a fluid is large, the flow velocity can be measured with high precision.
According to a fifth aspect of the present invention, there is provided a flow velocity measuring apparatus for measuring flow velocity of a fluid which flows, comprising: a plurality of signal sound transmitting/receiving units disposed in a fluid that flows, for transmitting/receiving a signal sound; a phase difference detecting unit for detecting a phase difference between a signal sound properly transmitted and received by the plurality of signal sound transmitting/receiving units to thereby allow the signal sound to propagate to the upstream or downstream side in the fluid and the original signal; a phase synchronizing unit for eliminating a phase difference detected by the phase difference detecting unit to obtain synchronization; a detecting unit for detecting time or oscillation frequency required to complete the phase synchronization in the phase synchronizing unit; and a flow velocity calculating unit for calculating flow velocity of the fluid by referring to, on the basis of the time or oscillation frequency detected by the detecting unit, flow velocity which is preset in correspondence with the time or oscillation frequency.
According to the fifth aspect, when two signal sound transmitting/receiving units are disposed in a fluid, a signal sound is transmitted from one of the signal sound transmitting/receiving units and received by the other unit. Transmission and reception are alternately switched between the two signal sound transmitting/receiving units, and a signal sound is allowed to propagate to the upstream and downstream sides in the fluid. Further, when three signal sound transmitting/receiving units are disposed in a fluid, the signal sound transmitting/receiving unit in the center is used as a
Komatsu Eisaku
Matsushima Keiichi
Barlow John
Lorusso, Loud & Kelly
Surpass Industry Co. Ltd.
Walling Meagan S.
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