Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Reexamination Certificate
2001-12-18
2004-03-23
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
Reexamination Certificate
active
06708570
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for measuring a flow rate and a flow velocity of a fluid by utilizing ultrasonic wave, and an ultrasonic flow rate meter. And, it also relates to a method for measuring a temperature or pressure of a fluid without contact by utilizing ultrasonic wave, and an ultrasonic thermometer and an ultrasonic pressure gage.
BACKGROUND ART
Recently, for a flow rate meter for measuring a flow rate of a fluid, an ultrasonic flow rate meter which utilizes ultrasonic wave has been used.
In the ultrasonic flow rate meter, oscillators are disposed in a conduit for flowing the fluid at a longitudinal direction spaced. And, an ultrasonic wave is emitted from the one oscillator and received by the other oscillator, while an ultrasonic wave are emitted from the other oscillator and received by the one oscillator. By a difference in a nultrasonic wave propagation time from the emission to the reception in each case, a flow velocity of the fluid in the conduit is obtained, whereby a flow rate thereof will be determined.
And, for a thermometer or a pressure gage for measuring a temperature or a pressure of a fluid, an ultrasonic thermometer or an ultrasonic pressure gage, which utilize a semiconductor sensor, has been proposed.
PROBLEMS TO BE SOLVED BY THE INVENTION
Such the conventional ultrasonic flow rate meter employs the time difference method or the phase difference method, as measurement method. The ultrasonic wave propagation time varies according to a property, a temperature and a pressure condition of the propagation material. If a flow rate is so large that a variation range in the propagation time can be neglected as an error, there will be no problem. However, when the flow rate is too small for the variation range, it will be difficult to determine the flow rate accurately due to such the variations.
And, it is difficult to arrange such the conventional thermometer or the pressure gage at a same place where a flow velocity is measured by an ultrasonic flow meter. Also, it is difficult to measure a temperature or a pressure of a fluid without contact to the fluid without preventing the fluid flow.
In view of the problems, the object of the present invention is to provide a flow rate measurement method and a flow velocity measurement method by utilizing an improved measurement method (a frequency variable method) by which a flow rate can be measured accurately, and an ultrasonic flow rate meter. In the method, because a phase of the received ultrasonic wave varies in response to a flow velocity V in the conduit, a frequency of the transmitted ultrasonic wave will be changed by a PLL circuit such that the phase becomes equal to a phase under a condition of a flow velocity in the conduit being zero (V=0). Here, since the changed frequency relates a flow velocity, measuring the difference in the frequency will determine the flow velocity accurately.
Further, the object of the present invention is to provide, a temperature and a pressure measurement methods by utilizing an improved measurement method (a frequency variable method) by which a temperature or a pressure can be measured accurately, an ultrasonic thermometer and an ultrasonic pressure gage. In the method, because a phase of the received ultrasonic wave varies in response to a time difference of an ultrasonic velocity in the conduit, the time difference being caused by a change in a temperature or a pressure of the fluid in the conduit, a frequency of the transmitted ultrasonic wave will be changed by a PLL circuit such that the phase becomes equal to a phase under a condition of a reference temperature (for example, 20° C.) in the conduit. Since the changed frequency relates a temperature and a pressure in the conduit, measuring the difference in the frequency will be determine the temperature or the pressure of the fluid in the conduit accurately.
MEANS FOR SOLVING THE PROBLEMS
In order to solve the problems, the present invention provides a flow rate measurement method, which measures a flow rate of a fluid flowing through a conduit, comprises the following steps: preparing a reference ultrasonic velocity such that the fluid is in a standard condition, measuring an ultrasonic velocity A by transmitting an ultrasonic wave from one side and receiving the ultrasonic wave at the other side in the fluid flowing through the conduit, measuring an ultrasonic velocity B by transmitting an ultrasonic wave from the other side and receiving the ultrasonic wave at the one side in the fluid flowing through the conduit, averaging the ultrasonic velocity A and the ultrasonic velocity B thereby to obtain an absolute ultrasonic velocity in the fluid, dividing a difference between the ultrasonic velocity A and the ultrasonic velocity B by 2 thereby to obtain a temporary flow velocity of the fluid, correcting the temporary flow velocity by using a difference between the reference ultrasonic velocity and the absolute ultrasonic velocity thereby to determine an accurate flow velocity of the fluid, and determining a flow rate of the fluid by using the accurate flow velocity and a cross section area of the conduit.
In the flow rate measurement method according to the present invention, the ultrasonic velocities A and B, variable by a temperature or a pressure of the fluid flowing through the conduit, are obtained by a transmission and a reception of an ultrasonic wave. So, an accurate flow velocity can be determined by correcting the temporary flow velocity without measurement of a temperature or a pressure of the fluid. Accordingly, a flow rate of the fluid can be determined accurately.
The ultrasonic flow rate meter according to the present invention, which measures a flow rate of a fluid flowing through a conduit, comprises the following devices: a first ultrasonic wave transmission and reception device disposed on the outside of the conduit, a second ultrasonic wave transmission and reception device disposed on the outside of the conduit part away from the first ultrasonic wave transmission and reception device, a first phase difference detector connected to the second ultrasonic wave transmission and reception device, a first PLL type loop connection disposed between the first phase difference detector and the first ultrasonic wave transmission and reception device, a second phase difference detector connected to the first ultrasonic wave transmission and reception device, a second PLL type loop connection disposed between the second phase difference detector and the second ultrasonic wave transmission and reception device, and a measurement controller for obtaining a flow rate of the fluid.
The ultrasonic flow rate meter according to the present invention is provided with a measurement controller, which measures, controls and operates in a manner described as follows. In a fluid flowing through a conduit at a flow velocity Vx, an ultrasonic wave transmitted from the first ultrasonic wave transmission and reception device is received by the second ultrasonic wave transmission and reception device. Then, a phase difference in the ultrasonic wave at the transmission and the reception will be detected by the first phase difference detector.
When the phase difference is detected, a transmission frequency of the first ultrasonic wave transmission and reception device is gradually changed by the first loop connection until the phase difference becomes zero, and thus a transmission frequency is determined when the phase difference becomes zero. From the determined transmission frequency or the wavelength, an ultrasonic velocity A in the fluid will be obtained.
Next, an ultrasonic wave transmitted from the second ultrasonic wave transmission and reception device is received by the first ultrasonic wave transmission and reception device. Then, a phase difference in the ultrasonic wave at the transmission and the reception is detected by the second phase difference detector.
When the phase difference will be detected, a transmission frequency of the second ultrasonic wave transmission and recep
Komatsu Eisaku
Matsushima Keiichi
Ohkawa Michio
Lefkowitz Edward
Sughrue & Mion, PLLC
Surpass Industry Co. Ltd.
Thompson Jewel V.
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