Ultrasonic flow meter with reduced noise

Details Ultrasonic flow meter with reduced noise Ultrasonic flow meter with reduced noise

2000-12-15

2002-12-10

Patel, Harshad (Department: 2855)

Measuring and testing

Volume or rate of flow

By measuring vibrations or acoustic energy

C073S861290

Reexamination Certificate

active

06490933

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ultrasonic flow meter suitable for use in tube or pipe line.
2. Description of the Prior Art
As prior art techniques for measuring a flow rate of a fluid such as gases or liquids flowing in a tube or pipe line, various apparatus such as orifices and nozzles are known and of late, ultrasonic flow meters utilizing ultrasonic wave have widely been spread.
FIG. 7
shows a figure for illustrating the principle of an ultrasonic flow meters, in which when a first oscillator
102
and second oscillator
103
are fitted to a measurement pipe
101
through a constant distance L, and an ultrasonic wave is transmitted from one of the first oscillator
102
and second oscillator
103
and received by the other of the second oscillator
103
and first oscillator
102
, there occurs a difference between a time t1 required when the ultrasonic wave from the first oscillator
102
reaches the second oscillator
103
and another time t2 required when the ultrasonic wave from the second oscillator
103
reaches the second oscillator
102
.
When the sonic velocity in a fluid is c and a velocity of the fluid is v, the following calculation formula is concluded:
t
1
=L
/(
c+v
)  {circle around (1)}
t
2
=L
/(
c−v
)  {circle around (2)}
1
/t
1−1
/t
2=2
v/L
  {circle around (3)}
v=L/
2(1
/t
1−1
/t
2)  {circle around (4)}
That is, a formula {circle around (3)} is derived by subtracting the recipropcal number of a formula {circle around (2)} from the recipropcal number of a formula {circle around (1)} and this formula {circle around (3)} is rearranged based on v to obtain a formula {circle around (4)}. According to this formula {circle around (4)}, the flow velocity v of the fluid can be given if the distance L, time t1 and t2 are determined. When the thus obtained flow velocity v is multiplied by the inner cross-sectional area of the measurement pipe
101
, the flow rate can be obtained.
As an invention based on the above described principle, for example, there is an “ultrasonic flow meter” disclosed in JP-A-10-122923, which is constructed of such a simple structure that a measurement tube
1
is provided with ring-shaped ultrasonic oscillators
2
A and
2
B, and a gap with the tube
1
is filled with grease
3
,
3
to acoustically combine the measurement tube
1
with the ultrasonic oscillators
2
A and
2
B, as shown in
FIG. 3
of the same publication. These marks are same as described on this publication. The inner part of the measurement tube
1
so smooth that cleaning of contamination is not required and the apertures of the ultrasonic oscillators
2
A and
2
B can be rendered smaller to comply with the aperture of the measurement tube
1
, thus reducing the aperture of the measurement tube
1
.
FIG. 8
shows a figure for illustrating the problems of an ultrasonic flow meters of the prior art, in which when ultrasonic oscillators
2
A and
2
B are fitted to the measurement pipe
1
, the ultrasonic oscillator
2
A being used as a sending side and the ultrasonic oscillator
2
B being used as a receiving side, an oscillating wave fundamentally propagates along an arrow {circle around (1)} in a fluid (medium) flowing in the measurement tube
1
. During the same time, the measurement tube
1
itself functions as a propagation material and an oscillating wave shown by an arrow {circle around (2)} propagates to the ultrasonic oscillators
2
B.
Thus, the oscillating wave of the arrow {circle around (2)} sometimes becomes a noise to affect unfavourably the flow measurement. When the propagation speed of the arrow {circle around (2)} is close to that of the arrow {circle around (1)}, in particular, influences thereof are larger.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ultrasonic flow meter capable of moderating influences of the oscillating wave propagating through the measurement tube itself, whereby the above described problems of the prior art can be solved.
The above described object can be attained by an ultrasonic flow meter comprising a measurement tube for flowing a fluid to be subjected to measurement, said tube being constructed of a metallic or metal-like material capable of propagating ultrasonic wave and being free from obstacles hindering the flow of the fluid in the tube, a first oscillator fitted to the outer circumference of the measurement tube, a second oscillator fitted to the outer circumference of the measurement tube at a predetermined interval along the flow of the fluid from the first oscillator and an acoustic filter fitted to the measurement tube for cutting off high frequency range of the oscillating wave propagating through the oscillating tube, in which the flow rate of a fluid is measured based on a time difference between a time required when the ultrasonic wave from the upstream oscillator reaches the downstream oscillator and another time required when the ultrasonic wave from the downstream oscillator reaches the upstream oscillator.


REFERENCES:
patent: 4445389 (1984-05-01), Potzick et al.
patent: 4454767 (1984-06-01), Shinkai et al.
patent: 5131279 (1992-07-01), Lang et al.
patent: 5179862 (1993-01-01), Lynnworth
patent: 5269191 (1993-12-01), Wada
patent: 5868437 (1999-02-01), Teague
patent: 6122956 (2000-09-01), Klausner et al.
patent: 10-122923 (1998-05-01), None

Affiliated with

Also associated with

Rating

Ultrasonic flow meter with reduced noise does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ultrasonic flow meter with reduced noise, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasonic flow meter with reduced noise will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2992337