Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2000-06-07
2002-07-23
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S597000, C073S609000
Reexamination Certificate
active
06422081
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ultrasonic speed meter and an ultrasonic speed measuring method, and more specifically to an apparatus and method for measuring the sonic speed propagated through a sample including bubbles.
2. Background
FIG. 4
is a block diagram showing an ultrasonic transmitter-receiver installed in an ultrasonic speed meter. A reflection board
2
b
is provided at a specific position distant from the ultrasonic transmitter-receiver
2
a,
and the space between the ultrasonic transmitter-receiver
2
a
and the reflection board
2
b
is filled with the sample. Under such arrangement, ultrasonic waves sent from oscillating elements (not shown) provided on the ultrasonic transmitter-receiver
2
a
are received by receiving elements (not shown) provided on the ultrasonic transmitter-receiver
2
a
and then converted to electric signals.
When an ultrasonic wave is propagated through a sample, the ultrasonic speed meter can seek the sonic speed c by using a propagation period T and a propagation distance L in accordance with the following equation: c=L/T. By using the sonic speed c, it is possible to calculate a physical value of the sample, for example, the density.
The overlap method and the sing-around method are generally known as the method for seeking the propagation period T with accuracy.
The overlap method is configured as shown in FIG.
5
and FIG.
6
. Specifically, square waves Ws outputted from a square wave oscillator
101
are divided into divided waves Ds by a divider
107
. The divided waves Ds are inputted to a pulsar
102
. The pulsar
102
generates drive pulses Pd, which are inputted to an ultrasonic transmitter-receiver
103
. In addition, the receiving wave obtained here is inputted to an oscilloscope
105
via an amplifier
104
.
On the other hand, the oscilloscope
105
is driven by the output of the square wave oscillator
101
. Therefore, when the period of the square wave Ws driving the oscilloscope
105
matches with that of the reflected wave Sr obtained from the ultrasonic transmitter-receiver
103
, the monitor of the oscilloscope gets static and the period at that time becomes the period T.
In the above method, since adjusting the oscillating frequency of the square wave oscillator
101
by hand can keep the displaying of the oscilloscope static, there is a problem that it is impossible to perform the automatic measurement.
The sing-around method is configured as shown in FIG.
7
. Specifically, a pulsar
201
oscillates drive pulses according to the input of starting trigger, and said drive pulses are inputted to the ultrasonic transmitter-receiver
103
. According to the receiving waves from the ultrasonic transmitter-receiver
103
, a pulse forming unit
203
forms a new trigger, and said new trigger is inputted to the pulsar
201
. In this case, the pulses formed by the pulse forming unit
203
are inputted into a frequency counter
204
, and the frequency counter
204
can calculate the period T according to the counted value that the frequency counter
204
has obtained for a specific time.
The prescribed method is easy to be subjected to the influence of the configuration of external circuits and etc. The obtained period T can be represented by a additional value of a true period &tgr;
o
and the circuit delay time &tgr;
e
.
Accordingly an ultrasonic speed meter disclosed in Japanese Laid-open Publication No. H06-235721 is arranged as shown in
FIG. 8
that the accurate propagation period T can be measured automatically by using a local oscillator generating continuous waves
First, after receiving the receiving wave at least twice from the ultrasonic transmitter-receiver
103
in accordance with the drive pulses oscillated at a specific time by a drive pulse oscillating circuit
301
, dividing means
302
divides the first receiving wave and the second receiving wave. And the drive pulse oscillating circuit
301
generates next drive pulse based on the first receiving wave {circle around (
1
)} while the local oscillator
304
oscillates a pulse corresponding to the propagation period T based on the second receiving wave {circle around (
2
)}. According to thus generated pulses, a time counting circuit
305
may count the propagation period T. And moreover, while the pulse corresponding to the first receiving wave {circle around (
1
)} extracted from the output of the local oscillator
304
is made to be a reference pulse of the local oscillator
304
, the extracted pulse corresponding to the second receiving wave {circle around (
2
)} is made to be a reference pulse of the drive pulse oscillating circuit
301
.
Since the ultrasonic speed meter disclosed in Japanese Laid-open Publication No. H06-235721 needs a minimum of two receiving waves every one transmitting wave (a drive pulse), there is a problem that a sufficient measurement result cannot be obtained in case of a sample including bubbles. This is to say; the ultrasonic speed meter cannot obtain two or more receiving waves every transmitting wave because the ultrasonic wave is attenuated by the influence of the bubbles, with the result that the continuous oscillation is disturbed and the measurements scatter widely.
SUMMARY OF THE INVENTION
Considering the problems in the prior arts described above, the present invention has an object to provide an ultrasonic speed meter and ultrasonic speed measuring method, even if there arc bubbles in a sample, that is able to measure the sonic speed of the ultrasonic wave with high accuracy.
In order to achieve the above object, the invention adopts the following means. And the invention presupposes an ultrasonic speed measuring method an shown in
FIG. 1
that an ultrasonic wave transmitted from an ultrasonic transmitter is propagated between the ultrasonic transmitter and an ultrasonic receiver, and according to a propagation time of the propagating ultrasonic wave the sonic speed can be sought.
In the ultrasonic speed measuring method, continuous oscillating waves may be oscillated synchronizing a phase with the timing of receiving at least one receiving wave that the ultrasonic receiver has received according to a plural times transmissions, and it is arranged to measure the period of pulses oscillated by a local oscillator for determining the transmission timing based on the delayed receiving wave. Specifically, after a receiving wave received by an ultrasonic receiver is delayed for a specific period, continuous oscillating waves may be oscillated synchronizing the phase only with the receipt timing of the delayed receiving wave. And according to the continuous oscillating waves, it is arranged to measure the period of pulses oscillated by a local oscillator for determining the transmission timing. Therefore the ultrasonic speed can be sought by using the propagation time based on the period thus measured.
As a result of the above configuration, it is possible to perform the phase synchronization only on the received signals so that the stable measurement can be carried out without the influence of bubbles.
REFERENCES:
patent: 3992679 (1976-11-01), Isono
patent: 4492117 (1985-01-01), Chubachi
patent: 5125273 (1992-06-01), Negita
patent: 5214955 (1993-06-01), Yost et al.
patent: 5557047 (1996-09-01), Koide
patent: 5856622 (1999-01-01), Yamamoto
Kawaguchi Kenji
Yasuda Masanori
Greigg Ronald E.
Kyoto Electronics Manufacturing Co., Ltd.
Saint-Surin Jacques M.
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