Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Patent
1997-04-18
2000-05-23
Fuller, Benjamin R.
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
G01F 166
Patent
active
060653515
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of measuring a flow rate of gas or liquid by utilizing ultrasonic waves and to an ultrasonic flow meter which executes the method of measuring.
BACKGROUND ART
U.S. Pat. No. 4,483,202 discloses an ultrasonic flow meter. The flow meter comprises a conduit through which a fluid flows and a pair of ultrasonic transducers disposed in the conduit along a line which is inclined by a predetermined angle with respect to a fluid flowing direction. In the operation, initially, an ultrasonic wave is emitted from the ultrasonic transducer disposed on the upstream side with respect to the flowing direction, toward the downstream side, and is received by the ultrasonic transducer on the downstream side. Then the propagation time from the emission to the reception of the ultrasonic wave is determined. Subsequently, an ultrasonic wave is emitted from the ultrasonic transducer disposed on the downstream side with respect to the flowing direction, toward the upstream side, and is received by the ultrasonic transducer on the upstream side, and the propagation time from the emission to the reception of the ultrasonic wave is determined. Substituting the two propagation times into a well-known equation yields the velocity of the fluid, with which the rate of flow is determined.
In such a well-known ultrasonic flow meter as described above, both velocity and rate of flow are measured by emitting ultrasonic waves at a predetermined time interval regardless of the flow rate. As a result, the conventional ultrasonic flow meter has a large power consumption, which causes a battery to run down in a short period of time.
SUMMARY OF THE INVENTION
The invention is intended to provide a method and an apparatus for measuring flow rate of a fluid with ultrasonic waves in which power consumption can be minimized by measuring the flow rates at a suitable time interval depending on a flow rate.
An ultrasonic measuring method in accordance with the invention comprises:
(a) emitting an ultrasonic wave in a direction which is the same as or opposite to a flow of fluid;
(b) receiving the ultrasonic wave;
(c) determining a propagation time from the emission to the reception of the ultrasonic wave;
(d) determining a flow rate from the propagation time;
(e) setting a delay time corresponding to the flow rate on the basis of a relationship between the flow rate and the delay time in which the delay time decreases with increase in the flow rate; and
(f) repeating (a) to (e) after the lapse of the delay time.
The relation between the flow rate and the delay time can be set so that the delay time decreases linearly, stepwise, or inversely with increase in the flow rate.
Another method for measuring a flow rate in accordance with the invention comprises:
(a) emitting an ultrasonic wave in a direction which is the same as or opposite to a flow of fluid;
(b) receiving the ultrasonic wave;
(c) determining a propagation time from the emission to the reception;
(d) determining a flow rate from the propagation time;
(e) storing the flow rate as flow rate data;
(f) executing (a) to (e) at least twice;
(g) setting a delay time corresponding to the flow rate from the stored flow rate data on the basis of a relation between the flow rate and the delay time in which the delay time decreases with increasing in the flow rate; and
(h) repeating (a) to (e) after the lapse of the delay time.
Another method for measuring a flow rate in accordance with the invention comprises:
(a) emitting an ultrasonic wave in a direction which is the same as or opposite to a flow of fluid;
(b) receiving the ultrasonic wave;
(c) determining a propagation time from the emission to the reception;
(d) determining a flow rate from the propagation time;
(e) storing the flow rate as flow rate data;
(f) executing (a) to (e) at least twice;
(g) setting a delay time corresponding to the flow rate from the stored flow rate data on the basis of a relation between the flow rate and the delay time where the delay time decreases with inc
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Nagaoka Yukio
Nawa Motoyuki
Ohji Kenzo
Fuller Benjamin R.
Matsushita Electric - Industrial Co., Ltd.
Thompson Jewel V.
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