Abstrict An ultrasonic flow meter includes a conduit through which a fluid
flows, an ultrasonic generator, a receiver for receiving ultrasonic
waves on the upstream or downstream side of the generator, a time
counter for determining the propagation time of the ultrasonic wave,
a flow rate calculator for calculating the flow rate from the propagation
time, and a timing controller. The timing controller sets a delay
time corresponding to the flow rate measured from the relation between
a flow rate which is set in advance, and the measured delay time.
After the passage of this delay time the ultrasonic wave is emitted
from the generator on the basis of a driving signal outputted from
a trigger section and the flow rate is determined. Since the flow
rate is thus measured with the delay time suitable for the flow
rate, the flow rate is correctly determined, and power consumption
is reduced.
Claims We claim:
1. A method for measuring a flow rate, said method comprising:
(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 emission of the ultrasonic
wave to reception of the ultrasonic wave;
(d) determining a flow rate based on the propagation time;
(e) setting a delay time corresponding to the flow rate based on
a flow rate to delay time relationship, wherein the flow rate to
delay time relationship is characterized in that the delay time
decreases with increase in flow rate; and
(f) repeating (a) to (e) after the delay time has elapsed.
2. A method for measuring a flow rate as claimed in claim 1 wherein,
in the flow rate to delay time relationship, the delay time decreases
inversely with increase in flow rate.
3. A method for measuring a flow rate as claimed in claim 1 wherein,
in the flow rate to delay time relationship, the delay time decreases
linearly with increase in flow rate.
4. A method for measuring a flow rate as claimed in claim 1 wherein,
in the flow rate to delay time relationship, the delay time decreases
stepwise with increase in flow rate.
5. A method for measuring a flow rate, said method comprising:
(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 emission of the ultrasonic
wave to reception of the ultrasonic wave;
(d) determining a flow rate based on 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 based on a flow rate to delay time relationship,
wherein the flow rate to delay time relationship is characterized
in that the delay time decreases with increase in flow rate; and
(h) repeating (a) to (e) after the delay time has elapsed.
6. A method for measuring a flow rate, said method comprising:
(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 emission of the ultrasonic
wave to reception of the ultrasonic wave;
(d) determining a flow rate based on 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 based on a flow rate to delay time relationship,
wherein the flow rate to delay time relationship is characterized
in that the delay time decreases with increase in flow rate;
(h) judging from a plurality of flow rate data which have been
stored, whether the flow rate is increasing or decreasing at present
time;
(h1) correcting and shortening the delay time according to a value
of the flow rate data when the flow rate is increasing;
(h2) correcting and prolonging the delay time according to a value
of the flow rate data when the flow rate is decreasing; and
(i) repeating (a) to (e) after the corrected delay time has elapsed.
7. A method for measuring a flow rate, said method comprising:
(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 emission of the ultrasonic
wave to reception of the ultrasonic wave;
(d) determining a flow rate based on the propagation time;
(e) storing the flow rate as flow rate data and erasing an oldest
flow rate data that has been stored;
(f) resetting a repetition number, indicative of a number of times
an ultrasonic wave is to be emitted for a given flow rate, based
on a plurality of stored flow rate data and based on a flow rate
to repetition number relationship, wherein the flow rate is repetition
number relationship is characterized in that the repetition number
decreases with increase in flow rate; and
(g) repeating (a) to (f).
8. A method for measuring a flow rate, said method comprising:
(a) setting a delay time on the basis of a relationship between
time information and an amount of a fluid consumed;
(b) emitting an ultrasonic wave in a direction which is the same
as or opposite to a flow of the fluid;
(c) receiving the ultrasonic wave;
(d) determining a propagation time from emission of the ultrasonic
wave to reception of the ultrasonic wave;
(e) determining a flow rate on the basis of the propagation time;
(f) adjusting the delay time based on the flow rate, wherein the
delay time decreases with increase in flow rate; and
(g) repeating (b) to (f) after the delay time has elapsed.
9. A method for measuring a flow rate as claimed in claim 8 wherein
the time information is information indicative of time of day.
10. A method for measuring a flow rate as claimed in claim 8 wherein
the time information is information indicative of year, month, and
date.
11. A method for measuring a flow rate, said method comprising:
(a) setting a delay time based on information indicative of a consumption
of a fluid;
(b) emitting an ultrasonic wave in a direction which is the same
as or opposite to a flow of the fluid;
(c) receiving the ultrasonic wave;
(d) determining a propagation time from emission of the ultrasonic
wave to reception of the ultrasonic wave;
(e) determining a flow rate on the basis of the propagation time;
(f) adjusting the delay time based on the flow rate, wherein the
delay time decreases with increase in flow rate; and
(g) repeating (b) to (f) after the delay time has elapsed.
12. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic wave generator, provided in said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or a downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid; operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time of the ultrasonic wave from said ultrasonic wave generator
to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
a signal generator operable to generate a signal at a time interval
corresponding to the flow rate based on a flow rate to time interval
relationship, wherein the flow rate to time interval relationship
is characterized in that the time interval decreases with increase
in flow rate; and
a driving device operable to drive said ultrasonic wave generator
in response to the signal.
13. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic wave generator, provided in said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid, operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time of the ultrasonic wave from said ultrasonic wave generator
to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
a delay time setting device operable to set a delay time corresponding
to the flow rate based on a flow rate to delay time relationship,
wherein the flow rate to delay time relationship is characterized
in that the delay time decreases with increase in flow rate; and
a driving device operable to drive said ultrasonic wave generator
after the delay time has elapsed.
14. An ultrasonic flow meter as claimed in claim 13 wherein, in
the flow rate to delay time relationship, the delay time decreases
inversely with increase in flow rate.
15. An ultrasonic flow meter as claimed in claim 13 wherein, in
the flow rate to delay time relationship, the delay time decreases
linearly with increase in flow rate.
16. An ultrasonic flow meter as claimed in claim 13 wherein, in
the flow rate to delay time relationship, the delay time decreases
stepwise with increase in flow rate.
17. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic wave generator, provided in said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or a downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid, operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time of the ultrasonic wave from said ultrasonic wave generator
to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
a storage device operable to store at least two flow rates determined
by said second calculating device, as flow rate data;
a delay time setting device operable to set a delay time based
on the flow rate data stored in said storage device and based on
a flow rate to delay time relationship, wherein the flow rate to
delay time relationship is characterized in that the delay time
decreases with increase inflow rate; and
a driving device operable to drive said ultrasonic wave generator
and said receiver after the delay time has elapsed.
18. An ultrasonic flow meter as claimed in claim 17 wherein said
storage device is operable to store a plurality of flow rate data
and to erase an oldest flow rate data that has been previously stored
upon storing new flow rate data, so that the delay time is set based
on a mean value of the stored flow rate data.
19. An ultrasonic flow meter as claimed in claim 17 further comprising:
a judging device operable to judge, from a plurality of flow rate
data which have been previously stored, whether the flow rates is
increasing or decreasing at present; and
a correcting device operable to correct and shorten the delay time
according to a value of the flow rate data when the flow rate is
increasing and to correct and prolong the delay time according to
a value of the flow rate data when the flow rate is decreasing.
20. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
a pair of ultrasonic oscillators provided in said conduit such
that one oscillator is positioned on an upstream side of the other
oscillator with respect to a flowing direction of the fluid, wherein
each of said ultrasonic oscillators is capable of emitting and receiving
ultrasonic waves;
a flow rate measuring device operable to determine a flow rate
based on a propagation time of an ultrasonic wave from the one oscillator
to the other oscillator and based on the propagation time of an
ultrasonic wave from the other oscillator to the one oscillator;
a repeating device operable to repeat, for a determined number
of times, a switching between a first state where the one oscillator
emits the ultrasonic wave and the other oscillator received the
ultrasonic wave and a second state where the other oscillator emits
an ultrasonic wave and the one oscillator receives the ultrasonic
wave; and
a resetting device operable to reset the determined number based
on the flow rate determined by said flow rate measuring device based
on a flow rate to determined number relationship, wherein the flow
rate to determined number relationship is characterized in that
the determined number decreases with increase in flow rate.
21. An ultrasonic flow meter as claimed in claim 20 wherein, in
the flow rate to determined number relationship, the determined
number decreases inversely with increase in flow rate.
22. An ultrasonic flow meter as claimed in claim 20 wherein, in
the flow rate determined number relationship, the determined number
decreases linearly with increase in flow rate.
23. An ultrasonic flow meter as claimed in claim 20 wherein, in
the flow rate to determined number relationship relation, the determined
number decreases stepwise with increase in flow rate.
24. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic-wave generator, provided in said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or a downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid, operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time of the ultrasonic wave from said ultrasonic wave generator
to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
an output device operable to output at least either of information
indicative of year, month, and date and information indicative of
time of day;
a delay time setting device operable to set a delay time according
to the information from said output device and operable to change
the delay time, wherein the delay time is decreased when the flow
rate increases; and
a driving device operable to drive said ultrasonic wave generator
and said receiver after the delay time has elapsed.
25. An ultrasonic flow meter for use with fluid and equipment which
consumes the fluid, said meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic wave generator, provided in said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or a downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid, operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time of the ultrasonic wave from said generator to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
an informing device operable to inform of an operating state of
the equipment which consumes the fluid and to which the conduit
is to be connected;
a delay time setting device operable to set a delay time according
to the operating state and operable to change the delay time, wherein
the delay time is decreased when the flow rate increases; and
a driving device operable to drive said ultrasonic wave generator
and said receiver after the delay time has elapsed.
26. An ultrasonic flow meter comprising:
a conduit through which a fluid is to flow;
an ultrasonic wave generator, provided on said conduit, operable
to emit an ultrasonic wave into the fluid;
a receiver provided in said conduit on an upstream or a downstream
side of said ultrasonic wave generator with respect to a flowing
direction of the fluid, operable to receive the ultrasonic wave;
a first calculating device operable to determine a propagation
time in which the ultrasonic wave propagates from said ultrasonic
wave generator to said receiver;
a second calculating device operable to determine a flow rate based
on the propagation time;
a driving device operable to drive said ultrasonic wave;
a storage device operable to store the flow rate determined by
said second calculating device, as flow rate data; and
a breaker operable to cut, for a predetermined period of time,
power to at least any one of said first calculating device, said
second calculating device, and said driving device when the flow
rate data of a flow rate of zero occurs a predetermined number of
times in succession.
Description 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. 4483202 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 increase
in the flow rate;
(h) judging from a plurality of flow rate data which have been
stored, whether the flow rate is increasing or decreasing at present;
(h1) correcting and shortening the delay time according to a value
of the flow rate data when the flow rate is increasing;
(h2) correcting and prolonging the delay time according to a value
of the flow rate data when the flow rate is decreasing; and
(i) repeating (a) to (e) after the lapse of the corrected 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
of the ultrasonic wave;
(d) determining a flow rate from the propagation time;
(e) storing the flow rate as flow rate data and erasing the oldest
flow rate data that has been stored;
(f) resetting the number of repetition from a plurality of stored
flow rate data on the basis of a relation between flow rate and
delay time in which the number of repetition decreases with increase
in the flow rate; and
(g) repeating (a) to (f).
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 the 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 on the basis of a relationship between
time information, such as information on time of day and/or information
on month and date, and an amount of the fluid consumed; and
(f) 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 a 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 on the basis of the information on a consumption
of the fluid; and
(f) repeating (a) to (e) after the lapse of the delay time.
An ultrasonic flow meter in accordance with the invention comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided in the conduit;
(c) a receiver for receiving the ultrasonic wave, which receiver
being provided in the conduit on an upstream or a downstream side
of the generator with respect to the flowing direction of the fluid;
(d) a first calculating device operable to determine a propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) a signal generator operable to generate signals at a time interval
corresponding to the flow rate on the basis of a relationship between
the flow rate and the time interval where the time interval decreases
with increase in the flow rate; and
(g) a driving device operable to drive the ultrasonic-wave generator
in response to the signals.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided in the conduit;
(c) a receiver for receiving the ultrasonic wave, the receiver
being provided in the conduit on the upstream or downstream side
of the generator with respect to a flowing direction of the fluid;
(d) a first calculating device operable to determine a propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) a delay time setting device operable to set a delay time corresponding
to the flow rate on the basis of a relationship between the flow
rate and the delay time where the delay time decreases generally
with increase in the flow rate; and
(g) a driving device for driving the ultrasonic-wave generator
after the lapse of the delay time.
The relation between flow rates and measuring-time intervals or
delay times is set so that the delay time decreases linearly, stepwise,
or inversely with increase in the flow rate.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided in the conduit;
(c) a receiver for receiving the ultrasonic wave, the receiver
being provided in the conduit on an upstream or a downstream side
of the generator with respect to a flowing direction of the fluid;
(d) a first calculating device operable to determine the propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) a storage device operable to store at least two flow rates
determined by the calculating devices, as flow rate data;
(g) a delay time setting operable to set a delay time on the basis
of the flow rate data stored in the storage device and on the basis
of a relationship between the flow rate and the delay time where
the delay time decreases with increase in the flow rate; and
(h) a driving device operable to drive the ultrasonic-wave generator
and the receiver after the lapse of the delay time.
The storage device, which stores a plurality of flow rate data,
preferably erases the oldest flow rate data that has been stored,
upon storing new flow rate data, so that a delay time is set on
the basis of the mean value of the stored flow rate data.
The ultrasonic flow meter preferably comprises a judging device
for judging from a plurality of flow rate data which have been stored
whether the flow rate is increasing or decreasing at present, and
a correcting device for correcting and shortening the delay time
according to a value of the flow rate data when the flow rate is
increasing and for correcting and prolonging the delay time according
to a value of the flow rate data when the flow rate is decreasing.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) a pair of ultrasonic oscillators which are provided in the
conduit so that one oscillator is positioned on an upstream side
of the other oscillator with respect to a flowing direction of the
fluid and each of which is capable of emitting and receiving ultrasonic
waves;
(c) a flow rate measuring device operable to determine a flow rate
by a propagation time of an ultrasonic wave from the one oscillator
to the other oscillator and by the propagation time of an ultrasonic
wave from the other oscillator to the one oscillator;
(d) a repeating device operable to repeat a predetermined number
of times a switching between a first state where the one oscillator
emits the ultrasonic wave and the other oscillator receives the
ultrasonic wave and a second state where the other oscillator emits
an ultrasonic wave and the one oscillator receives the ultrasonic
wave; and
(e) a resetting device operable to reset the number of repetition
on the basis of the determined flow rate and on the basis of a relationship
between the flow rate and the number of repetition where the number
of repetition decreases with increase in the flow rate. The number
of repetition is set so as to decrease linearly, stepwise, or inversely
with increase in the flow rate.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided in the conduit;
(c) a receiver for receiving the ultrasonic wave, the receiver
being provided in the conduit on an upstream or a downstream side
of the generator with respect to a flowing direction of the fluid;
(d) a first calculating device operable to determine a propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) an output operable to output at least either of information
on year, month, and date and information on time of day;
(g) a setting device operable to set a delay time according to
the information from the output device; and
(h) a driving device operable to drive the ultrasonic-wave generator
and the receiver after the lapse of the delay time.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided in the conduit;
(c) a receiver for receiving the ultrasonic wave, the receiver
being provided in the conduit on an upstream or a downstream side
of the
generator with respect to a flowing direction of the fluid;
(d) a first calculating device operable to determine a propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) an informing device operable to inform of an operating state
of an equipment which consumes the fluid and to which the conduit
is connected;
(g) a delay time setting device operable to set a delay time according
to the operating state; and
(h) a driving device operable to drive the generator and the receiver
after the lapse of the delay time.
Another ultrasonic flow meter in accordance with the invention
comprises:
(a) a conduit through which a fluid flows;
(b) an ultrasonic-wave generator for emitting an ultrasonic wave
into the fluid, the generator being provided on the conduit;
(c) a receiver for receiving the ultrasonic wave, the receiver
being provided on the conduit on an upstream or a downstream side
of the generator with respect to a flowing direction of the fluid;
(d) a first calculating device operable to determine the propagation
time of the ultrasonic wave from the generator to the receiver;
(e) a second calculating device operable to determine a flow rate
by the propagation time;
(f) a driving device operable to drive the generator; (g) a storage
device operable to store the flow rate determined by the second
calculating device, as flow rate data; and
(g) (h) a breaker for cutting, for a predetermined period of time,
the power to at least any one the first calculating device, the
second calculating device, and the driving device when the flow
rate data of the flow rate of zero occurs a predetermined number
of times in succession.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a control for an ultrasonic
flow meter of a first embodiment;
FIG. 2 illustrates a relationship (a characteristic curve) between
flow rate and measuring-time interval, wherein the measuring-time
interval decreases linearly with increase in the flow rate;
FIG. 3 illustrates another relationship (a characteristic curve)
between flow rate and measuring-time interval, wherein the measuring-time
interval decreases stepwise with increase in the flow rate;
FIG. 4 illustrates another relation (a characteristic curve) between
flow rate and measuring-time interval, wherein the measuring-time
interval decreases in inverse proportion to the increasing flow
rate;
FIG. 5 illustrates a relation (a characteristic curve) between
flow rate and delay time, wherein the delay time decreases linearly
with increase in the flow rate;
FIG. 6 illustrates another relationship (a characteristic curve)
between flow rate and delay time, wherein the delay time decreases
stepwise with increase in the flow rate;
FIG. 7 illustrates another relation (a characteristic curve) between
flow rate and delay time, wherein the delay time decreases in inverse
proportion to the increasing flow rate;
FIG. 8 is a block diagram illustrating a control for the ultrasonic
flow meter of a second embodiment;
FIG. 9 is a part of a flow chart illustrating the control for the
ultrasonic flow meter in FIG. 8;
FIG. 10 illustrates a relationship (a characteristic curve) between
flow rate and the measuring-time interval (and the delay times)
corrected in response to the state of increase or decrease in the
flow rate;
FIG. 11 is a block diagram illustrating a control for the ultrasonic
flow meter of a third embodiment;
FIG. 12 is a part of a flow chart illustrating the control for
the ultrasonic flow meter in FIG. 11;
FIG. 13 is a block diagram illustrating a control for the ultrasonic
flow meter of a fourth embodiment;
FIG. 14 is a part of a flow chart illustrating the control for
the ultrasonic flow meter in FIG. 13;
FIG. 15 is a block diagram illustrating a control for the ultrasonic
flow meter of a fifth embodiment;
FIG. 16 is a flow chart illustrating the control for the ultrasonic
flow meter in FIG. 15;
FIG. 17 is a block diagram illustrating a control for the ultrasonic
flow meter of a sixth embodiment; and
FIG. 18 is a flow chart illustrating the control for the ultrasonic
flow meter of FIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, preferred embodiments of the invention
will be described. FIG. 1 is a block diagram illustrating a control
circuit for an ultrasonic flow meter of the first embodiment in
which the ultrasonic flow meter is generally indicated by reference
numeral 1. In the flow meter 1 a conduit indicated by reference
numeral 2 which is circular in cross section, is connected to a
gas burner (not shown), in which a fluid (i.e., gas) to be supplied
to the burner flows in a direction indicated by arrow 4. An oscillator
indicated by reference numeral 6 is a generator which emits an ultrasonic
wave and an oscillator indicated by reference numeral 8 is a receiver
which receives the ultrasonic wave emitted from the oscillator 6.
The oscillators 6 and 8 are mounted in the conduit 2 so as to confront
each other on a line 12 which intersects a central axis 10 of the
conduit 2 at a predetermined angle .phi.. A trigger section indicated
by reference numeral 14 outputs a trigger signal at a timing determined
by a method which will be described below. A generator indicated
by reference numeral 16 upon receiving the trigger signal, outputs
a burst signal for energizing the oscillator 6. An amplifier indicated
by reference numeral 18 amplifies a signal that the oscillator 8
has emitted when detecting an ultrasonic wave. A comparator indicated
by reference numeral 20 generates and then outputs a signal which
corresponds to a time (propagation time) from the emission of an
ultrasonic wave by the oscillator 6 to the reception of the ultrasonic
wave by the oscillator 8. A time counter indicated by reference
numeral 22 calculates the propagation time according to the output
signal from the comparator 20. A flow rate calculator indicated
by reference numeral 24 calculates a flow rate of the fluid flowing
in the conduit 2 from the propagation time, according to a calculation
which will be described below. A timing controller indicated by
reference numeral 26 determines, on the basis of the flow rate,
a timing at which the trigger section 14 outputs the trigger signal.
In this embodiment, the timing is determined from a measuring-time
interval according to a relationship (a characteristic curve) of
flow rate versus measuring-time interval, shown in FIG. 2 in which
the measuring-time interval decreases linearly with increasing the
flow rate.
An operation of the flow meter 1 will be described below. When
the trigger signal is transmitted from the trigger section 14 the
generator 16 generates and outputs a burst signal based upon the
trigger signal. The oscillator 6 is energized by the burst signal
to emit the ultrasonic wave toward the oscillator 8. The ultrasonic
wave is received by the oscillator 8 and a receiving signal of
the oscillator 8 is amplified by the amplifier 18. The comparator
20 then generates a signal which corresponds to the propagation
time of the ultrasonic wave and outputs the signal to the time counter
22. The time counter 22 calculates the propagation time and then
the flow rate calculator 24 calculates the flow rate from the propagation
time. Subsequently, the timing controller 26 then determines a measuring-time
interval corresponding to the determined flow rate on the basis
of the relationship shown in FIG. 2. Specifically, the measuring-time
interval is set shorter if the flow rate measured at the present
time is larger than the flow rate measured at the last time, while
the measuring-time interval is set longer if the flow rate has become
smaller. Then, the trigger section 14 outputs a trigger signal,
at the measuring-time interval which has been newly set, to energize
the oscillator 6 to emit the ultrasonic wave. The ultrasonic wave
is detected by the oscillator 8 and the flow rate is measured. After
that, the above-described process is repeated.
According to the invention, the flow rate is measured more frequently
as it increases, and therefore it is possible to determined a cumulative
value of the flow rates in an apparatus like a gas-meter which is
required to determined the cumulative value with greater presicion,
in spite of the fact that measurement errors in the flow rate provide
a great influence on the cumulative value.
The calculation of the propagation time in the time counter 22
will be described below. Assume that a velocity at which an ultrasonic
wave propagates in a fluid at rest is (c) and that a velocity of
the fluid is (v), a propagation velocity of the ultrasonic wave
in a direction along which the fluid flows is (c+v). The propagation
time (t) of the ultrasonic wave from the oscillator 6 to the oscillator
8 is given by the following equation (1):
In the equation (1), (L) is a distance between the oscillators
6 and 8.
The equation (1) can be transformed into the following equation
(2):
According to this equation, the flow velocity can be determined
by measuring the propagation time t because L and c are known. The
flow rate (Q) on the other hand is given by the following equation
(3):
In the equation (3), (S) is the cross-sectional area of the conduit
2 and (K) is the correction coefficient.
The relationship between flow rate and measuring-time interval
may be such that the measuring-time interval decreases stepwise
with the increasing flow rate, as shown in FIG. 3 or may be such
that the measuring-time interval is inversely proportional to the
flow rate, as shown in FIG. 4.
In the first embodiment, although the measuring-time interval is
determined at the timing controller 26 from the measured flow rate
on the basis of a predetermined relationship between flow rate and
measuring-time interval; a delay time of the trigger signal to be
outputted from the trigger section 14 may be determined from the
measured flow rate so that the trigger section 14 is energized after
the lapse of the delay time.
The relationship between flow rate and delay time may be any one
of a linear relation (FIG. 5), a stepwise relation (FIG. 6), and
an inverse relation (FIG. 7), as far as the delay time generally
decreases with the increasing flow rate.
SECOND EMBODIMENT
FIG. 8 illustrates an ultrasonic flow meter 1A of the second embodiment,
which includes many elements in common with the ultrasonic flow
meter of FIG. 1 and like elements are designated by like reference
numerals because like elements achieve similar functions, respectively.
To the ultrasonic flow meter 1A, however, added is a storing section
28 for storing flow rate data. In the storing section 28 a predetermined
number of flow rate values calculated by the flow rate calculator
24 are sequentially stored as flow rate data, and the data is updated
by replacing the oldest flow rate data with the newest flow rate
data. On the basis of the mean value of the plurality of stored
flow rate data, the measuring-time interval or the delay time is
set at the timing controller 30 according to any one of the relationships
of FIGS. 2 to 4 or of FIGS. 5 to 7 respectively.
The relationships between flow rate and measuring-time interval
and flow rate and delay time are preferably corrected with consideration
to whether the flow rate is increasing or decreasing at present.
For example, as shown in the flow chart of FIG. 9 the timing controller
30 judges from the flow rate data stored in the storing section
28 whether the flow rate is increasing or decreasing at present.
When the flow rate is increasing, the measuring-time interval and
the delay time are corrected to be shorter than those of which to
be set with respect to the same flow rate when the flow rate is
stable; when the flow rate is decreasing the measuring-time interval
and, the delay time is corrected to be longer. Subsequently, a trigger
signal is outputted on the basis of the measuring-time interval
or the delay time which has been thus corrected. The relationship
between flow rate and measuring-time interval or delay time which
has been corrected in this way is shown in FIG. 10. Such a correction
of flow rate has an advantage that the increase in flow rate can
be accurately measured, for example, even in the case that the flow
rate increases sharply.
THIRD EMBODIMENT
FIG. 11 illustrates an ultrasonic flow meter 1B of a third embodiment,
which meter 1B has many elements in common with the ultrasonic flow
meter shown in FIG. 1 and like elements are designated by like
reference numerals because like elements achieve similar functions,
respectively. To the ultrasonic flow meter 1B, a function is added
by which the measuring-time interval and the delay time are changed
depending upon whether it is a time zone in which gas is typically
consumed or not. Specifically, the ultrasonic flow meter 1B comprises
a clock 32 and the present time outputted from the clock 32 is
delivered to a timing controller 34. As shown in the flow chart
of FIG. 12 the timing controller 34 judges from the time information
whether or not it is in the hours when gas is consumed in large
quantities. For example, a midnight time zone from twelve o'clock
midnight to five o'clock in the morning is set as a low gas-consumption
time zone and the rest is set as a high gas-consumption time zone,
and a determination is made whether it is in the low or high gas
consumption time zone at present. When it is judged that the present
time belongs to the low gas-consumption hours, the measuring-time
interval (or the delay time) is set at a predetermined longer period
of time. The measuring-time interval or the delay time which is
set at this stage is different from and independent of the time
determined by a flow rate on the basis of one of the relationships
shown in FIGS. 2 to 4 (or FIGS. 5 to 7). Subsequently, whether the
flow rate has varied or not is judged; if the flow rate has varied,
the measuring-time interval or the delay time is newly set according
to the flow rate newly measured on the basis of one of the relationships
shown in FIGS. 2 to 4 or FIGS. 5 to 7 respectively.
In accordance with the embodiment, an unnecessary power consumption
can be reduced by setting the measuring-time interval or the delay
time longer in the midnight hours when gas is not used. However,
if the gas is consumed in midnight, the flow rate is measured at
certain measuring-time intervals or with time delays corresponding
to the flow rates.
In an area where the amount of consumption of a fluid such as gas
varies depending upon seasons, the information on month and date,
instead of or along with the information on time of day, may be
outputted from the clock and referred to for controlling the measurement
of flow rates.
FOURTH EMBODIMENT
FIG. 13 illustrates an ultrasonic flow meter 1C of a fourth embodiment,
which meter 1C has many elements in common with the ultrasonic flow
meter shown in FIG. 1 and like elements are designated by like
reference numeral because like elements achieve similar functions,
respectively. In the ultrasonic flow meter 1C, operating states
of equipments in which gas is consumed, for example, a heater 36
a stove 38 and a hot-water supply 40 are inputted into a timing
controller 42. As shown in the flow chart of FIG. 14 the timing
controller 42 judges whether the gas-consuming equipment 36 38
or 40 is deactivated or not. When it is judged that all the gas-consuming
equipments are deactivated, the measuring-time interval (or the
delay time) is set to a predetermined longer period of time. The
measuring-time interval (or the delay time) which is set in this
way is different from and independent of the time determined according
to a flow rate on the basis of one of the relationship shown in
FIGS. 2 to 4 (or FIGS. 5 to 7). Subsequently, whether the flow rate
has varied or not is judged, and if the flow rate has varied, a
measuring-time interval or a
delay time is newly set from a flow rate newly measured on the
basis of one of the relationship shown in FIGS. 2 to 4 or FIGS.
5 to 7 respectively. In accordance with the embodiment, an unnecessary
power consumption can be reduced by setting the measuring-time interval
or the delay time longer when gas is not consumed.
FIFTH EMBODIMENT
FIG. 15 illustrates an ultrasonic flow meter 1D of a fifth embodiment,
which meter 1D has many elements in common with the ultrasonic flow
meter shown in FIG. 1 and like elements are designated by like
reference numerals because like elements achieve similar functions,
respectively. In the ultrasonic flow meter 1D, oscillators 44 and
46 which have both the functions of emitting and receiving ultrasonic
waves are mounted in the conduit 2 so as to oppose each other on
a line 12 which intersects the central axis 10 of the conduit 2
at a predetermined angle .phi.. An oscillator-switching section
48 alternately switches the oscillators between one state for emitting
ultrasonic waves and the other state for receiving ultrasonic waves.
A repetition-setting section 50 sets the number of times the oscillators
44 and 46 repeat the emission of an ultrasonic wave. A repetition
controller 52 switches a first state where one oscillator 44 emits
the ultrasonic wave the number of times corresponding to a flow
rate and the other oscillator 46 receives the ultrasonic wave, to
a second state where the other oscillator 46 emits the ultrasonic
wave the same number of times and the one oscillator 44 receives
the ultrasonic wave, and vice versa. The relationship between flow
rate and the number of repetition is set so that the number of repetition
generally decreases with increasing flow rate.
The operation of the flow meter 1D mentioned above will be specifically
described below with reference to a flow chart shown in FIG. 16.
Assume that the number of repetition is set at (n) by the repetition-setting
section 50 the first state is established by the switching section
48. After that, a trigger signal is outputted from the trigger section
14 and the burst signal is outputted from the generator 16. An ultrasonic
wave is thereby emitted from the oscillator 44 toward the other
oscillator 46 with a predetermined delay time. A signal received
by the oscillator 46 is amplified in the amplifier 18 and compared
with a reference signal in the comparator 20. The propagation time
of the ultrasonic wave is then calculated by the time counter 22.
Subsequently, whether or not an ultrasonic wave has been emitted
(n) times from the oscillator 44 is judged. If the ultrasonic wave
has been emitted (n) times, the propagation times of the ultrasonic
waves emitted (n) times are totaled by the time counter. If the
ultrasonic wave has been emitted fewer than (n) times, on the other
hand, another trigger signal is outputted again from the trigger
section 14 to execute the emission and reception of an ultrasonic
wave.
When the measurement in the first state is completed, the oscillator-switching
section 48 is switched into the second state. Thus the operation
in which an ultrasonic wave is emitted from the oscillator 46 and
received by the other oscillator 44 is repeated (n) times, and then
the propagation times of the ultrasonic waves emitted (n) times
are totaled.
Subsequently, the flow rate is determined on the basis of the totals
or averages of the propagation times in the first state and in the
second state. Whether the flow rate has increased or decreased is
then judged by comparing the flow rate newly measured with the flow
rate measured last time, and the number of repetition corresponding
to the flow rate newly measured is set in the section 50 for setting
the number of repetition. The number of repetition set in this way
is such that the number of repetition generally decreases with increase
in flow rate, and therefore, even a low flow rate can be accurately
measured.
The calculation of a flow velocity and a flow rate in the embodiment
will be described below. Assuming the velocity (c) of the ultrasonic
wave in a fluid at rest and the flow velocity (v) of the fluid,
the propagation velocity of the ultrasonic wave in the direction
of the flow is given as (c+v), and the propagation velocity of the
ultrasonic wave in the direction opposed to the flow direction is
given as (c-v). The total T1 of the propagation times in the flow
direction and the total T2 of the propagation times in the direction
opposed to the flow direction are given by equations (4) and (5),
respectively. ##EQU1## In the equations (4) and (5), .phi. is an
intersectional angle between the central axis of the conduit and
the line connecting the oscillators, and n is the number of repetition.
In accordance with the equations (4) and (5), the total of the
measurements of the flow velocities is given by an equation (6)
below:
In accordance with the equation (6), the total of the flow velocities
is given by an equation (7) below:
In the equation (7), .SIGMA.Qn, (K), and (S) represent the total
of the flow velocities, a correction coefficient, and the cross-sectional
area of the conduit, respectively.
As is evident from the equations (6) and (7), the total of the
flow rate values increases with increase in the number of times
of the measurement. In other words, even in the case of a low flow
velocity, increasing the number of times of the measurement causes
the totals of the flow velocity values and the flow rate values
to increase, thus making an error included in each measurement relatively
small. In the case of a high flow velocity, on the contrary, even
decreasing the number of times of the measurement permits a relative
measurement error to remain small because the difference between
T1 and T2 is large.
In the invention, for this reason, the repetition-setting section
50 sets the number of repetition at a large number in the case of
a low flow rate, while the section 50 sets the number of repetition
at a small number in the case of a high flow rate. The relation
between the flow rates and the numbers of repetition has only to
be such that the number of repetition generally decreases with increase
in the flow rate, and the relation is set so that the number of
repetition decreases linearly, stepwise, or inversely with increase
in the flow rate.
It has been described that one oscillator emits the ultrasonic
wave (n) times and then the other oscillator emits the ultrasonic
wave (n) times; however, an operation in which one oscillator emits
the ultrasonic wave once and then the other oscillator emits the
ultrasonic wave once may be executed as many times as the number
of repetition.
SIXTH EMBODIMENT
FIG. 17 illustrates an ultrasonic flow meter 1E of a sixth embodiment,
which meter 1E has many elements in common with the ultrasonic flow
meter shown in FIG. 1; and like elements are designed by like numerals
because like elements achieve similar functions, respectively. The
flow meter 1E comprises a breaker 54 and, as shown in the flow chart
of FIG. 18 a plurality of flow rate values calculated in a flow
rate calculator 24 are stored in a memory 56 as flow rate data.
When the flow rate is judged to be zero from the flow rate data
in the memory 56 the number of times the rate has been successively
judged to be zero is stored. In the case that the flow rate has
been judged to be zero a predetermined number of times in succession,
the breaker 54 is driven to cut for a predetermined period of time
at least one of the powers of the trigger section, the generator
16 the amplifier 18 the comparator 20 the time counter 22 and
the flow rate calculator 24. As long as a fluid does not flow, therefore,
the measuring-time intervals are made long so that the power consumption
can be saved. |