Doppler ultrasonic flowmeter, and processor and method thereof with quantization error correction
View Patent ↗In a Doppler ultrasonic flowmeter, to obtain a precise flow rate a flow rate calculation equation that corrects a quantization error occurring to a spatial resolution is used. An ultrasonic transducer transmits/receives ultrasonic pulses, and subject the resulting received signals to A/D conversion after a predetermined process is applied thereto. A computation control section calculates the flow velocity distribution. Then, the flow rate is calculated based on the flow rate calculation equation, which corrects the quantization error occurring to the spatial resolution.
1. A Doppler ultrasonic flowmeter for measuring, using an ultrasonic Doppler shift, a flow rate of fluid flowing inside a conduit, comprising:
ultrasonic wave transmission/reception means for transmitting to the fluid an ultrasonic pulse with an arbitrary pulse repetition frequency, and for receiving a resulting ultrasonic echo to extract a Doppler shift component through a predetermined process;
flow velocity distribution calculation means for calculating a flow velocity distribution of the fluid based on the Doppler shift component extracted by the ultrasonic wave transmission/reception means; and
flow rate calculation means for calculating a flow rate of the fluid based on the calculated flow velocity distribution of a predetermined integration range and a quantization error occurring to a spatial resolution
wherein the flow rate calculation means calculates the flow rate (Q) based on the following equation:
Q
=
2
π
(
v
0
·
r
0
′
·
Δ
r
0
′
+
∑
i
=
1
N
-
1
v
1
·
r
i
·
Δ
r
i
+
v
N
·
r
N
′
·
Δ
r
N
′
)
=
2
π
[
v
0
·
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
+
∑
i
=
1
N
-
1
(
r
i
·
Δ
r
i
)
·
v
i
+
v
n
·
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
]
where
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
is a flow rate coefficient of a starting channel,
(r i ·Δr i )·v i is a flow rate conversion factor,
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
is a flow rate coefficient of an end channel, and
where v is the flow velocity of the respective channel, r is the distance from the center of the conduit to the center of the respective channel, Δr is the width of the respective channel.
2. The Doppler ultrasonic flowmeter according to claim 1 , wherein the flow rate calculation means corrects the quantization error by considering only the region of the integration range occupied by a channel at a starting position and a channel at an end position of the integration range.
3. A processor in a Doppler ultrasonic flowmeter for measuring, using an ultrasonic Doppler shift, a flow rate of fluid flowing inside a conduit, comprising:
flow velocity distribution calculation means for calculating a flow velocity distribution of the fluid based on a Doppler shift component as a result of a predetermined process applied to a reception signal of an ultrasonic echo, which is a reflection wave of an ultrasonic pulse provided into the conduit; and
flow rate calculation means for calculating a flow rate based on the calculated flow velocity distribution of a predetermined integration range and a quantization error occurring to a spatial resolution
wherein the flow rate calculation means calculates the flow rate (Q) based on the following equation:
Q
=
2
π
(
v
0
·
r
0
′
·
Δ
r
0
′
+
∑
i
=
1
N
-
1
v
1
·
r
i
·
Δ
r
i
+
v
N
·
r
N
′
·
Δ
r
N
′
)
=
2
π
[
v
0
·
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
+
∑
i
=
1
N
-
1
(
r
i
·
Δ
r
i
)
·
v
i
+
v
n
·
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
]
where
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
is a flow rate coefficient of a starting channel,
(r i ·Δr i )·v i , is a flow rate conversion factor,
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
is a flow rate coefficient of an end channel, and
where v is the flow velocity of the respective channel, r is the distance from the center of the conduit to the center of the respective channel, Δr is the width of the respective channel.
4. The processor according to claim 3 , wherein the flow rate calculation means corrects the quantization error by considering only the region of the integration range occupied by a channel at a starting position and a channel at an end position of the integration range.
5. A method of computing a flow rate of fluid flowing inside a conduit in a Doppler ultrasonic flowmeter using an ultrasonic Doppler shift, the method comprising the steps of:
calculating, with a flow velocity distribution calculating means, a flow velocity result of a predetermined process applied to a reception signal of an ultrasonic echo, which is a reflection wave of an ultrasonic pulse provided into the conduit; and
calculating, with a flow rate calculation means, a flow rate predetermined integration range and a guantization error occurring to a spatial resolution, wherein the flow rate (Q) is calculated based on the following equation:
Q
=
2
π
(
v
0
·
r
0
′
·
Δ
r
0
′
+
∑
i
=
1
N
-
1
v
1
·
r
i
·
Δ
r
i
+
v
N
·
r
N
′
·
Δ
r
N
′
)
=
2
π
[
v
0
·
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
+
∑
i
=
1
N
-
1
(
r
i
·
Δ
r
i
)
·
v
i
+
v
n
·
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
]
where
(
1
2
·
r
0
+
r
1
2
)
·
(
r
0
+
r
1
2
)
is a flow rate coefficient of a starting channel,
(r i ·Δr i )·v i is a flow rate conversion factor,
(
1
2
·
(
D
2
+
r
N
-
1
+
r
N
2
)
)
·
(
D
2
-
r
N
-
1
+
r
N
2
)
is a flow rate coefficient of an end channel, and
where v is the flow velocity of the respective channel, r is the distance from the center of the conduit to the center of the respective channel, Δr is the width of the respective channel.
6. The method according to claim 5 , wherein the calculation of the flow rate corrects the quantization error by considering only the region of the integration range occupied by a channel at a starting position and a channel at an end position of the integration range.
7. A storage device storing a computer program that contains codes for calculating the flow rate according to the method of claim 5 .