JP2013064643A - Method and apparatus for correcting zero point of ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for correcting a zero point of an ultrasonic flowmeter, which can timely correct the zero point without requiring difficult environment setting such as passage blockage and pressure adjustment.SOLUTION: The ultrasonic flowmeter zero point correcting method and its apparatus for detecting a flow rate of fluid by installing a pair of ultrasonic sensors 2, 2 oppositely each other on the upstream and downstream of a passage 1 includes a flow rate correction step for converting a reflection time difference between forward reflection time and reverse reflection time of a measurement wave W into an offset value and updating a level of the offset value as a zero point of a flow rate to be guided by the ultrasonic flowmeter.

Description

  The present invention relates to an ultrasonic flow meter, and more particularly, to a zero correction method and apparatus for accurately detecting a zero flow condition.

  In an ultrasonic flow meter, a pair of ultrasonic sensors are installed in a positional relationship across the flow path and facing each other upstream and downstream of the flow path through which the fluid flows, and the direction in which the fluid flows (forward direction) The flow rate of the fluid is detected on the basis of the difference between the time required to pass the transmission waveform and the time required to pass the transmission waveform in the direction opposite to the fluid flow (reverse direction).

  However, the required time has an error due to a characteristic difference of the ultrasonic sensor, and due to the error, an offset occurs in the flow rate of the fluid derived from the required time. And the said offset also arises a secular change and a secular change, and causes the difficulty in the measurement of exact flow volume (for example, refer patent document 3).

  Conventionally, various offset correction methods have been provided. In Patent Document 1 below, a predetermined period is set as a zero point measurement period, and the minimum flow rate measured by the ultrasonic sensor during this period is the gas flow rate. The method of setting the zero point of the gas is described, and in Patent Document 2, when the gas is not used, the gas flow path is shut off, and the gas pressure downstream of the gas flow path shut-off portion is detected in that state, thereby A method is described in which the presence / absence is confirmed, and when it is confirmed that there is no pressure drop, the flow rate is measured and the flow rate at that time is set to the zero point.

JP 2000-111043 A JP 2002-116076 A Japanese Patent No. 3888946

However, as seen in the above-mentioned conventional method, in order to measure and correct the zero flow rate, it is performed at the time of manufacturing not connected to the pipe, or when connected to the pipe, It has been necessary to create an environment in which no gas is flowing in the pipe through which the ultrasonic sensor is interposed, such as by closing the shut-off valve so as not to be affected by the pressure fluctuation of the pipe, by stopping use.
In a normal use environment, it is difficult to accurately correct the zero in the installed state because it cannot be determined when the gas is flowing and shut off.

  The present invention has been made in view of the above circumstances, and zero-point correction is performed in a timely manner without going through extremely difficult environmental settings such as blocking the flow of the flow path and setting the pressure in the flow path to normal pressure. It is an object of the present invention to provide a zero point correction method and apparatus for an ultrasonic flow meter that can be performed.

An ultrasonic flowmeter zero correction method according to the present invention made to solve the above-described problem is a positional relationship between a pair of ultrasonic sensors upstream and downstream of a flow path and across the flow path and facing each other. The flow rate of the fluid is detected based on the difference between the time required to pass the measurement wave in the direction of fluid flow and the time required to pass the measurement wave in the direction against the fluid flow. In the zero-point correction method of the ultrasonic flowmeter that
The upstream ultrasonic sensor is set to the transmission mode, the measurement wave is transmitted from the upstream ultrasonic sensor to the downstream ultrasonic sensor, and then the upstream ultrasonic sensor is set to the reception mode. The measurement wave is received by an ultrasonic sensor on the upstream side of the transmission source, and a first time measurement step for detecting a forward and backward time from transmission to reception; and
Set the downstream ultrasonic sensor to the transmission mode, transmit the measurement wave from the downstream ultrasonic sensor to the flow side ultrasonic sensor, and then set the downstream ultrasonic sensor to the reception mode. A second time measuring step of receiving the measurement wave by an ultrasonic sensor downstream of a transmission source and detecting a reverse round trip time from transmission to reception;
A flow rate correction step is performed in which the difference between the round trip time between the forward and reverse round trip times is converted into an offset value for flow rate measurement, and the level of the offset value is updated as a zero point of the flow rate to be guided by the ultrasonic flowmeter. .

An ultrasonic flowmeter zero correction apparatus according to the present invention, which has been made to solve the above-described problems, includes a pair of ultrasonic sensors upstream and downstream of a flow path, positions that cross the flow path and face each other. The flow rate of the fluid is determined based on the difference between the time required to pass the measurement wave in the direction of fluid flow and the time required to pass the measurement wave in the direction against the fluid flow. In the zero point correction device of the ultrasonic flow meter to detect,
Set the ultrasonic sensor on the upstream side to the transmission mode, transmit the measurement wave from the ultrasonic sensor on the upstream side to the ultrasonic sensor on the downstream side, set the ultrasonic sensor on the upstream side to the reception mode, and transmit The process of receiving the measurement wave with the ultrasonic sensor upstream of the transmission source,
The downstream ultrasonic sensor is set to the transmission mode, the measurement wave is transmitted from the downstream ultrasonic sensor to the upstream ultrasonic sensor, the downstream ultrasonic sensor is set to the reception mode and transmitted. A flow rate measuring means for performing processing for receiving a measurement wave by an ultrasonic sensor on the downstream side of the transmission source;
Calculates the forward / return time from transmission to reception when receiving the upstream ultrasonic sensor and receiving the same, and when transmitting the downstream ultrasonic sensor and receiving the upstream ultrasonic sensor The reverse round trip time from transmission to reception is calculated, the round trip time difference between the forward round trip time and the reverse round trip time is derived, the round trip time difference is converted into the flow measurement offset value, and the flow rate detection means determines the level of the offset value. Computation means for updating as the zero point of the flow rate to be guided is provided.
A zero-point correction device may be provided that includes output adjustment means for increasing the transmission output of the measurement wave to the correction output when the correction control means is operated.

The forward and backward reciprocation times are theoretically the same regardless of the flow of the flow path because they have the same environment and path and are affected by the same flow of fluid. However, due to the difference in the characteristics of the upper and lower sensors, a common offset value occurs regardless of the presence or absence of the flow of the flow path.
If the offset value is used for zero point correction, zero point correction can be performed in a timely manner without going through extremely difficult environment settings such as blocking the flow of the flow path and setting the pressure in the flow path to normal pressure. .

(A): A block diagram showing an example of a zero point correction method employed in the ultrasonic flow meter according to the present invention, and (B): a timing chart showing the principle of the ultrasonic flow meter according to the present invention. It is explanatory drawing which showed the example of arrangement | positioning and operation | movement of an ultrasonic sensor in the ultrasonic flow measurement method by this invention. It is the flowchart which showed an example of the process in the zero point correction method of the ultrasonic flowmeter by this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an ultrasonic flowmeter zero correction method and apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 shows an ultrasonic flowmeter in which a pair of ultrasonic sensors (hereinafter referred to as sensors) 2 and 2 are arranged obliquely across a flow path (for example, a pipe line) 1 through which a fluid (gas in this example) flows. An example is shown.

  In this example, a burst wave (measurement wave) W is transmitted from one sensor 2, the burst wave W is received by the other sensor 2, and the time required from transmission to reception is measured, thereby the flow path In order to measure the flow rate of the gas flowing through 1, a pair of ultrasonic sensors 2 and 2, a flow measurement control means 8 for controlling the operation of the ultrasonic sensors 2 and 2 in a flow measurement mode, and the ultrasonic wave A zero-point correction control means 3 for controlling the operation of the sensors 2 and 2 in a zero-point correction mode and an arithmetic means 7 for performing an operation using the outputs of both sensors 2 and 2 are provided in the arithmetic means 7 based on the calculation result. In addition to the zero point correction control unit 3, a round trip time detection unit 4, an offset detection unit 5, and a zero point correction unit 6 that contribute to correction of a zero point used for flow rate measurement are provided.

[Flow measurement mode]
This measurement detects the difference between the time required to pass the burst wave W in the fluid flow direction (forward direction) and the time required to pass the burst wave W in the direction opposite to the fluid flow (reverse direction). Then, the flow rate of the fluid is derived based on the difference.

At that time, the flow rate measurement control means 8 first sets the upstream ultrasonic sensor (hereinafter referred to as “upper sensor”) 2 to the transmission mode and the downstream ultrasonic sensor (hereinafter referred to as “lower sensor”) 2. The burst wave W is transmitted from the upper sensor 2 toward the lower sensor 2 through the process of setting the reception mode. The calculating means 7 receives the time of transmission of the upper sensor 2 and the time of reception of the lower sensor 2 and calculates a required time from transmission to reception (hereinafter referred to as “order required time”).
Subsequently, the flow rate measurement control unit 8 transmits a burst wave W from the lower sensor 2 to the upper sensor 2 through a process of setting the lower sensor 2 to the transmission mode and setting the upper sensor 2 to the reception mode. The calculating means 7 receives the time of transmission of the lower sensor 2 and the time of reception of the upper sensor 2 and calculates a required time from transmission to reception (hereinafter referred to as “reverse required time”).
The calculating means 7 derives the forward time difference between the forward required time and the reverse required time, and converts the forward time difference into the flow rate of the fluid and outputs it.

[Zero correction mode]
First, the zero point correction control means 3 transmits a burst wave W from the upper sensor 2 to the lower sensor 2 through processing for setting the upper sensor 2 to the transmission mode.
Next, the process of setting the upper sensor 2 to the reception mode, the burst wave W transmitted first is received by the upper sensor 2 of the transmission source.
The round trip time detection means 4 calculates the time required from transmission to reception (hereinafter referred to as “forward round trip time”) in response to the transmission of the upper sensor 2 and the reception of the sensor 2.

Subsequently, the zero point correction control means 3 transmits a burst wave W from the lower sensor 2 to the upper sensor 2 through processing for setting the lower sensor 2 to the transmission mode.
Next, the burst wave W transmitted first is received by the lower sensor 2 of the transmission source through the process of setting the lower sensor 2 to the reception mode.
The round trip time detection means 4 receives the time of transmission of the lower sensor 2 and the time of reception of the upper sensor 2 and calculates the required time from transmission to reception (hereinafter referred to as “reverse round trip time”).
At this time, in consideration of the fact that the path from transmission to reception doubles due to the round trip, the transmission output of the burst wave W is increased to the correction output, and the transmission output of the burst wave W is measured in the flow rate measurement mode. It is desirable to provide an output adjusting means that provides a function such as lowering the output. In this example, the zero point correction control means 3 and the flow rate measurement control means 8 are provided with output adjustment means for adjusting the output (amplitude) of the measurement wave W together with the transmission / reception modes of the ultrasonic sensors 2 and 2. To do.

  The offset detection means 5 derives a round trip time difference between the forward and backward round trip times, and converts the round trip time difference into an offset value for flow rate measurement and outputs it. For example, a value obtained by deriving the round trip time difference between the forward and backward round trip times in the zero point correction mode and subtracting the round trip time difference between the forward round trip time and the reverse round trip time at the time of factory shipment may be used as the offset value.

  The zero point correcting means 6 updates the level of the offset value output from the offset detecting means 5 as the zero point of the flow rate that the ultrasonic flowmeter should guide in the flow rate measurement mode, and performs the calculation by the calculation means in the subsequent flow rate measurement mode. It is used for processing (for example, processing such as subtracting the offset value from the required time in the flow rate measurement mode may be performed).

1 channel,
2 ultrasonic sensors,
3 Zero point correction control means,
4 round trip time detection means,
5 offset detection means,
6 Zero correction means,
7 calculation means,
8 Flow measurement control means,

Claims (3)

A direction in which the fluid flows by installing a pair of ultrasonic sensors (2, 2) upstream and downstream of the flow path (1) so as to cross the flow path (1) and to face each other. Ultrasonic flow rate that detects the flow rate of fluid based on the difference between the time required to pass the measurement wave (W) and the time required to pass the measurement wave (W) in the direction against the fluid flow In the zero correction method of the meter,
The upstream ultrasonic sensor (2) is set to the transmission mode, the measurement wave (W) is transmitted from the upstream ultrasonic sensor (2) toward the downstream ultrasonic sensor (2), and then the upstream The ultrasonic sensor (2) on the side is set to the reception mode, the measurement wave (W) is received by the ultrasonic sensor (2) on the upstream side of the transmission source, and the forward and backward time from transmission to reception is detected. A first time measurement step;
The downstream ultrasonic sensor (2) is set to the transmission mode, the measurement wave (W) is transmitted from the downstream ultrasonic sensor (2) to the flow ultrasonic sensor (2), and then downstream. The ultrasonic sensor (2) on the side is set to the reception mode, the measurement wave (W) is received by the ultrasonic sensor (2) on the downstream side of the transmission source, and the reverse round trip time from transmission to reception is detected. A second time measurement step;
A flow rate correction step is performed in which the difference between the round trip time between the forward and reverse round trip times is converted into an offset value for flow rate measurement, and the level of the offset value is updated as a zero point of the flow rate to be guided by the ultrasonic flowmeter. Ultrasonic flow meter zero correction method. A direction in which the fluid flows by installing a pair of ultrasonic sensors (2, 2) upstream and downstream of the flow path (1) so as to cross the flow path (1) and to face each other. Ultrasonic flow rate that detects the flow rate of fluid based on the difference between the time required to pass the measurement wave (W) and the time required to pass the measurement wave (W) in the direction against the fluid flow In the total zero correction device,
The upstream ultrasonic sensor (2) is set to the transmission mode, and the measurement wave (W) is transmitted from the upstream ultrasonic sensor (2) to the downstream ultrasonic sensor (2). A process of setting the ultrasonic sensor (2) to the reception mode and receiving the transmitted measurement wave (W) by the ultrasonic sensor (2) on the upstream side of the transmission source;
The downstream ultrasonic sensor (2) is set to the transmission mode, the measurement wave (W) is transmitted from the downstream ultrasonic sensor (2) toward the upstream ultrasonic sensor (2), and the downstream ultrasonic sensor (2) is transmitted. A zero point correction control means (3) for performing processing for setting the ultrasonic sensor (2) to the reception mode and receiving the transmitted measurement wave (W) by the ultrasonic sensor (2) on the downstream side of the transmission source;
When the upstream ultrasonic sensor (2) is transmitted and when the sensor (2) is received, the forward and backward time from transmission to reception is detected, and the downstream ultrasonic sensor (2) is transmitted. A round trip time detecting means (4) for detecting a reverse round trip time from transmission to reception upon receipt of the upstream ultrasonic sensor (2);
An offset detection means (5) for deriving a round trip time difference between the forward and reverse round trip times and converting the round trip time difference into an offset value for flow measurement;
A zero point correction device for an ultrasonic flow meter, comprising zero point correction means (6) for updating the level of the offset value as a zero point of a flow rate to be guided by the ultrasonic flow meter. The zero point correction device for an ultrasonic flowmeter according to claim 2, further comprising output adjusting means for increasing the transmission output of the measurement wave (W) to the correction output when the correction control means (3) is operated.

Images