JP2002214002A - Flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flow meter that can accurately measure even a low flow rate. SOLUTION: A measured passage 3 is connected between a flow meter 1 at an upstream side and a flow meter 2 at a downstream side. A flow rate flowing down in the measured passage 3 can be computed and measured as a difference between both the flow meters 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter, and more particularly, to a flow meter capable of accurately measuring the flow rate even when the flow rate is small.

[0002]

2. Description of the Related Art Conventionally, various types of flowmeters such as a Karman vortex flowmeter, an electromagnetic flowmeter, a positive displacement flowmeter, and a Coriolis flowmeter have been used. For example, a Karman vortex flowmeter detects the number of Karman vortices generated when a fluid passes through a vortex generator provided in a flow path, and converts the fluid flow rate or the passing flow rate.

[0003]

The conventional flowmeter described above has a problem in that a small flow rate cannot be measured accurately even though the flow rate varies, and the measurement target is limited. For example, the Karman vortex flow meter measures the flow rate using the fact that the Strouhal number is constant in a range of a predetermined Reynolds number in the flow path and the vortex frequency and the fluid flow velocity are in a proportional relationship in this range, When the flow rate decreases, the measurement becomes impossible because the Reynolds number decreases and the Strouhal number does not remain constant.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a flowmeter capable of accurately measuring the flow rate of a passing fluid even when the flow rate is small, so that the measurement range is not limited by the passing flow rate. It is.

[0005]

Means for Solving the Problems The present invention, which has been made to solve the above problems, is provided in a flow path of a measurement fluid and measures a flow rate passing through the flow path. A flowmeter is arranged in series, a flow path to be measured for measuring the flow rate is connected between the plurality of flowmeters arranged in series, and a flowmeter on the upstream side and a flowmeter on the downstream side of the measured flow path And a calculation unit for calculating the flow rate through the measured flow path from the difference between the measured values.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow path to be measured is connected between a plurality of flow meters arranged in series, and the flow rate to be measured is determined from the difference between the measured values of the flow meters upstream and downstream of the flow path to be measured. By calculating the flow rate passing through the road, the flow rate passing through the flow path to be measured can be reduced by setting the flow rate passing through the upstream and downstream flow meters to a flow rate that can be measured accurately. Even small flow rates that cannot be measured by a single flow meter can be accurately calculated and measured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a flow meter is composed of an upstream flow meter 1, a downstream flow meter 2, and a measured flow path 3 connected between the two. The flowmeters 1 and 2 may be any conventional Karman vortex flowmeter, electromagnetic flowmeter, positive displacement flowmeter, or Coriolis flowmeter, as long as they can independently measure the flow rate. .

The flow meter 1 is connected to a pipe 4 and a valve 5 on the inlet side, and a valve 6 and a pipe 7 on the outlet side. The pipe 7 is connected to the flow meter 2 via the valve 8, and is branched and connected to the flow path 3 to be measured. The outlet of the flow meter 2 is connected to a pipe 10 via a valve 9. The fluid flowing down from the pipe 4 passes through the flow meter 1 and further flows down to the flow meter 2, and a part of the fluid flows down to the flow path 3 to be measured.

A fluid using device 12 is connected to the measured flow path 3 via a valve 11. In the present embodiment, the minute flow rate flowing into the fluid use device 12 is measured and calculated by the flow meters 1 and 2 and a calculation unit (not shown).

The flow rate flowing down the pipes 4 to 7 is measured by the flow meter 1, and the flow rate flowing down the pipes 7 to 10 is measured by the flow meter 2. These measurement values are sent to a calculation unit (not shown), and the difference between them is calculated as a flow rate flowing down the flow path 3 to be measured, and is displayed or stored.

The flow rates flowing down the flow meters 1 and 2 are set so as not to cause errors in the flow meters 1 and 2 so that the flow rates can be accurately measured by the flow meters 1 and 2 respectively. The flow rate flowing down the measured flow path 3 can be accurately calculated from the difference between the two. For example, if the measured values of the two flowmeters 1 and 2 are the same value, the flow rate flowing down the flow path 3 to be measured is zero, and theoretically such a minimum measured flow rate can be measured from zero.

When the fluid flows back through the measured flow path 3,
In other words, when the fluid flows down from the fluid using device 12 to the flow path 3 to be measured, the valve 6 is closed and the valves 8 and 9 are opened, so that the flow meter 2 allows the fluid to flow from the fluid using device 12 to the pipeline 10. It is also possible to measure the flow rate that flows back to.

In this embodiment, an example in which two flow meters 1 and 2 are used has been described. However, even if three or more flow meters are used, the same can be used.

[0014]

As described above, according to the present invention, the flow path to be measured is connected between a plurality of flow meters arranged in series, and the measurement of the flow meters upstream and downstream of the flow path to be measured is performed. By calculating the passing flow rate of the measured flow path from the value difference,
Even if the flow rate passing through the flow path to be measured is a very small flow rate that cannot be measured by a single flow meter, it can be accurately calculated and measured. Therefore, measurement from a small flow rate in the flow path to be measured becomes possible, and the measurement target is not limited.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a flow meter according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upstream flow meter 2 Downstream flow meter 3 Flow path to be measured 4 Inlet pipe 10 Outlet pipe 12 Fluid using device

Claims (1)

[Claims] 1. A method for measuring a flow rate passing through a flow path provided in a flow path of a measurement fluid, wherein a plurality of flow meters are arranged in series, and between the plurality of flow meters arranged in series. An arithmetic unit that connects a flow path to be measured for measuring a flow rate and calculates a flow rate of the flow path to be measured from a difference between a measured value of a flow meter on an upstream side and a flow meter on a downstream side of the measured flow path. A flowmeter characterized by comprising: