JPH0682282A - Measuring equipment for flow rate - Google Patents

Abstract

PURPOSE:To reduce a pressure loss as much as possible and, thereby, to measure highly precisely a flow rate in a range from a small flow rate area to a large flow rate area. CONSTITUTION:A valve 3 for changing the cross-sectional area of a flow passage 1 is provided and a differential pressure between the upstream side and the downstream side of this valve 3 is obtained. This differential pressure is controlled by a controller 6 so that it be prescribed in relation to a reference pressure, and based on a control signal outputted from this controller 6, a flow rate is computed by a flow rate computing circuit 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas meter or a gas flow rate measuring device applicable to detection of gas leaks, etc., and relates to improvement of a device for measuring a flow rate by forming an orifice in a flow passage. .

[0002]

2. Description of the Related Art As a means for measuring the flow rate of gas such as gas, an orifice is formed in a flow path and a flow rate measuring means for calculating the flow rate by detecting the differential pressure before and after the orifice, or a hot wire type in the flow path. A measuring means for measuring the flow rate by attaching the above flow sensor is known.

[0003]

However, in the case of the above flow rate measuring means, since the allowable range of pressure loss in the flow rate measuring section is suppressed to a low level, one orifice is used to measure a flow rate of 20 times or more, for example. Is difficult to do. Further, in the case of a flow sensor, it is difficult to accurately measure from a large flow rate to a small flow rate range, and drift may occur due to a change with time or the like. However, there is no method for automatically calibrating this drift in the conventional flow sensor.

An object of the present invention is to provide a flow rate measuring device capable of accurately measuring from a small flow rate range to a large flow rate range while suppressing pressure loss as low as possible.

[0005]

The structure of the present invention is as follows. 1. A gas flow passage, a valve whose cross-sectional area can be freely changed, a differential pressure detection means for detecting a differential pressure generated between upstream and downstream of the valve in the flow passage, and a constant differential pressure. A flow rate measuring device comprising a controller for controlling the valve as described above and a flow rate calculating circuit for calculating a flow rate based on a signal output from the controller. 2. A flow channel through which gas flows, a valve whose cross-sectional area can be freely changed, a flow velocity detecting means for detecting the flow velocity between the upstream and downstream of the valve in the flow channel, and the flow velocity so as to keep the flow velocity constant. A flow rate measurement device consisting of a controller that controls the valve and a flow rate calculation circuit that calculates the flow rate based on the signal output from this controller. 3. A flow passage through which gas flows, a valve whose cross-sectional area can be freely changed, a bypass flow passage that bypasses the valve in the flow passage, and a flow velocity detection means that detects the flow velocity of gas in the bypass flow passage. And a controller for controlling the valve so as to keep the flow velocity constant and a flow rate calculation circuit for calculating a flow rate based on a signal output from the controller.

[0006]

When the fluid flows in the flow passage, the differential pressure or the flow velocity before and after the valve or the flow velocity in the bypass flow passage is detected. Then, this pressure or flow velocity is compared with a predetermined reference value, the opening degree (cross-sectional area) of the valve is controlled to change the cross-sectional area of the flow path, and the pressure or flow velocity actually measured becomes the reference value. Control to maintain a constant difference. Then, the flow rate calculation circuit calculates the flow rate based on the control signal of this valve.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which a differential pressure is detected to measure a flow rate, and corresponds to claim 1.

1 is a flow path, 2 is an orifice, 3 is a flow path 1
A valve capable of changing the cross-sectional area of (orifice 2),
4 is a drive device for the valve 3, 5 is a pressure sensor, 5a is a pressure input line, 5b is a pressure output line, 6 is a controller,
Reference numeral 7 is a differential pressure signal extraction line, 8 is a reference signal line, and 9 is an input from the differential pressure signal extraction line 7 and a reference signal input line 8
A comparison circuit for comparing with the reference signal input from the above, and the difference compared here is input to the controller 6. 1
Reference numeral 0 denotes a flow rate signal line, which detects the signal from the controller 6 and inputs this to the flow rate calculation circuit 11 to calculate the flow rate.

In the case of the above embodiment, the pressure difference between the pressure input line 5a and the pressure output line 5b is detected by the pressure sensor 5, this differential pressure signal is taken out via the differential pressure signal output line 7, and this difference is detected. Input to the controller 6. Controller 6
Sends a signal to the drive device 4 of the valve 3 so that the difference from the reference pressure becomes constant, and the cross-sectional area of the flow path 1 by the valve 3 is adjusted. A signal input from the controller 6 to the driving device is simultaneously input to the flow rate calculation circuit 11, and the flow rate is calculated based on this signal.

FIG. 2 shows an embodiment in which the flow velocity is detected and the flow amount is measured, and corresponds to claim 2.

In this embodiment, the flow velocity sensor 12 is attached in front of the valve 3 in the orifice portion, and the flow velocity detected by the flow velocity sensor 12 is input to the comparison circuit 9 and compared with the reference flow velocity. Subsequent control examples and flow rate calculation examples are the same as in the case of using the pressure sensor. The flow velocity sensor 12a may be attached after the valve 3 instead of attaching the flow velocity sensor 12 before the valve 3.

FIG. 3 corresponds to claim 3 as an embodiment in which a bypass line for bypassing the valve is attached and the flow rate of the fluid flowing through this bypass line is detected to measure the flow rate.

In this embodiment, a bypass line 13 for bypassing the valve 3 is attached and the bypass line 13 is also installed.
A bypass velocimeter 14 is attached to, and a signal from the velocimeter 14 is input to the comparison circuit 9 to be compared with a reference flow velocity, and a control is performed so that a constant amount of fluid flows in the bypass line 13. The subsequent control example and flow rate calculation example are the same as those of the pressure sensor use example.

Although the valve 3 is plate-shaped in the above-mentioned embodiment, it may be a tube that is thermally contracted / expanded as long as the cross-sectional area of the flow path 1 can be changed.
The valve 3 can change the cross-sectional area of the flow path 1 and may be any valve as long as it can be automatically controlled.

The effects of the present invention are as follows. a. By making the pressure loss constant, the energy of the pressure loss can be utilized to the maximum even in the low flow rate region, so that highly sensitive flow rate measurement can be performed even in the low flow rate region. Therefore, it is effective not only for normal flow rate measurement but also for leak detection means. b. Since the pressure sensor and the flow velocity sensor are used to keep the differential pressure or the flow velocity constant, there is no need to perform linear calibration of the sensor performance or carelessly perform multipoint calibration. Therefore, it suffices that the accuracy is high only at specific pressure and flow velocity points, and the valve can be configured with high accuracy even if it is driven by using, for example, a step motor. c. Since the flow rate becomes 0 by closing the valve, the 0 point of the sensor can be automatically calibrated. d. Even if the pressure on the downstream side of the valve rises due to temperature change and the like, the valve is closed in cases other than the bypass system, so there is no concern about backflow.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention using a pressure sensor.

FIG. 2 is an explanatory diagram of an embodiment of the present invention using a flow velocity sensor.

FIG. 3 is an explanatory diagram of an embodiment of the present invention using a bypass.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 flow path 2 orifice 3 valve 4 drive device 5 pressure sensor 5a pressure input line 5b pressure output line 6 controller 7 differential pressure signal extraction line 8 reference signal input line 9 comparison circuit 10 control signal input line 11 flow rate calculation circuit 12, 12a flow velocity Sensor 13 Bypass line 14 Bypass flow velocity sensor

Claims (3)

[Claims] 1. A flow passage through which a gas flows, a valve whose cross-sectional area can be freely changed, and differential pressure detection means for detecting a differential pressure generated between upstream and downstream of the valve in the flow passage, A flow rate measuring device comprising a controller that controls the valve so as to keep the differential pressure constant, and a flow rate calculation circuit that calculates a flow rate based on a signal output from the controller. 2. A flow passage through which a gas flows, a valve whose cross-sectional area can be freely changed, a flow velocity detecting means for detecting a flow velocity between upstream and downstream of the valve in the flow passage, and a constant flow velocity. A flow rate measuring device comprising a controller that controls the valve so that the flow rate is calculated as follows, and a flow rate calculation circuit that calculates a flow rate based on a signal output from the controller. 3. A flow path through which a gas flows, a valve whose cross-sectional area can be freely changed, a bypass flow path which bypasses the valve in the flow path, and a flow velocity of the gas in the bypass flow path. A flow rate measuring device comprising a flow rate detecting means for detecting, a controller for controlling the valve so as to keep the flow rate constant, and a flow rate calculating circuit for calculating a flow rate based on a signal output from the controller.