JPH05231885A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To detect only a flow signal without being affected by sound pressure and vibration by subtracting the sound pressure signal of a sound pressure sensor and small differential pressure signal of a small differential pressure sensor. CONSTITUTION:On a fluidic flowmeter body, a small differential pressure sensor 14 and a sound pressure sensor 16 are provided. A differential amplifier 22 is provided to detect flowrate signal C by subtracting the small differential pressure signal A of the small differential pressure sensor 14 and the sound pressure signal B of the sound pressure sensor 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidic flow meter for measuring the flow rate of gas or liquid fluid.

[0002]

2. Description of the Related Art The structure of a main body into which a fluid of a fluidic flow meter flows is generally as follows (Japanese Patent Laid-Open No. 63-313018).

That is, an injection nozzle and a pipe expanding portion are formed in the pipe contracting portion in that order in the flow direction, and a pair of control nozzles are provided at the boundary between the injection nozzle and the pipe expanding portion. Toward a direction substantially perpendicular to the injection direction of the nozzle, and formed to face each other, to form a pair of return flow passages connecting each of the control nozzles and the downstream side of the conduit expansion portion, A target is provided in order to stabilize the switching of the flow direction in the enlarged pipe section.

A fine differential pressure sensor is provided on the upper surface of the main body in the vicinity of the injection nozzle in order to detect a pressure change due to the change in the flow direction of the jet flow from the injection nozzle.

The fine differential pressure signal A detected by the fine differential pressure sensor 100 is converted into a bandpass filter 102 and a Schmitt trigger element 104 as shown in the block diagram of FIG.
Through, the counter 106 is directly measured, and the number of measurements measured by the counter 106 is displayed on the display 108. That is, in the frequency of the slight differential pressure signal A proportional to the flow rate, the bandpass filter 102 and the Schmitt trigger element 104 remove the frequency component outside the measurement range, and then the counter 106 measures the frequency. It is converted into a flow rate and displayed on the display 108.

As a result, the flow rate of the fluid flowing into the main body of the fluidic flow meter can be digitally counted.

[0007]

In the conventional method of measuring the flow rate of the fluidic flow meter, the frequency component within the measurement range of the fine differential pressure signal A measured by the fine differential pressure sensor 100 is externally applied. However, there is a problem in that noise such as noise and vibration enters, and the noise directly passes through the bandpass filter 102 and the Schmitt trigger element 104 and is counted by the counter 106. In particular, there is a problem that the fine differential pressure sensor 100 reacts to a sound coming from outside the main body of the fluidic flow meter to increase noise.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present invention has been made in view of the above problems, even if external noise or vibration noise is included in the fine differential pressure signal of the fine differential pressure sensor attached to the body of the fluidic flow meter. It is intended to provide a fluidic flow meter that can measure only the flow rate of a required gas or liquid.

[0009]

A fluidic flowmeter of the present invention is provided with a fine differential pressure sensor and a sound pressure sensor in a main body of the fluidic flowmeter, and a fine differential pressure signal and a sound pressure sensor of the fine differential pressure sensor are provided. The subtracting means for detecting the flow rate signal by subtracting the sound pressure signal of the above is provided.

[0010]

[Operation] With the fluidic flow meter with the above configuration,
The noise due to the sound pressure and vibration on the slight differential pressure signal detected by the slight differential pressure sensor is subtracted by the sound pressure signal of the pressure sensor to remove these noise components, and only the necessary slight differential pressure signal is obtained. To detect.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a body 12 of a fluidic flowmeter 10 showing an embodiment of the present invention. The main body 12 includes a conduit reducing portion 2 on the fluid inlet side of the main body 12.
First, the injection nozzle 3 and the conduit enlarged portion 5 are formed in that order in the flow direction. A pair of control nozzles 6a and 6b are provided at the boundary between the injection nozzle 3 and the duct expanding portion 5 so as to extend substantially at right angles to the injection direction of the injection nozzle, and
A pair is formed facing each other. In addition, both control nozzles 6
A pair of return flow paths 7a and 7b are formed to connect the respective a and 6b to the downstream side of the expanded pipe section 5. Further, a target 8 is provided for stabilizing the flow direction switching in the expanded pipe section 5.

Reference numeral 14 is a slight differential pressure sensor mounted on the upper surface of the main body 12. The fine differential pressure sensor 14 is provided with a pair of detection tubes 14a and 14b so as to be located at the bases of the control nozzles 6a and 6b, and the fine differential pressure change caused by the change in the flow direction of the jet flow from the injection nozzle 3 That is, the pressure difference between the pair of detection tubes 14a and 14b is detected by the piezoelectric film inside the fine differential pressure sensor 14, and is converted into a fine differential pressure signal A which is an electric signal and output.

Reference numeral 16 denotes a sound pressure sensor such as a microphone, which is attached near the detection tube 14a of the slight differential pressure sensor 14. The sound pressure sensor 16 is a slight differential pressure sensor 1.
The sound and vibration near the detection tube 14a of No. 4 are detected.

Next, a block diagram of the electric system of this embodiment will be described with reference to FIG.

Reference numeral 18 is an amplifier for amplifying the fine differential pressure signal A output from the fine differential pressure sensor 14.

Reference numeral 20 is a correction amplifier for correcting and amplifying the sound pressure signal B output from the sound pressure sensor 16. When the flow rate flowing into the main body 12 is 0, the correction amplifier 20 has a function of previously canceling the characteristic curve for the external sound and vibration of the slight differential pressure sensor 14 on the sound pressure signal B side. When the pressure signal B and the small differential pressure signal A are subtracted as described later, the small differential pressure signal A of the small differential pressure sensor 14 is transmitted to the main body 12 without being affected by the sound and vibration when the flow rate is zero. It only responds to the flow rate flowing in.

Reference numeral 22 is a differential amplifier that takes the difference between the slight differential pressure signal A output from the amplifier 18 and the sound pressure signal B output from the correction amplifier 20. This differential amplifier 22
Subtracts noise due to sound pressure or vibration on the slight differential pressure signal A by the sound pressure signal B detected by the sound pressure sensor 16 and extracts only the frequency related to the original flow rate in the slight differential pressure signal A. And outputs a flow rate signal C.

In the above fluidic flow meter 10, the differential amplifier 22 subtracts the sound pressure signal B from the noises of the sound and vibrations on the slight differential pressure signal A,
Since the flow rate signal C having only the frequency detected only by the flow rate can be taken out, noise due to sound pressure or vibration is not counted unlike the conventional fluidic flowmeter.

The flow rate signal C output from the differential amplifier 22 is the bandpass filter 102 and the Schmitt trigger element 1 as in the conventional block diagram of FIG.
After 04, it is counted by the counter 106, and the flow rate without noise is displayed by the indicator 108.

FIG. 3 shows the average time (hereinafter referred to as the average time) required for the flow count to have an error of 1% or less using the fluidic flowmeter 10 of this embodiment and a conventional fluidic flowmeter. , Which is simply called the average time).

In the case of this experiment, the size of noise is 6
0 dB, frequency 10 Hz, 30 Hz, 100 Hz
The experiment was conducted with three types, and the average time of each was measured by this example and the conventional fluidic flowmeter.

According to this, in the conventional fluidic flowmeter, the average time is 3 when the frequency is 10 Hz.
It took 0.7 seconds for the fluidic flowmeter 10 of the present embodiment to decrease to 0.7 seconds, and for 30 Hz, the average time was 1 second, which was 0.25 seconds.
In the case of Hz, the average time was 0.2 seconds but 0.1
Seconds. Therefore, the average time is reduced to half or less, the flow rate with an error of 1% or less can always be counted in real time, and erroneous display is reduced.

The fluidic flow meter 10 of this embodiment is
As described above, the flowmeter is suitable mainly for industrial gas such as fuel gas and water, and for household use, but is not limited thereto.

The main body 1 of the fluidic flow meter 10
The structure of 2 is just an example,
It is not limited to this.

[0026]

As described above, according to the fluidic flowmeter of the present invention, the fine differential pressure signal of the fine differential pressure sensor is subtracted from the sound pressure signal of the sound pressure sensor to obtain a more accurate frequency proportional to the flow rate. Can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fluidic flow meter main body.

FIG. 2 is a block diagram of a fluidic flow meter of the present invention.

FIG. 3 is a comparison table comparing the average time in which the count number between the conventional fluidic flowmeter and the flowmeter of the present embodiment has an error of 1% or less.

FIG. 4 is a block diagram of a conventional fluidic flow meter.

[Explanation of symbols]

 10 ... Fluidic flowmeter 12 ... Main body 14 ... Fine differential pressure sensor 16 ... Sound pressure sensor 18 ... Amplifier 20 ... Correction amplifier 22 ... Differential amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahide Tsujishita 4-1-2, Hiranocho, Chuo-ku, Osaka City Osaka Gas Co., Ltd.

Claims (1)

[Claims] 1. A flow differential signal is detected by providing a fine differential pressure sensor and a sound pressure sensor in the body of a fluidic flow meter, and subtracting the fine differential pressure signal of the fine differential pressure sensor and the sound pressure signal of the sound pressure sensor. A fluidic flow meter characterized by being provided with subtraction means for