JPS63250527A - Fine flow rate measuring method - Google Patents

Abstract

PURPOSE:To measure a fine flow rate with high accuracy by injecting an air bubble into fluid to be measured and generating a pulse by a photoelectric conversion system when the air bubble passes the start point and end point of a flow passage. CONSTITUTION:Air bubbles that the liquid L to be measured with flows in one direction contains indeterminately are removed by an air bubble escape valve 2 and an air pulse for one pulse is injected into the flow passage by an air bubble generator A. When the air bubble passes the start point S as the fluid L to be measured flows, the air bubble passes between an LED 7 and a phototransistor 8 to generate variation in the output of the phototransistor 8 owing to the difference in refractive index between the air and liquid, the difference in light transmissivity, or light irregular reflection at a vapor/liquid- phase part. Similarly, when the air bubble passes the end point E, the output of a phototransistor 10 varies. The flow rate is measured from a relational expression based upon the sectional area of the flow passage and the time difference between the point of time when the output of the phototransistor 8 varies and the point of time when the output of the phototransistor 10 varies.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method capable of measuring minute flow rates (including flow velocity) of liquids with high precision, regardless of viscosity, specific gravity, etc.

<Prior Art> As a method for measuring minute flow rates of liquid, a flow meter type, a droplet counting type, and the like are known.

Problems to be Solved> With one type of flow meter, the minimum measurable flow rate is about 0.05 to 0.1 m41/min, and the measurement range is about one digit with one type of flow meter. It is narrow and prone to reading errors, and furthermore, errors are likely to occur due to changes in the viscosity, specific gravity, etc. of the liquid.

In the droplet counting method, the upper limit of the measurable range is low (because the output is a digital signal, a long sampling time is required for precision measurement in the ultra-fine flow rate range,
Errors occur due to liquid viscosity, specific gravity, etc., and are easily affected by vibration.

Furthermore, the method of sampling the liquid for an arbitrary period of time is inferior in terms of accuracy and labor, and can only obtain data on average values over a long period of time.

Technical Means for Solving the Problems> An object of the present invention is to provide a method that eliminates the problems in the above-mentioned methods and can measure minute flow rates with high precision.

The method for measuring a minute flow rate according to the present invention includes providing a photo sensor at each of the starting point and the ending point of a flow path having a constant cross-sectional area, and mixing air bubbles into the liquid to be measured immediately before the liquid to be measured passes through the starting point. This method is characterized by generating pulses when the bubble passes through the starting point and ending point, and measuring the flow rate based on these pulses.

<Example> The present invention will be explained below with reference to the drawings.

In FIG. 1, l is a flow path having a constant cross-sectional area Φ.

S is a starting point and E is an ending point, and a light emitting diode (LED) 7<9> and a phototransistor 8<10> are provided at each position with a flow path in between.

A is a bubble generator provided in front of the starting point S, and is composed of a solenoid 6, a bellows 5 (or cylinder), a check valve 3.4, and the like. 2 is an air release valve provided in front of the bubble generator. 11 and 12 are L located behind the starting point
It is an ED and a phototransistor, and when a bubble passes, it generates a signal, activates the solenoid 6, and mixes the bubble into the liquid to be measured.

In the above, L is the liquid to be measured that flows in one direction, and the air bubbles contained in this liquid are removed by the bubble relief valve 2.
The bubble generator A mixes one pulse of bubbles into the flow path. When the bubble passes through the starting point S as the liquid to be measured flows, the bubble crosses the LED 7 and the phototransistor 8, and the difference in refractive index between gas and liquid, the difference in light transmittance,
Alternatively, the output of the phototransistor 8 changes due to diffuse reflection of light in the gas/liquid phase portion. Similarly, when the bubble passes through the end point E, a change occurs in the output of the phototransistor IO. Therefore, the flow rate can be measured from the time difference between the time when the output of the phototransistor 8 and the time when the output of the phototransistor 10 changes and the cross-sectional area of the flow path.

That is, if the time difference is Δt, the flow path cross-sectional area is S, and the distance between the starting point and the ending point is l, the flow rate Q can be calculated as Δ t .

In this case, in terms of the electronic circuit, measurement must be started or ended only with a positive or negative pulse in the differential output at the time of output level transition of each phototransistor, and measurement must be started with a pulse from the phototransistor 8 at the starting point. After that, no matter what signal is generated, as long as it does not affect the measurement circuit unless a stop pulse is applied by the phototransistor 10, it is possible to measure either the liquid/vapor phase portion or the gas/liquid phase portion of the bubble. However, measurement is possible even in cases where the phototransistor outputs in the gas phase and liquid phase are reversed (for example, in the case of a transparent liquid, the output of the liquid phase is higher due to the water lens effect, and vice versa in the case of a transparent liquid).

In the above, the flow path cross-sectional area S is usually 0.10" to 100"
It is preferable that the length of the bubble is 1 iris to 1
It is preferable to set it to 00 m■.

FIG. 2 shows a measuring device for carrying out the present invention, and FIG.
The diagram shows signals at predetermined locations in FIG.

In Figure 2, ■ is the negative pulse generator at the starting point, ■ is the negative pulse generator at the end point, and ■ is the negative pulse generator for operating the solenoid of the bubble generator, and the polarity changes when the level of the phototransistor changes. It consists of a comparator that inverts, a differentiation circuit that takes out only the negative pulse when the polarity is inverted, and a diode, and the output is as shown in Figure 3. These three pulses regulate the timing of flow measurement and repeated injection of bubbles. ■ and ■ are flip-flops, which do not receive the previous sensor signal until the next sensor signal arrives after the output is reversed, and ensure error-free measurement interval passage time and appropriate bubble generation even when bubbles occur in succession. , ■ is an amplifier, which adjusts the appropriate gain defined by the offset of the flip-flop ■, the integrating circuit constant ■, and the desired measurement range, and enters the integrating circuit ■. The capacitor of the integrating circuit (2) is discharged by the analog switch (2) at the timing shown in FIG. 3 in preparation for the next measurement cycle.

The analog switch ■ becomes conductive immediately after the integration (timekeeping) is completed,
Input the integral value into sample hold [phase] and hold this input value until the next new integral value is input. When the hold value is given to the next stage division term intermediate unit ■, it is inversely proportional to time,
Information proportional to the bubble velocity (liquid velocity), that is, proportional to the flow rate, can be obtained, and analog output can be obtained by performing arbitrary scaling using a DC amplifier @.

This can be made into a flow meter by means of a suitable ammeter or A/D converter and segment display. Analog output can be output to a recorder, input to a microcomputer via an A/D converter, etc., and is also effective for automatic control of fluid systems.

In FIG. 2, ``■'' and ``■'' are delayed pulse generators, which generate pulses indicated by ◎ and ``■'' in FIG. 3, respectively, to operate the analog switch ``■''. In FIG. 2, ``■'' is a solenoid driving transistor, which generates a pulse shown by ``■'' in FIG. 3, operates the solenoid of the bubble generator described above, and injects bubbles into the flow path.

<Effects of the Invention> The minute flow rate measurement method according to the present invention is as described above, and when air bubbles are injected into the fluid to be measured and the air bubbles collide with the starting point and end point of the flow path, photoelectric conversion occurs. A pulse is generated using this method, and the time difference between these pulses is reciprocally converted by an electronic circuit to obtain an analog output proportional to the flow rate. The flow rate can be measured with high accuracy because the bubbles flow together with the fluid to be measured and because the electric signal processing is highly accurate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a minute flow rate measurement method according to the present invention,
FIG. 2 is an explanatory diagram showing a minute flow rate measuring device used in the present invention, and FIG. 3 is an explanatory diagram showing signal waveforms at predetermined locations in FIG. In the figure, 1 is a flow path, S is a starting point, E is an end point, 7 and 9 are light emitting diodes, 8.10 is a phototransistor, and A is a bubble generator. γII! J ■ [Yes] @■■■■■■00 Procedural master's letter (spontaneous) 1988 5 J, 1290 1. Indication of the case 1985 Patent Application No. 085999 2. Name of the invention Micro flow rate measurement method 3. Relationship with the case of the person making the amendment Patent Applicant Address: 1-1-2-6, Shimohozumi, Ibaraki City, Osaka Prefecture Contents of amendment +11 As shown in the attached sheet, Figure 3 has been amended first.

Claims (1)

[Claims] A photo sensor is provided at each of the starting point and the ending point of a flow path with a constant cross-sectional area, and just before the liquid to be measured passes through the starting point, air bubbles are injected into the liquid to be measured, the air bubbles are mixed, and the air bubbles reach the starting point. and generate a pulse when passing the end point,
A minute flow rate measurement method characterized by measuring flow rate using these pulses.