JPS6343692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for measuring soap membrane passage time, which is an important measurement factor when measuring the flow rate of a gas to be measured, in a soap membrane flowmeter.

<Prior art> A soap film flow meter uses a measuring gas introduced into a volume tube to push up a soap film, and this soap film is used to detect start detectors and stop detectors placed at regular intervals on the volume tube. The time T passing between
This is based on the principle that the flow rate S (=V/T) of the measurement gas is measured from this time T and the volume V of the volume tube between both detectors (this is referred to as the volume value).

Here, the start detector and the stop detector generally have an optical configuration in which a light emitter and a light receiver are provided facing each other with a volume tube in between. Therefore, the time T for the soap film to pass between the two detectors is determined based on the time point at which the upper surface of the soap film passes, which is the time point at which both detectors detect the soap film. However, it has been found that when the time T is determined based on the point in time when the upper surface of the soap film passes the detector, a non-negligible error may occur in the flow rate measurement. According to the inventor's findings, this is because the thickness of the soap film detected by the start detector changes when detected by the stop detector due to changes in the tube diameter due to the moisture level of the inner wall of the volumetric tube. This is due to the fact that it is changing.

<Purpose of the Invention> In view of the above, the present invention provides a method for changing the thickness of a soap film between when it is detected by a start detector and when it is detected by a stop detector. The present invention provides a useful method for making flow measurements without introducing errors.

<Configuration and Effects of the Invention> In order to achieve the above object, the present invention provides a start detector and a stop detector at regular intervals on a volume tube, and detects the soap that is pushed up by the measuring gas introduced into the volume tube. In a soap film type flowmeter, the flow rate of the measurement gas is measured from the time it takes for the soap film to pass between both detectors and the volume value between both detectors. The gist is that the time taken to pass between both detectors is determined based on the time point at which the lower surface of the soap film is detected by both detectors.

The lower surface of the soap film is the contact interface with the measuring gas. Therefore, if the time is measured based on the point at which the bottom surface of the soap film passes both detectors as in the present invention, the time is equal to the time for the measured gas to increase by an amount equal to the volume value, and the change in film thickness is unaffected. Therefore, it is possible to accurately measure the flow rate from this time and volume value.

To measure the time it takes for the bottom surface of the soap film to pass between two detectors, there are two methods: detect the top surface and film thickness of the soap film and measure indirectly from these values, or directly measure the bottom surface of the soap film. This method can be implemented by any method of detecting the passing time of the passing time.

Example 1 Figure 1 shows an example of a method for indirectly measuring the time T for the lower surface of a soap film to pass through both detectors, in which 1 is a volume tube, and the lower part is a bellows 2 for generating a soap film. are arranged in series, a measurement gas inlet section 3 is provided at the side, and a gas outlet section 4 is provided at the upper end. 5 is a start detector, and 6 is a stop detector. Both detectors 5 and 6 have a configuration in which a light emitter and a light receiver are placed facing each other. 7 and 8 are preamplifiers that shape and amplify the detection signals of detectors 5 and 6;
9 is a signal reading section, 10 is a microprocessor, 1
1 is a clock pulse oscillator, 12 is a memory section, 13
is the display.

Soap film detection signals A from detectors 5 and 6,
B is shaped by preamplifiers 7 and 8 as shown in FIG. 2, read by a signal reading section 9, and sent to a microprocessor 10. In the microprocessor,
By matching these detection signals A and B with the clock pulse CP from the oscillator 11, we measure the passage time t ₁ on the upper surface of the soap film as in the conventional method, and also measure the film thicknesses t ₂ and t ₃ at the positions of each detector 5 and 6. are measured and temporarily stored in the storage unit 12. Next, call up the time signals t ₁ to _{t 3} stored in the storage unit 12,
The microprocessor 10 performs arithmetic processing based on the following equation, and the resulting passage time T of the lower surface of the soap film is displayed on the display 13.

T=t ₁ −t ₂ +t ₃ Example 2 FIG. 3 shows a method for directly measuring the passage time T of the lower surface of the soap film, in which 14 is a differential circuit, 15 is a clipper, and 16 is a counter.

The soap film signals A and B detected by the detectors 5 and 6 are waveform-shaped by the preamplifiers 7 and 8, and then
The signal is applied to the differentiating circuit 14 and differentiated as shown in FIG. 4C. Of these differential signals A ₁ , A ₂ , B ₁ , B ₂ , only the negative signals A ₂ and B ₂ pass through the clipper 15,
It is added to the counter 16 (Fig. D). counter 1
6 is the count start signal for the first differential signal _A2 ,
The second differential signal _B2 is used as a count stop signal, during which the clock pulse from the oscillator 11 is
Count CP (Figure H). Therefore, counter 1
The count number 6 is equal to the time T required for the lower surface of the soap film to pass through the stop detector 6 after passing through the start detector 5 . counter 16
The count number is displayed on the display 13.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for implementing a method of indirectly measuring passage through the lower surface of a soap film as an embodiment of the present invention, FIG. 2 is a waveform diagram explaining the operation of the circuit in FIG. 1, and FIG. FIG. 4 is a block diagram for implementing a method of directly measuring the passage time T of the lower surface of a soap film as another embodiment of the present invention, and FIG. 4 is a waveform diagram illustrating the operation of the circuit of FIG. 3. 1...Volume tube, 5...Start detector, 6
...stop detector.

Claims (1)

[Claims] 1. A start detector and a stop detector are installed at regular intervals on the volume tube, and both detectors detect the soap film pushed up by the measurement gas introduced into the volume tube. In a soap film type flowmeter that measures the flow rate of the measured gas from the time it takes to pass and the volume value between both detectors, the time it takes for the soap film to pass between the detectors is determined by the time it takes for the soap film to pass between the detectors. A method for measuring soap film passage time in a soap film type flowmeter, characterized in that the determination is based on the time point detected by a detector.