JP2006242804A - Concentration measuring method and device of gas or liquid in mixed gas or liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a higher time resolution than a conventional technology, and to simplify circuit adjustment for measuring a molecular concentration. <P>SOLUTION: An ultrasonic wave having a constant amplitude is propagated as long as a fixed distance in a gas flow 10 comprising a plurality of different gases by an ultrasonic transmitting element 16. The propagated and damped ultrasonic wave is received by an ultrasonic receiving element 18, and the amplitude of the received ultrasonic wave is measured. The concentration of one gas included in the gas flow 10 is determined from the measured amplitude of the ultrasonic wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for measuring the concentration of a gas or liquid in a mixed gas or liquid. The present invention relates to fields that require high-time resolution and high-precision measurement of molecular concentrations and changes in stationary bodies and fluids regardless of liquids and gases, such as chemical plants, engines, and pollution detection (for example, hydrogen It can be applied to gas leak detection).

  Conventionally, for example, as a method for measuring the molecular concentration of a gas and its change, the “dielectric relaxation method” for measuring the dielectric constant of a substance, or the substance by the difference in time passing through the column due to the chemical nature of the substance. There is a gas chromatograph to discriminate, or “absorption spectrum measurement” for measuring an electromagnetic wave absorption distribution.

Although these measurement methods can accurately measure the type and concentration of gas molecules, the apparatus is complicated and does not have the ability to detect high time resolution, high accuracy concentration and its change.
In addition, an ultrasonic wave is transmitted in response to an ultrasonic wave generation signal such that the voltage change has a voltage change equal to or higher than the slew rate of the operational amplifier used for measurement, and the ultrasonic wave is passed through the gas in the measurement target region. The ultrasonic wave after passing is converted into an electrical signal to generate an ultrasonic reception signal, the ultrasonic generation signal and the ultrasonic reception signal are amplified by the operational amplifier, and the transmission-side triangular wave and the reception obtained by the amplification are received. Each side triangular wave is compared with a predetermined threshold voltage to detect a time point that is equal to or higher than the predetermined threshold voltage, and the time difference between the time points that are equal to or higher than the predetermined threshold voltage, that is, passed ultrasonic waves One of the co-applicants of the present application has proposed a method of measuring the concentration (average molecular weight) of the gas by measuring the difference in arrival time (see Japanese Patent No. 3584290).
Japanese Patent No. 3584290

  The technique disclosed in Japanese Patent No. 3584290 has a time resolution of about 500 microseconds, but it has been difficult to achieve a higher time resolution. Further, since the measurement of a very short time difference is performed by an analog circuit, it is necessary to perform circuit adjustment. However, because of the analog circuit, it is difficult to easily handle this circuit adjustment.

  Therefore, an object of the present invention is to realize a time resolution higher than that of the prior art and simplify circuit adjustment for measuring the molecular concentration.

  The object of the present invention is a method for measuring the concentration of one predetermined gas or liquid in a mixed gas composed of a plurality of different gases or a mixed liquid composed of a plurality of different liquids, which exceeds a certain size. Sending sound waves into the gas mixture or liquid mixture; propagating the ultrasonic waves through the gas mixture or liquid mixture at a certain distance; and measuring the magnitude of the propagated ultrasonic waves; Determining the concentration of the one predetermined gas or liquid based on the measured magnitude of the ultrasonic wave.

According to one aspect of the present invention, it is preferable to measure a change in the concentration of the one predetermined gas or liquid by performing the series of steps intermittently or continuously.
According to another aspect of the present invention, the method of the present invention includes the step of delivering and measuring using the gas mixture or liquid mixture comprising the one predetermined gas or liquid in various known concentrations. To measure the magnitude of the propagated ultrasound and pre-calibrate the measured magnitude of the ultrasound to the concentration of the one predetermined gas or liquid. Is preferred.

According to still another aspect of the present invention, in the method of the present invention, the number of the different gases or liquids is preferably 2, and the gas mixture or liquid mixture is preferably a fluid.
The above-mentioned problem of the present invention is an apparatus for measuring the concentration of one predetermined gas in a mixed gas composed of a plurality of different gases or a mixed liquid composed of a plurality of different liquids, and having a certain size. Ultrasonic transmission means for transmitting ultrasonic waves into the mixed gas or mixed liquid; and ultrasonic reception means arranged at a certain distance from the ultrasonic transmission means, the ultrasonic transmission means Ultrasonic wave receiving means for receiving ultrasonic waves attenuated by propagating through the mixed gas or mixed liquid interposed between the ultrasonic wave receiving means and the size of the ultrasonic wave received by the ultrasonic wave receiving means And a concentration determining means for determining the concentration of the one predetermined gas or liquid based on the above.

  According to one curved surface of the present invention, the ultrasonic wave receiving means sends out ultrasonic waves intermittently or continuously, the ultrasonic wave receiving means receives ultrasonic waves sent intermittently or continuously, It is preferable that the concentration determining means further determines a change in the concentration of the one predetermined gas or liquid based on the magnitude of the ultrasonic wave received intermittently or continuously.

  According to another aspect of the present invention, the concentration determining means propagates the mixed gas or liquid containing the one predetermined gas or liquid at various known concentrations using the device. Calibration means for measuring the magnitude of the ultrasonic wave and calibrating the measured ultrasonic magnitude with respect to the concentration of the one predetermined gas or liquid is received in advance by the ultrasonic wave receiving means. Preferably, the magnitude of the ultrasound is determined using the calibration means to determine the concentration of the one predetermined gas or liquid.

  According to still another aspect of the present invention, in the apparatus of the present invention, the number of the different gases or liquids is preferably 2, and the mixed gas or mixed liquid is preferably a fluid.

  The apparatus and method of the present invention receives ultrasonic waves that have been attenuated by propagating through the gas mixture to be measured, and measures the magnitude of the received ultrasonic waves. For example, when an ultrasonic wave of 400 KHz is used, it is possible to obtain a very high time resolution of 5 microseconds.

  Further, since it is only necessary to measure the magnitude of the received ultrasonic wave, the circuit adjustment for measuring the molecular concentration is as simple as almost unnecessary.

  First, the principle of the present invention will be described with reference to FIG. FIG. 1 schematically shows a configuration when the present invention is applied to measuring the molecular concentration of a gas in a chamber. The gas stream 10 flows in the direction of arrow 14 in the chamber 12. An ultrasonic transmission element 16 is provided on one of the walls at both ends of the chamber 12 in a direction orthogonal to the flow direction of the gas flow 10 indicated by an arrow 12 and faces the ultrasonic transmission element 16 on the other wall. Thus, an ultrasonic receiving element 18 is provided. The distance between the ultrasonic transmission element 16 and the ultrasonic reception element 18 is kept constant. The ultrasonic wave transmitted from the ultrasonic transmission element 16 propagates or passes through the gas flow 10 in the direction indicated by the arrow 20 and is received by the ultrasonic reception element 18. The ultrasonic wave propagating in the gas flow 10 is attenuated due to the gas flow 10 as compared with the case of propagating in a vacuum having the same propagation distance as the propagation distance in the gas flow. Accordingly, when the gas flow 10 exists, the magnitude of the ultrasonic wave received by the ultrasonic wave receiving element 18 is less than the magnitude of the ultrasonic wave transmitted from the ultrasonic wave transmitting element 16 due to the attenuation caused by the gas flow 10. Only small. Generally, the amount of attenuation increases as the average molecular weight of the gas stream 10 (more generally including stationary gas) increases. That is, the magnitude of the ultrasonic wave received by the ultrasonic wave receiving element 18 decreases as the average molecular weight of the gas increases.

  Here, for example, assuming that the gas flow 10 is composed of air and nitrogen gas, and the molecular concentration (in average molecular weight) of nitrogen gas (excluding nitrogen contained in the air) is a measurement target, the ultrasonic reception element 18 receives the gas flow 10. The magnitude of the ultrasonic wave that is generated decreases as the molecular concentration of the nitrogen gas increases. This is because oxygen has a higher molecular weight than nitrogen and air is a mixture of gaseous oxygen and nitrogen, so that the average molecular weight of the gas stream 10 decreases as the molecular concentration of the nitrogen gas increases. Accordingly, the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18 is measured in advance using the gas flow 10 containing nitrogen gas having various known molecular concentrations, and the measured ultrasonic magnitude and the nitrogen gas are measured. If the relationship (or conversion) between the molecular concentration of the gas and the gas flow 10 including the molecular concentration of the unknown nitrogen gas is calibrated, the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18 is measured. Using the above calibration, the molecular concentration of the unknown nitrogen gas can be determined. The calibration may be in any form of a calibration curve, a calibration table, and a calibration (or conversion) formula.

Further, even if calibration is not performed in advance, a change in the molecular concentration of nitrogen gas can be obtained by measuring a temporal change in the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18.
Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 2 is a circuit diagram showing a schematic configuration of the ultrasonic wave generation circuit 30 according to a preferred embodiment of the present invention. The ultrasonic generation circuit 30 in FIG. 2 corresponds to the ultrasonic transmission element 16 in FIG. The ultrasonic generation circuit 30 includes an electric signal oscillation unit 32 and an ultrasonic oscillation unit 34. The electric signal oscillating unit 32 includes an oscillation / frequency dividing circuit 36 having an oscillation and frequency dividing function, a resistance group 38, and a switch group 40 that selects a resistance of the resistance group 38 and designates a frequency division ratio. The ultrasonic oscillator 34 includes an ultrasonic transducer 42 and a drive circuit 44 for applying a voltage to the ultrasonic transducer 42, and the drive circuit 44 includes a drive transistor 46.

  The oscillating / dividing circuit 36 oscillates at 12.8 MHz, and is configured to output an electrical signal having an oscillation frequency of 400 KHz or 800 KHz depending on the selection of the switches of the switch group 40.

  The driving transistor 46 is driven, that is, switched by an electric signal output from the electric signal oscillating unit 32, for example, an electric signal of 400 KHz, and a voltage corresponding to the switching state of the driving transistor 46 is applied to the ultrasonic transducer 42. The ultrasonic transducer 42 generates 400 KHz ultrasonic waves. The 400 KHz ultrasonic waves are sent out from the ultrasonic transducer 42 toward the gas flow 10 shown in FIG. In addition, when generating a 400 KHz ultrasonic wave, the ultrasonic vibrator 42 is used for 400 KHz, and when an 800 KHz ultrasonic wave is oscillated and transmitted, a 800 KHz wave is used. Therefore, when generating an ultrasonic wave of 800 KHz, an ultrasonic vibrator for 800 KHz is used, and by selecting a switch of the switch group 40, the electric signal oscillator 32 generates an electric signal having an oscillation frequency of 800 KHz. . In the present invention, it is not always necessary to configure the ultrasonic wave generation circuit 30 to generate ultrasonic waves having a plurality of oscillation frequencies as described above, and it may be configured to generate ultrasonic waves having one oscillation frequency. .

  The ultrasonic generation circuit 30, the electric signal oscillating unit 32, and the ultrasonic oscillating unit 34 are of ordinary circuit type in the technical field and are well known, and therefore will not be described in further detail. In the present invention, the ultrasonic wave generation circuit 30 is not limited to any circuit format, and may be any circuit format.

  FIG. 3 is a circuit diagram showing a schematic configuration of the ultrasonic reception and molecular concentration output circuit 50 according to a preferred embodiment of the present invention. The ultrasonic reception and molecular concentration output circuit 50 corresponds to the ultrasonic reception element 18 shown in FIG. The ultrasonic reception and molecular concentration output circuit 50 includes an ultrasonic reception unit 52, a high-pass filter 54, an amplification unit 56, a rectification unit 58, a peak / hole unit 60, and a determination unit 62. The ultrasonic receiving unit 52 includes an ultrasonic transducer 64 for receiving ultrasonic waves. FIG. 3 shows an ultrasonic wave reception and molecular concentration output circuit 50 that receives an ultrasonic wave of 400 KHz, and in this case, the ultrasonic transducer 64 is for 400 KHz. When the ultrasonic wave reception and molecular concentration output circuit 50 receives 800 KHz ultrasonic waves, the ultrasonic vibrator 64 for 800 KHz is used.

  FIG. 4 shows the state of signals transmitted from the ultrasonic wave generation circuit 30 in FIG. 2, that is, the transmission wave of the ultrasonic waves, and the signal in the main part of the ultrasonic wave reception and molecular concentration output circuit 50 in FIG. 4A and 4B show ultrasonic waves, the form converted into an electric signal, that is, the amplitude thereof is expressed as a voltage. From the ultrasonic transducer 42 of the ultrasonic oscillator 34 in the ultrasonic generation circuit 30, a sinusoidal ultrasonic wave 70 with very little noise component shown in FIG. 4A is transmitted. When the ultrasonic wave 70 propagates through the gas flow 10 shown in FIG. 1, a received wave 72 having a smaller magnitude than the ultrasonic wave 70 is attenuated by the gas flow 10, and the ultrasonic wave reception and molecular concentration output circuit 50. Is received by the ultrasonic transducer 64 of the ultrasonic receiver 52. Since the molecular weight of the gas flow 10 fluctuates with time, the fluctuation component is superimposed on the waveform of the received wave 72 as shown in FIG.

  The ultrasonic reception wave 72 received by the ultrasonic transducer 64 of the ultrasonic reception unit 52 is converted into an electric signal by the ultrasonic reception unit 52, the fluctuation component is removed by the high-pass filter 54, and then the amplification unit 56. It is amplified by. The amplified electric signal is half-wave rectified by the diode of the rectifying unit 58 to obtain a waveform as shown in FIG. This rectification may be full-wave rectification. The half-wave rectified electric signal is peak-held in the peak hole portion 60, and the waveform 76 as shown in FIG. 4D is output to the output of the peak hole portion 60 (ie, point A shown in FIG. 3). Is obtained. The peak voltage value of the waveform 76 represents the magnitude of the received ultrasound 72, specifically the magnitude of the amplitude of the ultrasound 72, and thus the concentration (or average molecular weight) of the gas to be measured in the gas stream 10. Will be expressed.

  3 determines when the peak voltage value of the waveform 76 exceeds a predetermined threshold voltage (corresponding to a predetermined threshold concentration of the measurement target gas included in the gas flow 10). Information that informs that the gas to be measured is present more than a predetermined threshold concentration is output on / off, and the determination unit 62 can be arbitrarily provided depending on the application.

  Further, the ultrasonic wave reception and molecular concentration output circuit 50, the ultrasonic wave reception unit 52, the high pass filter 54, the amplification unit 56, the rectification unit 58, and the peak hole unit 60 are of a circuit type that is normal in the technical field, As it is well known, no further details will be given. In the present invention, the ultrasonic reception and molecular concentration output circuit 50 is not limited to any circuit format, and may be any circuit format.

  FIG. 5 shows a gas supply system capable of switching gas at high speed while maintaining the same flow rate per time, and measuring the molecular concentration of the gas in the chamber according to the preferred embodiment of the present invention shown in FIGS. A configuration when used in an apparatus is shown. Reference numerals shown in FIG. 5 that are the same as those shown in FIGS. 1 to 3 indicate components indicated by the same reference numerals in those figures. The gas supply system 80 adjusts the switching solenoid valve appropriately to change the molecular concentration of nitrogen gas contained in the gas flow 10 from 0% (ie, only air) to 100% (ie, nitrogen) while maintaining the same flow rate. (Only gas) can be changed arbitrarily.

  Using the gas supply system shown in FIG. 5, an experiment was conducted to confirm the gas separation performance of the apparatus shown in FIGS. 1 to 4 in which the present invention was applied to the measurement of the gas molecular concentration. In this experiment, the distance between the ultrasonic transmission element 16 (or transmission-side ultrasonic transducer 42) and the ultrasonic reception element 18 (or reception-side ultrasonic transducer 64) is 3 mm, and air (molecular weight 28.8) The concentration of nitrogen (molecular weight 28) and its change were detected. Specifically, the switching solenoid valve of the gas supply system 80 has only air (100% air), that is, a gas flow 10 of 0% nitrogen, and then the switching solenoid valve is switched to change the gas flow 10 to nitrogen only. (Nitrogen 100%), only nitrogen was allowed to flow for 400 milliseconds, and the switching solenoid valve was switched again to return to air only (air 100%), that is, the gas flow 10 with 0% nitrogen.

  FIG. 6 shows the results of the above experiment. A signal output curve 100 shown in FIG. 6 is an output signal at point A of the peak hole portion 60 of the ultrasonic wave reception and molecular concentration output circuit 50 shown in FIG. In FIG. 6, a bar denoted by reference numeral 102 indicates a period during which the switching solenoid valve of the gas supply system 80 is switched to nitrogen, S in the bar 102 indicates a point in time when the solenoid valve switches to nitrogen, and E indicates a solenoid valve. Represents the point of time when switching to air. The signal output curve shown in FIG. 6 shows fluctuations due to fluctuations of gas molecules. As a result of measuring the S / N ratio, a high S / N ratio was obtained as compared with the apparatus disclosed in Patent Document 1 which is about 80 dB and 42 dB. It can be seen from FIG. 6 that an output with a high S / N ratio is obtained. The gas supply system 80 has a structure capable of switching the gas at high speed. However, since there is a distance from the gas supply system 80 to a point where the gas flow 10 crosses the ultrasonic wave, the gas switching time by the electromagnetic valve and the gas switching system 80 There is a delay of about 100 ms between the change of the ultrasonic wave reception level due to the change. Accordingly, the rising of the curve 100 is slightly delayed, that is, the rising is delayed by about 100 ms from the time S when the solenoid valve is switched to nitrogen, and further, the chamber 12 is filled with nitrogen from the graph of FIG. (See reference numeral 104) can also be confirmed. A flat region 106 is seen when only nitrogen is present in the chamber 12, and it can be seen that the chamber 12 is stable in a state filled with nitrogen. In addition, it is possible to confirm in real time the change in molecular concentration in real time when switching to air again (see reference numeral 108). In addition, it can be seen that the voltage value of the output signal is smaller for air (molecular weight 28.8) than for nitrogen (molecular weight 28), and for gases having a higher average molecular weight, the amount of attenuation passing through them is larger than for gases having a smaller average molecular weight.

  In this way, changes in the molecular concentration of nitrogen or air in the gas stream 10 consisting of a mixture of nitrogen and air can be measured. In addition, if the above output signal is measured in advance with a gas flow 10 having various molecular concentrations of nitrogen (or air) and the output signal characteristics are calibrated with the corresponding known molecular concentrations, absolute The concentration can be measured. In the present invention, the calibration may be any method as long as the molecular concentration can be converted from the output signal, such as a glass, a table, and a conversion formula. The apparatus of the present invention may include a microprocessor, for example, and such a calibration means may be incorporated into the microprocessor.

  Further, for example, after the gas flow 10 is introduced into the chamber 12, the molecular concentration of the desired component gas of the stationary mixed gas can be measured by measuring the stationary state by closing the entrance and exit of the chamber 12. . In the present invention, the production of the gas mixture in a stationary state does not depend on any method and means, and may be in any manner.

  FIG. 7 shows the change in the case where the output signal of the sensor of the present invention, that is, the device of the present invention shown in FIGS. It is a figure which shows doing. In FIG. 7, reference numeral 120 indicates that the ultrasonic vibrators 42 and 64 are for 200 KHz, the electric signal oscillating unit 32 oscillates a 200 KHz electric signal, and the 200 KHz ultrasonic wave is transmitted from the ultrasonic oscillating unit 34. 3 shows the change of the output signal (output of point A of the peak hole portion 60 of the ultrasonic wave reception and molecular concentration output circuit 50 in FIG. 3) when fired, and reference numeral 122 is the ultrasonic vibrators 42 and 64. An output signal when the 400 kHz signal is emitted from the ultrasonic wave oscillating unit 34 after the 400 kHz signal is oscillated by the electric signal oscillating unit 32 (the ultrasonic wave reception and molecular concentration output in FIG. 3) is used. A change in the output of the point A of the peak hole portion 60 of the circuit 50 is shown. In addition, in order to make it easy to understand the change in the output signal due to the difference in the frequency of the emitted ultrasonic wave, that is, the difference in sensitivity, FIG. 7 shows the relative output voltage in the case of 200 KHz and 400 KHz, that is, the oxygen concentration of 10%. Sometimes relative voltage differences are shown to match the same voltage. FIG. 7 shows that the output signal changes linearly with respect to the mixing ratio. This means that the detection sensitivity of the average molecular weight of the gas increases as the frequency of the ultrasonic wave that irradiates the gas to be measured, here, the gas flow 10, that is, propagates through the gas stream 10, increases.

  In the apparatus disclosed in Patent Document 1, an analog circuit that measures a very short time difference is necessary. However, in the present invention, the magnitude of the received ultrasonic wave, in the above embodiment, the amplitude of the ultrasonic wave is detected. Therefore, chewing is easy, stable measurement can be performed, and the signal processing system can be simplified. Since this simple signal processing system and the above-described high S / N ratio can be obtained, it is possible to measure the molecular concentration with high accuracy, and therefore, the technique has high versatility.

  With respect to the accuracy of the time resolution, by using the peak / hole unit 60 shown in FIG. 3 or a sample and hold element or the like, 1 / (400 k when a frequency of 400 KHz is used, for example, a frequency of 400 KHz. / 2) = Time resolution up to 5 microseconds can be obtained in principle, and remarkably high time resolution can be obtained as compared with the order of 500 microseconds of the device disclosed in Patent Document 1. As a result, the molecular concentration can be measured at high speed.

  The distance between the transmission unit (ultrasonic transmission element 16) and the reception unit (ultrasonic reception element 18) is several millimeters (3 mm in the above embodiment), and the width of the measurement target gas mixture through which the ultrasonic wave passes is very large. Even if it is small, the molecular concentration can be measured.

  In the above embodiment, the amplitude of the ultrasonic wave propagating through the gas mixture to be measured and attenuated therein is measured, but the present invention represents the magnitude of the ultrasonic wave, for example, the power of the ultrasonic wave Any of these parameters may be measured.

  A preferred embodiment of the present invention has been described above by taking a gas as an example of a measurement object. However, the present invention is not limited to a gas, and a mixed liquid composed of a plurality of different liquids in the same configuration. Regardless of the fluid state or the stationary state, the measurement object can be used. In summary, for a mixed liquid composed of a plurality of different liquids, an ultrasonic wave of a certain magnitude is propagated through the mixed liquid and attenuated, and the magnitude (for example, amplitude) of the attenuated ultrasonic wave or its The change may be measured to measure the concentration of one predetermined liquid in the mixed liquid or the change thereof.

  The present invention provides a mixture ratio of a plurality of remaining gases or liquids with respect to one gas or liquid whose concentration is to be measured, even if there are three or more gas or liquid components contained in the mixed gas or liquid mixture to be measured. If the physical conditions are the same, it is possible to measure the concentration or change of the one gas or liquid.

FIG. 1 is a diagram schematically showing a configuration when the present invention is applied to measuring the molecular concentration of a gas in a chamber. FIG. 2 is a circuit diagram showing a schematic configuration of the ultrasonic wave generation circuit 30 according to a preferred embodiment of the present invention. FIG. 3 is a circuit diagram showing a schematic configuration of the ultrasonic reception and molecular concentration output circuit 50 according to a preferred embodiment of the present invention. FIG. 4 is a diagram showing the state of signals transmitted from the ultrasonic wave generation circuit 30 in FIG. 2, that is, the transmission wave of the ultrasonic waves, and signals in the main part of the ultrasonic wave reception and molecular concentration output circuit 50 in FIG. . FIG. 5 shows a gas supply system capable of switching gas at high speed while maintaining the same flow rate per time, and measuring the molecular concentration of the gas in the chamber according to the preferred embodiment of the present invention shown in FIGS. It is a figure which shows the structure at the time of using for the apparatus to do. FIG. 6 is a diagram showing the results of an experiment for confirming the gas separation performance of the apparatus shown in FIGS. 1 to 4 in which the present invention is applied to the measurement of the molecular concentration of gas using the gas supply system shown in FIG. is there. FIG. 7 is a diagram showing that the output signal of the apparatus of the present invention shown in FIGS. 1 to 3 changes when the frequency of the ultrasonic wave is changed with respect to a mixed gas in which the mixing ratio of oxygen and nitrogen is changed. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas flow 12 Chamber 16 Ultrasonic transmitting element 18 Ultrasonic receiving element 30 Ultrasonic generating circuit 32 Electric signal oscillating part 34 Ultrasonic oscillating part 36 Oscillation / frequency dividing circuit 40 Switch group 42 Ultrasonic vibrator 44 Driving circuit 46 Driving transistor DESCRIPTION OF SYMBOLS 50 Ultrasonic reception and molecular concentration output circuit 52 Ultrasonic reception part 54 High pass filter 56 Amplification part 58 Rectification part 60 Peak hole part 62 Determination part 80 Gas supply system 80

Claims (10)

A method for measuring the concentration of one predetermined gas or liquid in a mixed gas composed of a plurality of different gases or a mixed liquid composed of a plurality of different liquids, comprising:
Delivering ultrasonic waves of a certain magnitude into the gas mixture or liquid mixture;
Propagating the ultrasonic wave through the gas mixture or liquid for a certain distance, and measuring the magnitude of the propagated ultrasonic wave;
Determining the concentration of the one predetermined gas or liquid based on the measured magnitude of the ultrasonic wave.   The method according to claim 1, wherein a series of the steps are performed intermittently or continuously to measure a change in the concentration of the one predetermined gas or liquid.   Using the mixed gas or liquid containing the one predetermined gas or liquid in various known concentrations, the transmitting step and the measuring step are executed to measure the magnitude of the transmitted ultrasonic wave The method according to claim 1, further comprising the step of pre-calibrating the measured ultrasonic magnitude with respect to the concentration of the one predetermined gas or liquid.   The method according to claim 1, wherein the number of the different gases or liquids is two.   The method according to any one of claims 1 to 4, wherein the mixed gas or liquid is a fluid. An apparatus for measuring the concentration of one liquid in a predetermined gas in a mixed gas composed of a plurality of different gases or a mixed liquid composed of a plurality of different liquids,
Ultrasonic transmission means for transmitting ultrasonic waves of a certain size into the mixed gas or mixed liquid;
Ultrasonic wave receiving means disposed at a certain distance from the ultrasonic wave sending means, wherein the mixed gas or mixed liquid interposed between the ultrasonic wave sending means and the ultrasonic wave receiving means Ultrasonic receiving means for receiving ultrasonic waves that have been propagated and attenuated; and
An apparatus comprising: concentration determining means for determining the concentration of the one predetermined gas or liquid based on the magnitude of the ultrasonic wave received by the ultrasonic wave receiving means. The ultrasonic receiving means sends out ultrasonic waves intermittently or continuously,
The ultrasonic receiving means receives ultrasonic waves transmitted intermittently or continuously;
7. The apparatus according to claim 6, wherein the concentration determining means further determines a change in the concentration of the one predetermined gas or liquid based on the magnitude of the ultrasonic wave received intermittently or continuously. The concentration determining means includes
For the mixed gas or liquid mixture containing the one predetermined gas or liquid in various known concentrations, the device is used to measure the magnitude of the transmitted ultrasonic wave, and the measured ultrasonic wave Pre-calibrating means for calibrating the size of said one against the concentration of said one predetermined gas or liquid;
The apparatus according to claim 6 or 7, wherein the ultrasonic wave received by the ultrasonic wave receiving means is used to determine the concentration of the one predetermined gas or liquid using the calibration means.   The apparatus according to any one of claims 6 to 8, wherein the number of the different gases or liquids is two.   The apparatus according to claim 6, wherein the mixed gas or liquid is a fluid.

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