JP2014071109A - Ultrasonic gas concentration meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small oxygen content meter intended to be installed in an apparatus, which improves responsiveness to gas concentration change and reduces a failure risk of a control electronic circuit.SOLUTION: An ultrasonic gas concentration meter 5 uses one ultrasonic vibrator 4 performing two operations of transmission and reception to measure a time required for an outgoing ultrasonic sound to be reflected from a reflection plate 6 provided with a certain distance, and includes an ultrasonic vibrator of 100 kHz or greater so that residual vibration of the vibrator is decreased before the time when an ultrasonic sound reflection wave arrives. The ultrasonic gas concentration meter further performs measurement by programming of a microcomputer so that reception waveform processing is not executed until residual vibration caused by ultrasonic emission stops and so that only a reflection wave is determined to measure propagation time, thus obtaining an accurate propagation time. The reception waveform is amplified 1,000 times or more with an amplifier, is all-wave rectified, and is thereafter used as a trigger signal for acquiring propagation time. Thus, an electronic circuit configuration is achieved which can perform measurement with reduced measurement error.

Description

  The present invention is a device or device used in the medical field, and various ultrasonic gas concentrations (mixing ratios), especially oxygen concentrations, are propagated by ultrasonic waves in various gas mixtures flowing or staying in a storage system. It is a device that calculates using time.

  Traditionally, medical devices used from newborns to the elderly, especially those with poor breathing and patients with pulmonary disease, are air infused with high-concentration oxygen, that is, a mixture of nitrogen and oxygen. Supplied for use.

  Conventionally, there are oximeters for the purpose of calculating the mixture ratio (gas concentration) of the mixed gas from the propagation time of the ultrasonic wave, but two ultrasonic transducers dedicated to transmission and reception, both facing each other, Alternatively, the gas concentration is calculated by knowing the speed of sound by repeating transmission and reception with two ultrasonic transducers that alternately transmit and receive.

  In addition, since two ultrasonic transducers for transmitting and receiving are required, a dedicated circuit for transmitting and receiving is necessary, and the electronic circuit becomes complicated.

  In a medical device in which high-concentration oxygen-added air, that is, a mixed gas of nitrogen and oxygen is supplied for inhalation of a patient, it is desirable that the oxygen concentration of the mixed gas can be measured and managed with a simple measuring device.

  In a gas concentration meter that uses ultrasonic waves, when measuring the speed of sound accurately, in order to accurately know the displacement of the propagation time, the transmitting transducer and the receiving transducer are placed facing each other, and the propagation time due to the gas flow It is necessary to provide a mechanism that reduces the influence of the above, and this is an obstacle to the size because it is incorporated into a medical device or apparatus. Miniaturization is an issue in order to obtain an oxygen concentration meter for the purpose of incorporating the device.

  Further, in the above-described method, there is a problem that a change in gas concentration cannot be measured with good response because the gas flow in the propagation path cannot be increased.

  Furthermore, in order to perform measurement with good responsiveness, in order to avoid the influence of the propagation time due to the gas flow, a method of making two ultrasonic transducers face each other, alternately switching transmission and reception, and reciprocating the ultrasonic propagation path There is. However, in this method, the number of parts is increased and the control electronic circuit becomes complicated, and the failure risk of the complicated electronic circuit becomes a problem in order to be incorporated in a medical device or apparatus.

  In order to reduce the size, the ultrasonic gas concentration meter of the present invention uses a single ultrasonic vibrator that performs two functions of transmission and reception, and transmits a transmitted ultrasonic wave from a reflector provided at a certain distance. It is a method of measuring the time until it bounces.

  By using an ultrasonic vibrator of 100 kHz or higher so that the reverberation vibration of the vibrator is reduced in the time until the above-described ultrasonic reflected wave arrives, the vibrator can be downsized and the apparatus itself can be downsized.

  Until the reverberation vibration due to the transmission is settled, the processing of the received waveform is not performed, and only the reflected wave is judged, and the measurement by the programming of the microcomputer is performed so that the propagation time can be measured to obtain the accurate propagation time.

  The reception waveform is increased 1000 times or more by an amplifier, the waveform is subjected to full-wave rectification, and then used as a trigger signal for obtaining the propagation time, whereby an electronic circuit configuration capable of measurement with a small measurement error is obtained.

  In the present invention, only one ultrasonic transducer of 100 kHz or more is used, the propagation distance is increased by reflecting and reciprocating the ultrasonic signal, and the speed of sound, the gas concentration, the oxygen is transmitted with one ultrasonic element that is also used for transmission and reception. It is an ultrasonic gas concentration meter having a structure for calculating the concentration and measuring the speed of sound with high accuracy while being small.

一方、気体の分子量Ｍは音速Ｃと次の関係がある。

ここで、比熱比γ＝１．４、気体定数Ｒ＝８３１４、Ｔは絶対温度である。したがって、音速Ｃを求めることにより分子量Ｍが決まり、酸素濃度α_Ａが定められることを原理とした装置である。Regarding the relationship between gas concentration and sound velocity, if the gas mixture is two kinds of gas mixture of oxygen and nitrogen, the molecular weight M of the gas is the molecular weight M _{A of} oxygen, the molecular weight M _{B of} nitrogen, the oxygen concentration α _A and the nitrogen concentration α _B. Is represented by the following formula.

On the other hand, the molecular weight M of the gas has the following relationship with the speed of sound C.

Here, the specific heat ratio γ = 1.4, the gas constant R = 8314, and T is an absolute temperature. Therefore, the apparatus is based on the principle that the molecular weight M is determined by determining the sound velocity C, and the oxygen concentration α _A is determined.

It is desirable that the oxygen concentration of the mixed gas can be managed with a simple measuring device. If the sound speed of the gas is known, the molecular weight of the gas can be known, so the gas mixing ratio of the mixed gas, that is, the oxygen concentration can be calculated. The ultrasonic type gas concentration meter of the present invention is an oxygen concentration meter for the purpose of calculating the mixing ratio (gas concentration) of a mixed gas by knowing the sound speed of the fluid by measuring the propagation time of the ultrasonic wave. It is about.
The present invention is an ultrasonic gas concentration meter having the above-described configuration.

  The present invention can be reduced in size and can be easily incorporated into medical devices and apparatuses.

  In the present invention, by making a part of a medical device or apparatus that is an assembly partner a reflective surface, measurement that eliminates the influence of the flow of the mixed gas is possible.

It is an example of use of the present invention. 1 is an overall view of the present invention. It is an ultrasonic wave propagation of the present invention. This is a conventional ultrasonic wave propagation.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example in which the product of the present invention is attached to a medical device or apparatus. (1) makes the gas inlet and outlet separate independently. In (2), the gas inlet and outlet are shared, and the number is one.
FIG. 2 is an explanatory diagram of a configuration diagram of the product of the present invention.
FIG. 3 shows that the propagation distance of the ultrasonic signal of the product of the present invention is about twice that of the measurement unit in a reciprocating manner. This shows that the size can be reduced to a half of the propagation distance.
FIG. 4 is a diagram when two ultrasonic transducers are used for transmission and reception in the conventional ultrasonic method. Since the propagation distance of the ultrasonic signal is one direction, the propagation distance is almost the same as that of the measurement unit. Indicates that it is difficult to downsize.

  Conventionally, ultrasonic gas concentration and oximeters of the type incorporated in medical equipment and devices have used two ultrasonic transducers dedicated for transmission and reception. In order to measure the speed of sound by reflecting an ultrasonic signal, the present invention uses a single transducer for both transmission and reception, and simplifies the control circuit, so that the ultrasonic gas concentration meter is small and has few failures. As a result, it can be incorporated into small medical devices and devices.

1 Mixing gas flow path to be assembled 2 Tank 3 Measurement gas (gas) inlet 4 Ultrasonic transducer (transmission / reception)
5 Ultrasonic gas concentration meter of invention 6 Ultrasonic signal reflection surface 7 Measurement gas outlet 8 Connection cable 9 Ultrasonic transducer (transmission side)
10 Ultrasonic transducer (receiving side)

Claims (5)

  An apparatus for measuring gas concentration and oxygen concentration using one ultrasonic transducer, wherein the propagation speed is doubled by reflecting and reciprocating ultrasonic waves, and the sound speed is accurately known.   An apparatus for measuring a gas concentration and an oxygen concentration, characterized by transmitting and receiving an ultrasonic transducer to know the speed of sound.   An apparatus for measuring gas concentration and oxygen concentration, wherein the device is not affected by the flow of the mixed gas by reciprocating the propagation path.   An apparatus for measuring gas concentration and oxygen concentration, characterized in that the temperature is known by arranging a thermistor in the mixed gas.   An apparatus for measuring gas concentration and oxygen concentration, characterized in that it is not affected by the flow of mixed gas by reciprocating ultrasonic waves.

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