JPH06341949A - Concentration measuring device for gas dissolved in liquid - Google Patents

Abstract

PURPOSE:To provide a device which can measure the concentration of gas dissolved in liquid which flows through a flow passage instantaneously and continuously at any point of time. CONSTITUTION:A concentration measuring device 10 consists of an optical system and a control system. The optical system has a flow passage means 20, a plate-like cell 30, a light emitter 40, and a light receiver 50. The control system is a processing circuit. Liquid to be measured is in contact with the plate-like cell 30 in a bath 23. The light emitter 40 modulates infrared light radiated from a heater 41 and makes it enter the cell 30. Infrared light is reflected after it enters the liquid to be measured by 1/10 of wavelength of infrared light in the process in which it is reflected fully at a boundary between the cell 30 and liquid to be measured. In this process, infrared light having a specific wavelength is absorbed by gas dissolved in the liquid and radiated from the other end of the cell 30. The light receiver 50 divides infrared light radiated from the cell 30 into two by a prism mirror 51 and detects infrared light by light receiving elements 52, 53 via an optical band pass filter 54 and an optical wide region filter 55. The control system computes the concentration of dissolved gas based on the detected signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a device for measuring the concentration of gas dissolved in a liquid. More specifically, the present invention continuously measures the concentration of carbon dioxide dissolved in a liquid such as beer or carbonated drink, or continuously measures the concentration of various gases dissolved in a liquid chemical product. Apparatus for measuring manually.

[0002]

2. Description of the Related Art Conventionally, the concentration of gas dissolved in a liquid is
(1) Put the liquid to be measured in a closed container, (2) leave the liquid in the container for a certain period of time, (3) after that, measure the pressure in the container and the temperature of the liquid, and measure these. The results were converted into dissolved gas concentrations and measured.

[0003]

However, the conventional method has the following drawbacks. (1) The liquid must be left for a certain period of time. Therefore,
It takes time to measure. (2) Dissolved gas concentration cannot be measured continuously.
For example, in the manufacturing process of beer and carbonated drinks, the liquid is constantly flowing, so it is necessary to be able to grasp the concentration of dissolved gas at any time. If it is found from the measurement result that the product is defective, the product manufactured during the measurement becomes a defective product, and the product must be collected or discarded retroactively when the measurement is started.

An object of the present invention is to provide an apparatus capable of instantaneously and continuously measuring the dissolved gas concentration of a liquid flowing in a flow channel at any time.

[0005]

Means for Solving the Problems The present invention comprises means for forming a liquid flow path, a plate-shaped cell that traverses the flow path means and has both ends exposed to the outside of the flow path means, and one end of the cell. In a liquid comprising a light emitter for making infrared rays incident, a light receiver for detecting infrared rays emitted from the other end of the cell, and a processing circuit for calculating a gas concentration based on the infrared rays detected by the light receiver. The above-mentioned problems were solved by a dissolved gas concentration measuring device.

[0006]

The liquid continuously flows through the flow path means, and a new liquid constantly contacts the cell. The infrared rays emitted from the light emitter enter the cell. The incident infrared ray is emitted from the cell in a state where only a specific wavelength is particularly attenuated in the process of repeating reflection in the vicinity of the boundary between the cell and the liquid in the flow path means. The infrared light emitted from the cell is detected by the light receiver. The infrared light detected by the light receiver is converted into an electric signal, and the electric signal is converted into a dissolved gas concentration by the processing circuit.

[0007]

EXAMPLE A dissolved gas concentration measuring apparatus 10 according to the present invention
Is composed of the optical system shown in FIGS. 1 to 5 and the control system shown in FIG. The optical system includes the flow path means 20 and the plate-shaped cell 3
0, a light emitter 40 and a light receiver 50. The control system is a processing circuit, and the measurement circuit mounted on the measurement circuit board and the M
It consists of an MPU circuit mounted on a PU circuit board.

The flow path means 20 of this embodiment is a cylindrical tank 23 having a liquid inlet 21 and a liquid outlet 22. The liquid to be measured flows in through the inflow port 21, contacts the surface of the plate-shaped cell 30, and flows out through the outflow port 22. The flow passage means 20 may be a liquid transport pipe in a beer or carbonated beverages manufacturing apparatus, but it is preferable that the flow passage means 20 is a tank independent of the transport pipe and has a structure attachable to and detachable from the transport pipe.

The plate-shaped cell 30 extends through the tank 23 and both ends thereof are exposed to the outside of the tank 23. Cell 30 is shown in FIG.
Through FIG. 4 in more detail. Cell 30 has a length of 30
It is a plate having a size of 300 mm, a width of 10 to 30 mm, and a thickness of 2 to 5 mm. As a material of the cell 30, a single crystal or quasi-single crystal of germanium, gallium arsenide and silicon can be used. The cell further has the following configuration. (1) The surface of the cell 30 is entirely mirror-polished except for the end face in the width direction. (2) An angle of 30 to 60 ° is formed on the longitudinal end surface of the cell 30 so that infrared rays can easily enter. In the case of this embodiment, the angle is 45 °. (3) The widthwise end surface of the cell 30 is chamfered.

The cell 30 and the tank 23 have the following relationship. (1) Packings 24 and 25 are mounted between the cell 30 and the tank 23. (2) The contact portion between the cell 30 and the packings 24 and 25 is aluminum-coated so that infrared rays do not enter the packing side. (3) The sealing property between the cell 30 and the tank 23 is improved by chamfering the end face in the width direction.

Returning to FIG. 1, the light emitter 40 is provided at one end of the cell 30 and makes infrared rays enter the cell 30. The light emitter 40 includes a heater 41 that emits infrared light, a mirror 42 that focuses the infrared light on one end of the cell 30, and a chopper 43 that modulates the infrared light. Mirror 4
Instead of 2, a plate having slits may be provided between the heater 41 and one end of the cell 30.

The heater 41 has a diameter of 5 mm or less and a length of 10 to
30mm nichrome wire or tungsten wire built-in metal can cylinder heater, when heated to 600-1000 ℃, 1-12μm
It emits broadband infrared light having a wavelength of. Heater 4
In No. 1, ceramic coating or metallikon processing is applied to increase the luminous efficiency of infrared rays. Heater 4
The infrared rays radiated from 1 and the infrared rays reflected by the mirror 42 enter the cell 30.

As shown in FIG. 1 and FIG. 5, the chopper 43 is a metallic opening disk made of matte black paint and is fixed to the rotating shaft of the motor 44. The chopper 43 modulates wide band infrared rays to 10 to 60 Hz immediately before the infrared rays enter the cell 39.

The heater 41, the mirror 42 and the chopper 43 are provided on a movable table (not shown), which is inclined at 45 to 70 ° with respect to the center line of the cell 30 in the longitudinal direction. ing. Thereby, the incident angle of infrared rays can be changed.

The light receiver 50 has a prism mirror 51 for splitting the infrared rays emitted from the cell 30 into two and two light receiving elements 52 and 53. Prism mirror 51
Is 90 ° edge, size is 5 ~ 30mm. Between the prism mirror 51 and the one light receiving element 52, an optical bandpass filter 54 that transmits only infrared rays of a specific wavelength is transmitted.
Is provided. An optical broadband filter 55 is provided between the prism mirror 51 and the other light receiving element 53. Pyroelectric elements are used as the light receiving elements 52 and 53, but other than that, thermopile, PbSe
Elements can also be used.

Prism mirror 51, light receiving elements 52, 5
3, the optical bandpass filter 54 and the optical broadband filter 55 are provided on a movable table (not shown), and the movable table is 45 to 70 with respect to the center line of the cell 30 in the longitudinal direction.
It is designed to incline to °.

The concentration measuring device 10 further has a processing circuit. This processing circuit calculates the concentration of the dissolved gas based on the infrared rays detected by the light receiver 50.

The operation of the apparatus will be described below assuming that beer is the liquid to be measured and the carbon dioxide dissolved in the beer is to be measured, and then the arithmetic processing means in the processing circuit will be described.

First, the light emitter 4 is arranged so that the angles .theta.1 and .theta.2 between the optical axis and the longitudinal centerline of the tank 23 are 45 to 70.degree.
0 and the movable base of the light receiver 50 are adjusted.

Beer is pressurized to 0 to 4 kg / square centimeter (gauge pressure) and flows into the tank 23 through the inflow port 21. Cell 30 is constantly in contact with fresh beer.
The broadband infrared light modulated to 10 to 60 Hz by the chopper 43 enters from one end of the cell 30. The infrared rays incident on the cell 30 repeat total reflection at the boundary between the cell 30 and the beer, but in the process of total reflection, they enter the beer side by about 1/10 of the infrared wavelength and then are reflected. In the process of entering, infrared rays of 4 to 4.5 μm are particularly well absorbed and attenuated by carbon dioxide and radiated from the other end of the cell 30. Cell 3
The infrared ray radiated from 0 is split into two by the prism mirror 51.

One of the two divided infrared rays has a wavelength of 4-4.5 μm.
After passing through the optical bandpass filter 54 that allows only infrared rays in a certain wavelength range to pass within the range of, and only the infrared rays of 4 to 4.5 μm that have been particularly attenuated by carbon dioxide in beer, the light receiving element 52 electrically Converted to a signal.

The other infrared ray passes through an optical broadband filter 55 which transmits infrared rays over the entire range of 1 to 12 μm, and then is converted into an electric signal by a light receiving element 53. The electric signal obtained by converting the infrared rays that have passed through the optical broadband filter 55 hardly changes depending on the concentration of carbon dioxide in the beer, and the infrared output fluctuation of the heater 41 and the infrared rays emitted from other than the heater 41 (hereinafter, " It is used for noise cancellation due to light because it is changed only by stray light.

FIG. 6 shows a signal processing method of the measuring circuit incorporated in the measuring circuit board. The functions are as follows. (1) The infrared rays that have passed through the 4- to 4.5-μm optical bandpass filter 54 are converted into electric signals by the light receiving element 52 and then amplified by the specific optical head amplifier. (2) After that, a specific optical bandpass filter (BPS) adjusted to the infrared modulation frequency is used to reduce noise having frequencies other than the vicinity of the modulation frequency, and the noise is taken out from the photointerrupter with a chopper by way of the sync pulse generation circuit. Noise is further reduced by synchronizing and detecting with a signal having the same frequency as the modulated frequency of the infrared rays. (3) The noise-reduced signal is converted into a DC signal by the synchronization / detection / semi-integration circuit, then converted into a digital signal by the AD converter and sent to the MPU circuit. (4) The infrared rays that have passed through the optical broadband filter 55 are also converted into digital signals by the same method and sent to the MPU circuit.

The function of the MPU circuit is as follows. (1) In the MPU circuit, the voltage value of the DC signal obtained by converting the infrared rays that have passed through the optical bandpass filter 54 is divided by the voltage value of the DC signal obtained by converting the infrared rays that have passed through the optical broadband filter 55, and the infrared output of the heater 41 is output. Eliminates noise due to fluctuations and stray light. The calculated division value is stored in the MPU circuit. (2) First, the division value when the tank 23 is filled with water and measured is stored, and then the division value when the beer is filled in the tank 23 and measured is stored. (3) The converted value of carbon dioxide concentration obtained by multiplying the divided value of water by a coefficient is set to zero, and the divided value of beer is converted to the carbon dioxide concentration value and output to the LED. (4) It is also possible to prepare two sets of optical systems, continuously fill water in one tank for measurement, and continuously fill beer in the other tank for measurement, and perform the same treatment. .

After the measurement is started as described above, 60
Within seconds, it is possible to monitor the concentration change of dissolved carbon dioxide with an accuracy of ± 1% with respect to the full scale and continuously.

[0026]

According to the dissolved gas concentration measuring apparatus of the present invention, a plate-shaped cell is constantly contacted with a new liquid, and the attenuation factor of infrared rays of a specific wavelength in the contacting liquid is measured at any moment. Since the measurement can be performed continuously, the following effects are achieved. (1) It is possible to continuously and automatically perform the work of manually measuring the dissolved gas concentration, which was conventionally performed manually. (2) The time required to measure the dissolved gas concentration can be significantly reduced. (3) By continuously measuring the dissolved gas concentration at any given moment and continuously monitoring the dissolved gas concentration in the liquid, it is possible to instantly detect the occurrence of defective products and improve the product yield rate. it can.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a dissolved gas concentration measuring device according to the present invention.

FIG. 2 is a plan view of a plate cell.

FIG. 3 is a front view of a plate cell.

FIG. 4 is a sectional view taken along line 4-4 of FIG.

FIG. 5 is a plan view of a chopper.

FIG. 6 is a block diagram of a measurement circuit board.

[Explanation of symbols]

 10 Concentration measuring device 20 Flow path means 23 Tank 30 Plate cell 40 Light emitter 41 Heater 42 Mirror 43 Chopper 44 Motor 50 Light receiver 51 Prism mirror 52, 53 Light receiving element 54 Optical bandpass filter 55 Optical broadband filter

Claims (2)

[Claims] 1. A means for forming a liquid flow path, a plate-shaped cell that traverses the flow path means and has both ends exposed to the outside of the flow path means, and a light-emitter that allows infrared rays to enter from one end of the cell. An apparatus for measuring the concentration of dissolved gas in a liquid, comprising: a photodetector that detects infrared rays emitted from the other end of the cell; and a processing circuit that calculates a gas concentration based on the infrared rays detected by the photodetector. 2. The concentration measuring device for dissolved gas in liquid according to claim 1, wherein the liquid is beer or a carbonated beverage and the gas is carbon dioxide.