CN102928383A - Device for measuring gas concentration through optical interference method - Google Patents

Abstract

The invention provides a device for measuring gas concentration through an optical interference method. The device comprises an optical source, a cleft-tip-shaped gas chamber, a photoelectric sensor, a display device and a prompt device which are all arranged in a closed casing. The optical source comprises an optical source generator and a parallel optical beam expander which is arranged on an outgoing optical path of the optical source generator. The cleft-tip-shaped gas chamber is arranged in front of the parallel optical beam expander, and the photoelectric sensor is arranged at the gathering position of reflected light of the cleft-tip-shaped gas chamber and connected with the display device and the prompt device through signal lines. By means of the device, different interference fringes are generated due to optical path difference caused by different refractive indexes of an optical wave in gases with different concentration. The concentration of the gas is determined through the detection of the interference fringes. The device for measuring the gas concentration through the optical interference method has the advantages of being high in accuracy, wide in measurement range, easy to correct, simple, firm and durable.

Description

Apparatus for Measuring Gas Concentration by Optical Interferometry

Technical field :

The invention belongs to optical measurement technology, in particular to an optical gas measurement instrument.

Background technique:

Light waves can produce isoclinic interference fringes in different ways, which are mainly used in the measurement of tiny length and refractive index. The measurement of gas concentration has a wide range of demands in industrial production and laboratories, especially for the measurement of harmful gases. For example, my country's coal mine production safety detection system needs to detect toxic gases in coal mines. Most of the products so far are also designed for large-scale coal mines, and there are still some problems to be solved, such as: high equipment cost, large system volume, high operation and maintenance costs, poor sensor measurement stability, frequent adjustments, use The service life is short, the measurement accuracy of the equipment is limited, and it must be maintained by professionals.

Invention content:

In view of the above shortcomings, the applicant designed a device for measuring the concentration of gas (such as gas) by using the wedge-tip interference principle to overcome the problems of complex equipment, unstable measurement and inconvenient use in the prior art.

Technical scheme of the present invention is as follows:

A device for measuring gas concentration by optical interferometry, including a light source, a wedge-shaped gas chamber, a photoelectric sensor, a display device, and a prompting device, all of which are installed in an airtight casing to prevent the influence of external light. Unwanted directions entering the photoelectric sensor affect the measurement results.

The light source includes a point light source generator and a parallel beam expander, the parallel beam expander is arranged on the outgoing light path of the point light source generator, a wedge-shaped gas chamber is arranged in front of the parallel beam expander, and A photoelectric sensor is arranged at the converging place of the reflected light in the shaped gas chamber, and the photoelectric sensor is connected to the display and the prompting device through a signal line.

The wedge-shaped gas chamber is a triangular cavity formed by obliquely placed parallel glass plates and a plane mirror, and the cavity is used to contain the gas to be measured.

The invention uses the optical path difference caused by the different refractive index of light waves in different concentrations of gases to cause different interference fringes, and realizes the measurement of gas concentration by detecting the interference fringes. Its advantages are high accuracy, wide measurement range, and equipment Simple, rugged, and easy to calibrate. Equipped with gas concentration digital display system and multi-level prompt device, the operation is intuitive and quick.

Description of drawings

Fig. 1 is the functional block diagram of this device;

Figure 2 is a schematic diagram of the structure of the device.

Detailed ways:

The device is described in detail below in conjunction with the accompanying drawings:

The entire device is shown in Figures 1 and 2. The device includes a light source, a wedge-shaped gas chamber 2, a photoelectric sensor 3, a display device 4 and a prompting device 6, and each basic unit is integrally fixed in a housing 9. The casing is airtight to prevent the influence of external light. the

The light source includes a point light source generator 1 and a parallel light beam expander 6 , and the parallel light beam expander 6 is arranged on the outgoing light path of the point light source generator 1 .

The wedge-shaped gas chamber 2 is arranged in front of the parallel beam expander 6, which is actually a cavity supported between an inclined parallel glass plate 7 and a plane mirror 8. This cavity is used to hold the gas to be measured, and can be directly connected with The environment to be tested is connected, and the gas to be tested can also be filled and then closed.

The photoelectric sensor 3 is arranged at the converging place of the reflected light in the wedge-shaped gas chamber, and is used for sensing interference fringes, and converting continuously changing analog signals into stable digital signals.

The photoelectric sensor 3 is connected to the display 4 and the prompting device 5 through a signal line. The display 4 relies on the existing database, uses a certain algorithm to calculate the concentration of the gas to be measured, and sends it to the LED screen for display. The prompting device 5 includes two parts: a colored lamp reminder and a sound reminder, and is mostly used for monitoring the concentration of toxic gases in a special environment. When the gas to be tested is at the normal threshold, the green light is on, when the gas concentration exceeds the set first-level reminder threshold, the yellow light is on and a sound reminder is given, and when the gas concentration exceeds the set second-level reminder threshold, the red light is on and a sound reminder is given .

The principle of this device: the light source emits a parallel light beam with a certain angle. After the parallel light passes through the wedge-shaped gas chamber 2, interference fringes appear due to the optical path difference, and then reaches the photoelectric sensor 3 . The photoelectric sensor 3 senses interference fringes and converts the signal into a stable digital signal. The LED display 4 collects digital signals, calculates the concentration of the gas to be measured after relying on the data analysis of the existing database, and sends it to the LED screen for display. If there is a specific need, the reminding device 5 can be opened to automatically give corresponding prompts when the gas concentration reaches different concentrations.

How to use: If you use this device to measure the concentration of a specific gas in a specific environment, (for example, you need to detect the gas concentration in a coal mine), you only need to place the device in the air of the coal mine, open the wedge-shaped gas chamber of the device, and let it and The external air is connected, and after the gas diffuses stably in the gas chamber, the light source is turned on, and the parallel light beam shoots to the wedge-shaped gas chamber 2 at a certain angle, and both reflection and refraction occur at the parallel glass plate 7, and the reflected light Directly shoot to the photoelectric sensor 3. The refracted light must first pass through the gas to be measured, and then be reflected by the plane mirror 8 and then enter the photoelectric sensor 3. When passing through the gas to be measured, due to the different concentrations of the gas, it will be reflected by the plane mirror 8 and finally be reflected by the parallel glass. The light beam refracted by the plate 7 entering the sensor and the light directly entering the sensor through reflection have different optical path differences, forming interference fringes. The photoelectric sensor 3 reads and records these stripes and their changes, and then converts the stripe changes into a stable digital signal and sends it to the multi-level prompting device 5. The multi-level prompting device 5 compares the signal with the preset prompting threshold, to determine the mode and status of the prompt.

Claims (2)

1. A device for measuring gas concentration by light interferometry, characterized in that it comprises a light source, a wedge-shaped gas chamber (2), a photoelectric sensor (3), a display (4) and a prompting device (5), all of which are equipped with In an airtight casing (9); the light source includes a point source generator (1) and a parallel beam expander (6), and the parallel beam expander (6) is arranged at the point source generator (1) On the outgoing light path, a wedge-shaped gas chamber (2) is arranged in front of the parallel beam expander (6), and a photoelectric sensor (3) is arranged at the point where the reflected light of the wedge-shaped gas chamber converges. The photoelectric sensor (3) passes through the signal line Connect the display (4) and prompting device (5). 2. The device for measuring gas concentration by optical interferometry according to claim 1, characterized in that: the wedge-shaped gas chamber (2) is composed of an obliquely placed parallel glass plate (7) and a horizontally placed plane mirror ( 8) A triangular cavity is formed, which is used to hold the gas to be measured.

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