Optical fiber dissolved oxygen probe capable of eliminating cross influence of temperature and pressure and application of optical fiber dissolved oxygen probe

Abstract

The invention discloses an optical fiber dissolved oxygen probe capable of eliminating cross influence of temperature and pressure and application of the optical fiber dissolved oxygen probe. Comprising a cylinder, an optical fiber bundle, a matrix and an oxygen sensitive film, two completely independent spaces are arranged in the cylinder body, and the two spaces are divided into a detection channel and a reference channel; the optical fiber bundle is composed of seven optical fibers, and the central optical fiber is an input optical fiber connected with the laser machine and used for emitting a light source; six surrounding optical fibers are output optical fibers which are connected with a photoelectric detector and are used for receiving fluorescent light emitted by the oxygen sensitive film through excitation; the invention has the technical effects and advantages that compared with the prior art, the scheme adopts a completely passive structure for design, the size of the probe can be reduced, and as a temperature sensor or cooling equipment needs to be integrated with the probe in the prior art, the size of the probe is inevitably increased, and the cost is reduced. The dissolved oxygen cannot be detected in some narrow spaces; and a passive structural design is adopted, so that faults such as electromagnetic interference and burning of components due to water leakage can be prevented.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber dissolved oxygen probes, and more specifically to an optical fiber dissolved oxygen probe capable of eliminating the cross-effect of temperature and pressure and its application. Background Art

[0002] A large number of metal equipment, such as ship locks, sluice gates and other metal equipment, need to be installed in the shipping and transportation field. These equipment need to monitor the oxidation corrosion of the equipment in real time during long-term operation. The corrosion of metal equipment is closely related to the content of dissolved oxygen. Dissolved oxygen refers to the amount of oxygen dissolved in water, usually recorded as DO, expressed in milligrams of oxygen per liter of water. The amount of dissolved oxygen in water is an indicator of the self-purification ability of water bodies. It is closely related to the partial pressure of oxygen in the air, atmospheric pressure, water temperature and water quality. There are two common sensors for detecting dissolved oxygen in water: ion selective electrode sensors using electrochemical methods and optical sensors using fluorescence quenching methods. Fluorescence quenching sensors have rapid detection and a lifespan of several years, but they are expensive and easily affected by temperature changes, resulting in unsatisfactory measurement results.

[0003] (1) Prior art 1: Patent CN 213041740 U discloses an optical fiber sensing device for measuring dissolved oxygen in variable temperature water. The device includes a dissolved oxygen regulating module and a dissolved oxygen measuring module, wherein the dissolved oxygen regulating module includes a main control component, a heating component, a cooling component and a stirring component; the dissolved oxygen measuring module includes an optical fiber, a sensitive membrane, a light emitting diode, a photomultiplier and a lock-in amplifier; the heating component and the cooling component in the dissolved oxygen regulating module perform temperature control on the main control component, and the dissolved oxygen measuring module forms a closed loop to output measurement data for dissolved oxygen concentration calculation.

[0004] Disadvantages of the prior art 1

[0005] This technology adopts the installation of temperature measurement and control circuit, which will increase the size of the fiber optic dissolved oxygen sensor probe and have disadvantages such as poor environmental adaptability. If the sealing of the probe device is damaged, the circuit will fail and the error caused by temperature on the measurement result cannot be eliminated, resulting in low sensor measurement accuracy.

[0006] (2) Prior art 2: Patent CN 108458997 A discloses a dissolved oxygen optical fiber sensor, which includes an optical fiber probe and a light source integrated in a handheld housing, a light source driving module, a photoelectric conversion module, a signal conditioning module, a temperature compensation module, a data calculation module and a display module. A temperature sensor is integrated inside the protective head, and the temperature sensor is connected to the temperature compensation module through a metal wire. The calculation result is corrected according to the output of the temperature compensation module to obtain an accurate dissolved oxygen concentration value.

[0007] Disadvantages of the second prior art

[0008] The device requires a temperature sensor to be installed at the front end of the probe. If the temperature sensor is short-circuited or fails in the water, the real-time temperature value cannot be obtained, and compensation cannot be performed to obtain an accurate dissolved oxygen concentration value.

[0009] (3) Prior art 3: The document "Study on Characteristics of Fiber Optic Temperature and Dissolved Oxygen Sensors" discloses a dissolved oxygen fiber optic sensor, which includes a fiber optic dissolved oxygen probe and a fiber grating temperature sensor. The calculation result is corrected according to the temperature measurement result to obtain an accurate dissolved oxygen concentration value.

[0010] Disadvantages of the prior art 3

[0011] The device needs to install a temperature sensor at the front end of the probe, and the fiber optic Bragg temperature sensor requires additional demodulation equipment, which increases the cost of the device. In addition, the measured temperature needs to be combined with the characteristic curve to reversely infer the dissolved oxygen concentration, and the calculation is also relatively complicated.

[0012] In view of the above problems, the present invention proposes a fiber optic sensing device for measuring dissolved oxygen in water to eliminate the cross-effects of temperature and pressure. Temperature will affect the reduction of fluorescence intensity, so the present invention proposes a relative monitoring method to solve the problem that the existing fiber optic dissolved oxygen sensor has low accuracy when measuring dissolved oxygen content at different water temperatures and pressures. Summary of the invention

[0013] In order to overcome the above-mentioned defects of the prior art, the present invention provides a fiber optic dissolved oxygen probe which eliminates the cross-effect of temperature and pressure.

[0014] The technical solution of the present invention is as follows:

[0015] On one hand, the present invention provides an optical fiber dissolved oxygen probe that eliminates the cross-effects of temperature and pressure, comprising a barrel, an optical fiber bundle, a matrix, and an oxygen sensitive membrane;

[0016] There are two completely independent spaces inside the cylinder, and the two spaces are divided into a detection channel and a reference channel;

[0017] The optical fiber bundle is composed of 7 optical fibers, the central one is an input optical fiber connected to a laser machine for emitting a light source; the surrounding 6 are output optical fibers connected to a photoelectric detector for receiving the fluorescence emitted by the oxygen sensitive membrane when excited;

[0018] The optical fiber bundle is divided into a detection optical fiber bundle and a reference optical fiber bundle. One end of the detection optical fiber bundle is located in the detection channel and close to the inner wall of the corresponding oxygen sensitive membrane; one end of the reference optical fiber bundle is located in the reference channel and close to the inner wall of the corresponding oxygen sensitive membrane.

[0019] The substrate is arranged at the front end of the cylinder, and is a round transparent glass sheet. The oxygen sensitive film is coated on one surface of the substrate to realize the detection of dissolved oxygen.

[0020] For the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces outward, which is used to contact the liquid to be tested, and can detect the dissolved oxygen concentration in the liquid environment in real time; the substrate is a circular glass sheet with good light transmittance and thermal conductivity; for the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces inward, and is not in contact with the liquid to be tested, nor is it in contact with oxygen.

[0021] The inner surface of the cylinder is coated with a black coating to reduce the influence of stray light on the measurement results; the outer surface of the cylinder has a corrosion-resistant coating that can withstand the corrosion of acid and alkali substances in the liquid environment, effectively ensuring the normal operation of the probe.

[0022] When the substrate and the cylinder, and the optical fiber and the cylinder are coupled, a sealing rubber ring is used for sealing, which can withstand external pressure and the entry of liquid to damage the performance of the sensor.

[0023] In order to ensure that the light intensity values ​​received by the reference channel and the detection channel are consistent, the input optical fibers of the reference channel and the detection channel are connected to the same laser, which can solve the problem of mismatch in input light intensity.

[0024] On the other hand, the present invention provides an optical fiber dissolved oxygen probe that eliminates the cross-effects of temperature and pressure, and is used for oxygen concentration detection. The specific method is: when the external temperature changes, the temperature environment of the oxygen sensitive membranes of the reference channel and the detection channel is consistent, and the change of fluorescence intensity caused by temperature is also consistent; when the temperature is defined as T and the oxygen concentration is defined as Y, the fluorescence intensity value obtained by the reference channel is A, and the fluorescence intensity value obtained by the detection channel is B; since the oxygen content in the reference channel is 0, when the light intensity value of the reference channel changes at different temperatures, it is a change caused by the influence of temperature, so the light intensity value of the detection channel is subjected to difference processing with the light intensity value of the reference channel, and the accurate oxygen concentration content can be obtained, that is, oxygen concentration = BA.

[0025] Technical effects and advantages of the present invention:

[0026] Compared with the prior art, this solution adopts a fully passive structure for design, which can reduce the volume of the probe, because the prior art needs to integrate the temperature sensor or cooling device with the probe, which will inevitably increase the volume of the probe, and it is impossible to detect dissolved oxygen in some small spaces;

[0027] The passive structure design can prevent electromagnetic interference, water leakage and burning of components, and other faults, making the probe more intrinsically safe.

[0028] The dual-channel detection design eliminates the cross-effects of temperature and pressure;

[0029] Compared with the existing dissolved oxygen calculation algorithm, the data processing of the present invention is relatively simple. By performing difference processing on the output light intensity of the reference channel and the detection channel, the concentration value of dissolved oxygen after eliminating the influence of temperature and pressure can be obtained. There is no need to monitor the temperature and pressure and then perform inversion processing, which reduces the circuit structure and algorithm processing operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 Schematic diagram of the optical fiber bundle structure. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1

[0034] Purpose of the invention: When measuring dissolved oxygen in a liquid environment, optical fiber is easily affected by temperature and pressure, and traditional methods have disadvantages such as measurement circuit failure. The present invention improves the design of the optical fiber dissolved oxygen probe and adopts a passive structure to eliminate the cross-effect of temperature and pressure, thereby avoiding the disadvantages of circuit failure, increased probe volume, and complex structure.

[0035] like Figure 1 and Figure 2 The optical fiber dissolved oxygen probe shown in the figure eliminates the cross-effect of temperature and pressure, comprising a substrate 1, an oxygen sensitive membrane 2, a cylinder 3, and an optical fiber bundle 4;

[0036] There are two completely independent spaces inside the cylinder 3, which are divided into a detection channel 3a and a reference channel 3b;

[0037] The optical fiber bundle 4 is composed of 7 optical fibers, the central one is an input optical fiber 41 connected to a laser machine for emitting a light source; the surrounding 6 are output optical fibers 42 connected to a photoelectric detector for receiving the fluorescence excited by the oxygen sensitive membrane 2;

[0038] The optical fiber bundle 4 is divided into a detection optical fiber bundle 4a and a reference optical fiber bundle 4b. One end of the detection optical fiber bundle 4a is located in the detection channel 3a and close to the inner wall of the corresponding oxygen sensitive membrane; one end of the reference optical fiber bundle 4b is located in the reference channel 3b and close to the inner wall of the corresponding oxygen sensitive membrane.

[0039] The substrate 2 is a round transparent glass sheet, and the oxygen sensitive film 2 is coated on one surface of the substrate to detect dissolved oxygen.

[0040] For the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces outward, which is used to contact the liquid to be tested, and can detect the dissolved oxygen concentration in the liquid environment in real time; the substrate is a circular glass sheet with good light transmittance and thermal conductivity; for the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces inward, and is not in contact with the liquid to be tested, nor is it in contact with oxygen.

[0041] The inner surface of the cylinder is coated with a black coating to reduce the influence of stray light on the measurement results; the outer surface of the cylinder has a corrosion-resistant coating that can withstand the corrosion of acid and alkali substances in the liquid environment, effectively ensuring the normal operation of the probe.

[0042] When the substrate and the cylinder, and the optical fiber and the cylinder are coupled, a sealing rubber ring is used for sealing, which can withstand external pressure and the entry of liquid to damage the performance of the sensor.

[0043] In order to ensure that the light intensity values ​​received by the reference channel and the detection channel are consistent, the input optical fibers of the reference channel and the detection channel are connected to the same laser, which can solve the problem of mismatch in input light intensity.

[0044] Embodiment 2

[0045] The invention discloses an optical fiber dissolved oxygen probe which eliminates the cross-effect of temperature and pressure and is used for oxygen concentration detection. The specific method is as follows: when the external temperature changes, the temperature environment of the oxygen sensitive membranes of the reference channel and the detection channel is consistent, and the change of the fluorescence intensity caused by the temperature is also consistent; when the temperature is defined as T and the oxygen concentration is defined as Y, the fluorescence intensity value obtained by the reference channel is A, and the fluorescence intensity value obtained by the detection channel is B; since the oxygen content in the reference channel is 0, when the light intensity value of the reference channel changes at different temperatures, it is the change caused by the influence of temperature, so the light intensity value of the detection channel is subjected to difference processing with the light intensity value of the reference channel, so the accurate oxygen concentration content can be obtained, that is, the oxygen concentration = BA.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical fiber dissolved oxygen probe that eliminates the cross-effects of temperature and pressure, characterized in that: It includes a cylinder, an optical fiber bundle, a substrate, and an oxygen sensitive film; There are two completely independent spaces inside the cylinder, and the two spaces are divided into a detection channel and a reference channel; The optical fiber bundle is composed of 7 optical fibers, the central one is an input optical fiber connected to a laser machine for emitting a light source; the surrounding 6 are output optical fibers connected to a photoelectric detector for receiving the fluorescence emitted by the oxygen sensitive membrane when excited; The optical fiber bundle is divided into a detection optical fiber bundle and a reference optical fiber bundle. One end of the detection optical fiber bundle is located in the detection channel and close to the inner wall of the corresponding oxygen sensitive membrane; one end of the reference optical fiber bundle is located in the reference channel and close to the inner wall of the corresponding oxygen sensitive membrane. The substrate is a round transparent glass sheet, and the oxygen sensitive film is coated on one surface of the substrate to realize the detection of dissolved oxygen.

2. The optical fiber dissolved oxygen probe for eliminating the cross-effect of temperature and pressure according to claim 1, characterized in that: For the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces outward, which is used to contact the liquid to be tested, and can detect the dissolved oxygen concentration in the liquid environment in real time; the substrate is a circular glass sheet with good light transmittance and thermal conductivity; for the substrate corresponding to the detection channel, the surface coated with the oxygen sensitive film faces inward, and is not in contact with the liquid to be tested, nor is it in contact with oxygen.

3. The optical fiber dissolved oxygen probe for eliminating the cross-effect of temperature and pressure according to claim 1, characterized in that: The inner surface of the cylinder is coated with a black coating to reduce the influence of stray light on the measurement results; the outer surface of the cylinder has a corrosion-resistant coating that can withstand the corrosion of acid and alkali substances in the liquid environment, effectively ensuring the normal operation of the probe.

4. The optical fiber dissolved oxygen probe for eliminating the cross-effect of temperature and pressure according to claim 1, characterized in that: When the substrate and the cylinder, and the optical fiber and the cylinder are coupled, a sealing rubber ring is used for sealing, which can withstand external pressure and the entry of liquid to damage the performance of the sensor.

5. The optical fiber dissolved oxygen probe for eliminating the cross-effect of temperature and pressure according to claim 1, characterized in that: In order to ensure that the light intensity values ​​received by the reference channel and the detection channel are consistent, the input optical fibers of the reference channel and the detection channel are connected to the same laser, which can solve the problem of mismatch in input light intensity.

6. An optical fiber dissolved oxygen probe for eliminating the cross-effect of temperature and pressure according to any one of claims 1 to 5, characterized in that: Applied to oxygen concentration detection, the specific method is: when the external temperature changes, the temperature environment of the oxygen sensitive membrane of the reference channel and the detection channel is consistent, and the change of fluorescence intensity caused by temperature is also consistent; when the temperature is defined as T and the oxygen concentration is defined as Y, the fluorescence intensity value obtained by the reference channel is A, and the fluorescence intensity value obtained by the detection channel is B; since the oxygen content in the reference channel is 0, when the light intensity value of the reference channel changes at different temperatures, it is the change caused by the influence of temperature, so the light intensity value of the detection channel is subtracted from the light intensity value of the reference channel to obtain the accurate oxygen concentration, that is, oxygen concentration = BA.

Images