1. FBG-based monitoring device for gas quality of pressure steam sterilizer, which is characterized by comprising: the optical fiber grating demodulator comprises a light source, an optical fiber grating demodulator, a first optical fiber and a second optical fiber;

the light emitted by the light source is incident to the first optical fiber and the second optical fiber;

the first optical fiber is provided with an FBG temperature sensor with a packaging structure and used for sensing the internal temperature of the pressure steam sterilizer;

the second optical fiber is provided with a PI-FBG sensor for sensing the density of water molecules in the pressure steam sterilizer;

the fiber bragg grating demodulator is used for reading information sensed by the FBG temperature sensor and the PI-FBG sensor.

2. The monitoring device of claim 1, wherein the encapsulation structure is a capillary stainless steel armor.

3. The monitoring device of claim 1, wherein the PI-FBG is made of bare fiber grating coated polyimide.

4. The FBG-based monitoring method for the gas quality of the pressure steam sterilizer comprises the following steps:

temperature monitoring during sterilization: sealing the beltThe FBG temperature sensor with the structure and the PI-FBG are simultaneously placed in a sterilization chamber of the pressure steam sterilizer to be monitored, wherein the PI-FBG is calibrated with the over-temperature sensitivity K_TSensitivity K of water molecule density in water vapor_DAnd when the sterilization effect is qualified, the central wavelength range lambda of the PI-FBG in the sterilization period_s+ -Delta lambda, and the central wavelength shift Delta lambda of the PI-FBG caused by the difference between the density of the corresponding water molecules and the density of the saturated steam water molecules when the qualified vacuum air pressure value is P0 in the pre-vacuum period_DV(ii) a Recording the synchronous change values of the two sensors along with time in the whole working process of the pressure steam sterilizer in real time, judging whether the temperature of the pressure steam sterilizer in the sterilization period is qualified or not according to the test result of the FBG temperature sensor, and judging that the physical parameters of the pressure steam sterilizer are unqualified if the temperature in the sterilization period is unqualified; if the temperature in the sterilization period is qualified, judging the starting point, the middle point and the ending point of the pressure steam sterilizer in the sterilization period according to the test result of the FBG temperature sensor, and corresponding temperature values T_max1,T_max1And T_max3Calculating the arithmetic mean value T of the temperature in the sterilization period according to the formula (1) from the temperatures at the three time points_max：

T_max＝1/3*(T_max1+T_max2+T_max3) (1)；

Monitoring of water vapor saturation during sterilization: reading the central wavelengths of the PI-FBG at the starting point, the middle point and the ending point of the sterilization period time to be lambda respectively_S1、λ_S2And λ_S3If λ_Si(i ═ 1, 2, 3) not at λ_sWithin the range of +/-delta lambda, judging that the water vapor saturation of the pressure steam sterilizer in the sterilization period is unqualified; if λ_Si(i ═ 1, 2, 3) at λ_sWithin the range of +/-delta lambda, judging that the water vapor saturation of the pressure steam sterilizer in the sterilization period is qualified, and monitoring the vacuum degree in the next pre-vacuum period;

monitoring the vacuum degree in the pre-vacuum period: determining the point E of the vacuumizing ending time point in the pre-vacuum period according to the temperature change characteristics of the FBG temperature sensor in the pre-vacuum period, and reading the central wavelength lambda of the PI-FBG at the point E_DTAnd the corresponding temperature T, which can be calculated from equation (2) due to saturation at that timeShift delta lambda of PI-FBG central wavelength caused by difference of steam water molecule density and E point water molecule density_D：

Δλ_D＝(λ_s-λ_DT)-K_T·(T_max-T) (2)

Will be delta lambda_DDelta lambda from previous calibration_DVMaking comparison if | Δ λ_D|≥|Δλ_DVIf the vacuum degree of the pressure steam sterilizer reaches the requirement after the vacuum pumping is finished, the gas quality of the pressure steam sterilizer can be judged to be qualified by integrating that the temperature is qualified and the water vapor saturation in the sterilization period is qualified; otherwise, the vacuum degree of the pressure steam sterilizer does not meet the requirement when the pre-vacuum is finished, and the gas quality of the pressure steam sterilizer is judged to be unqualified.

5. The monitoring method according to claim 4, wherein the calibration of the PI-FBG: calibrating the temperature sensitivity K of the PI-FBG in the required temperature range by using a heating temperature-raising device_T(ii) a Calibration of PI-FBG water molecule density sensitivity K in water vapor by using qualified pressure steam sterilizer_DCentral wavelength range lambda of PI-FBG in sterilization period_sWhen the qualified vacuum air pressure value is P0, the central wavelength of the PI-FBG drifts by delta lambda caused by the difference between the density of the corresponding water molecule and the density of the saturated steam water molecule_DV。

6. The method of monitoring of claim 5, wherein the desired temperature range is from room temperature to 150 ℃.

7. A method of monitoring as claimed in any of claims 4 to 6 wherein the encapsulation structure is a capillary stainless steel sheath.

8. A method of monitoring as claimed in any of claims 4 to 6 wherein the PI-FBG is made of bare fibre grating coated polyimide.

Background

Sterilization of reusable medical devices is an important issue in the prevention of cross-infection in hospitals. The disinfection technical specification of medical institutions published in 2012 of China stipulates that heat-resistant and moisture-resistant medical instruments, instruments and articles, cotton dressing and cotton yarn dressing should be preferred to be a pressure steam sterilizer. Real-time monitoring of physical parameters, namely temperature and pressure, of a sterilization chamber in a sterilization process is an effective means for guaranteeing the sterilization effect. The national sanitary industry standard WS310.3-2016 specifically provides the daily specific requirements for monitoring temperature, pressure and corresponding time. According to the principle of steam sterilization, the mechanism of killing microorganisms by heat is mainly to solidify and oxidize proteins, directly damage cell membranes and cell walls, permanently damage nucleic acids of bacterial living substances and the like.

The monitoring of the physical parameters of the pressure steam sterilizer comprises two aspects of temperature and air pressure monitoring, and the essence of the air pressure monitoring is to ensure the quality of steam in a sterilization period. The gas quality of the existing pressure steam sterilizer is monitored by testing the pressure in a sterilization chamber, and the pressure monitoring means mainly comprises the following four methods: 1. a laboratory test method; 2. a field test method based on a wired electronic sensor; 3. a regular on-site inspection sterilizer self-carrying printing recording method; 4. wireless temperature and pressure sensor methods are used in the field.

For the former two monitoring means, the sterilizer needs to be disassembled, which affects the normal operation of the sterilizer and is not beneficial to the maintenance of instruments, so the former two detection methods are generally not popular in medical institutions.

The method is used by the current health supervision department, and the supervision department regularly checks the paper printing work record of the sterilizer sensor, but in the metering sense, the sterilizer sensor is not verified, and the data is lack of reliability.

For the field use wireless temperature and pressure sensor method, it is the electronic temperature and pressure sensing technology based on wireless sensing signal transmission technology, is the novel technology developed along with short distance wireless communication, but because the sensing chip of the wireless pressure sensor is in the cavity, the requirement for encapsulation is very high, so that the monitoring means is high in cost and high in price, and cannot be effectively popularized.

Disclosure of Invention

The invention provides a device and a method for monitoring gas quality of a pressure steam sterilizer based on Fiber Bragg Gratings (FBGs), which aim to solve one or more of the problems.

According to an aspect of the present invention, there is provided a FBG-based pressure steam sterilizer gas quality monitoring device, comprising:

the optical fiber grating demodulator comprises a light source, an optical fiber grating demodulator, a first optical fiber and a second optical fiber;

light emitted by the light source is incident to the first optical fiber and the second optical fiber;

the first optical fiber is provided with an FBG temperature sensor with a packaging structure and used for sensing the internal temperature of the pressure steam sterilizer;

a Polyimide-Coated Fiber Bragg Grating (PI-FBG) sensor for sensing the density of water molecules in the pressure steam sterilizer is arranged on the second optical Fiber;

the fiber grating demodulator is used for reading information sensed by the FBG temperature sensor and the PI-FBG sensor.

In some embodiments, the packaging structure of the present invention is a capillary stainless steel armor.

In some embodiments, the PI-FBG of the present invention is made of bare FBG coated polyimide.

According to another aspect of the present invention, there is provided a FBG-based pressure steam sterilizer gas quality monitoring method, comprising:

temperature monitoring during sterilization: simultaneously placing the FBG temperature sensor with the packaging structure and the PI-FBG sensor into a pressure steam sterilizer to be monitored, wherein the PI-FBG has calibrated over-temperature sensitivity K_TSensitivity K of water molecule density in water vapor_DAnd when the sterilization effect is qualified, the central wavelength range lambda of the PI-FBG in the sterilization period_s+ -Delta lambda, and the central wavelength shift Delta lambda of the PI-FBG caused by the difference between the density of the corresponding water molecules and the density of the saturated steam water molecules when the qualified vacuum air pressure value is P0 in the pre-vacuum period_DV(ii) a Recording the synchronous change values of the two sensors along with time in the whole working process of the pressure steam sterilizer in real time, judging whether the temperature of the pressure steam sterilizer in the sterilization period is qualified or not according to the test result of the FBG temperature sensor, and judging that the physical parameters of the pressure steam sterilizer are unqualified if the temperature in the sterilization period is unqualified; if the temperature in the sterilization period is qualified, judging the starting point, the middle point and the ending point of the pressure steam sterilizer in the sterilization period according to the test result of the FBG temperature sensor, and corresponding temperature values T_max1,T_max1And T_max3Calculating the arithmetic mean value T of the temperature in the sterilization period according to the formula (1) from the temperatures at the three time points_max：

T_max＝1/3*(T_max1+T_max2+T_max3) (1)；

Steam during sterilizationAnd (3) monitoring the saturation degree: reading the central wavelengths of the PI-FBG at the starting point, the middle point and the ending point of the sterilization period time to be lambda respectively_S1、λ_S2And λ_S3If λ_Si(i ═ 1, 2, 3) not at λ_sWithin the range of +/-delta lambda, judging that the water vapor saturation of the pressure steam sterilizer in the sterilization period is unqualified; if λ_Si(i ═ 1, 2, 3) at λ_sWithin the range of +/-delta lambda, judging that the water vapor saturation of the pressure steam sterilizer in the sterilization period is qualified, and monitoring the vacuum degree in the next pre-vacuum period;

monitoring the vacuum degree in the pre-vacuum period: determining the point E of the vacuumizing ending time point in the pre-vacuum period according to the temperature change characteristics of the FBG temperature sensor in the pre-vacuum period, and reading the central wavelength lambda of the PI-FBG at the point E_DTAnd the corresponding temperature T, and the shift Delta lambda of the central wavelength of the PI-FBG caused by the difference between the saturated steam water molecule density and the E point water molecule density at the moment can be calculated by the formula (2)_D：

Δλ_D＝(λ_s-λ_DT)-K_T·(T_max-T) (2)

Will be delta lambda_DDelta lambda from previous calibration_DVMaking comparison if | Δ λ_D|≥|Δλ_DVIf the vacuum degree of the pressure steam sterilizer reaches the requirement after the vacuum pumping is finished, the gas quality of the pressure steam sterilizer can be judged to be qualified by integrating that the temperature is qualified and the water vapor saturation in the sterilization period is qualified; otherwise, the vacuum degree of the pressure steam sterilizer does not meet the requirement when the pre-vacuum is finished, and the gas quality of the pressure steam sterilizer is judged to be unqualified.

The PI-FBG adopted by the invention is used as a sensor for sensing the density of water molecules, and has good high-temperature resistance. The PI-FBG sensor is matched with the FBG temperature sensor with the packaging structure, so that the steam quality of the sterilizer can be accurately evaluated. The FBG-based monitoring device for the gas quality of the pressure steam sterilizer can avoid electromagnetic interference, is suitable for multi-point monitoring in sterilization rooms with various capacities, does not increase the cost, is simple to operate, is convenient to carry, and has the capability of recording a large amount of data; the sensor has the characteristics of high temperature resistance, pressure resistance, moisture resistance and chemical corrosion resistance, and the FBG and the PI-FBG are passive devices, so that a power supply is not needed in the pressure steam sterilizer, and the sensor is safer. Therefore, the invention provides a feasible new approach for testing the physical parameters of the pressure steam sterilizer.

The vapor is condensed into water under a certain pressure, the volume of the vapor is reduced by 1870 times, so that the vapor can rapidly penetrate into the article, and latent heat can be released when the vapor is condensed into water, and the latent heat releases heat to an object when the vapor is condensed into water by contacting a cold object, so that the temperature of the object is rapidly increased. Saturated steam in a pressure steam sterilizer must meet the requirements of dryness (moisture content < 10%) and purity (cold air content < 5%). From thermal knowledge, the temperature and pressure of saturated steam obtained by heating water to boiling temperature and then evaporating all the water can be corresponded to the following equation:

wherein, P is saturated vapor pressure, A, B and C are constants, and T is thermodynamic temperature.

I.e. the pressure of the pure saturated steam corresponds to the temperature. The temperature and the air pressure in the pressure steam sterilizer in the national standard are required to meet the relation. Therefore, the pressure of the pressure steam sterilizer is tested to ensure that the gas in the sterilization chamber is dry and pure saturated steam; for pressure steam sterilization, the essence of the barometric pressure test is to detect whether the chamber is acceptably saturated with steam during the sterilization period. Therefore, the purpose of checking whether the physical parameters of the sterilizer are qualified can be achieved by judging whether the steam of the sterilizer is dry and pure saturated steam in the sterilization period and combining the temperature test.

In some embodiments, the calibration of the PI-FBG of the present invention: calibrating the temperature sensitivity K of the PI-FBG in the required temperature range by using a heating temperature-raising device_T(ii) a Calibration of PI-FBG water molecule density sensitivity K in water vapor by using qualified pressure steam sterilizer_DCentral wavelength range lambda of PI-FBG in sterilization period_s±Δλ，And when the qualified vacuum air pressure value is P0, the central wavelength drift Delta lambda of the PI-FBG caused by the difference between the density of the corresponding water molecule and the density of the saturated steam water molecule_DV。

In some embodiments, the temperature range required for the present invention is from room temperature to 150 ℃.

Drawings

Fig. 1 is a schematic diagram of a typical variation process of temperature and pressure in the work flow of a pressure steam sterilizer according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional structure diagram of a PI-FBG according to an embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a PI-FBG high temperature sensing characteristic testing apparatus of a pressure steam sterilizer according to an embodiment of the present invention.

FIG. 4(a) is a schematic spectrum of PI-FBG at 150 ℃ and 16 ℃.

FIG. 4(b) is a schematic diagram of the temperature sensing characteristics of PI-FBG at 150 deg.C to 16 deg.C.

FIG. 5 is a schematic diagram of a PI-FBG water molecule content sensing characteristic testing device according to an embodiment of the invention.

FIG. 6 is a graph showing the relationship between the center wavelengths of the C-D and PI FBGs shown in FIG. 1 over time in the device shown in FIG. 5.

FIG. 7 is a graph showing the shift of the center wavelength of the PI-FBG due to the water molecule density in the C-D segment shown in FIG. 1 in the device shown in FIG. 5.

FIG. 8 is a schematic structural diagram of an FBG-based pressure steam sterilizer gas quality monitoring device of the present invention.

FIG. 9 is a schematic view of a gas quality monitoring process in a pressure steam sterilizer according to an embodiment of the present invention.

Fig. 10(a) is a schematic diagram of temperature and pressure changes during real-time monitoring of the whole operation process of the pressure steam sterilizer according to an embodiment of the present invention.

Fig. 10(b) is a graph showing the variation of the central wavelengths of the PI-FBG and FBG for real-time monitoring of the whole operation process of the pressure steam sterilizer according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The present invention will be described in further detail with reference to the accompanying drawings.

Fig. 1 schematically shows a typical course of temperature and pressure changes in a work flow of a pressure steam sterilizer according to an embodiment of the present invention.

The working process of the pressure steam sterilizer is the process that the temperature and the air pressure change continuously along with time, and the working process of the common packaging Mode is shown in a reference figure 1:

1. a heating period (shown as stages 1-2 in figure 1).

2. A pre-vacuum period: vacuumizing by using a vacuum pump, and stopping the vacuum pump after the preset pressure is reached (-0.8 bar); distilled water generates steam through an evaporator and enters the sterilization chamber, and the steam is fed in a pulsating mode, so that the pressure in the sterilization chamber is increased; after reaching the preset pressure, removing water vapor and water, vacuumizing, repeating the steps for 3 times, and exhausting the air in the sterilization chamber; after the last pulse vacuum, the distilled water generates steam through the evaporator and enters the sterilization chamber, and the steam is pulsed to enable the pressure in the sterilization chamber to reach the set pressure and temperature (as shown in 2-3 stages in figure 1).

3. And (3) sterilization period: and (3) maintaining the pressure, keeping the temperature and sterilizing the mixture within a set time (as shown in 3-4 stages in figure 1).

4. And (3) exhausting period: after sterilization is complete, the water vapor is removed and the pressure is released (as shown in stages 4-5 in fig. 1).

5. And (3) drying period: when the pressure in the sterilization chamber is reduced to atmospheric pressure, the vacuum pump is started to perform vacuum drying (the pressure is reduced to-0.8 bar, as shown in 5-6 stages in FIG. 1).

6. Balancing period: after the vacuum drying is finished, air is input for cooling, so that the pressure in the sterilization chamber is gradually increased to the atmospheric pressure, and the sterilization is finished (as shown in 6-7 stages in figure 1).

In the sterilization period, two factors are used for influencing the pressure, one is that the saturated steam is not well insulated due to the long distance of the pipeline in the conveying process, and the steam generates excessive condensed water in the conveying process, so that the steam saturation is reduced, and the air pressure is reduced. The direct consequence is that wet packaging of the medical instruments occurs after sterilization, directly resulting in sterilization failure. In this case, under the condition of known temperature, the gas pressure in the sterilization chamber is lower than the saturated vapor pressure calculated by an Antoine formula, namely, the density of the water vapor in the sterilization chamber is lower than that in the saturated state, and the requirement of dry saturated vapor cannot be met. Therefore, whether the steam is saturated or not can be judged by testing the density of the gaseous water molecules in the sterilization chamber in the sterilization period.

Another reason is that the pre-vacuum stage is not sufficiently vacuum, leaving excess air trapped in the chamber. Because the latent heat of the saturated steam is far higher than that of the air, the heat penetration capacity of the saturated steam is higher than that of the air, and therefore, the sterilization effect is directly influenced due to the insufficient vacuum degree. According to the Dolton law of mixed gas, the pressure of the mixed gas is equal to the sum of the pressures of all components, and if the injected steam is qualified and has no air leakage, the gas pressure in the cavity in the sterilization period is higher than the saturated steam pressure calculated by an Antoine formula. From the analysis of the content of the water vapor, as the air also contains a certain amount of water vapor, when saturated steam enters the sterilization chamber and is heated to a determined temperature, the water vapor is condensed into liquid water, and the density of water molecules in the sterilization chamber is the same as that of water molecules in the saturated steam. It is not feasible to test the water molecule density to judge whether the vacuum degree is qualified. However, the pre-vacuum period is to evacuate air, and during the pre-vacuum period, the chamber is filled with pure water vapor from the end of the evacuation to the sterilization period (as shown in fig. 1, stages a-B). If the gas purity is not sufficient, the water molecule density will not match the pure water vapor density. At the moment, the test on the density of the water molecules can judge whether the vacuum degree of the sterilization chamber reaches the standard or not.

By combining the analysis, the judgment of whether the water vapor in the cavity in the sterilization period is saturated water vapor and the judgment of whether the gas is pure after the vacuumizing in the pre-vacuum period is finished are combined, so that whether the quality of the gas in the sterilization period is qualified can be evaluated.

Fig. 2 schematically shows the structure of a PI-FBG in a gas quality monitoring device for a fiber bragg grating based pressure steam sterilizer according to an embodiment of the present invention.

Referring to fig. 2, the PI-FBG (polyimide coated fiber bragg grating) 21 is composed of a bare fiber grating 211 and a polyimide coating layer 212 coated outside the bare fiber grating cladding.

PI-FBG can be prepared by the following method:

1. surface pretreatment of bare FBGs: and taking the complete FBG, and cutting off the complete FBG at a position 2-3 cm away from one of the grating area mark points and at a position 1.5 m away from the other mark point. Then, the grid-carved area and the vicinity thereof are wiped clean by dipping 95% alcohol in alcohol cotton.

2. Polyimide solution coating: the grating area of the treated FBG is completely immersed in a 20% polyimide solution (also called PI glue) to keep the immersed grating area as straight as possible.

The gate-etched region was soaked for about 20 minutes. The grill section is removed and suspended. Under the influence of gravity, the polyimide solution coated on the grid-etched part has a tendency to drop, and the FBG is allowed to stand for at least 10 minutes until the surface of the grid-etched part is coated with a continuous polyimide layer with uniform thickness.

3. Heating and curing: fix the FBG who coats the polyimide film and heat in the high temperature drying cabinet, the process of placing need be paid attention to and keep the coating position unsettled, need guarantee the inside cleanness of high temperature drying cabinet among the heating process. Heating to 120-130 ℃, keeping the temperature for 30 minutes, and fully volatilizing volatile matters in the polyimide solution to form a film; then heating to 180-200 ℃, and keeping the temperature for 10 minutes; then the temperature is continuously increased to 300 ℃ and the heating is carried out for at least 30 minutes, wherein the specific time period depends on the requirement of the final film-forming thickness.

4. And (3) cooling and forming: and placing the polyimide coated FBG which is heated and cured in a drying oven for natural cooling, and welding a jumper wire after cooling to room temperature to manufacture the PI-FBG sensor.

The PI-FBG sensor is prepared by coating the Bragg fiber grating on the polyimide sensitive to the density of water molecules, and the quality of gas in a sterilization room is tested.

The polyimide and water molecule act as typical physical adsorption, and PI-FBG is that the volume expansion of the polyimide coating layer generates strain after water absorption, and then the FBG senses the strain to test the change of the water molecule density.

For an bare FBG, when the temperature and the strain change, the central wavelength change Delta lambda of the FBG changes linearly, and the relationship between the central wavelength change Delta lambda and the strain change is as follows:

wherein λ is the central wavelength value of the FBG in a free state at a certain temperature, p_eLet ε be the effective elasto-optic coefficient of the fiber, ε be the amount of strain, α be the thermal expansion coefficient of the fiber, ξ be the thermo-optic coefficient of the fiber, and Δ T be the amount of temperature change. The volume expansion of the polyimide coating after water absorption will produce strain inside the FBG, and we define the density D of water molecules as the mass of water molecules per volume of gas (commonly used in literature as Δ RH, i.e. relative humidity)Characterizing the ratio of the content of water molecules in a unit volume at a certain temperature to the density of water molecules in saturated steam in a unit volume at the same temperature, the research object of the invention is a temperature-changing condition, so that the sensing characteristic of the sensor to water vapor is defined by the density of water molecules instead of relative humidity), namely:

wherein m is the mass of the water vapor in the container, and V is the volume of the container. The central wavelength of the PI-FBG is changed by delta lambda under the isothermal condition_DCan be expressed as:

wherein, K_DThe sensitivity of water molecule density sensing. When the temperature and the water molecule density are simultaneously changed, the central wavelength Delta lambda of the PI-FBG_DTCan be expressed as:

wherein, K_TIs the temperature sensitivity.

When the polyimide coating layer thickness was 49.5 μm, the sensitivity was 0.01427 nm/deg.C in the range of room temperature to 150 deg.C; the PI-FBG has piecewise linear response characteristic to the water molecule density.

According to national standards, the sensors used for the testing of physical parameters in pressure steam sterilizers are required to withstand high temperatures of up to 150 ℃. To this end, we first examine the temperature stability of the sensor.

Fig. 3 schematically shows a PI-FBG high temperature sensing characteristic testing apparatus according to an embodiment of the present invention.

The PI-FBG and the bare FBG sensor calibrated in advance are placed from an air hole at the top of the heating and warming equipment 54 (which can be equipment such as a constant temperature drying oven) and the probe positions of the two sensors are at the same height and do not touch the bottom of the constant temperature drying oven. The PI-FBG and the bare FBG tail fiber are connected with a high-precision fiber grating demodulator 53 (Shanghai Bai' an sensor Co., Ltd., FT810-04E, dynamic demodulation rate is 2500Hz, wavelength resolution is 0.1pm, wavelength measurement precision is +/-1 pm, time reading precision is 1 mu s) through jumper wires, the real-time change of the central wavelengths of the two sensors is tested, and then data acquisition equipment 52 such as a computer is accessed to record the real-time change of the central wavelengths of the two sensors in real time. The fiber grating demodulator 53 includes a light source, a central wavelength measuring device, a clock unit, etc., and the operation result can be displayed and recorded by a computer. Setting a constant-temperature drying oven to heat to 150 ℃, stopping heating, and naturally cooling to normal temperature. Because the temperature changes violently in the temperature rise process and the humidity change in the drying box is large, in order to reduce errors, the temperature drop process change data is taken to actually measure the temperature sensitivity of the PI-FBG. In the test process, spectrograms with the temperature of 150 ℃ and 16 ℃ are extracted successively (as shown in fig. 4 (a)), and the experimental result shows that the spectral shape of the PI-FBG has no significant change, which indicates that the PI-FBG has good temperature stability.

The calibrated bare FBG is used as a reference temperature sensor, the calculated PI-FBG temperature response characteristic is shown in fig. 4(b), the actually measured temperature sensitivity is 0.01427 nm/DEG C, the determination coefficient is 0.999, and the PI-FBG keeps good temperature linear sensitivity in the temperature range, and the polyimide coating layer has the sensitization effect on the temperature (the sensitivity of the bare FBG is 0.0123 nm/DEG C).

FIG. 5 schematically shows an experimental apparatus for calibrating the water molecule density sensing characteristics of the PI-FBG sensor in the present invention.

The calibration device comprises: the device comprises a qualified pressure steam sterilizer 50 with detected physical parameters, a digital pressure gauge 51, data acquisition equipment 52 such as a computer and the like, a fiber grating demodulator 53, a first optical fiber 10 and a second optical fiber 20. The fiber grating demodulator 53 is provided therein with a light source, and light emitted from the light source is incident on the first optical fiber and the second optical fiber. The FBG is engraved on the first optical fiber and used for sensing the internal temperature of the pressure steam sterilizer, the FBG is provided with a capillary stainless steel packaging structure, and the opening is sealed by self-setting resin; the second optical fiber is provided with a polyimide coated FBG (fiber Bragg Grating), namely PI-FBG, for sensing the density of water molecules in the pressure steam sterilizer. The fiber grating demodulator 53 is used for reading the information sensed by the FBG temperature sensor and the PI-FBG sensor.

The PI-FBG and the FBG are placed in a sterilization chamber of the qualified pressure steam sterilizer 50, and the sensor tail fiber with the diameter of 250 microns is led out through a cavity door of the qualified pressure steam sterilizer 50 and then connected to a fiber grating demodulator 53.

Referring to fig. 5, the device is a device for testing the sensing characteristics of the PI-FBG on the density of water molecules under the conditions of high temperature and high pressure of a pressure steam sterilizer. A digital pressure gauge 51 is connected into a qualified pressure steam sterilizer 50SEA steam sterilizer) and is connected to a data acquisition device 52 such as a computer through an RS485 interface to record the air pressure in the cavity in real time; no-load of the pressure steam sterilizer; PI-FBG and capillary stainless steel capsulate FBG put in stainless steel in the middle of sterilizer carry the thing tray, PI-FBG and FBG's tail fiber lead out pressure steam sterilizer 50 and connect to fiber grating demodulator 53 through the preceding sealing door, wherein capillary stainless steel capsulates FBG temperature sensor and is used for monitoring the intracavity temperature in real time, PI-FBG sensor receives the influence of temperature and hydrone density in the sterilization room simultaneously. Referring to fig. 1, from the end point C of the sterilization period to the start point D of the drying period, the pressure steam sterilizer opens the water discharge solenoid valve to discharge water vapor; and when the pressure in the sterilization chamber is reduced to the atmospheric pressure, starting the vacuum pump to vacuumize. Therefore, the sterilization chamber is filled with water vapor in the stage. The invention can evaluate the perception performance of PI-FBG to the density of water molecules by using the process.

The digital pressure gauge 51 can be used with great feelingThe intelligent communication pressure gauge has the measuring range of 5MPa and the precision of 0.2 grade, and meets the requirement of national standard on the air pressure test precision of 1000Pa of the sterilizer.

FIG. 6 schematically shows a graph of the center wavelength of a PI-FBG and a capillary stainless steel packaged FBG as a function of time for acceptable pressure steam sterilizer vent and dry periods (C-D periods).

Referring to fig. 6, during this time the chamber water vapor is vented and the temperature drops, at which time the chamber gas is considered approximately the ideal gas. According to ideal gas state equation (8):

PV＝nRT (8)

wherein P is gas pressure, V is gas volume, n is the amount of the substance of the gas, R is the constant of the universal gas, and T is the thermodynamic temperature of the system. The gas molecular density D is:

where M is the molar mass of the water molecule, where M is 18 g/mol.

The real-time air pressure is given by a barometer at the back of the sterilizer. The change values of the central wavelengths of the capillary stainless steel packaged FBG and the PI-FBG are given by the fiber grating demodulator 53 in real time, the temperature change value is calculated according to the change of the central wavelength of the capillary stainless steel packaged FBG, and the change curve of the central wavelength change along with the gas molecule density D is solved by the formula (7) and is shown in FIG. 7.

FIG. 7 schematically shows the shift in the center wavelength of PI-FBG caused by water molecule density during the pressure steam sterilizer C-D process.

Referring to FIG. 7, the PI-FBG showed good piecewise linear characteristics in response to the water molecule density D. The water molecule density interval is 97g/m respectively³～300g/m³、300g/m³～842g/m³、1097g/m³～1638g/m³Three sections, the water molecule density sensitivity of the PI-FBG is 8.9942 × 10 respectively^-4nm/(g/m³)、2.2272*10^-4nm/(g/m³) And 1.6236 x 10^-4nm/(g/m³) The coefficients were determined to be 0.993, 0.991, and 0.993, respectively. Except that the water molecule density interval is 842g/m³～1097g/m³And a segment, the determination coefficient of which is 0.366, is avoided in subsequent work because the determination coefficient of the segment is not high.

The reason that the air pressure in the sterilization period is unqualified under the condition that the temperature in the sterilization period is qualified is two reasons, namely that the saturation of the water vapor in the sterilization period is not required. For this factor, as can be seen from fig. 7, the water molecule density and the central wavelength of the PI-FBG have a piecewise linear relationship, so that under the condition that the temperature in the sterilization period is measured to be qualified, it is only required to test whether the wavelength of the PI-FBG at this time is within the range of the central wavelength of the PI-FBG in the sterilization period calibrated in advance to make a corresponding judgment. The second reason is that air is not completely discharged, so that air remains in the cavity in the sterilization period, and for the second reason, if the steam injected in the pre-vacuum period is qualified, saturated water vapor still exists in the sterilization period. However, the water molecule density in the sterilization chamber is different from the expected pure water vapor density because the air can not be completely emptied in the pre-vacuum period, so that the vacuum degree can be judged.

Fig. 8 schematically shows a monitoring device for gas quality of a pressure steam sterilizer based on FBG temperature sensors and PI-FBG sensors according to an embodiment of the present invention.

Referring to fig. 8, the capillary stainless steel armored FBG temperature sensor 11 and the PI-FBG sensor 21 are placed in the middle layer of the sterilization chamber of the pressure steam sterilizer 55 to be monitored, the tail fibers of the two sensors are led out through the front closing door of the sterilizer and are connected to the fiber grating demodulator 53, and the fiber grating demodulator 53 records the central wavelengths of the two sensors in the working process of the pressure steam sterilizer 55 to be monitored in real time.

Fig. 9 schematically shows a monitoring flow of the gas quality of the pressure steam sterilizer based on the FBG temperature sensor and the PI-FBG sensor according to an embodiment of the present invention.

This procedure is described below in terms of a test example. In order not to damage acceptable equipment, this example was conducted using a pressure steam sterilizer "non-wrap mode" with the sterilizer unloaded. This operation mode air pressure variation is shown in fig. 10(a), which is characterized in that the preliminary vacuum is performed only once. The process of using the PI-FBG sensor and the capillary stainless steel packaged FBG temperature sensor as shown in FIG. 2 in conjunction with testing the water vapor quality in the cavity is shown in FIG. 9:

s001: calibrating PI-FBG, and calibrating the temperature sensitivity K of the PI-FBG in the range from room temperature to 150 ℃ by using a heating and warming device 54_TAt 0.01427 nm/deg.C, the sterilization was calibrated using a qualified pressure steam sterilizer 50PI-FBG sensitivity K to water molecule density at saturation and near saturation of water molecule density in bacteria stage_D1.6236 x 10^-4nm/(g/m³) (ii) a The sensitivity of the sensor is 1.7837 × 10 along with the decrease of the density of water molecules^-5nm/(g/m³)、2.2272*10^-4nm/(g/m³) And 8.9942 x 10^-4nm/(g/m³). Center wavelength variation range lambda of PI-FBG in sterilization period_sThe +/-delta lambda is 1560.8450nm +/-0.0025 nm, and the central wavelength deviation delta lambda of the PI-FBG caused by the difference between the water molecule density of negative vacuum-0.8 bar (qualified vacuum degree) and the water molecule density of saturated steam_DV＝-0.3455nm。

S002: and (3) monitoring the temperature in the sterilization period, putting the PI-FBG and the FBG into the pressure steam sterilizer 55 to be monitored simultaneously, and recording the synchronous change values of the PI-FBG and the FBG along with the time in the whole sterilization process in real time. According to the test result of the FBG temperature sensor (as shown in fig. 10 (b)), the temperature in the sterilization period is judged to be qualified; determining a starting point, a middle point and an end point of the sterilization period time; and a corresponding temperature value T_max1,T_max1And T_max3Calculating the arithmetic mean value T of the temperature in the sterilization period according to the formula (1) from the temperatures at the three time points_maxThe temperature is 135.6 ℃; and determining the point E of the vacuumizing ending time point in the pre-vacuum period according to the temperature change characteristics in the pre-vacuum period.

S003: monitoring the water vapor saturation during the sterilization period, reading the central wavelength lambda of the PI-FBG at the starting point, the middle point and the ending point of the time of the sterilization period_S1、λ_S2And λ_S31560.8457nm, 1560.8450nm and 1560.8431nm respectively, all at lambda_sThe range of +/-delta lambda (1560.8450nm +/-0.0025 nm) can judge that the water vapor saturation reaches the requirement in the sterilization period.

S004: monitoring the vacuum degree in the pre-vacuum period, and reading the central wavelength lambda of the central wavelength of the PI-FBG at the E point in the pre-vacuum period_DT1560.1178nm, corresponding to a temperature T of 110.9 ℃, expressed by the formula (7). DELTA.. lambda._D＝(λ_s-λ_DT)-K_T·(T-T_max) And can calculate to obtain delta lambda_D-0.3597nm, due to | Δ λ_D|＞|Δλ_DVTherefore, the vacuum degree can be judged to be qualified.

S005: and (4) conclusion: in the example, the air pressure value of the measured E point is-0.835 bar, which meets the requirement of the vacuum degree of the equipment, so the test scheme is consistent with the measured measurement. Thereby verifying the feasibility of this test protocol.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing examples can be modified, or some technical features can be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.