CN114323350A - Automatic calibration method for temperature sensor in water film-forming fire extinguishing agent - Google Patents
Automatic calibration method for temperature sensor in water film-forming fire extinguishing agent Download PDFInfo
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- CN114323350A CN114323350A CN202111652446.9A CN202111652446A CN114323350A CN 114323350 A CN114323350 A CN 114323350A CN 202111652446 A CN202111652446 A CN 202111652446A CN 114323350 A CN114323350 A CN 114323350A
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Abstract
The invention discloses an automatic calibration method of a temperature sensor in a water film-forming fire extinguishing agent, which uses 3 temperature sensors to respectively transmit the temperatures of the inner part and the outer wall of a storage tank and air to a microcontroller, the heat transmission inside and outside the storage tank is periodically and temporarily stopped under a certain condition, and 3 transmitted temperatures are equal, so that the automatic calibration of the temperature sensor in the water film-forming fire extinguishing agent is realized by a program designed at the end of the microcontroller.
Description
Technical Field
The invention relates to the field of sensors, in particular to a method for automatically calibrating a temperature sensor in a solution on a high-concentration sol solution storage tank, and particularly relates to a method for automatically calibrating a temperature sensor in a water film-forming fire extinguishing agent storage tank.
Background
The water filming fire extinguishing agent is a concentrated fire extinguishing agent solution containing about 70% of water and about 30% of surfactant, foaming agent, foam stabilizer, etc., and belongs to a sol concentrated solution containing a large amount of high molecular substances. Its specific heat capacity and heat transfer performance are between that of water and solid solute. The water-filming fire extinguishing agent is generally stored in a stainless steel tank for a long time for later use, and in order to increase the stability, the stainless steel storage tank is generally provided with a plurality of adjustable supporting legs for supporting the tank.
The effectiveness of the water-film-forming fire extinguishing agent is directly related to the reliability of a fire extinguishing system, and the storage life of the water-film-forming fire extinguishing agent is directly related to the storage temperature (Yuan, Xie Jun, Han Yonghe, and the like). In order to estimate the remaining life of the aqueous film-forming fire suppressant, it is necessary to obtain its exact temperature at any time, typically by centrally locating a temperature sensor inside the tank. Because the water film-forming fire extinguishing agent contains a large amount of corrosive substances, the temperature sensor is easy to corrode and generate zero drift, so that the reading is inaccurate. In order to identify the zero drift, the simplest method is to arrange at least 3 temperature sensors in the tank body and compare the readings at any time, but the temperature sensors are easy to lose efficacy and need to be replaced due to the strong corrosivity of the water film-forming fire extinguishing agent, and the sensors need to be replaced frequently when at least 3 temperature sensors are arranged in the tank body, so that the stable storage state of the water film-forming fire extinguishing agent is not maintained, and certain waste is caused.
The invention aims at the problems of reliability monitoring and calibration of a temperature sensor placed in a water film-forming fire extinguishing agent, and provides a method for calibrating the temperature sensor placed in the water film-forming fire extinguishing agent in a tank body by using readings of an outer wall of the tank body and an external air temperature sensor.
Disclosure of Invention
Aiming at the problem that a temperature sensor arranged in the water film-forming fire extinguishing agent is easy to corrode and generates zero drift, the method for calibrating the temperature sensor arranged in the water film-forming fire extinguishing agent in the storage tank by utilizing the outer wall of the tank body and an external air temperature sensor is provided.
The purpose of the invention is realized by the following scheme: an automatic calibration method for temperature sensors in a water film-forming fire extinguishing agent is realized by connecting 3 temperature sensors arranged at different positions with a microprocessing unit (MCU), and comprises the following steps:
(1) respectively placing 3 calibrated temperature sensors in the inner liquid surface, the outer wall and the external air of the water film-forming fire extinguishing agent stainless steel storage tank, and connecting the temperature sensors with the MCU; the temperature data generated by the three are recorded as the internal temperature, the external temperature and the air temperature respectively, and the MCU collects the data every 10 minutes and synchronously draws the temperature curves generated by the three; from evening to morning of the second day, the air temperature and the external temperature enter a descending interval and are intersected with the internal temperature curve; when the temperature sensors work normally, the three temperature curves are intersected at one point, which is called a pair of meter points;
(2) the MCU continuously tracks the pair of the table points through comparison logic, and when 3 continuous table points deviate, namely three curves cannot intersect at one point in an error range, a correction program is started to realize automatic correction or guide a worker to execute correction operation and judge whether the internal temperature sensor needs to be replaced.
Further, the flow of the MCU for main sensor calibration is as follows:
s1, continuously collecting the data of the internal temperature, the external temperature and the air temperature by the MCU, and forming an internal temperature curve, an external temperature curve and an air temperature curve by the temperature data collected in a specified time interval;
s2, judging whether the counter point is abnormal or not, and if not, judging that the sensor is normal; if so, correcting the internal temperature deviation value to enable the three-line unification of the meter points and continuously collecting data;
s3, after correcting the over-internal temperature deviation value, continuously judging whether the counter point is abnormal, if not, setting a new deviation value for the internal temperature sensor; if so, requesting to recalibrate or replace the outside temperature and the air temperature sensor and continuing to collect temperature data;
s4, for the recalibration or replacement of the outside temperature and air temperature sensors, judging whether the counter points are abnormal, if so, requesting to replace the inside temperature sensors, and then continuously collecting the inside temperature, the outside temperature and the air temperature data by the MCU; otherwise, the sensor is normal.
Preferably, the time interval between the data collection and the comparison in the step (2) is 10 minutes, the temperature precision required by the comparison is 0.1 ℃, namely, the difference between any two data of the internal temperature, the external temperature and the air temperature is not more than 0.1 ℃ at the set point determined by the program.
Preferably, the water film-forming fire extinguishing agent storage tank is made of stainless steel, is erected on the ground by support legs and is not directly irradiated by sunlight, and the external temperature sensor is arranged below the liquid level and is coated by the heat insulation block.
The water film-forming fire extinguishing agent is a high-concentration sol solution with 70% of water and 30% of solute.
The storage tank contains enough water film-forming fire extinguishing agent, and transient heat balance can be realized inside and outside the storage tank in the day and night alternating process, so that curves of internal temperature, external temperature and air temperature periodically meet at one point, namely the table point is checked.
Preferably, a DS18B20 series low-cost temperature sensor is adopted, and the temperature measurement precision is 0.1 ℃.
Experiments show that when the stainless steel storage tank is provided with the support legs, the liquid stored in the stainless steel storage tank is high-concentration sol, and the storage position is not directly irradiated by sunlight, as the requirements of (1) the high-concentration sol has higher specific heat capacity and better heat transfer performance, (2) the stainless steel tank body has better heat transfer performance and lower specific heat capacity, (3) the stainless steel storage tank is provided with the support legs, so that the contact area with the ground is smaller, and (4) the stainless steel storage tank is not directly irradiated by sunlight and other 4 characteristics are met, the temperature in the tank body is mainly influenced by the air temperature. The internal temperature will fluctuate smoothly and repeatedly in day and night following the air temperature. The external temperature is always between the air temperature and the internal temperature, which means that the external temperature is responsible for the heat exchange between the liquid in the tank and the external air.
The specific case that the heat transfer phenomenon is formed under certain conditions is shown as the table points, and the specific requirements are as follows: (1) the storage tank body basically only exchanges heat with air and cannot be directly irradiated by sunlight, (2) the tank body needs to have better heat transfer capacity and smaller heat capacity, and (3) the liquid in the tank has larger heat capacity and better heat transfer performance. Since the water film-forming fire extinguishing agent tank satisfies the above conditions, it is possible to check whether or not zero drift occurs in the internal temperature sensor (main sensor) by using the counter point.
The invention uses 3 temperature sensors to respectively transmit the temperature of the inner part of the storage tank, the outer wall of the storage tank and the air to the microcontroller, the heat transmission inside and outside the storage tank is periodically and temporarily stopped under a certain condition, and the 3 transmitted temperatures are equal, thereby realizing the automatic calibration of the temperature sensors in the water film-forming fire extinguishing agent by a program designed at the microprocessor end. The advantages are as follows:
the advantage of using the counter point is that (1) the working condition of the main sensor in the fire extinguishing agent liquid can be checked only by using the temperature sensors arranged on the outer wall and in the air, and because the water film-forming fire extinguishing agent has corrosiveness, the life expectancy of the water film-forming fire extinguishing agent and the main sensor is far longer than that of the main sensor, and compared with the case that a plurality of main sensors are arranged in the tank, the cost is saved; (2) the MCU can judge the fault and guide the disposal by simple cyclic comparison operation without processing a complex heat transfer formula with a large number of parameters.
Drawings
FIG. 1: the arrangement mode of the sensor is indicated;
FIG. 2 is a drawing: a typical curve change rule of internal temperature, external temperature and air temperature;
FIG. 3: FIG. 2 is a partial enlargement highlighting the points of the pair at 4780 minutes;
FIG. 4 is a drawing: a logic block diagram of MCU for main sensor correction;
the reference numbers in the figures illustrate:
1-water film-forming fire extinguishing agent storage tank; 2-the inner water forms the liquid level of the film-forming fire extinguishing agent;
3-internal temperature sensor; 4-external temperature sensor; 5-air temperature sensor; respectively connected with a microprocessing unit 6-MCU;
7-insulating block; 8-support leg.
Detailed Description
The device is realized by respectively connecting an internal temperature sensor 3 arranged below the liquid level 2 of the water film-forming fire extinguishing agent in a water film-forming fire extinguishing agent storage tank 1, an external temperature sensor 4 and an air temperature sensor 5 on the outer wall of the water film-forming fire extinguishing agent storage tank 1 with a microprocessing unit MCU (microprogrammed control Unit), wherein the internal temperature sensor 3 is arranged in the water film-forming fire extinguishing agent storage tank 1 as a main sensor, the automatic calibration of the main sensor is realized by 1 air temperature sensor 5 arranged outside the storage tank and 1 external temperature sensor arranged on the wall of the storage tank, and the specific arrangement mode of the hardware is shown in the attached drawing 1.
The water film-forming fire extinguishing agent storage tank 1 is a stainless steel storage tank and is erected on the ground through support legs 8 and is not directly irradiated by sunlight, and the external temperature sensor 4 is arranged below the liquid level 2 of the water film-forming fire extinguishing agent and is coated by a heat insulation block 7.
The temperature data returned by the 3 temperature sensors are continuously monitored by the MCU to obtain 3 temperature curves which are respectively recorded as an inner temperature curve (corresponding to the main sensor), an outer temperature curve (corresponding to the outer wall sensor) and an air temperature curve (corresponding to the sensor arranged in the air). When the series of conditions are met, the fluctuation law of the curves of the internal temperature, the external temperature and the air temperature is shown in the attached figure 2. The greatest feature is that the temperature profile and the external temperature profile decrease rapidly from the evening of each day (about 17 hours) until the next morning (about 7 hours), during which time (about 21 nights) the internal temperature profile is traversed at an angle of more than 45 °. Experiments show that the curves of the internal temperature, the external temperature and the air temperature intersect at a point in the error range of the temperature sensor. The physical significance of this point is that when the internal temperature and the air temperature are equal, the heat exchange on the surface of the tank body of the aqueous film forming fire extinguishing agent storage tank 1 is temporarily stopped, and therefore the external temperature will also be equal to the internal temperature and the air temperature. Since the phenomenon of intersection of 3 lines at one point occurs constantly at about 21 nights each day, as if 3 sensors were performing a "table-pair" operation each day to verify the operating condition of each other, we define this phenomenon as a "table pair", the intersection point common to the three temperature curves is called the "table pair point", fig. 3 is a partial enlargement of fig. 2, and a table pair point located at 4780 minutes is marked. The various pairs of points are also identified by arrows in figure 2.
The specific implementation method comprises the following steps:
(1) the MCU6 plots the inside, outside and air temperatures synchronously, as shown in fig. 2 and 3, and identifies pairs of points therein by comparison.
(2) When the pair of meter points deviate, that is, the three temperature curves cannot intersect at one point within the error range, a correction program is started, zero point automatic calibration is firstly realized for the main sensor, whether the pair of meters can be realized again is judged, if not, a worker is guided to execute correction operation and judge whether the main sensor needs to be replaced, and the specific execution logic is shown in fig. 4.
In this embodiment, the temperature sensor is a low-cost sensor of DS18B20 series.
The sampling data interval of the MCU is 10 minutes, the judgment standard of the table points is +/-0.1 ℃ of each curve, and if the intersection of the three temperature curves can be realized, the main sensor is judged to work normally.
The system is installed on a water film-forming fire extinguishing agent storage tank 1 and continuously tracks:
(1) a rectangular vertical stainless steel storage tank with support legs and a length of 40 cm, a width of 20 cm and a height of 40 cm is filled with a water film-forming fire extinguishing agent, wherein the water film-forming fire extinguishing agent comprises the following components in percentage by weight: 70% of water, 12% of urea, 7% of CAB, 08109% of APG, 1% of JR-4001% and 1% of FC-1341%.
(2) Three temperature sensors of the type DS18B20 were mounted on the water-film fire extinguishing agent tank 1 in the manner shown in FIG. 1 and connected to the MCU 6.
(3) The returned data of the three temperature sensors are continuously recorded at the MCU terminal according to a set program, the time periods of the recorded data and the processed data are both 10 minutes, the 'counter-point' is identified through cyclic comparison, the data of the internal temperature, the external temperature and the air temperature are obtained, and the data are drawn as shown in attached figures 2 and 3.
(4) When the comparison point is abnormal, namely the difference between any two data of the internal temperature, the external temperature and the air temperature exceeds 0.1 ℃ at the comparison point determined by the program, the automatic calibration program is started, and the working logic is as shown in the attached figure 4:
s1, continuously collecting the data of the internal temperature, the external temperature and the air temperature by the MCU, and forming an internal temperature curve, an external temperature curve and an air temperature curve by the temperature data collected in a specified time interval;
s2, judging whether the counter point is abnormal or not, and if not, judging that the sensor is normal; if so, correcting the internal temperature deviation value to enable the three-line unification of the meter points and continuously collecting data;
s3, after correcting the over-internal temperature deviation value, continuously judging whether the counter point is abnormal, if not, setting a new deviation value for the internal temperature sensor; if so, requesting to recalibrate or replace the outside temperature and the air temperature sensor and continuing to collect temperature data;
s4, for the recalibration or replacement of the outside temperature and air temperature sensors, judging whether the counter points are abnormal, if so, requesting to replace the inside temperature sensors, and then continuously collecting the inside temperature, the outside temperature and the air temperature data by the MCU; otherwise, the sensor is normal.
The advantage of using the counter point is that (1) the working condition of the main sensor in the fire extinguishing agent liquid can be checked only by using the temperature sensors arranged on the outer wall and in the air, and because the water film-forming fire extinguishing agent has corrosiveness, the life expectancy of the water film-forming fire extinguishing agent and the main sensor is far longer than that of the main sensor, and compared with the case that a plurality of main sensors are arranged in the tank, the cost is saved; (2) the MCU can judge the fault and guide the disposal by simple cyclic comparison operation without processing a complex heat transfer formula with a large number of parameters.
The above examples are merely illustrative for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (7)
1. The automatic calibration method of the temperature sensor in the water film-forming fire extinguishing agent is characterized in that the automatic calibration method is realized by connecting 3 temperature sensors arranged at different positions with a microprocessing unit (MCU), and comprises the following steps:
(1) respectively placing 3 calibrated temperature sensors in the inner liquid surface, the outer wall and the external air of the water film-forming fire extinguishing agent stainless steel storage tank, and connecting the temperature sensors with the MCU; the temperature data generated by the three are recorded as the internal temperature, the external temperature and the air temperature respectively, and the MCU collects the data every 10 minutes and synchronously draws the temperature curves generated by the three; from evening to morning of the second day, the air temperature and the external temperature enter a descending interval and are intersected with the internal temperature curve; when the temperature sensors work normally, the three temperature curves are intersected at one point, which is called a pair of meter points;
(2) the MCU continuously tracks the pair of the table points through comparison logic, and when 3 continuous table points deviate, namely three curves cannot intersect at one point in an error range, a correction program is started to realize automatic correction or guide a worker to execute correction operation and judge whether the internal temperature sensor needs to be replaced.
2. The method for automatically calibrating a temperature sensor in an aqueous film forming fire extinguishing agent according to claim 1, wherein the calibration is started according to the following procedure:
s1, continuously collecting the data of the internal temperature, the external temperature and the air temperature by the MCU, and forming an internal temperature curve, an external temperature curve and an air temperature curve by the temperature data collected in a specified time interval;
s2, judging whether the counter point is abnormal or not, and if not, judging that the sensor is normal; if so, correcting the internal temperature deviation value to enable the three-line unification of the meter points and continuously collecting data;
s3, after correcting the over-internal temperature deviation value, continuously judging whether the counter point is abnormal, if not, setting a new deviation value for the internal temperature sensor; if so, requesting to recalibrate or replace the outside temperature and the air temperature sensor and continuing to collect temperature data;
s4, for the recalibration or replacement of the outside temperature and air temperature sensors, judging whether the counter points are abnormal, if so, requesting to replace the inside temperature sensors, and then continuously collecting the inside temperature, the outside temperature and the air temperature data by the MCU; otherwise, the sensor is normal.
3. The method for automatically calibrating a temperature sensor in an aqueous film-forming fire extinguishing agent according to claim 1 or 2, wherein the time interval between the data collection and the comparison in the step (2) is 10 minutes, and the comparison requires a temperature accuracy of 0.1 ℃, that is, at the set point determined by the program, the difference between any two of the internal temperature data, the external temperature data and the air temperature data is not more than 0.1 ℃.
4. The method according to claim 1, wherein the tank is made of stainless steel and is supported on the ground without direct sunlight, and the external temperature sensor is disposed below the liquid level and covered by a heat-insulating block.
5. The method according to claim 1, wherein the aqueous film-forming fire extinguishing agent in step (1) is a high concentration sol solution containing 70% water and 30% solute.
6. The method according to claim 1, wherein the tank of step (1) contains enough water film-forming fire-extinguishing agent and a transient thermal equilibrium between the inside and outside of the tank is achieved during the day and night alternation process, so that the curves of inside temperature, outside temperature and air temperature periodically meet at a point, i.e. a point-to-point relationship.
7. The method for automatically calibrating a temperature sensor in an aqueous film-forming fire extinguishing agent according to claim 1, wherein a DS18B20 series temperature sensor is adopted in the step (1), and the temperature measurement precision is 0.1 ℃.
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| CN115944878A (en) * | 2022-12-23 | 2023-04-11 | 上海纳米技术及应用国家工程研究中心有限公司 | Service life estimation device for vehicle-mounted water film-forming fire extinguishing agent |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115944878A (en) * | 2022-12-23 | 2023-04-11 | 上海纳米技术及应用国家工程研究中心有限公司 | Service life estimation device for vehicle-mounted water film-forming fire extinguishing agent |
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