Method and system for preventing condensation of ultrasonic liquid level meter

Abstract

A method and system for preventing condensation of an ultrasonic liquid level meter. The method comprises: connecting a heat tracing unit to an ultrasonic liquid level meter, and deploying a temperature monitoring module; on the basis of a measurement result of the monitoring module, calculating the dew point of the surface of a probe of the ultrasonic liquid level meter; and comparing the dew point with the surface temperature of the liquid level meter measured by the monitoring module and, on the basis of a heating control execution module, performing dynamic temperature control. By means of deploying the heating unit and the temperature monitoring module, the present invention measures the surface temperature of the probe in real time and, on the basis of the calculated dew point, dynamically adjusts heating power, such that the surface temperature of the probe is higher than the dew point temperature, thus effectively avoiding condensation and solving the effect of environment temperature and humidity on the precision of liquid level measurement.

Description

Preventing condensation method and system of ultrasonic liquid level meter TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial automation, and in particular to a preventing condensation method and system of ultrasonic liquid level meter. BACKGROUND

[0002] In recent years, with the continuous improvement of industrial automation, wireless remote monitoring technology has been widely used in various industries. Among them, the ultrasonic liquid level meter gradually becomes the mainstream product in the field of liquid level remote monitoring due to its advantages such as no need to directly contact the medium, wide measurement range, and convenient installation.

[0003] The traditional ultrasonic liquid level meter usually adopts a non-contact measurement principle, uses the difference in the propagation characteristics of sound velocity in different media to measure the time difference between the transmitted wave and the received wave, and then calculates the liquid level of the measured liquid. However, this measurement method is easily affected by the ambient temperature and humidity, especially in harsh environments, the probe surface is prone to condensation, which reduces the measurement accuracy and even causes failure. In order to solve this problem, the industry has proposed various methods to prevent condensation, such as using a protective cover to isolate the probe from the external environment, coating a condensation-preventing coating on the probe surface, etc. However, these methods have certain limitations, such as the protective cover increasing the measurement error, the coating easily aging and falling off, etc., and it is difficult to fundamentally solve the condensation problem.

[0004] Therefore, how to effectively prevent the condensation of the ultrasonic liquid level meter probe and ensure the accuracy and reliability of the measurement data has become a key technical problem to be solved. The present application proposes a preventing condensation method of ultrasonic liquid level meter, which is characterized by deploying a heating unit and a temperature monitoring module to detect the probe surface temperature in real time, and dynamically adjusting the heating power according to the calculated dew point, so that the probe surface temperature is higher than the dew point temperature, thereby effectively avoiding condensation and completely solving the influence of environmental temperature and humidity on the liquid level measurement accuracy, which has important theoretical significance and application value. SUMMARY

[0005] In view of the problems existing in the existing condensation prevention methods, the present application is proposed.

[0006] Therefore, the problem to be solved by the present application is that it is difficult to fundamentally solve the condensation problem.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a preventing condensation method of ultrasonic liquid level meter, which comprises,

[0009] Detecting the probe surface temperature of an ultrasonic liquid level meter and the environmental humidity, and calculating the dew point temperature of the probe surface of the ultrasonic liquid level meter according to the temperature and humidity;

[0010] Comparing the difference between the dew point temperature and the probe surface temperature, determining a heating control parameter according to the difference and the environmental humidity;

[0011] Controlling the heating unit to heat the probe of the ultrasonic liquid level meter according to the heating control parameter, so that the probe surface temperature is higher than the safety threshold of the dew point temperature to prevent dewing.

[0012] As a preferred scheme of the dewing prevention method of the ultrasonic liquid level meter, wherein: the dew point temperature is calculated according to the relationship between the dew point temperature, the saturated water vapor pressure and the relative humidity, comprising the following steps:

[0013] Improving the semi-empirical formula;

[0014] Obtaining the optimal empirical coefficient by big data fitting;

[0015] Calculating the dew point temperature according to the improved semi-empirical formula.

[0016] As a preferred scheme of the dewing prevention method of the ultrasonic liquid level meter, wherein: the dew point also includes judging whether to heat according to the dew point and the relative humidity, as follows:

[0017] When the temperature difference value is greater than twice the safety temperature difference threshold, it means that the temperature difference is large, and the liquid level meter is in a relatively safe state, without considering the humidity factor and without heating operation; the temperature difference value is the measured ultrasonic liquid level meter probe surface value minus the dew point value;

[0018] When the temperature difference value is greater than the safety temperature difference threshold but less than twice the safety temperature difference threshold, it means that the temperature difference is moderate, and further judgment is performed: when the temperature difference value is greater than 0 and the relative humidity is greater than n, the medium power preventive heating is performed; when the relative humidity is greater than m but less than or equal to n, the small power heating is performed; when the relative humidity is less than m, the operation without heating is performed; if the temperature difference is less than 0 and the absolute humidity is greater than n, the maximum power heating is performed; when the absolute humidity is greater than m and less than n, the large power heating is performed; when the relative humidity is less than m, the large power heating is performed.

[0019] When the absolute value of the temperature difference value is less than or equal to the safety threshold, it means that the temperature difference is small, and the liquid level meter is in a critical state, and further judgment is performed: when the temperature difference value is greater than 0 and the relative humidity is greater than n, the large power heating is performed; when the relative humidity is greater than m and less than or equal to n, the medium power heating is performed; when the relative humidity is less than m, the small power preventive heating is performed; if the temperature difference value is less than 0 and the relative humidity is greater than m, the maximum power heating is performed; when the relative humidity is less than m, the large power heating is performed.

[0020] As a preferred scheme of the method for preventing dew formation of the ultrasonic liquid level meter, the dynamic temperature control is performed by a silicon controlled rectifier (SCR) voltage regulating circuit.

[0021] The voltage regulating circuit comprises,

[0022] A direct current voltage is obtained through a rectifier filter circuit, the direct current voltage is connected to an anode of the SCR, a cathode of the SCR is connected to one end of a heating tape, a gate of the SCR is connected to a PWM output of a microcontroller for providing a trigger pulse signal, the other end of the heating tape is grounded, and an interference suppression circuit comprising an RC notch circuit and a protection diode is connected in parallel across the SCR.

[0023] As a preferred scheme of the method for preventing dew formation of the ultrasonic liquid level meter, the dynamic temperature control is regulated according to a control algorithm.

[0024] The control algorithm comprises the following steps:

[0025] A fractional order is used to replace a classical integral.

[0026] A temperature and humidity correction is performed.

[0027] The original actual power is added to the control algorithm to obtain a corrected power value.

[0028] As a preferred scheme of the method for preventing dew formation of the ultrasonic liquid level meter, the corrected power value is combined with the temperature and humidity correction and the original actual power, and is shown in the following formula:

[0029] ;

[0030] wherein, P out is an output, ΔP is a power deviation, K P , K i、 K d are proportional, integral and differential coefficients, n is a fractional order integrator parameter, and Γ is a Gamma function. is a fractional order differential operator, is a fractional order differential order, is a temperature and humidity correction function, is a liquid level meter surface temperature, is a dew point temperature, and RH is a relative humidity. is an original actual power.

[0031] As a preferred scheme of the method for preventing dew formation of the ultrasonic liquid level meter, the dynamic adjustment is performed according to the corrected power value.

[0032] When the liquid level meter probe surface temperature value is greater than the dew point value, the power value of the heat tracing band is set to a smaller holding power, and when the liquid level meter probe surface temperature value is less than the dew point value, the actual power output of the current heat tracing band is measured in real time, the power deviation is calculated, and is substituted into the control algorithm, and the control algorithm calculates the adjusted power output;

[0033] If the adjusted power data is greater than the maximum power of the heat tracing band, the heat tracing band is driven to heat according to the maximum power, and otherwise, the heat tracing band is driven to heat according to the adjusted power.

[0034] In a second aspect, an embodiment of the present application provides a dew prevention system of an ultrasonic liquid level meter, which comprises:

[0035] The dew prevention system and the heat tracing unit;

[0036] The dew prevention system comprises a detection module, a dew point calculation module and a heating control execution module;

[0037] The monitoring module is used to install high-precision temperature sensors at key positions of the liquid level meter, and to monitor the surface temperature of the liquid level meter and the air temperature and humidity in real time;

[0038] The dew point calculation module is used to calculate the current dew point temperature by using a formula or a table lookup method based on the measured temperature and humidity data;

[0039] The heating control execution module is used to start heating control if the surface temperature of the liquid level meter is lower than the set value of the dew point temperature, and to adjust the power of the heat tracing band by using a thyristor so that the temperature is maintained within a safe value range above the dew point temperature;

[0040] The heat tracing unit heats according to the heating control parameters of the heating control execution module.

[0041] In a third aspect, an embodiment of the present application provides a computer device, which comprises a memory and a processor, and the memory stores a computer program, wherein: the processor implements any step of the dew prevention method of the ultrasonic liquid level meter when executing the computer program.

[0042] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, wherein: the computer program is executed by a processor to implement any step of the dew prevention method of the ultrasonic liquid level meter.

[0043] The present application has the beneficial effects that by deploying the heating unit and the temperature monitoring module, the probe surface temperature is detected in real time, the heating power is dynamically adjusted according to the calculated dew point, the probe surface temperature is higher than the dew point temperature, the dew generation is effectively avoided, the influence of the environmental temperature and humidity on the liquid level measurement accuracy is completely solved, and the present application has important theoretical significance and application value. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Fig. 1 is a diagram showing that the time of signal emission to reception of the dew prevention method of the ultrasonic liquid level meter is proportional to the liquid level in the container.

[0046] Fig. 2 is a false echo diagram of the dew prevention method of the ultrasonic liquid level meter.

[0047] Fig. 3 is an entity experiment diagram of the dew prevention method of the ultrasonic liquid level meter. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings in the specification. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0049] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0050] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment that excludes other embodiments.

[0051] The present application is described in detail in conjunction with the schematic drawings, and in the detailed description of the embodiments of the present application, the cross-sectional view of the device structure will be partially enlarged without the general proportion for the convenience of illustration, and the schematic drawings are only examples which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in the actual manufacture.

[0052] Meanwhile, in the description of the present application, it should be noted that the terms "upper, lower, inner and outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first, second or third" are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0053] In the present application, unless otherwise explicitly specified and limited, the terms "mounting, connection, connection" should be understood broadly, for example: it can be fixed connection, detachable connection or integral connection; it can also be mechanical connection, electrical connection or direct connection, it can also be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0054] Embodiment 1

[0055] Referring to FIGS. 1 and 2, the first embodiment of the present application provides a method for preventing dew condensation of an ultrasonic liquid level meter, comprising:

[0056] S1: The ultrasonic liquid level meter is connected to the heat tracing unit, and the temperature monitoring module is deployed.

[0057] The heat tracing tape is wound around the ultrasonic liquid level meter and connected to the heat tracing tape power cabinet, and the upper part is covered with thermal insulation cotton.

[0058] Among them, the aluminum-plated heating element electric heat tracing tape is selected, which has large heating capacity and can provide high linear power output of 180-300W / m. In order to ensure that the heat is evenly distributed along the tape body without hot spot phenomenon, parallel heating element design is adopted. The outer sheath is made of flame-retardant silicone rubber or fluoroplastic braid, which is waterproof and corrosion-resistant, and has long service life. The outer diameter is less than 10mm, which is convenient for winding and reduces thermal inertia. The overall structure is compact, suitable for installation in small space of liquid level meter probe.

[0059] The thermal insulation cotton uses nano aerogel felt with an aluminum foil surface, and the thermal resistance is as low as 0.033m 2K / W, the aerogel micropore diameter is only 2-50nm, realizing nanometer thermal insulation, aiming at flame retardant and hydrophobicity, the flame retardant level reaches A1 level, non-combustion, non-toxic smoke release super-hydrophobic surface, moisture-proof and mildew-proof. 。

[0060] Further, in order to ensure that the electric heat tracing band can automatically keep the best prevention dew condensation condition according to the temperature and humidity of the surrounding environment, a temperature control switch is provided for the electric heat tracing band, the temperature control switch has a manual / automatic heating control and temperature calibration function. And high-precision temperature and humidity sensors are installed on the surface of the probe and the electric heat tracing band.

[0061] The temperature and humidity sensors on the surface of the probe are used to detect the temperature and humidity of the ultrasonic level meter probe. When the temperature of the air outside the probe is higher than the temperature on the surface of the probe, and the humidity of the outside air is also too high, a large amount of dew will condense on the surface of the probe. When the probe surface dew condenses, it will produce "false echo" and affect the measurement. The specific performance is: 1, liquid level sudden rise; 2, liquid level frequent large swing.

[0062] Further, the analog-to-digital converter (ADC) collects the analog voltage signal of the sensor interface circuit and converts it into a digital quantity and transmits it to the CPU, and adopts multiplexing, multiple ADCs are connected to multiple temperature sensors, and the surface temperature of the ultrasonic level meter, the current environment temperature, the external environment humidity and the like are collected and transmitted to the CPU.

[0063] S2: calculating the dew point of the surface of the ultrasonic level meter probe according to the detection result of the detection module.

[0064] According to the measurement value of the sensor collected by the ADC, the dew point temperature of the probe surface is calculated, and the specific process is as follows:

[0065] Based on the Magnus formula, the formula calculates the saturation water vapor pressure es at a given temperature T, but does not directly give the calculation method of the dew point temperature Td. According to the thermodynamic principle, the dew point temperature Td and the saturation water vapor pressure es and the relative humidity RH exist the following function relationship:

[0066] Td=f(es,RH)

[0067] Compared with Magnus-Tetens approximate formula, Magnus-Tetens approximate formula can more accurately calculate Td:

[0068]

[0069] Wherein, A=17.62, B=243.12℃, C=0.0184℃, arctanh is the inverse hyperbolic tangent function.

[0070] In order to take the influence of relative humidity RH into account and improve the scope of application, the above formula is improved as follows:

[0071]

[0072] The term (1-RH) is introduced to extend the scope of application of the formula from RH=100% to any RH value. However, it is found in practice that the temperature T also has a certain nonlinear influence on the dew point temperature, so a trigonometric function term is introduced to correct it:

[0073]

[0074] where D, E, F, G, and H are empirical coefficients, ln is the natural logarithm, and cos and sin are the cosine and sine functions, respectively.

[0075] It should be noted that the numerical fitting method is used to solve these empirical coefficients. First, a large number of actual measured temperature T, relative humidity RH, and corresponding dew point temperature Td data samples are collected, and the collected data are divided into training set and test set two parts, and the difference between the predicted dew point temperature and the actual value is measured according to the mean square error (MSE):

[0076]

[0077] where N is the total number of data samples, is the predicted dew point temperature, is the actual dew point temperature. The training set data is substituted into the formula, and the numerical optimization algorithm (such as gradient descent, L-BFGS, etc.) minimizezer is used to minimize the cost function MSE by continuously adjusting the values of the empirical coefficients D, E, F, G, and H, so that the cost function MSE is minimized. When the cost function converges to a minimum value, the corresponding D, E, F, G, and H values are the optimal empirical coefficients.

[0078] And when the ambient temperature T and relative humidity RH are known, es can be calculated by the following formula:

[0079]

[0080] Substitute es into the improved Magnus-Tetens formula to calculate the accurate dew point temperature Td. It is worth mentioning that the improved formula of the present scheme is applicable to the temperature range of-45℃<T<60℃, and the error is less than 0.35℃.

[0081] Further, the temperature difference value Δ and the safety temperature difference threshold value are defined, where the temperature difference value Δ is defined as the measured ultrasonic liquid level meter probe surface value minus the dew point value, and the safety temperature difference threshold value is artificially set. Preliminary judgment is made on Δ: Δ> It indicates that the temperature difference is large, the liquid level meter is in a relatively safe state, and the humidity factor does not need to be considered, and heating operation is not required.

[0082] When It indicates that the temperature difference is moderate, and further judgment is performed. If Δ>0 and RH>80%, medium-power preventive heating is performed; if 60%<RH≤80%, small-power heating is performed; and if RH≤60%, heating operation is not required. If Δ<0, maximum-power heating is performed when RH>80%; large-power heating is performed when 60%<RH≤80%; and medium-power heating is performed when RH≤60%.

[0083] When It indicates that the temperature difference is small, and the liquid level meter is in a critical state. Further judgment is performed. If Δ>0 and RH>80%, large-power heating is performed; if 60%<RH≤80%, medium-power heating is performed; and if RH≤60%, small-power preventive heating is performed. If Δ>0 and RH>60%, maximum-power heating is performed; and if RH≤60%, large-power heating is performed.

[0084] It indicates that the temperature of the liquid level meter has been lower than the dew point temperature, and serious dewing is likely to occur, and maximum-power heating operation needs to be immediately performed.

[0085] S3: Comparing the dew point with the liquid level meter surface temperature detected by the detection module, dynamic temperature control is performed according to the heating control execution module.

[0086] The temperature control of the heat tracing band is controlled by a silicon controlled rectifier (SCR). The silicon controlled rectifier is a semi-controlled power electronic device. The effective value of an alternating current circuit can be adjusted by controlling the conduction angle. A corresponding SCR voltage regulating circuit is provided. The circuit adjusts the effective value of the alternating current circuit by controlling the conduction angle of the SCR, thereby controlling the heating power of the heat tracing band. The connection is as follows:

[0087] An alternating current power supply obtains a direct current voltage Vdc through a rectification and filtering circuit. Vdc is connected to the anode of the SCR. The cathode of the SCR is connected to one end of the heat tracing band. The gate of the SCR is connected to the PWM output of the microcontroller, which is used to provide a trigger pulse signal. The other end of the heat tracing band is grounded. An interference suppression circuit is connected in parallel across the SCR, including an RC notch circuit and a protection diode.

[0088] By adjusting the duty cycle of the PWM signal, the time of SCR conduction can be changed, thereby controlling the effective current passing through the heat tracing band and realizing power regulation.

[0089] Further, according to the judgment logic of the aforementioned temperature control module, the required heating power setting value is obtained, the actual power output of the current heat tracing band is measured, the power deviation is calculated, and then the output of the controller is adjusted according to ΔP through the PID control algorithm.

[0090] The classical PID control algorithm is applied to the heat tracing band power control, as shown in the following formula:

[0091]

[0092] wherein, is the controller output, and ΔP is the power deviation, , , are proportional, integral and differential coefficients, respectively.

[0093] Since the classical integral in the classical PID is sensitive to noise, it is replaced by a fractional integral, and since the classical differential amplifies high-frequency noise, it is replaced by a fractional differential:

[0094]

[0095] wherein n is a fractional differential integrator parameter, and Γ is a Gamma function. When n = 1, it is equivalent to a classical integral; when 0 < n < 1, it has a smoothing filtering effect. is a fractional differential operator, is a fractional differential order (0 <1). When = 1, it is equivalent to a classical differential; when 0 <1, it has an inhibitory effect on high-frequency noise.

[0096] Further, in order to match the control output with the actual environmental state, a correction function is introduced:

[0097]

[0098] wherein, are temperature and humidity correction functions, is the liquid level gauge surface temperature, is the dew point temperature, and RH is the relative humidity. The function can be designed according to the actual situation, for example, when is much higher than , tends to 1 and does not need to be corrected; when is close to , gradually increases to increase the power output.

[0099] Finally, to ensure power continuity, the original actual power is added:

[0100]

[0101] Through the above steps, the temperature and humidity correction functions are introduced on the basis of the classic PID algorithm, and the optimized and improved power control formula of the heat tracing band in line with the scheme is finally obtained. It not only has stronger noise suppression ability and control performance, but also can dynamically adjust the control output according to the actual environmental state, so as to realize the intelligent control of the heating power of the heat tracing band.

[0102] Need to be explained, , , The coefficient acquisition needs to be carried out through parameterized experiment. First, the mathematical model equation of the heat tracing band heating system is established to describe the relationship between the input and output. The corresponding differential equation model is established by using the heat conduction principle and the law of conservation of energy. The proportional, integral and differential coefficient rate deviation, are taken as free parameters and substituted into the mathematical expression of the controller, so that these parameters can be used to describe the dynamic characteristics of the controller. Specifically, according to the known heat conduction equation:

[0103]

[0104] Where, ρ is the density, c is the specific heat capacity, T is the temperature, t is the time, k is the thermal conductivity, and q is the heat source term.

[0105] For the heat tracing band heating system, it is simplified to one-dimensional case, and the control input is introduced, that is, the heating power of the heat tracing band:

[0106]

[0107] Where, x is the spatial coordinate, is the position of the heat tracing band, is the Dirac delta function.

[0108] By applying appropriate boundary conditions and initial conditions, the analytical or numerical solution of the system can be obtained, which describes the response of the temperature T(x,t) to the heating power .

[0109] Through the above established mathematical model of the heat tracing band heating system, the following steps are used to obtain the parameters of the PID controller , , :

[0110] The continuous-time differential equation model is discretized to obtain a discrete-time model:

[0111]

[0112] where x(k) is the state variable, is the control input (heating power), Ad and Bd are the discretized system matrices;

[0113] Further, an incremental PID controller is used, and the control rate is:

[0114]

[0115] where e(k) is the tracking error, i.e., the difference between the set value and the actual output, i.e., , u(k) is the control input, i.e., .

[0116] Further, the incremental PID controller is coupled with the controlled object (discrete-time model) to obtain a closed-loop system model:

[0117]

[0118] where , Γ is a system matrix, which depends on Ad, Bd and the sampling period.

[0119] Select an appropriate performance index J, and construct the objective function, i.e., minimize j, which is equivalent to minimizing the function of J with respect to , , :

[0120]

[0121] An optimization algorithm is used to solve the above objective function to obtain the optimal values of , , , and then the obtained values are substituted into the closed-loop system model for verification, and the coefficients based on the coefficients can be calculated .

[0122] Further, the maximum power of the heating band , and the control objective is to maintain the surface temperature of the liquid level gauge at 2 degrees above the dew point temperature.

[0123] The set power value is obtained, i.e., a step function is designed, when , ; when , (One smaller holding power). Current , therefore .

[0124] Measuring actual power output , the heater tape controller will measure the actual power output of the current heater tape in real time, assuming the initial value = 0W. Calculate the power deviation ΔP, .

[0125] Further, using the PID parameters obtained in the previous , , Calculate the control increment ΔU, add the original actual power and the temperature and humidity correction to get the specific power size that needs to be corrected , when exceeds the maximum power of the heater tape , then the heater tape will heat according to the maximum power , when Rises to the required temperature, it will switch to , the heater tape turns to small power to keep heating, if Continue to rise to Above, stop heating, and wait for Fall.

[0126] Repeat the above closed-loop control, the system will continue to monitor , And RH, repeat the above process to achieve dynamic control of the surface temperature of the liquid level meter.

[0127] Further, the embodiment also provides a dew prevention system for an ultrasonic liquid level meter, comprising:

[0128] A dew prevention system and a heating unit;

[0129] The dew prevention system comprises a detection module, a dew point calculation module and a heating control execution module;

[0130] The monitoring module is used for installing high-precision temperature sensors at key parts of the liquid level meter to monitor the surface temperature of the liquid level meter and the air temperature and humidity in real time;

[0131] The dew point calculation module is used for calculating the current dew point temperature based on the measured temperature and humidity data by using a formula or a table lookup method;

[0132] The heating control execution module is used for starting heating control if the surface temperature of the liquid level meter is lower than the set value of the dew point temperature, and adjusting the power of the heater tape by a thyristor to maintain the temperature of the heater tape in a safe value range above the dew point temperature;

[0133] The heat tracing unit heats according to a heating control parameter of the heating control execution module.

[0134] The embodiment further provides a computer device suitable for the method for preventing dew formation of the ultrasonic liquid level meter, including a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions to realize the method for preventing dew formation of the ultrasonic liquid level meter proposed in the above embodiment.

[0135] The computer device can be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for running of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to perform wired or wireless communication with external terminals, and the wireless communication can be realized through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or can be a key, a trackball or a touchpad arranged on the shell of the computer device, or can be an external keyboard, a touchpad or a mouse and the like.

[0136] The embodiment further provides a storage medium having a computer program stored thereon, and the program is executed by a processor to realize the method for preventing dew formation of the ultrasonic liquid level meter proposed in the above embodiment.

[0137] The storage medium proposed in the embodiment belongs to the same inventive concept as the data storage method proposed in the above embodiment, and the technical details not described in the embodiment can be referred to the above embodiment, and the embodiment has the same beneficial effects as the above embodiment.

[0138] Embodiment 2

[0139] Referring to FIG. 1, a second embodiment of the present application is provided, and the embodiment provides a method for preventing dew formation of an ultrasonic liquid level meter. In order to verify the beneficial effects of the present application, economic benefit calculation and simulation experiments are performed for scientific demonstration.

[0140] In order to verify the feasibility and effectiveness of the scheme, the present application performs the following tests:

[0141] 1) One ultrasonic liquid level meter is prepared, the model is LU78, and the measurement range is 0-10m;

[0142] 2) for its surrounding winding aluminum heater electric heat tracing band 1, model JCR220V, rated power 220W / m;

[0143] 3) cover the liquid level meter probe above the nano aerogel felt 1, thickness 50mm;

[0144] 4) install double channel temperature and humidity sensor 3, 1 probe surface, 2 environment, model SHT35;

[0145] 5) install main control module 1, integrated AT89C51 single chip microcomputer, A / D converter ADC0809;

[0146] 6) install heat tracing band controller 1, using fractional order PID control algorithm, SCR silicon controlled rectifier regulation;

[0147] 7) after connecting all parts, place the whole system in a constant temperature and humidity chamber, simulate various environmental conditions;

[0148] 8) solidification software algorithm, initialization device parameters, start data collection;

[0149] Among them, in the software algorithm, the environmental temperature T, relative humidity RH and the empirical coefficient values of D, E, F, G, H in formula (8) are respectively:

[0150] D=0.963, E=17.27, F=237.7, G=6.112, H=0.09035. Δ is 2℃, 1℃.

[0151] PID parameters are obtained by mathematical modeling + optimization algorithm: =1.5, =0.5, =0.2, α=0.85, n=0.6. The specific experimental data are as follows:

[0152] Table 1 experimental data table

[0153]

[0154] From the above table, under various different environmental temperature and humidity conditions, compared with the traditional equipment, the improved device of the application can make the liquid level meter probe surface temperature Ts maintain above the safe value of dew point temperature Td.

[0155] As serial numbers 1 and 2, when T=25℃, RH=60%, the traditional equipment Ts=11.8℃, which is lower than Td=12.4℃ 0.6℃, which is extremely likely to occur dew; while the improved equipment Ts=14.2℃, which is higher than Td 2.8℃, which is in a safe state.

[0156] The difference between Ts and Td is 2.4℃, which effectively avoids dew.

[0157] When the serial numbers are 5 and 6, although RH is as high as 80%, the temperature difference Δ is still 1.7℃, which also avoids dew.

[0158] When the serial numbers are 7 and 8, T is as low as 15℃, but Ts can be maintained at a safe value of 9.2℃, which is 2.2℃ higher than Td.

[0159] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method of preventing condensation in an ultrasonic liquid level meter, characterized by: The application relates to a method for controlling the temperature of an ultrasonic liquid level meter probe, comprising the following steps: detecting the probe surface temperature and the ambient humidity of the ultrasonic liquid level meter, and calculating the dew point temperature of the probe surface of the ultrasonic liquid level meter according to the temperature and humidity; comparing the difference between the dew point temperature and the probe surface temperature, determining a heating control parameter according to the difference and the ambient humidity; controlling the heating unit to heat the probe of the ultrasonic liquid level meter according to the heating control parameter, so that the probe surface temperature is higher than a safety threshold of the dew point temperature, to prevent dewing.

2. The method of preventing dew condensation of an ultrasonic liquid level meter according to claim 1, characterized by: The dew point temperature is calculated according to the relationship between the dew point temperature, the saturated water vapor pressure and the relative humidity, and comprises the following steps: improving a semi-empirical formula; obtaining optimal empirical coefficients by using big data fitting; calculating the dew point temperature according to the improved semi-empirical formula.

3. The method of claim 2, wherein the ultrasonic liquid level meter is a probe type ultrasonic liquid level meter. The dew point also comprises judging whether to heat according to the dew point and the relative humidity, as follows: when the temperature difference value is greater than twice the safety temperature difference threshold, it is indicated that the temperature difference is large, and the liquid level meter is in a relatively safe state, and the humidity factor does not need to be considered, and no heating operation is needed; the temperature difference value is the measured ultrasonic liquid level meter probe surface value minus the dew point value; when the temperature difference value is greater than the safety temperature difference threshold but less than twice the safety temperature difference threshold, it is indicated that the temperature difference is moderate, and further judgment is performed; when the temperature difference value is greater than 0 and the relative humidity is greater than n, medium-power preventive heating is performed; when the relative humidity is greater than m but less than or equal to n, small-power heating is performed; when the relative humidity is less than m, no heating operation is needed; when the temperature difference value is less than 0 and the absolute humidity is greater than n, maximum-power heating is performed; when the absolute humidity is greater than m and less than n, large-power heating is performed; when the relative humidity is less than m, large-power heating is performed. when the absolute value of the temperature difference value is less than or equal to the safety threshold, it is indicated that the temperature difference is small, and the liquid level meter is in a critical state, and further judgment is performed; when the temperature difference value is greater than 0 and the relative humidity is greater than n, large-power heating is performed; when the relative humidity is greater than m and less than or equal to n, medium-power heating is performed; when the relative humidity is less than m, small-power preventive heating is performed; when the temperature difference value is less than 0 and the relative humidity is greater than m, maximum-power heating is performed; when the relative humidity is less than m, large-power heating is performed.

4. The method of claim 3, wherein the ultrasonic liquid level meter is a probe type ultrasonic liquid level meter. The dynamic temperature control is realized through a silicon controlled rectifier (SCR) voltage regulating circuit. The voltage regulating circuit comprises, a direct current voltage is obtained through a rectification and filtering circuit, the direct current voltage is connected with the anode of the SCR, the cathode of the SCR is connected with one end of a heating tape, the gate of the SCR is connected with the PWM output of a microcontroller, and is used for providing a trigger pulse signal; the other end of the heating tape is grounded, and an interference suppression circuit is connected in parallel at the two ends of the SCR, and the interference suppression circuit comprises an RC slit circuit and a protection diode.

5. The method of claim 4, wherein the ultrasonic liquid level meter is a probe type ultrasonic liquid level meter. The dynamic temperature control is realized according to a control algorithm. The control algorithm comprises the following steps: adopting a fractional order to replace a classical integral; performing temperature and humidity correction; adding the original actual power to the control algorithm to obtain a corrected power value.

6. The method of claim 5, wherein the ultrasonic liquid level meter is a probe type ultrasonic liquid level meter. The corrected power value is combined with the temperature and humidity correction and the original actual power, and is shown in the following formula: ； wherein for the controller output, ΔP is the power deviation, 、 、 respectively the proportional, integral and derivative coefficients, n is the fractional order differentiator parameter, and Γ is the Gamma function, for fractional derivative operators, for the fractional derivative order, for temperature and humidity correction functions, For liquid level gauge surface temperature, T is the dew point temperature, RH is the relative humidity, is the original actual power.

7. The method of claim 6, wherein the ultrasonic liquid level meter is a probe type ultrasonic liquid level meter. The dynamic adjustment is performed according to the corrected power value, When the liquid level meter probe surface temperature value is greater than the dew point value, the power value of the heat tracing band is set to a smaller holding power, and when the liquid level meter probe surface temperature value is less than the dew point value, the actual power output of the current heat tracing band is measured in real time, the power deviation is calculated, and substituted into the control algorithm, and the control algorithm calculates the adjusted power output; If the adjusted power data is greater than the maximum power of the heat tracing band, the heat tracing band is driven to heat according to the maximum power, otherwise it is heated according to the adjusted power.

8. A dew-prevention system for an ultrasonic liquid level meter, based on the dew-prevention method for an ultrasonic liquid level meter according to any one of claims 1 to 7, characterized by: Comprise, The anti-condensation system and the heat tracing unit; The anti-condensation system comprises a detection module, a dew point calculation module and a heating control execution module; The monitoring module is used to install high-precision temperature sensors at key positions of the liquid level meter, and to monitor the surface temperature of the liquid level meter and the air temperature and humidity in real time; The dew point calculation module is used to calculate the current dew point temperature based on the measured temperature and humidity data using a formula or a lookup table method; The heating control execution module is used to start heating control if the liquid level meter surface temperature is lower than the set value of the dew point temperature, and to adjust the power of the heat tracing band through a thyristor to maintain the temperature within a safe value range above the dew point temperature; The heat tracing unit heats according to the heating control parameters of the heating control execution module. 9.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is characterized in that: The processor executes the computer program to realize the steps of the anti-condensation method of the ultrasonic liquid level meter according to any one of claims 1-7.

10. A computer readable storage medium having stored thereon a computer program, characterized in that: The computer program is executed by the processor to realize the steps of the anti-condensation method of the ultrasonic liquid level meter according to any one of claims 1-7.

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