Temperature compensation algorithm of temperature sensor in water quality on-line monitor

Abstract

The invention provides a temperature compensation algorithm of a temperature sensor in a water quality online monitor. The temperature compensation formula is T corrected water temperature = T0-(T0-T1) / [1-1 / exp (t1 / t)], after the water temperature is calculated and corrected through a formula, the corrected water temperature close to the actual water temperature can be obtained within 1-4 minutes, the error is + / -0.3 DEG C to 1 DEG C, and about 20 minutes are needed in the traditional method; when the curve of the change of the corrected water temperature along with the time is gradually stable, the calculation end point is shown, and the temperature of the calculation end point is the corrected water temperature required by the target; therefore, formula calculation correction is carried out on the actually measured water temperature in a short time, the corrected temperature close to the actual water temperature is obtained and displayed on the instrument, and the monitoring efficiency and the monitoring accuracy are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature compensation algorithms for temperature sensors, and in particular relates to a temperature compensation algorithm for a temperature sensor in an online water quality monitoring instrument. Background Art

[0002] In aquaculture, fish tanks, etc., it is necessary to use online water quality monitors to monitor dissolved oxygen, pH, temperature, total nitrogen, etc. in the water. According to the actual needs of different sites, some small online water quality monitors only include three functions: dissolved oxygen, pH, and temperature. The dissolved oxygen sensor, pH sensor, and temperature sensor are set in a thick plastic sleeve, which is used for packaging and protection.

[0003] However, due to the thick tube wall of the rough plastic sleeve, the temperature sensor has poor contact with water. Since the thick tube wall is made of plastic with poor thermal conductivity, when the online water quality monitor is immersed in water, the measured temperature is obviously lower or higher than the actual water temperature. After slowly transferring heat to the temperature sensor from the outside to the inside, it takes about 20 minutes before the measured temperature of the online water quality monitor is basically the same as the actual water temperature, resulting in a slow response speed of the temperature sensor, which seriously affects the working efficiency of the online water quality monitor, and further seriously affects the normal operation of aquaculture, fish tanks, etc.

[0004] Therefore, how to provide a temperature compensation algorithm to perform formula calculation and correction on the measured water temperature in a short time, obtain a corrected temperature close to the actual water temperature and display it on the instrument, thereby improving monitoring efficiency and monitoring accuracy, is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a temperature compensation algorithm for a temperature sensor in an online water quality monitoring instrument.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A temperature compensation algorithm for the temperature sensor in an online water quality monitor. The temperature compensation formula is:

[0008] T 修正水温 =T0-(T0-T1) / [1-1 / exp(t1 / t)];

[0009] T0 is the actual water temperature measured by the temperature sensor when the water quality online monitor starts to correct the water temperature after being immersed in water (zero time point), in degrees Celsius;

[0010] t1 is the number of seconds from time zero to the current real time, in seconds;

[0011] T1 is the real-time measured water temperature of the temperature sensor at the current time t1, in degrees Celsius;

[0012] t is the time constant, t is 200.

[0013] Preferably, the temperature sensor is a platinum thermal resistor, and the platinum wire in the platinum thermal resistor includes the following elements in percentage by mass: 0.007%-0.009% Rh, 0.005%-0.007% Ir, 0.003%-0.005% Pd, 0.001%-0.003% La, 0.0005%-0.0015% Ce, 0.0005%-0.0015% Gd, 0.0005%-0.0015% Yb, the contents of Co, Cu, B, Si, and Cd are all less than 30ppm, and the balance is Pt.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects:

[0015] In the present application, when the curve of the corrected water temperature over time gradually becomes horizontal and stable and approaches a horizontal straight line without obvious up and down fluctuations, or when the corrected water temperature gradually becomes stable over time and no longer fluctuates obviously, it indicates that it is the calculation end point, and the temperature of the calculation end point is the corrected water temperature required for the target;

[0016] After calculation and correction by the formula provided in this application, the corrected water temperature close to the actual water temperature can be obtained in 1-4 minutes, with an error of ±(0.3℃-1℃), while the traditional method starts from immersion in water, and gradually transfers heat to the temperature sensor from the outside to the inside, and it takes about 20 minutes to display a stable apparent water temperature close to the actual water temperature;

[0017] The corrected water temperature calculated by the formula provided in this application is only a temperature required for emergency use and for a short period of time. When the immersion time in water is long enough, such as 3-6 hours, the apparent water temperature is naturally close to the actual water temperature due to sufficient heat transfer for a long enough time, and temperature compensation correction is no longer required at this time;

[0018] The corrected water temperature calculated by the formula provided in this application is an estimated temperature, and its error is much larger than the normal measurement error of the temperature measuring instrument. Therefore, the estimated temperature should be applied to ambiguous occasions and purposes, and cannot be used as an accurate and correct temperature to avoid causing production accidents;

[0019] This enables the measured water temperature to be corrected by formula calculation in a short period of time, and the corrected temperature close to the actual water temperature is obtained and displayed on the instrument, thereby improving monitoring efficiency and accuracy. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] This application provides a temperature compensation algorithm for a temperature sensor in an online water quality monitor. The temperature compensation formula is:

[0022] T 修正水温 =T0-(T0-T1) / [1-1 / exp(t1 / t)];

[0023] T0 is the actual water temperature measured by the temperature sensor when the water quality online monitor starts to correct the water temperature after being immersed in water (zero time point), in degrees Celsius;

[0024] t1 is the number of seconds from time zero to the current real time, in seconds;

[0025] T1 is the real-time measured water temperature of the temperature sensor at the current time t1, in degrees Celsius;

[0026] t is the time constant set according to different water quality online monitoring instruments, and t is 200.

[0027] In one embodiment of the present application, the temperature sensor is a platinum thermal resistor, and the platinum wire in the platinum thermal resistor includes the following elements in mass percentage: 0.007%-0.009% Rh, 0.005%-0.007% Ir, 0.003%-0.005% Pd, 0.001%-0.003% La, 0.0005%-0.0015% Ce, 0.0005%-0.0015% Gd, 0.0005%-0.0015% Yb, the contents of harmful elements Co, Cu, B, Si, and Cd are all <30ppm, and the balance is Pt;

[0028] The present application optimizes the composition formula of the platinum wire, so that the platinum wire and the platinum thermal resistor have a series of advantages such as high uniformity, high precision, high stability, long life, high response speed, and radiation resistance.

[0029] In the present application, the dissolved oxygen sensor in the online water quality monitor is a membrane electrode dissolved oxygen sensor or a fluorescence dissolved oxygen sensor.

[0030] In the present application, the function exp(x) represents a natural exponential function, that is, an exponential function with a real number e (e≈2.71828) as the base, and its expression is exp(x)=e x, an represents the product of n a's. The characteristic of this function is that its derivative is equal to itself. The natural exponential function is widely used in calculus, probability theory, statistics and other fields. It is used to describe the process of exponential growth or decay, as well as some distributions related to probability density functions.

[0031] In this application, thermal resistors are the most commonly used temperature sensors in the medium and low temperature zones; thermal resistor temperature measurement is based on the property that the resistance value of a metal conductor increases with the increase of temperature to measure temperature; its main features are high measurement accuracy and stable performance; among them, the measurement accuracy of platinum thermal resistors is the highest, and it is not only widely used in industrial temperature measurement, but also made into a standard reference instrument; thermal resistors are mostly made of pure metal materials, with platinum and copper being the most widely used. In addition, materials such as nickel, manganese and rhodium have begun to be used to manufacture thermal resistors; there are many types of temperature sensing materials commonly used for metal thermal resistors, and the most commonly used is platinum wire; in addition to platinum wire, the metal thermal resistor materials used for industrial measurement also include copper, nickel, iron, iron-nickel, etc. Platinum resistors, referred to as platinum thermal resistors, have resistance values ​​that change with temperature changes. It has a series of products such as PT100 and PT1000, etc. It is suitable for high-precision temperature equipment such as medical, motor, industry, temperature calculation, satellite, meteorology, resistance value calculation, etc., and has a very wide range of applications. Pt100 is a platinum thermal resistor, and its resistance value will change with the change of temperature. The 100 after pt means that its resistance value is 100 ohms at 0℃, and its resistance value is about 138.5 ohms at 100℃. Platinum thermal resistors include ceramic elements, glass elements, and mica elements. Platinum thermal resistors are made of platinum wires wound around ceramic frames, glass frames, and mica frames respectively, and then processed through complex processes.

[0032] The methods and devices not described in detail in the present invention are all prior art and will not be described in detail.

[0033] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0034] Example 1

[0035] Table 1 Calculation process data of Example 1 (measured water temperature is lower than actual water temperature and t is 200 and interval is 4 seconds)

[0036]

[0037]

[0038] According to Table 1 above, we can get that after 40 seconds, the corrected water temperature enters the same 37℃ range as the actual water temperature, and then the corrected water temperature gradually stabilizes around 37.50℃-37.70℃ within 40 seconds-80 seconds. The corrected water temperature after gradual stabilization can be regarded as the final corrected water temperature. Although the error with the actual water temperature is large, the corrected water temperature starts with 37, which is correct and indistinguishable from the actual water temperature, which is sufficient for some ambiguous occasions.

[0039] Example 2

[0040] Table 2 Calculation process data of Example 2 (measured water temperature is higher than actual water temperature and t is 200 and interval is 4 seconds)

[0041] Time (seconds) Measured water temperature / ℃ t1 / second Corrected water temperature / ℃ Actual water temperature / ℃ 1.00 33.70(T0) 0 5.00 33.40 4.00 18.55 27.70 10.00 33.30 9.00 24.61 27.70 15.00 33.20 14.00 26.30 27.70 20.00 33.00 19.00 25.98 27.70 25.00 33.00 24.00 27.51 27.70 30.00 32.80 29.00 27.03 27.70 35.00 32.80 34.00 27.94 27.70 40.00 32.50 39.00 26.93 27.70 45.00 32.50 44.00 27.62 27.70 50.00 32.30 49.00 27.26 27.70 55.00 32.20 54.00 27.36 27.70 60.00 32.10 59.00 27.44 27.70 65.00 31.90 64.00 27.13 27.70 70.00 31.90 69.00 27.53 27.70 75.00 31.70 74.00 27.23 27.70 80.00 31.70 79.00 27.57 27.70 85.00 31.50 84.00 27.29 27.70 90.00 31.40 89.00 27.30 27.70 95.00 31.30 94.00 27.30 27.70

[0042] According to Table 2 above, we can get that: after 45 seconds, the corrected water temperature enters the same 27℃ range as the actual water temperature, and then the corrected water temperature gradually stabilizes around 27.30℃-27.60℃ within 45 seconds-95 seconds. The corrected water temperature after gradual stabilization can be regarded as the final corrected water temperature. Although the error with the actual water temperature is large, the corrected water temperature starts with 27, which is correct and indistinguishable from the actual water temperature, which is sufficient for some ambiguous occasions.

[0043] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temperature compensation algorithm for a temperature sensor in an online water quality monitor, characterized in that: The temperature compensation formula is: T 修正水温 =T0-(T0-T1) / [1-1 / exp(t1 / t)]; T0 is the actual water temperature measured by the temperature sensor when the water quality online monitor starts to correct the water temperature after being immersed in water (zero time point), in degrees Celsius; t1 is the number of seconds from time zero to the current real time, in seconds; T1 is the real-time measured water temperature of the temperature sensor at the current time t1, in degrees Celsius; t is the time constant, t is 200.

2. The temperature compensation algorithm of the temperature sensor in the online water quality monitoring instrument according to claim 1 is characterized in that: The temperature sensor is a platinum thermal resistor, and the platinum wire in the platinum thermal resistor includes the following elements in percentage by mass: 0.007%-0.009% Rh, 0.005%-0.007% Ir, 0.003%-0.005% Pd, 0.001%-0.003% La, 0.0005%-0.0015% Ce, 0.0005%-0.0015% Gd, 0.0005%-0.0015% Yb, the contents of Co, Cu, B, Si, and Cd are all less than 30ppm, and the balance is Pt.

Images