KR0135730B1 - Method and apparatus for digitally determining the level of - Google Patents

Abstract

The present invention is difficult to determine the water level due to poor thermohydraulic conditions, and the measurement of the water level using a heating thermocouple, which is mainly used when the liquid phase and the vapor phase are present together, the inaccuracy of the measurement caused by the delay of the reaction time and the poor environment The present invention aims to realize a digital water level determining method and apparatus for more efficiently connecting a measurement signal to a central digital signal processing facility by improving the signal transmission system and simplifying the signal transmission system.

The present invention for achieving the above object is a thermocouple device for outputting a temperature difference according to the change of the water level as a corresponding signal, zero compensation for zero-compensating and linearizing the input signal connected to the thermocouple device 10 and A linearization means 31, an A / D converter 32 for converting the analog signal from the zero compensation and linearization means 31 into a digital signal, and variables and set points necessary for time delay compensation The memory 34 recording the setpoint vector and the digital signal are received from the A / D converter 32 at regular time intervals to perform time delay compensation and compare the information with the information recorded in the memory 34 to determine the level. And a digital input / output device 35 for outputting a corresponding logic signal in accordance with the determination result by the microprocessor 33.

Description

Digital water level determination method and device

1 is a schematic illustration of an apparatus for measuring water level using a conventional analog transmitter.

2 is a view schematically showing a device for measuring the water level using the water level determination device according to the present invention.

3 is a block diagram showing the water level determining apparatus of the present invention.

4 is a view comparing the determination time by the time delay compensated signal and the determination time by the time delay compensated signal in one level determination device.

* Description of the symbols for the main parts of the drawings *

10 thermocouple device 11: water tank

12 conventional transmitter 14 central signal processing apparatus

20: digital water level determination unit 21: parallel / serial converter

31: Zero compensation and linearization means 32: A / D converter

33: microprocessor 34: memory

35: digital input / output device

The present invention is for measuring the level of the storage tank, and more particularly relates to a digital level determination method and apparatus for determining the level of the fluid in a tank containing a high temperature fluid and steam, such as a nuclear power plant.

Existing water level determination methods currently used include a method using a mechanical flow element using buoyancy, a method using pressure difference at two or more points hitting a branch, a method using radiation, ultrasound or laser. In addition, there is a method of measuring discrete water levels by using a heated wire element such as a heating pair or heat resistance. Among them, the method using buoyancy or pressure difference is problematic in terms of reliability because of the inaccurate measurement, and the method using radiation, ultrasound, or laser is expensive and difficult to maintain. In the case of an abnormal fluid storage tank or the like, a method using a heating thermocouple or a heat resistance element is mainly used.

The method using the thermocouple is different from the thermal conductivity coefficients of the fluid and gas, so that the change in the output value is rapid when the fluid passes through the thermocouple to measure the change in the output level to determine the water level. It is mainly used when it is difficult to apply the pressure difference measurement method because of poor thermohydraulic conditions such as water level measurement, and it is advantageous to determine whether the set water position has passed. However, the method using the thermocouple also has the disadvantage that accurate measurement is impossible due to the difference in response time when the change of the output value is not sensitive to the change of the water level in the application field which needs to measure the water level with high precision. There is this.

In addition, when applied to an actual plant, as shown in FIG. 1, all signals from the thermocouples 10 are transmitted to the central signal processing unit 14 through the transmitter 12 to transmit the central signal processing unit 14. ), We get the information about the water level from the processed signal. The transmitter 12 existing between the signal source and the central signal processing apparatus 14 mainly plays a role of amplifying the signal and converting the signal into a current or voltage conforming to an industrial standard.

Recently, a technology for digitalizing and processing arithmetic, ambient temperature correction, and linearization required for amplification using a microprocessor such as a smart transmitter or an intelligent transmitter has been developed. The intelligent transmitter converts the signal input from the instrument into a digital signal, processes the signal using a digital microprocessor, and then converts the digital value back into an analog value for output to a conventional analog system or outputs the digital signal. It is a structure to output as a digital communication signal for communication.

As described above, the conventional transmitter 12 only has a difference in whether the processing method is digital or analog internally, and has a configuration that must pass through the central signal processing device 14 to actually process and process data. In particular, when processing a signal obtained by using a device such as a heating thermocouple (10) for measuring the water level, all signals must be transmitted and processed as an analog value, which is expensive to install and maintain, and requires a central signal processing device ( In addition to overloading 14), it also has the disadvantage of complicating the signaling system and lowering reliability. In addition, when using a digital communication method, signals from multiple heating thermocouples must be assigned to each of the broadcasting communication channels that are frequently used in a metrology control facility in order to measure one parameter of tank level. The disadvantage is that multiple channels are required for transmission.

Therefore, the present invention is difficult to measure the water level in poor thermo-hydraulic conditions in order to solve the above disadvantages, and in measuring the water level using a heating thermocouple mainly used when the liquid phase and the vapor phase together, the delay of the reaction time and the environment The purpose of the present invention is to realize a digital level determination method and apparatus for more efficiently connecting measurement signals to a central digital signal processing facility by improving the measurement inaccuracy caused by the poor quality and simplifying the signal transmission system.

The water level determination method of the present invention for achieving the above object is to determine the input vector F by calculating the first and second differential of the signal from the signal value corresponding to the temperature difference of the thermocouple element 10, and the determination Comparing the input vector F determined in the step with a set of setpoint vectors S composed of the setpoints stored in the memory 34, and in the comparing step, all components of the input vector F If it is greater than the corresponding component, it is determined that the water level has passed the thermocouple element 10, and if one or more of the components of the input vector F is less than the corresponding component of the set point vector S, the water level is less than or equal to the thermocouple element 10. And determining that it is.

In addition, the apparatus of the present invention is connected to the thermocouple element 10 and the thermocouple element 10 for outputting a temperature difference according to the change of the water level as a corresponding signal, as shown in FIG. And linearization means 31 for linearizing and linearizing, an A / D converter 32 for converting the analog signal from the zeroing and linearization means 31 into a digital signal, and variables necessary for time delay compensation. Memory 34 recording a setpoint vector composed of the set points and the setpoints, and receiving a digital signal from the A / D converter 32 at regular time intervals to perform time delay compensation and write the stored data into the memory 34. And a digital input / output device 35 that outputs a corresponding logic signal in accordance with the determination result of the microprocessor 33.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

First, the steps of signal processing according to the configuration of the present invention will be described with reference to FIG.

The thermocouple element 10 outputs a difference in temperature according to the water level in the tank as a corresponding voltage or current. Then, zero compensation and linearization is performed by the zero compensation and linearization means 31 and the A / D converter 32 converts it into a digital signal value. The microprocessor 33 compensates the time delay of the measurement signal and determines whether the water level has reached the corresponding thermocouple element by using the water level determination method of the present invention.

Next, as shown in FIG. 2, the parallel data output from each of the digital water level determination devices 20 according to the water level determination result is converted into serial data through the parallel / serial converter 21 to be converted into a central digital signal. Sent to the signal processing facility.

Here, time delay compensation is made by obtaining a temperature difference ΔT (t) to be compensated using Newton's cooling law represented by the differential equation (1) below.

In the above formula, T is the measured temperature, t is a variable representing time, τ is a time constant representing the time delay of the system, and a and b represent the slope and intercept, respectively, at the actual temperature change.

In other words, when the solution of the differential equation (1) is obtained, the measurement temperature T is determined as in the following equation (2).

T (t) = Ce ^{-t / τ} + at + (b-aτ) (2)

In the above formula, C represents a constant.

Further, the temperature difference ΔT (t) to be compensated is given by the following equations (3) and (4).

ΔT (t) = T (t) -Tc (t) (3)

In the above formula, Tc (t) represents the temperature after the compensation is performed.

Now, by using the second numerical numerical approximation in Equation (4), the following Equation (5) can be obtained.

Where ΔT represents the signal sampling interval and T (t-Δt) and T (t-2Δt) represent the one sample delayed measurement temperature and the two sample delayed measurement temperature, respectively.

Therefore, using equations (3) and (5), the time delay compensated signal (current) fc (t) is compensated from the signal (current) value f (t) corresponding to the temperature difference of the thermocouple element 10. It can be calculated as

fc (t) = f (t) -Δf (t) (7)

The variables required for equation (6) are stored in the microprocessor 33 and the memory 34. FIG. 4 is a view comparing the determination time by the time delay compensated signal and the determination time by the time delay compensated signal in the one water level determination device 20 of FIG. 2. As shown in Fig. 4, the noisy measurement signal was processed to detect the level in 217.29 seconds.

Next, the level determination method will be described, and the input vector F will be defined as follows.

F = [fc (t) fc (t) f'c (f)] (8)

Where fc (t) and f'c (t) can be obtained by the following equation.

Next, a set point vector S for the input vector r is defined as follows.

Where each component in the S vector that is a 3x3 matrix is given by

sn1 = an1 τ · σ + i (12)

sn3 = an3 (n = 1, 2 or 3) (14)

In equations (12) to (14), τ represents the time delay of the entire system, σ represents the magnitude of noise under normal conditions, and μ and i represent the compensation time and the normal signal, respectively.

sn1 is a set point for fc (t) which represents a normal signal considering the amount of noise due to time delay. It monitors whether the signal flows over a certain level. This value is obtained by increasing the amount of time delay or noise in the system. It is set high. sn2 is a set point for the slope of the change in fc (t) and monitors whether the slope of the change is severe. It is set to be lower as the delay time τ is large and is set as the compensation time μ is large. Sn3 is a value for monitoring the trend of the gradient of change as a set point for the inflection point of fc (t).

In addition, the vector G which is a 3x3 matrix is defined as follows.

Therefore, since G1, G2, and G3 are variables indicating the degree of change of X with respect to the set points, they can be used as information on the change of the water level. For example, consider the case of G1.

G1 = [g11 g12 g13]

= F-S1 = [fc (t) -s11 f'c (t) -s12 fc (t) -s13] (16)

Here, g11 is a value representing the magnitude of the set point s11 in consideration of fc (t) and the amount of noise due to time delay, and it can be seen that fc (t) is larger than a normal signal in the case of g110. g12 represents the magnitude of f'c (t) and the set point s12 relative to the slope of the change. As the delay time τ increases, s12 decreases, so even if the slope is slightly changed, g12? 0, and the compensation time μ is set high. The more you limit g12 to greater than zero. Here, the reason for compensating the signal double by the equations (7) and (13) is to prevent unnecessary overshoot and destabilization of the entire system.

Similarly, g13 is a value indicating the magnitude of the set point s13 with respect to the inflection point of fc (t) and fc (t), and when fc (t) becomes s13 or more, it becomes s130.

In the present invention, when g11, g12, and g13 have a value greater than 0 using not only g11 but also g11, g12, and g13, it is possible to determine accuracy in determining the water level by judging that the water level has passed the thermocouple.

In addition, even though a set of set points such as G1 is actually accurate to some degree, for example, according to a preferred embodiment of the present invention, at least two of G1, G2, and G3 are zero using 2/3 logic. It is desirable to have a larger gabit to identify the change in water level. This is because different set points need to be used depending on the situation. In this case, constant values an1, an2, and an3 required to set the set points sn1, sn2, and sn3 may be appropriately selected and used according to the use environment.

According to the present invention as described above, by using the first derivative and the second derivative of the measurement signal as well as the measurement signal to improve the inaccuracy of the measurement caused by the delay of the reaction time and poor environment, the digital signal It is possible to connect the signal transmitter to the digital signal processing facility more efficiently by providing a as an output.

In addition, while the present invention has been described with reference to exemplary embodiments, these descriptions should not be construed in a limiting sense. It will be apparent to those skilled in the art that the present invention may be variously modified, combined, or otherwise carried out with reference to the detailed description of the invention. Accordingly, the following claims should be regarded as including all such modifications and embodiments.

Claims (21)

In a device for determining the water level of a water tank by comparing a signal corresponding to a temperature difference of the thermocouple element 10 with a set point indicating a signal value in a steady state, the thermocouple outputting a temperature difference according to the change of the water level as a corresponding signal. A zero compensation and linearization means 31 connected to the element 10, the thermocouple element 10 for zero compensation and linearization of an input signal, and an analog signal from the zero compensation and linearization means 31. An A / D converter 32 for converting into a signal, a memory 34 recording a set point vector comprising variables and set points necessary for time delay compensation, and the A / D converter 32 at regular time intervals Determination results in the microprocessor 33 and the microprocessor 33 that receive digital signals from the digital signal to perform time delay compensation and compare the information with the information recorded in the memory 34. And a digital input / output device (35) for outputting a corresponding logic signal according to the set point vector, wherein the setpoint vector recorded in the memory (34) is a setpoint for the input signal and a setpoint for the slope of the change of the input signal. And a set point for an inflection point of the input signal, wherein the set point for the input signal and the set point for the slope are set to compensate for time delay. In a method of determining the water level of a water tank by comparing a signal corresponding to a temperature difference of the thermocouple element 10 with a set point representing a signal value in a steady state, the signal value corresponding to the temperature difference of the thermocouple element 10. Calculating an input vector F by calculating first and second derivatives of the signal; and setting the input vector F determined in the determining step to a set of set point vectors S comprising the set points stored in the memory 34; In the comparing step and the comparing step, if the level of all components of the input vector F is greater than the corresponding component of the set point vector S, it is determined that the water level has passed the thermocouple element 21, and one of the components of the input vector F Determining that the water level is less than or equal to the thermocouple element 10 when the above is less than the corresponding component of the set point vector S, wherein the set point vector S is Level determination method characterized in that it comprises a set point s1, s3 setpoint for the inflection point of the set point and the signal s2 for the slope of the change of the signal of the signal group. 3. The method of claim 2, wherein the set point s1 for the signal and the set point s2 for the slope are set to compensate for time delay. 3. The method of claim 2, wherein the signal is a signal that compensates for a measurement signal corresponding to a temperature difference of the thermocouple element (10). 5. The method of claim 4, wherein the time delay compensation is performed according to the following equation. fc (t) = f (t) -Δf (t) (Where f (t) and fc (t) represent the measured signal and the time delay compensated signal, respectively, and Δt represents the signal sampling interval.) 4. The method of claim 3, wherein the set point vector S is set as follows. S = [s1 s2 s3] s1 = a1 τ σ + i s3 = a = 3 Where τ represents the time delay of the entire system, σ represents the magnitude of the noise under normal conditions, μ, i represents the compensation time and the normal signal, respectively, and a1, a2 and a3 Is a constant determined.) In a method of determining the water level of a water tank by comparing a signal corresponding to a temperature difference of the thermocouple element 10 with a set point representing a signal value in a steady state, the signal value corresponding to the temperature difference of the thermocouple element 10. Calculating the first and second derivatives of the signal to determine an input vector F; three sets of setpoint vectors S1 comprising the set points stored in the memory 34 with the input vector F determined in the determining step; Comparing each of S2 and S3, and outputting a first logical signal as an intermediate value when all components of the input vector F are larger than corresponding components of the set point vector in the comparing step, respectively, Outputting a second logical signal as a median value if at least one of the components is less than a corresponding component of the set point vector and at least two of the median values from the output step It is determined that the water level has passed the thermocouple element 10 when the first logic signal has an intermediate value, and the water level is less than or equal to the thermocouple element 1-1 when an intermediate value of 1 or less of the intermediate value has the first logic signal. And the set point vectors S1, S2, and S3 are set points s11, s21, s31 for the signal and set points s12, s22, s32 for the slope of the change of the signal; And a set point (s13, s23, s33) for the inflection point of the signal, respectively. 8. The method of claim 7, wherein the set point for the signal and the set point for the slope are set to compensate for time delay. 8. The method of claim 7, wherein the signal is a signal obtained by delay-compensating a measurement signal corresponding to a temperature difference of the thermocouple element (10). 10. The method of claim 9, wherein the time delay compensation is performed according to the following equation. fc (t) = f (t) -Δf (t) (Where f (t) and fc (t) represent the measured signal and the time delay compensated signal, respectively, and Δt represents the signal sampling interval.) 10. The method of claim 8, wherein the set vectors S1, S2, and S3 are set as follows. sn1 = an1 τ · σ + i sn3 = an3 (n = 1, 2 or 3) Where τ represents the time delay of the entire system, σ represents the magnitude of the noise under normal conditions, μ, i represents the compensation time and the normal signal, respectively, and an1, an2 and an3 Is a constant determined.) Determining whether or not the water level has reached the plurality of thermocouple elements 10 from the signal values corresponding to the temperature difference of the plurality of thermocouple elements 10, and outputs the corresponding logic signal according to whether or not the water level is reached to configure parallel data And converting the configured parallel data into serial data by the parallel / serial converter 21, and transmitting the converted parallel data. The determination of whether the water level is reached comprises a signal from a signal value corresponding to a temperature difference of the thermocouple element 10. Determining an input vector F by calculating the first and second derivatives of, and comparing the input vector F determined in the determining step with a set of set point vectors S composed of the set points stored in the memory 34. And in the comparing step, if all components of the input vector F are larger than corresponding components of the set point vector S, the water level is the thermocouple element. Determining that the water level is less than or equal to the thermocouple element 10 when one or more of the components of the input vector F are less than the corresponding component of the set point vector S. How to judge the water level. The method of claim 12, wherein the signal is a signal obtained by delay-compensating a measurement signal corresponding to a temperature difference of the thermocouple element (10). The method of claim 13, wherein the time delay compensation is performed according to the following equation. fc (t) = f (t) -Δf (t) (Where fc (t) and fc (t) represent the signal and time delay compensated signal, respectively, and Δt represents the signal sampling interval.) 13. The method of claim 12, wherein the set point vector S comprises a set point s1 for the signal, a set point s2 for the slope of the change in the signal, and a set point s3 for the inflection point of the signal. The set point s2 for the point s1 and the slope is set to compensate for time delay. The method of claim 15, wherein the set point vector S is set as follows. S = [s1 s2 s3] s1 = a1 τ σ + i s3 = a3 Where τ represents the time delay of the entire system, σ represents the amount of noise under normal conditions, μ, i represents the compensation time and the normal signal, respectively, and a1, a2 and a3 Is a constant determined.) Determining whether or not the water level has reached the plurality of thermocouple elements 10 from the signal values corresponding to the temperature difference of the plurality of thermocouple elements 10, and outputs the corresponding logic signal according to whether or not the water level is reached to configure parallel data And converting the configured parallel data into serial data by the parallel / serial converter 21, and transmitting the converted parallel data. The determination of whether the water level is reached comprises a signal from a signal value corresponding to a temperature difference of the thermocouple element 10. Calculating first and second derivatives of and determining an input vector F; and three sets of setpoint vectors S1 comprising the set points stored in the memory 34 of the input vector F determined in the determining step; Comparing each of S2 and S3, and in the comparing step, if all components of the input vector F are larger than corresponding components of the set point vector, the first logical scene Are respectively output as intermediate values, and if at least one of the components of the input vector F is less than the corresponding component of the set point vector, respectively outputting the second logical signal as the intermediate values and the intermediate values from the output steps When two or more intermediate values have the first logic signal, it is determined that the water level has passed the thermocouple element 10. When the intermediate value of 1 or less of the intermediate values has the first logic signal, the water level has the thermocouple element 10. And determining the following level. 18. The number determination method according to claim 17, wherein the signal is a signal obtained by delay-compensating a measurement signal corresponding to a temperature difference of the thermocouple element (10). 19. The method of claim 18, wherein the time delay compensation is performed according to the following equation. fc (t) = f (t) -Δf (t) (Where fc (t) and fc (t) denote signals and time delay compensated signals, respectively, and Δt denotes signal sampling intervals.) 18. The method of claim 17, wherein the set point vectors S1, S2, and S3 are set points s11, s21, s31 for the signal and set points s12, s22, s32 for the slope of the change in the signal and the signal. And a set point (s13, s23, s33) for the inflection point of respectively, wherein the set point for the signal and the set point for the slope are set to compensate for time delay. 21. The method of claim 20, wherein the set point vectors S1, S2, S3 are set as follows. sn1 = an1 τ · σ + i sn3 = an3 (n = 1, 2 or 3) Where τ represents the time delay of the entire system, σ represents the amount of noise under normal conditions, μ, i represents the compensation time and the normal signal, respectively, and an1, an2 and an3 Is a constant determined.)