Correcting method for solar water heater capacitance water level sensor measuring value

Abstract

The invention discloses a correction method for capacitance water level sensor measured value of solar energy water heater, its control-flow analysis is as follows: A. presuppose corrected condition; B. wait for the feeding water function to start up; C. judge whether or not the water level is not less than 90%; D. begin to time after taking notes of the practical water level capacity value; E. beyond the schedule time judge whether or not the capacity value becomes larger, if not, go to the next step, otherwise, go back to the last step; F, stop feeding water; G. compare with the capacity value of A point taken before, if the error exists, go back to wait feeding water function starting up program, otherwise, go to the next step; H. take place of the capacity value taken before; I. correct the capacity value of other water level point automatically, go back to wait feeding water function starting up program ; the solar energy water heater using the correction method above has the advantages of simple structure, high resolving power, good precontrol ability, small influence of sediment incrustation, and long service life.

Description

technical field [0001] The invention relates to an intelligent measurement and control technology for a solar water heater, in particular to a method for using a computer display controller to correct a capacitive water level sensor to measure the water level measurement value of a water storage tank of the solar water heater. Background technique [0002] As we all know, the capacitive water level sensor is made according to the principle of capacitance. The capacitance is composed of two polar plates and a medium. Changing the medium will change the capacitance. The higher the sensor is submerged by water as the medium of the capacitance, the greater the capacitance will be. The rise and fall changes linearly, and the water level in the water storage tank can be detected by detecting the capacitance, which is especially convenient in the automatic control of the water level or liquid level, such as figure 1 As shown, it has the advantages of low...

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Problems solved by technology

[0003] However, when the capacitive water level sensor is used in solar water heaters, since the diameter of the inner tank of the solar water heater is usually only 300mm, the obtained capacitance change value is only about 100P, and the use environment is very harsh. If you want to have higher display and control accuracy , the accuracy and stability of the measured value is particularly important

However, the capacitive water level sensor has fatal flaws in this aspect. The first is that the initial value of the structural capacitance is poorly consistent due to the assembly process, and the capacitance values ​​​​of the zero water level and the full water point need to be pre-set randomly. , the moisture level of the sensor can be measured differently, the site environment conditions are different, and the predetermined value is difficult to guarantee the accuracy of the next measurement; the second is that the temperature characteristic of the capacitive water level sensor is relatively poor, and it is affected by the medium temperature and the ambient temperature during use. The initial value of its structural capacitance will also become larger or smaller; the third is that after using for a period of time, affected by the high-temperature steam in the storage tank of the solar water heater, the initial value of the structural capacitance of the sensor will become smaller and smaller after the overall tide changes. Large, the measurement error can reach more than 30%. When the above phenomenon occurs, although the linear relationship between the capacitance and the water level will not change, but because the predetermined measurement constant is inconsistent with the actual capacitance value, the water level calculated by the computer display controller and the water level will not change. There will be a very large error in the actual water level, and frequent miscontrol or out-of-control accidents will cause capacitive water level sensors to have no practical value in solar water heaters

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