Control method of rapid high-precision cold mirror type dew-point instrument

Abstract

The invention relates to a control method of a rapid high-precision cold mirror type dew-point instrument. A dew point chamber, a photoelectrical detecting system, a refrigerating system, a temperature measuring system and a single-chip microcomputer control processing system are included. Composite control of two control modes is adopted for the system. Firstly, a threshold value is set, and the system measures light energy of reflected light of reaction frost layer thickness in real time, calculates the difference value Rx of the current light energy and a control target value and the change rate delta Rx of the light energy and carries out fuzzy processing control if Rx is larger than the threshold value. Control processing is carried out according to a proportional-integral (PI) control rule when the error Rx is smaller than the threshold value, working current is controlled to enable the light energy to reach the control target value, the change rate of the light energy is controlled within the allowable range, proportional-integral control is stopped, and a dew point value is output. By means of fuzzy control, good transient performance can be obtained, the balance time of the system can be shortened, measurement can be accelerated, but an integration element is lacked, the system static error cannot be eliminated, errors are caused by measurement, and proportional-integral control can eliminate the system static error and improve precision. Thus, through composite application of fuzzy control and proportional-integral control, the response speed of the system is increased, and the measurement precision of the system is improved.

Description

technical field [0001] The invention relates to a control method for chilled mirror dew point measurement, which can eliminate system oscillation caused by control imbalance, speed up dew point measurement, and improve measurement accuracy. Background technique [0002] The chilled mirror dew point meter is a typical photoelectric dew point meter, which consists of a dew point chamber, a photoelectric detection system, a refrigeration system, a temperature measurement system and a single-chip microcomputer control processing system. The measurement principle is: the measured gas passes through the condensing mirror of the dew point chamber, and with the cooperation of the single-chip microcomputer control processing system and the photoelectric detection system, the water vapor in the gas gradually reaches saturation through equal pressure refrigeration, and at this time there will be frost or frost on the cold mirror. Dew, when the frost layer or dew layer on the cold mirro...

AI Technical Summary

Problems solved by technology

Then measure the dew point temperature value through the temperature measurement system, and then obtain the water vapor content in the sample gas through conversion according to the dew point value. At present, most of the market is PID control, among which PID adjustment is the adjustment method of fixed ratio, integral and differential coefficient. Since the coefficient value is fixed throughout the test, the adaptability of the adjustment system is poor, and the measurement process is similar to a damped vibration waveform. Repeated oscillations cause prolonged measurement time, and may even fail to reach a stable state without reading values

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