Chilled-mirror type dew point instrument control method

Abstract

A cold mirror type dew point instrument is used to measure the dew point. Under the conditions of a high-temperature operational environment or measuring low-humidity gas or measuring low-humidity gas in a high-temperature environment or manual misoperation, a system oscillation will be caused by system control maladjustment and consequently the dew point is hard to be measured or can not be measured. The control method provided by the invention can set a corresponding current regulation step length according to the luminous energy deviation or the different intervals of luminous energy deviation change ratio in the process of dew elimination, regulate the size of the refrigeration current through adding or deducting a current value equal to the step length to the present refrigeration current to control the mirror surface temperature for controlling the thickness of a frost layer, and consequently the luminous energy is enabled to gradually approach a target value. That is to say, the frost layer on the mirror surface gradually approaches the specific thickness, thereby eliminating the oscillation brought about by the system control maladjustment. The method can finely adjust and control the thickness of the mirror surface frost layer during dew elimination, thereby avoiding the system oscillation or stopping the system oscillation, and realizing the dew point measurement which is hard to be realized or can not be realized in the prior art.

Description

technical field [0001] The invention relates to a control method of a chilled mirror dew point meter, more specifically, a method for eliminating system oscillation caused by control imbalance in the chilled mirror dew point meter. Background technique [0002] The principle of dew point measurement by chilled mirror dew point meter is as follows: a beam of light source is irradiated on the planed mirror surface which can control the temperature, and the reflected light is received by the receiving tube of photoelectric sensor. When the mirror surface is clean and dry, its reflected light is the largest, that is, the emitted light is 100% reflected and received by the photoelectric sensor receiving tube. When the condensed water forms a frost layer on the mirror surface, the emitted light is scattered, so that the intensity of the received reflected light is weakened. The received signal is amplified and then sent to the processor through A / D conversion. After calculation, ...

AI Technical Summary

Problems solved by technology

However, the above two methods are difficult or impossible to measure the dew point in some special cases, such as working in a high temperature environment or measuring low humidity gas or measuring low humidity gas in a high temperature environment and system oscillation caused by improper human operation

The main cause of system oscillation is: although the formation of the mirror frost layer is positively correlated with the temperature of the cold end of the cold pump, there is a certain hysteresis

When the frost layer is too thick, the cold pump will be cut off, the temperature of the cold end will rise rapidly, the gas passing through the mirror is very dry, and the speed of water molecules condensing on the mirror is lower than the speed of escaping from the mirror, and the frost layer will become thinner; although When the frost layer is about to reach a certain thickness, the current recovers quickly, but because the mirror surface temperature cannot be lowered quickly, the frost layer will become too thin or even disappear

At this time, the cold pump starts to force the cooling quickly, and the mirror surface quickly condenses the frost layer, which again causes the dew frost layer to be too thick, and the cycle repeats

Especially in high temperature environment, due to the accumulation of heat at the hot end of the cold pump, it is difficult to dissipate, the cooling capacity of the cold pump gradually decreases, and sometimes it is even difficult to cool the cold end to a temperature lower than the dew point again, and the dew point is difficult or impossible to measure

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