CN-122016929-A - High-precision anti-interference cold mirror dew point measuring device and method based on semiconductor refrigeration

CN122016929ACN 122016929 ACN122016929 ACN 122016929ACN-122016929-A

Abstract

The invention discloses a high-precision anti-interference cold mirror dew point measuring device and method based on semiconductor refrigeration, and relates to the technical field of atmospheric environment monitoring and precise instrument manufacturing. The device mainly comprises an optical measurement module, a temperature measurement module and a control processing unit. According to the method, the mirror surface is cooled through the semiconductor refrigerator, and the control processing unit is integrated with the self-adaptive PID algorithm to dynamically adjust the refrigerating power. Light emitted by the collimation light source is received by the reflection photoelectric sensor after being reflected by the reflection mirror surface, and the reflection light intensity is dynamically compensated based on the reference light signal through the change of the reflectivity so as to eliminate common mode interference. The measuring method comprises the steps of initializing and recording a multi-path optical signal baseline, controlling the mirror surface to be cooled step by step and synchronously monitoring, calculating and processing the optical signal in real time, judging the condensation start based on a dynamic threshold value, switching to PID control to enable the temperature to be in fine balance near the dew point, recording a stable value, correcting and outputting a final dew point value by using a compensation model, stopping refrigeration, enabling the mirror surface to be evaporated and reset by using waste heat, and entering the next cycle.

Inventors

LIU MINGYUAN
BAI ZHIXUAN
XUE QIQI
QIE XIUSHU
BIAN JIANCHUN
JIANG RUBIN
WANG CAIXIA
SUN ZHULING

Assignees

中国科学院大气物理研究所

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (10)

1. High-precision anti-interference cold mirror dew point measuring device based on semiconductor refrigeration, which is characterized by comprising: The measuring cavity (1) is provided with a channel allowing the gas to be measured to flow through, and a cavity temperature sensor (2) is arranged in the measuring cavity (1); the reflecting mirror surface (3) is arranged in the measuring cavity (1); The cold end of the semiconductor refrigerator (4) is in heat conduction connection with the reflecting mirror surface (3) and is used for adjusting the temperature of the reflecting mirror surface (3); The cold end temperature sensor (5) is embedded into the reflecting mirror surface (3) and is used for precisely measuring the temperature of the reflecting mirror surface (3); The optical measurement module comprises a collimation light source (6) and a reflection photoelectric sensor (7), wherein light emitted by the collimation light source (6) is reflected by the reflection mirror surface (3) and then received by the reflection photoelectric sensor (7), and the optical measurement module is used for detecting the change of the reflectivity of the reflection mirror surface (3) so as to judge the condensation state; Further comprises: The scattered photoelectric sensor (8) is arranged in the measuring cavity (1), the photosensitive surface of the scattered photoelectric sensor faces the reflecting mirror surface (3), but the scattered photoelectric sensor is not coplanar with an incident light path of the collimation light source (6) and a receiving light path of the reflecting photoelectric sensor (7) and is used for receiving scattered light signals generated by dew drops when the reflecting mirror surface (3) is condensed; The reference light path module comprises a reference photoelectric sensor (9) and a reflecting plate (10) and is used for monitoring the light intensity fluctuation of the collimation light source (6) or the interference of the ambient background light in real time; The control processing unit (11) is respectively and electrically connected with the cold end temperature sensor (5), the reflection photoelectric sensor (7), the scattering photoelectric sensor (8), the reference photoelectric sensor (9) and the semiconductor refrigerator (4), and is configured to execute the following operations: Acquiring and fusing reflected light signals from the reflected photoelectric sensor (7), scattered light signals from the scattered photoelectric sensor (8) and reference light signals from the reference photoelectric sensor (9) in real time, and dynamically compensating the reflected light intensity based on the difference value of the reflected light signals and the reference light signals so as to eliminate common mode interference; Fusion judgment is carried out according to the change rate of the compensated reflected light intensity signal S r and the scattered light intensity signal S s so as to adaptively determine the starting point and the stable state of mirror surface condensation; After the dew condensation is judged, based on the reading of the cold end temperature sensor (5), compensation calculation is carried out by combining a pre-stored historical temperature drift data model, and a final dew point temperature value is output.
2. The high-precision anti-interference chilled-mirror dew point measuring device based on semiconductor refrigeration according to claim 1, wherein the control processing unit (11) is configured to simultaneously acquire and process a reflected light intensity signal S r obtained by the reflected photosensor (7) and a scattered light intensity signal S s obtained by the scattered photosensor (8), wherein the reflected light intensity signal S r will fall upon condensation and the scattered light intensity signal S s will rise upon condensation.
3. The high-precision anti-interference chilled mirror dew point measuring device based on semiconductor refrigeration according to claim 1, wherein the reflecting mirror surface (3) is provided with a mirror surface anti-fouling coating, the coating is a hydrophobic oleophobic and optically transparent film, and the mirror surface anti-fouling coating is a hard optical coating made of silicon dioxide or magnesium fluoride.
4. The high-precision anti-interference chilled-mirror dew point measuring device based on semiconductor refrigeration according to claim 1, further comprising a radiator (12) and a fan (13) connected with the hot end of the semiconductor refrigerator (4), wherein a hot end temperature sensor (14) is embedded on the radiator (12).
5. The high-precision anti-interference chilled-mirror dew point measurement device based on semiconductor refrigeration according to claim 1, characterized in that the control processing unit (11) is configured to execute an adaptive temperature control strategy, employing maximum power refrigeration during the pre-cooling phase, converting to PID proportional-integral-derivative control when approaching the predicted dew point temperature, to smooth the dew point and prevent overshoot.
6. The high-precision anti-interference chilled-mirror dew-point measuring device based on semiconductor refrigeration according to claim 1, wherein an insulating layer (15) is arranged on the periphery of the measuring cavity (1).
7. A measuring method for the high-precision anti-interference chilled-mirror dew point measuring device based on semiconductor refrigeration according to claim 1, characterized by comprising the following steps: S1, initializing and establishing a base line, namely enabling gas to be measured to flow through a measuring cavity (1) at a constant flow rate, starting an optical measuring module and a reference light path module, controlling a processing unit (11) to read and record an initial value of a reflecting photoelectric sensor (7) as a reflecting light intensity base line S r 0, simultaneously reading and recording an initial value of a reference photoelectric sensor (9) as a background light intensity base line S b 0, and reading and recording an initial value of a scattering photoelectric sensor (8) as a background scattering light base line S s 0; S2, active cooling and synchronous monitoring, wherein a control processing unit (11) controls a semiconductor refrigerator (4) to be electrified and starts a fan (13), the reflecting mirror surface (3) is cooled by a first power according to a stepped or linear cooling strategy to enable the temperature of the reflecting mirror surface (3) to be reduced, and mirror surface temperature T, a reflected light intensity signal S r , a reference light intensity signal S b and a scattered light intensity signal S s are synchronously collected according to a preset frequency; S3, signal processing and condensation starting judgment, namely calculating the compensated effective reflected light intensity signal S eff in real time, wherein the calculation formula is S eff = (S r -S r 0) - k (S b -S b 0, k is a preset calibration coefficient, and simultaneously calculating the change rate dS eff /dt of the effective reflected light intensity signal S eff along with time; The control processing unit (11) is configured to determine that mirror condensation starts based on at least one of the following logics, and record the mirror temperature at this time as an initial dew point temperature T 1 : a) Logic one, when dS eff /dt exceeds a preset first dynamic threshold THR 1 for the first time and delta S s exceeds a preset scattered light intensity threshold THR s at the same time, determining that condensation starts; b) Logic two, when the change rate d (delta S s )/dt of delta S s exceeds a preset second dynamic threshold THR 2 for the first time, judging that condensation starts; S4, temperature balance and stability measurement, wherein the control processing unit (11) switches the control mode of the semiconductor refrigerator (4) into a PID proportional-integral-derivative control mode, finely adjusts the working current of the semiconductor refrigerator, enables the temperature of the reflecting mirror (3) to fluctuate within a preset micro range near the initial dew point temperature T 1 until the effective reflection signal S eff is stabilized to a new steady state value, the dew condensation state is stable, and records the corresponding average mirror temperature in the steady state as the stable dew point temperature T 2 ; S5, temperature compensation and result output, namely substituting the stable dew point temperature T 2 into a pre-stored temperature compensation model to calculate to obtain a corrected final dew point temperature value T corrected , outputting the compensated dew point temperature value, immediately cutting off the power supply of the semiconductor refrigerator (4), and stopping refrigeration; S6, after refrigeration is stopped, the fan (13) is stopped, the waste heat of the radiator (12) is utilized to heat the hot end of the semiconductor refrigerator (4), the temperature of the cold end and the temperature of the reflecting mirror surface (3) rise, condensation and evaporation are carried out on the mirror surface, when the reflected light intensity signal S r reaches a set ratio of the reflected light intensity baseline S r 0 or more, and the absolute value of the temperature difference between the cold end temperature sensor (5) and the cavity temperature sensor (2) is less than or equal to a preset temperature difference threshold value, the system is judged to be reset to a ready state, and the next measuring cycle is started after the step S2 is automatically returned.
8. The method according to claim 7, wherein in step S3, the change rate dS eff /dt of the effective reflected light intensity signal S eff with time is calculated based on a discrete-time signal system, specifically as follows: assuming that the system collects the signal with a fixed sampling period Δt, at any nth sampling instant: The value of S eff at the current time is S eff (n), and the value of S eff at the last sampling time is S eff (n-1); The rate of change at the current time, S eff /dt, can be calculated by a first order backward differential approximation, given by: , Wherein: S eff /dt is the rate of change of the effective reflected light intensity signal S eff over time in units of signal units per second; s eff (n) is an effective reflection signal value obtained by calculation of the nth sampling; S eff (n-1) is the effective reflection signal value obtained by the n-1 (i.e. last) sampling calculation; Δt is a fixed sampling time interval, which is a fixed parameter of the system; The change rate d (delta S s )/dt of the scattered light signal increment delta S s with time t is calculated based on a discrete time signal system, and the calculation formula is specifically as follows: , Wherein: d (ΔS s )/dt is the rate of change of the scattered light signal delta over time in units of signal units per second; Δs s (n) is the scattered light signal increment calculated at the nth sampling, Δs s (n)=S s (n)-S s ; ΔS s (n-1) is the increment of the scattered light signal calculated in the n-1 th time, i.e. the last sampling, ΔS s (n-1)= S s (n-1) -S s ; S s (n) , S s (n-1) the original measurement value of the scattered photosensor (8) at the nth and the nth-1 samplings; Δt is a fixed sampling time interval, which is a fixed parameter of the system.
9. The method according to claim 7, wherein in step S3, the dynamic threshold is set by using a first threshold value higher in the fast-falling stage of the mirror temperature and a second threshold value lower than the first threshold value when the mirror temperature approaches the predicted dew point temperature.
10. The method for measuring the dew point measuring device of a high-precision anti-interference chilled mirror based on semiconductor refrigeration according to claim 7, wherein the temperature compensation model in the step S5 is a polynomial compensation model: , Wherein T 2 is the stable dew point temperature, a, b, c are coefficients obtained through experimental high-precision calibration, and T corrected is the compensated dew point temperature value.

Description

High-precision anti-interference cold mirror dew point measuring device and method based on semiconductor refrigeration Technical Field The invention relates to the technical field of atmospheric environment monitoring and precise instruments, in particular to a cold mirror dew point meter for measuring the dew point temperature of gas and a measuring method thereof. Background Dew point temperature is an important parameter for measuring absolute humidity of gas, and has wide application in the fields of meteorological observation, industrial process control, laboratory analysis, aerospace and the like. The cold mirror dew point meter is regarded as one of the reference methods for dew point measurement because of its direct measurement principle, high precision and good long-term stability. However, the conventional cold mirror dew point meter still faces a plurality of technical challenges in practical application, namely, mirror pollution interference, long-term exposure of a mirror surface to gas to be measured, and extremely easy adsorption of dust, oil stain and other pollutants in the air, so that unpredictable drift of a reflectivity base line occurs, the accuracy of dew condensation judgment is seriously influenced, and even erroneous judgment is generated. Frequent manual cleaning maintenance severely affects the continuous operation capability of the equipment. Ambient light interferes with the light source fluctuation, accidental intrusion of the ambient light or aging and fluctuation of the light source itself can be received by the photoelectric sensor, measurement noise is introduced, and weak reflectivity change can not be accurately detected due to the interference during low dew point (extremely dry) measurement. The condensation criterion is single, and the traditional method mostly adopts a fixed reflectivity change threshold value as the condensation criterion. However, under different humidity ranges and different cooling rates, the dynamic process of condensation formation is different, the adaptability of the fixed threshold is poor, and early or late judgment is easy to cause, so that the accuracy is affected. Temperature measurement and systematic errors, and accuracy and position of mirror temperature measurement directly affect the final result. Thermal resistance, self-heating effect, and thermal inertia of the semiconductor refrigerator at the embedded location of the sensor may introduce systematic temperature measurement errors. The traditional cooling design of the cold mirror dew point meter is often insufficient, so that the temperature of the hot end of the semiconductor refrigerator is too high to establish effective temperature difference, and the lower measurement limit and the reliability of the semiconductor refrigerator at high ambient temperature are limited. Therefore, there is a strong need for a high reliability cold mirror dew point measurement device and method that is resistant to contamination, interference, intelligent judgment and automatic compensation of systematic errors. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide a high-precision anti-interference cold mirror dew point measuring device and a method thereof. In order to achieve the purpose, the invention has the core innovation of integrating the technical proposal of passive protection, active anti-interference and intelligent algorithm compensation. Firstly, in the passive protection layer, the invention adds a mirror surface antifouling coating on the surface of the reflecting mirror surface of the core. The coating is made of hydrophobic and oleophobic optically transparent materials (such as silicon dioxide), so that water drops, oil drops and most of particle pollutants can be effectively prevented from being directly adhered to the mirror surface substrate, the pollutants are more easily taken away by gas flowing through the coating, the cleaning period of the mirror surface is greatly prolonged, and the long-term stability of the reflectivity base line is maintained. Secondly, in the aspect of active anti-interference, the invention innovatively introduces a reference light path module. In addition to the reflective photoelectric sensor for measuring the reflected light intensity, a reference photoelectric sensor is additionally arranged to directly or indirectly monitor the output of the light source or the ambient background light. The control processing unit can dynamically cancel common mode interference caused by light source intensity fluctuation and ambient light change by calculating the difference value of the two sensor signals, so that reflectivity change signals caused by mirror surface dew condensation are extracted, the signal to noise ratio is obviously improved, and the advantages are obvious particularly when the low dew point is measured. Finally, at the intelligent processing level, the control processing unit is the brain