CN111044567A - Chilled-mirror dew point hygrometer capable of quickly measuring extremely low dew point - Google Patents
Chilled-mirror dew point hygrometer capable of quickly measuring extremely low dew point Download PDFInfo
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- CN111044567A CN111044567A CN201911407807.6A CN201911407807A CN111044567A CN 111044567 A CN111044567 A CN 111044567A CN 201911407807 A CN201911407807 A CN 201911407807A CN 111044567 A CN111044567 A CN 111044567A
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- G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
- G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
- G01N25/68—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point by varying the temperature of a condensing surface
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Abstract
The invention relates to the field of dew point temperature measurement, in particular to a cold mirror type dew point instrument capable of quickly measuring an extremely low dew point, which comprises a gas circuit system, a light circuit system, a refrigerating system and a control system, wherein the gas circuit system comprises a test cavity, a sampling pipeline and an auxiliary humidifying unit, the auxiliary humidifying unit comprises a humidifying pipeline and an electromagnetic valve, and two ends of the humidifying pipeline are connected with two openings of the sampling pipeline; the light path system comprises an emission light source, a mirror surface and a photosensitive receiver, wherein the mirror surface is positioned in the test cavity, the emission light source irradiates the mirror surface, and reflected light is received by the photosensitive receiver; the refrigerating system comprises a semiconductor refrigerator and a compressor refrigerator for performing pre-refrigeration treatment on the semiconductor refrigerator, wherein the cold end of the semiconductor refrigerator is connected to the bottom of the mirror surface, and the hot end of the semiconductor refrigerator is installed on an evaporator of the compressor refrigerator; the control system is electrically connected with the gas circuit system, the light path system and the refrigerating system. The invention can measure the extremely low dew point, and has the advantages of high measuring speed, high accuracy and strong stability.
Description
Technical Field
The invention relates to the field of dew point temperature measurement, in particular to a cold mirror type dew point meter capable of quickly measuring an extremely low dew point.
Background
Humidity is used as a measurement parameter for evaluating the moisture content in gas, has strict index requirements in many civil and national defense scientific research and production fields, and the application field of humidity measurement is continuously expanded and the requirements are higher and higher along with the development of scientific technology. For example, in weaponry, aerospace, aviation, nuclear power, ships, electronic industry, general assembly, secondary cannon, navy, air force and other systems, various compressed gases are widely used, and whether the humidity of the compressed gas is qualified or not affects the normal use of weaponry. Most of the humidity of the compressed gas belongs to a low humidity range, and various low humidity measuring instruments or sensors for measuring the humidity of the compressed gas need to be checked or calibrated regularly by adopting a humidity measuring standard; the dew point temperature is the temperature at which water vapor begins to condense into water or ice during the cooling of the gas, and the concept of humidity of the gas is precisely disclosed.
The cold mirror dew point instrument can meet the requirements of most low humidity verification and calibration, can also be used for precise humidity measurement in a low humidity range, and is important and universal metering scientific instrument equipment in the humidity field; when the traditional chilled-mirror dew point instrument is used for measuring the dew point temperature, because the content of water vapor in gas is very low, even if a very thin frost layer is formed on a mirror surface, the time is required for several hours, the measuring time is long, and the measuring speed is very slow; secondly, the refrigeration module of the existing chilled-mirror dew-point hygrometer cannot reduce the temperature of the mirror surface to be extremely low, and has limitation on measurement of extremely low dew points;
in view of the above, it is an urgent need in the art to provide a chilled mirror dew point meter capable of rapidly measuring an extremely low dew point.
Disclosure of Invention
The invention aims to provide a chilled mirror dew point instrument capable of quickly measuring an extremely low dew point, which can measure the extremely low dew point, and has the advantages of high measuring speed, high accuracy and strong stability.
In order to solve the technical problems, the technical scheme of the invention is as follows: a chilled mirror dew point hygrometer capable of quickly measuring an extremely low dew point comprises a gas circuit system and an auxiliary humidification unit, wherein the test chamber comprises a gas inlet and a gas outlet, a sampling pipeline is connected to the gas inlet, two openings are sequentially formed in the side wall of the sampling pipeline in the axial direction, the auxiliary humidification unit comprises a humidification pipeline and an electromagnetic valve, two ends of the humidification pipeline are connected to the two openings of the sampling pipeline, and the electromagnetic valve is arranged between the port of the humidification pipeline and the opening of the sampling pipeline and used for controlling the on-off between the humidification pipeline and the sampling pipeline;
the light path system comprises an emission light source, a mirror surface and a photosensitive receiver, wherein the mirror surface is positioned in the test cavity, the emission light source irradiates the mirror surface, and reflected light is received by the photosensitive receiver; the bottom of the mirror surface is provided with a temperature measuring resistor for measuring the temperature of the mirror surface;
the refrigerating system is used for cooling the mirror surface and comprises a semiconductor refrigerator and a compressor refrigerator which performs pre-cooling treatment on the semiconductor refrigerator, wherein the cold end of the semiconductor refrigerator is connected to the bottom of the mirror surface, and the hot end of the semiconductor refrigerator is arranged on an evaporator of the compressor refrigerator;
the control system is electrically connected with the gas circuit system, the light path system and the refrigerating system and is used for controlling the opening and closing of the electromagnetic valve; the temperature sensor is used for collecting photoelectric signals of the photosensitive receiver and temperature signals of the temperature measuring resistor, controlling the refrigeration and heating of the refrigeration system to the mirror surface according to the photoelectric signals and the temperature signals, enabling a condensation layer on the mirror surface to reach a dynamic balance state, and collecting the temperature signals of the temperature measuring resistor in the dynamic balance state of the condensation layer, namely dew point temperature.
According to the scheme, the humidifying pipeline is made of a nylon material, the nylon material is a moisture-absorbing and air-impermeable material, water vapor molecules in the atmosphere enter the sampling pipeline through fine pores in the nylon material, the humidity in the sampling pipeline and the humidity in the atmosphere reach inside and outside balance, and the purpose of humidifying can be achieved by bringing the water vapor molecules in the humidifying pipeline into the sampling gas circuit by opening the electromagnetic valve.
According to the scheme, the test cavity comprises a base and a top cover arranged on the base, wherein an air inlet and an air outlet are formed in two sides of the base, the bottom end of the top cover is concave inwards to form a hollow cavity with the base, the mirror surface is positioned in the cavity, and the air inlet and the air outlet are communicated with the cavity and positioned at two ends of the cavity; the transmitting light source and the photosensitive receiver are both positioned in the top cover, and a light path channel for light path transmission is arranged in the top cover; the base and the top cover are in detachable sealing connection; the test cavity is formed by oxidizing and processing alloy materials, and the inside of the test cavity is blackened;
when an extremely low dew point temperature region is measured, the amount of dew condensation or frost on the mirror surface is very small, the mirror surface is sufficiently smooth and has no viscous force, the formed trace amount of dew or frost can be taken away by airflow, and if vortex or severe temperature field distribution is formed on the gas around the mirror surface, the measurement of the dew point temperature can be correspondingly influenced, so the design of the test cavity structure directly influences the stability degree of the dew point of the mirror surface; the test cavity is formed by oxidizing and processing an alloy material, blackening treatment is carried out on the inner part of the test cavity, the test cavity is formed by oxidizing and processing the alloy material, so that the test cavity has certain corrosion resistance, the blackening treatment reduces secondary reflection of light, and the measurement accuracy is improved; the test chamber is simple in structure and small in volume, and can ensure smooth gas flow, so that the interference caused by air flow disturbance is effectively reduced, the base and the top cover are in detachable sealing connection, the test chamber can be taken out after the mirror surface is polluted by sample gas in a detachable mode, the mirror surface is convenient to clean, meanwhile, the cleaning and maintenance in the future are convenient, the air tightness of the test chamber is kept in a multi-layer sealing mode, the tested gas is prevented from being interfered by external environment air, and the measurement accuracy is improved.
According to the scheme, the sampling pipeline is a stainless steel pipeline with the interior polished at high precision; preferably, the sampling pipeline adopts a stainless steel pipeline polished by an EP-grade inner wall, trace water molecules attached to the pipeline wall are reduced as much as possible, the problem of long response time during measurement of the extremely low dew point is effectively solved, all joints on the air inlet pipeline and the air outlet pipeline are sealed in a VCR (vacuum cassette recorder) mode, the stainless steel pipeline polished internally adopts a precise laser welding mode, no dead angle inside the pipeline is ensured, and the air path circulation is smooth.
According to the scheme, the mirror surface is made of a copper material with good heat conduction performance, and the surface of the mirror surface is plated with rhodium or gold, so that the mirror surface has stable reflection coefficient and certain corrosion resistance; a copper block is arranged between the lower part of the mirror surface and the semiconductor refrigerator, the temperature measuring resistor is arranged in the copper block, and good thermal conductivity is kept between the copper block and the semiconductor refrigerator, so that the temperature gradient between the platinum thermal resistor and the mirror surface can be reduced to the minimum; the temperature measuring resistor is a PT100 platinum thermal resistor.
According to the scheme, the gas circuit system also comprises a pressure sensor and a flowmeter which are arranged at the gas outlet of the test cavity; the pressure sensor measures the pressure of the sample gas in the current pipeline and carries out standard dew point value conversion under normal pressure, the sample gas is discharged through the flowmeter, the flowmeter is convenient to observe whether the flow characteristic of the sample gas is stable or not, and whether the flow value is in a reasonable range or not.
According to the scheme, the semiconductor refrigerator is formed by stacking four stages of semiconductor refrigeration sheets; the semiconductor refrigerating plate is a Peltier element, and a multistage superposition method can be adopted to obtain low temperatures of different degrees, and the temperature difference between the cold end and the hot end can reach 105 ℃ during four-stage refrigeration.
According to the scheme, the compressor refrigerator comprises a compressor, a condenser and an evaporator; the compressor sucks in low-pressure steam from the evaporator, the steam is compressed to increase the pressure of the steam and then sent to the condenser, the steam is condensed into high-pressure liquid in the condenser, the liquid is expanded to form low-pressure liquid and then sent to the evaporator, the low-pressure liquid is evaporated by absorbing heat in the evaporator to form low-pressure steam, and then the low-pressure steam is sent to the compressor to complete the refrigeration cycle.
According to the scheme, the control system comprises a microprocessor, a mirror surface temperature measuring circuit, an A/D conversion circuit, a D/A conversion circuit, a power operational amplifier circuit and a power supply; the A/D conversion circuit and the D/A conversion circuit are electrically connected with the microprocessor, the mirror surface temperature measuring circuit is electrically connected with the A/D conversion circuit, and the power operational amplifier circuit is electrically connected with the D/A conversion circuit;
the mirror surface temperature measuring circuit is used for converting the resistance value of the temperature measuring resistor into a corresponding voltage signal; the A/D conversion circuit is used for receiving a voltage signal of the temperature measuring resistor and a photoelectric signal of the photosensitive receiver, converting the voltage signal and the photoelectric signal into digital signals and transmitting the digital signals to the microprocessor, the digital signals are processed by the microprocessor and output to the D/A conversion circuit, and the refrigeration digital signals are fed back to the refrigeration system through the power operational amplifier circuit to realize refrigeration and heating of the mirror surface; the microprocessor is also used for controlling the emission light source to emit light and controlling the electromagnetic valve to open and close; the power supply is used for supplying power to the emission light source.
According to the scheme, the mirror surface temperature measuring circuit is a four-wire temperature measuring circuit, so that high measuring precision is guaranteed, and meanwhile, the mirror surface temperature measuring circuit has good reliability, stability and anti-interference capability.
The invention has the following beneficial effects:
the refrigeration module of the invention controls the temperature of the mirror surface by combining a compressor refrigerator and a semiconductor refrigerator, and finally makes the temperature of the mirror surface balanced on the dew point temperature of the measured gas, the mirror surface is arranged at the cold end of the semiconductor refrigerator, the hot end of the semiconductor refrigerator is arranged on a cooler (or an evaporator) of the compressor refrigerator, the compressor refrigerator is a high-power refrigerator and performs pre-refrigeration treatment on the semiconductor refrigerator, so that the temperature of the mirror surface can be reduced to very low temperature, and the dew point instrument does not need to be provided with a circulating cooling water device and can detect extremely low dew point; the refrigeration control mode of the semiconductor refrigerator is current control, so that high-precision temperature control can be realized, the accuracy is high, the stability is strong, and the use is convenient;
when the extremely low dew point temperature is measured, because the content of water vapor in the gas is very low, even a very thin frost layer is formed on the mirror surface, a long time is needed, the auxiliary humidifying unit solves the problem that the mirror surface is stable for a long time under the extremely low dew point so as to improve the measuring speed in the low humidity range, the auxiliary humidifying unit enables the mirror surface to be frosted quickly, and when the sample gas is extremely dry, the measuring speed and the stability of the result can be still ensured, so that the sample gas is quickly and accurately stabilized, and the aim of quick measurement is fulfilled.
Drawings
FIG. 1 is a schematic diagram of the overall structure of an embodiment of the present invention;
FIG. 2 is a block diagram of a gas circuit system according to an embodiment of the present invention;
FIG. 3 is a schematic view of the humidification principle of an auxiliary humidification unit in an embodiment of the present invention;
FIG. 4 is a graph comparing the effect of using an auxiliary humidification unit in an embodiment of the present invention;
fig. 5 is a block diagram schematically illustrating a control system according to an embodiment of the present invention.
Reference numerals: 1. a test chamber; 101. a base; 101a, an air inlet; 102b, an air outlet; 102. a top cover; 103. a chamber; 2. a sampling pipeline; 3. a humidifying pipeline; 4. an electromagnetic valve; 5. an emission light source; 6. a mirror surface; 7. a photosensitive receiver; 8. a temperature measuring resistor; 9. a semiconductor refrigerator; 10. a compressor refrigerator; 11. a pressure sensor; 12. a flow meter; 13. an insulating layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1 to 5, the present invention is a chilled mirror type dew point hygrometer capable of rapidly measuring an extremely low dew point, which includes a gas path system, a light path system, a refrigeration system and a control system;
the gas circuit system comprises a test chamber 1, a sampling pipeline 2 and an auxiliary humidification unit, wherein the test chamber 1 comprises a gas inlet 101a and a gas outlet 101b, the sampling pipeline 2 is connected to the gas inlet 101a, two openings are sequentially formed in the side wall of the sampling pipeline 2 in the axial direction, the auxiliary humidification unit comprises a humidification pipeline 3 and an electromagnetic valve 4, two ends of the humidification pipeline 3 are connected to the two openings of the sampling pipeline 2, and the electromagnetic valve 4 is arranged between the port of the humidification pipeline 3 and the opening of the sampling pipeline 2 and used for controlling the on-off between the humidification pipeline 3 and the sampling pipeline 2;
the optical path system comprises an emission light source 5, a mirror surface 6 and a photosensitive receiver 7, wherein the mirror surface 6 is positioned in the test cavity 1, the emission light source 5 irradiates the mirror surface 6, and reflected light is received by the photosensitive receiver 7; the bottom of the mirror surface 6 is provided with a temperature measuring resistor 8 for measuring the temperature of the mirror surface 6;
the refrigerating system is used for cooling the mirror surface 6 and comprises a semiconductor refrigerator 9 and a compressor refrigerator 10 for performing pre-refrigeration treatment on the semiconductor refrigerator 9, wherein the cold end of the semiconductor refrigerator 9 is connected to the bottom of the mirror surface 6, and the hot end of the semiconductor refrigerator 9 is installed on an evaporator of the compressor refrigerator 10;
the control system is electrically connected with the gas circuit system, the light path system and the refrigerating system and is used for controlling the opening and closing of the electromagnetic valve 4; the temperature sensor is used for collecting a photoelectric signal of the photosensitive receiver 7 and a temperature signal of the temperature measuring resistor 8, controlling the refrigeration and heating of the mirror surface 6 by the refrigeration system according to the photoelectric signal and the temperature signal, enabling a condensation layer on the mirror surface 6 to reach a dynamic balance state, and collecting the temperature signal of the temperature measuring resistor 8, namely dew point temperature, when the condensation layer is in the dynamic balance state.
Referring to fig. 1, in the optical path system, an optical signal emitted from a light emitting source 5 is reflected by a mirror 6 and sent to a photosensitive receiver 7 for measuring the intensity of the directional reflected light. When the air enters from the air inlet 101a on the left side and passes through the mirror surface 6, the intensity of the reflected light is maximum when the mirror surface 6 is very clean and dry, and conversely, when dew condensation starts on the mirror surface 6, diffuse reflection occurs after the light irradiates on the mirror surface 6, and the reflected light signal received by the photosensitive receiver 7 is weakened. When the temperature of the mirror surface 6 is higher than the dew point temperature of the gas, the gas to be detected enters the test cavity 1 from the gas inlet 101a, at the moment, the mirror surface 6 is in a clean and dry state, the light rays emitted by the emission light source 5 are projected on the mirror surface 6 to be basically and completely reflected, then the photosensitive receiver 7 receives signals and feeds back output photoelectric signals in time, and a control system loop is prompted to control a refrigeration system to refrigerate the cold mirror; the temperature of the mirror surface 6 will continuously decrease along with the refrigeration function of the refrigerator, until the dew point temperature of the gas is near, the cold mirror gradually begins to dewfall (frost), at this time, the incident light before the dew point temperature of the gas will cause the diffuse reflection phenomenon on the mirror surface 6, the reflected light signal received by the photosensitive receiver 7 will decrease, the change will enter the dynamic balance state through the response of the control system, and the temperature of the mirror surface 6 will be kept at the dew point temperature of the sample gas.
In the gas circuit system, when an extremely low dew point temperature region is measured, the amount of dew condensation or frost on the mirror surface 6 is very small, the mirror surface 6 is sufficiently smooth and has no viscous force, the formed trace amount of dew or frost can be taken away by gas flow, and if gas around the mirror surface 6 forms vortex or has severe temperature field distribution, the measurement of the dew point temperature can be correspondingly influenced, so the stability degree of the dew point of the mirror surface 6 is directly influenced by the design of the structure of the test cavity 1; the testing chamber 1 in this embodiment includes a base 101 and a top cover 102 disposed on the base 101, an air inlet 101a and an air outlet 101b are disposed on two sides of the base 101, a hollow chamber 103 is formed by the bottom end of the top cover 102 being concave inwards and the base 101, the mirror surface 6 is located in the chamber 103, and the air inlet 101a and the air outlet 101b are communicated with the chamber 103 and located at two ends of the chamber 103; the transmitting light source 5 and the photosensitive receiver 7 are both positioned in the top cover 102, and a light path channel for light path transmission is arranged in the top cover 102; the test chamber 1 is formed by oxidation treatment of alloy materials, so that the test chamber has certain corrosion resistance; in order to reduce the secondary reflection of light, the interior of the test cavity 1 needs to be blackened; the test chamber 1 has a simple structure and a small volume, and can ensure smooth gas flow, thereby effectively reducing the interference caused by gas flow disturbance; the base 101, the top cover 102 and the mirror surface 6 of the test chamber 1 are designed to be detachable, so that the mirror surface 6 can be conveniently cleaned after the mirror surface 6 is polluted by sample gas, and the components are designed to be in a multi-layer sealing form, so that the tested gas is prevented from being interfered by ambient air.
The mirror surface 6 is made of copper material with good heat conductivity, and the surface of the mirror surface is plated with rhodium or gold, so that the mirror surface has stable reflection coefficient and certain corrosion resistance; a copper block is arranged between the lower part of the mirror surface 6 and the semiconductor refrigerator 9, and the temperature measuring resistor 8 is arranged in the copper block; the temperature measuring resistor 8 is a PT100 platinum thermal resistor, good thermal conductivity is kept between a copper block at the lower part of the mirror surface 6 and the semiconductor refrigerator 9, and the temperature gradient between the platinum thermal resistor and the mirror surface 6 can be reduced to the minimum.
With reference to fig. 1 to 4, the sampling pipeline 2 is a stainless steel pipeline with an internal polished high-precision, in this embodiment, the sampling pipeline 2 adopts an EP-grade stainless steel pipeline with an internal polished wall, so as to reduce trace water molecules attached to the pipeline wall as much as possible, and effectively improve the problem of long response time during measurement of an extremely low dew point; all joints on the air inlet sampling pipelines 2 and the air outlet pipelines are sealed in a VCR mode, and the stainless steel pipelines subjected to internal polishing adopt a precision laser welding mode, so that no dead angle is formed in the pipelines, and the air channels are smooth in circulation.
Fig. 2 shows a flow chart of the gas circuit system in this embodiment, in general, the sample gas to be tested has pressure, the sample gas enters the testing chamber 1 through the sample gas inlet, the temperature sensor measures the dew point temperature value, the process consumes a lot of time for balancing the dew point sensor when the gas source is extremely dry, i.e. the dew point is extremely low, in order to shorten the balance time and enable the mirror surface 6 to respond quickly and stabilize the current measured value, the auxiliary humidification unit humidifies the sample gas for a short time, the sample gas passes through the pressure sensor 11 after passing through the test chamber 1, the pressure sensor 11 is used for measuring the pressure of the sample gas in the current pipeline and carrying out dew point conversion under normal pressure, the recorded dew point display value is the standard dew point value under normal pressure, finally the sample gas is discharged through the flow meter 12, the flow parameter at the moment is displayed on a screen, and the purpose is to facilitate observation of whether the flow characteristic of the sample gas is stable or not and whether the flow value is in a reasonable range or not.
Fig. 3 is a schematic diagram of the auxiliary humidification unit, and referring to fig. 1, the electromagnetic valve 4 includes a first electromagnetic valve 4 and a second electromagnetic valve 4 disposed at two openings of the sampling pipeline 2, when the sample gas is extremely dry, i.e. at an extremely low dew point, the first electromagnetic valve 4 and the second electromagnetic valve 4 in the humidification pipeline 3 can be started by a control system control relay, and are temporarily opened, and at this time, the water vapor in the humidification pipeline 3 enters the main gas path, i.e. the sampling pipeline 2; the humidifying pipeline 3 is composed of a section of pipeline made of nylon material, water vapor molecules in the atmosphere can enter the pipeline through fine pores in the nylon material, the humidity in the pipeline can be in balance with the humidity in the atmosphere, the water molecules in the humidifying pipeline 3 can be brought into the sampling pipeline 2 by short-time opening so as to achieve the humidifying purpose, the humidifying purpose is to quickly frost on the mirror surface 6, and due to the fact that the opening time is short, and few water vapor molecules enter through the nylon material, measuring errors cannot be caused due to the intervention of the water vapor; in this embodiment, the nylon material is nylon 66, and the trademark is PA 66.
Fig. 4 shows a graph comparing the effects of using an auxiliary humidification unit, and the control system controls the operation of the auxiliary humidification unit when measuring a low dew point temperature region. Because a small amount of water vapor enters the sampling pipeline 2, the initial formation of frost on the mirror surface 6 is accelerated, so that the low dew point measuring time which needs several hours originally is shortened to dozens of minutes, and the measuring speed of the extremely low dew point range is greatly improved. Referring to fig. 4, when measuring the dew point around-60 ℃, the test time can be shortened from more than 1 hour to about 20 minutes by using the auxiliary humidifying unit.
The refrigerating system consists of two parts, namely a semiconductor refrigerator 9 and a compressor refrigerator 10 which are formed by Peltier elements, and heat insulation layers 13 are arranged on the peripheries of the semiconductor refrigerator 9 and the compressor refrigerator 10.
Semiconductor refrigeration, also known as peltier refrigeration, is a refrigeration technology that produces negative thermal resistance, when direct current passes through a galvanic couple formed by connecting two different materials (NP elements) in series, heat can be absorbed and released at the two ends of the galvanic couple respectively, so that the purpose of refrigeration can be achieved. The cold end of the semiconductor refrigerator 9 is connected with the mirror surface 6, and when the other end of the semiconductor refrigerator is used as a heat dissipation end, the mirror surface 6 can be refrigerated; in order to obtain low temperature of different degrees, a multi-stage superposition method can be adopted, the higher the temperature of the hot end is, the higher the refrigeration efficiency is, and the larger the temperature difference of the cold end and the hot end is. The refrigeration control mode of the semiconductor refrigeration piece is current control, high-precision temperature control can be realized, high-precision temperature measurement and control can be realized through the temperature measuring resistor 8 and the control system, and the response speed of the semiconductor refrigerator 9 is very high; in this embodiment, the semiconductor refrigerator 9 is formed by stacking four stages of semiconductor refrigerating sheets, the control system controls the cooling of the cold mirror to a required temperature value, and reverse current heating can be applied as required to eliminate condensed dew drops or frost; manufactured by Tianjin Konjac, model number TEC 4-24708.
The compressor refrigerator 10 is a high-power refrigerator, performs pre-cooling treatment on the semiconductor refrigerator 9, and works in cooperation with the semiconductor refrigerator 9 to integrally control the temperature of the mirror surface 6. In this embodiment, the compressor/refrigerator 10 includes a compressor, a condenser, an evaporator, a liquid storage tank, a filter, a temperature control meter, a compressor solenoid valve, and an expansion valve; in this embodiment, the whole refrigeration process of the compressor refrigerator 10 is as follows: compressor-condenser-liquid storage tank-filter-temperature control meter-hand valve-compressor solenoid valve-expansion valve-evaporator-hand valve-compressor, so that the refrigeration can be circulated. The compressor is used for compressing the steam with lower pressure into the steam with higher pressure, so that the volume of the steam is reduced, and the pressure is increased; the compressor sucks the steam with lower pressure from the evaporator, the steam with lower pressure is sent into the condenser after the pressure is increased, the steam is condensed into liquid with higher pressure in the condenser, the liquid with lower pressure is sent into the evaporator after passing through the expansion valve, the steam with lower pressure is obtained by heat absorption and evaporation in the evaporator and then is sent into the inlet of the compressor, thereby completing the refrigeration cycle;
the filter absorbs only moisture for filtering out blocking impurities. The temperature control meter is used for collecting temperature measurement signals and controlling the switching value output through temperature setting, so that the purpose of electrical control is achieved. The hand valve is used for switching on and off the compressed air. The compressor solenoid valve is used for protecting the evaporimeter, prevents that the evaporimeter from freezing, and during the refrigeration operation, can long-pending a large amount of liquid refrigerants of staying in condenser and the liquid storage pot, when shutting down, especially during the trip temporarily, if the refrigerant is closed to no compressor solenoid valve, have a large amount of refrigerants and still flow in the evaporimeter through the expansion valve, the refrigerated water does not flow this moment, and the refrigerated water in the evaporimeter can freeze.
FIG. 5 shows a control system of the present embodiment, which includes a microprocessor, a mirror temperature measuring circuit, an A/D converting circuit, a D/A converting circuit, a power operational amplifier circuit, and a power supply; the A/D conversion circuit and the D/A conversion circuit are electrically connected with the microprocessor, the mirror surface temperature measuring circuit is electrically connected with the A/D conversion circuit, and the power operational amplifier circuit is electrically connected with the D/A conversion circuit;
the mirror surface temperature measuring circuit is used for converting the resistance value of the temperature measuring resistor 8 into a corresponding voltage signal; in this embodiment, mirror surface temperature measurement circuit is four-wire system temperature measurement circuit, when guaranteeing higher measurement accuracy, still has fine reliability, stability and interference killing feature.
The A/D conversion circuit is used for receiving the voltage signal of the temperature measuring resistor 8 and the photoelectric signal of the photosensitive receiver 7, converting the voltage signal and the photoelectric signal into digital signals and feeding back the digital signals to the microprocessor; the A/D conversion circuit can adopt the existing analog-to-digital conversion circuit, and a common signal amplifier and a common filter circuit can be arranged between the A/D conversion circuit and the temperature measuring resistor 8 as well as between the A/D conversion circuit and the photosensitive receiver 7, so that the data accuracy is improved.
The microprocessor sends a control instruction to the refrigeration module according to the photoelectric signal acquired by the photosensitive receiver 7 and the voltage signal acquired by the temperature measuring resistor 8, and adjusts the refrigeration module to ensure that the condensation, evaporation or sublimation of water vapor in the measured gas on the mirror surface 6 reaches dynamic phase balance, and the temperature of the mirror surface 6 is maintained at a constant value, namely the dew point temperature or the frost point temperature; the microprocessor is also used for controlling the emission light of the emission light source 5 and controlling the opening and closing of the electromagnetic valve 4, when the air source is extremely dry, the electromagnetic valve 4 is opened, and a humidifying air path is added in the original dew point detection air path, so that the mirror surface 6 is quickly frosted; the microprocessor is also responsible for controlling related additional functions of the instrument, and the microcontroller is also connected with a digital interface and an interactive screen for human-computer interaction to display a human-computer interaction interface; in this embodiment, the microprocessor may be a system-on-a-chip microcontroller C8051F120 from silicon corporation, usa; the interactive screen can adopt a 7-inch full-color high-resolution liquid crystal screen, and the digital interface comprises an Ethernet TCP/IP interface, an RS-232 interface or a USB interface.
The D/A conversion circuit is used for digital-to-analog conversion, and the existing analog-to-digital conversion circuit can be adopted to transmit the refrigeration digital signal to the power operational amplifier circuit.
The power operational amplifier circuit amplifies the refrigeration signal and feeds the amplified refrigeration signal back to the signal ends of the semiconductor refrigerator 9 and the compressor refrigerator 10 in the refrigeration system, so as to realize refrigeration and heating of the mirror surface 6.
The power supply is used to power the emitting light source 5 and the microcontroller.
The control system of the invention takes a microcontroller as a core, carries out corresponding processing on the collected photoelectric signals, firstly controls a compressor refrigerator 10 to carry out precooling, controls the power of a semiconductor refrigerating sheet, cools a mirror surface 6, gradually starts to condense (frost) on the mirror surface 6, then heats the mirror surface 6, eliminates the dew (frost) surface, and finally leads the temperature of the mirror surface 6 to be balanced on the dew point temperature of the gas to be measured and keep small fluctuation when the condensation, evaporation or sublimation of the water vapor in the gas to be measured on the mirror surface 6 reaches dynamic phase balance, thus obtaining the dew point temperature.
The invention is a high-precision, wide-range, stable and quick dew point sensor, fills the blank of the dew point detection field of-90 to-100 ℃, can be widely applied to the fields of national defense, electric power, gas, meteorology, electronics, petroleum, chemical engineering, measurement and the like, and is used as a standard instrument for humidity measurement.
The foregoing is a more detailed description of the present invention that is presented in conjunction with specific embodiments, and the practice of the invention is not to be considered limited to those descriptions. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (10)
1. The utility model provides a but chilled mirror dew point hygrometer of rapid survey extremely low dew point which characterized in that: the method comprises the following steps:
the gas circuit system comprises a test chamber (1), a sampling pipeline (2) and an auxiliary humidification unit, wherein the test chamber (1) comprises a gas inlet (101a) and a gas outlet (101b), the sampling pipeline (2) is connected to the gas inlet (101a), two openings are sequentially formed in the side wall of the sampling pipeline (2) in the axial direction, the auxiliary humidification unit comprises a humidification pipeline (3) and an electromagnetic valve (4), the two ends of the humidification pipeline (3) are connected to the two openings of the sampling pipeline (2), and the electromagnetic valve (4) is arranged between the opening of the humidification pipeline (3) and the opening of the sampling pipeline (2) and used for controlling the on-off between the humidification pipeline (3) and the sampling pipeline (2);
the light path system comprises an emission light source (5), a mirror surface (6) and a photosensitive receiver (7), wherein the mirror surface (6) is positioned inside the test cavity (1), the emission light source (5) irradiates the mirror surface (6), and reflected light is received by the photosensitive receiver (7); the bottom of the mirror surface (6) is provided with a temperature measuring resistor (8) for measuring the temperature of the mirror surface (6);
the refrigerating system is used for cooling the mirror surface (6) and comprises a semiconductor refrigerator (9) and a compressor refrigerator (10) for performing pre-refrigeration treatment on the semiconductor refrigerator (9), wherein the cold end of the semiconductor refrigerator (9) is connected to the bottom of the mirror surface (6), and the hot end of the semiconductor refrigerator (9) is installed on an evaporator of the compressor refrigerator (10);
the control system is electrically connected with the gas circuit system, the light path system and the refrigerating system and is used for controlling the opening and closing of the electromagnetic valve (4); the temperature sensor is used for collecting photoelectric signals of the photosensitive receiver (7) and temperature signals of the temperature measuring resistor (8), controlling the refrigeration and heating of the refrigeration system to the mirror surface (6) according to the photoelectric signals and the temperature signals, enabling a condensation layer on the mirror surface (6) to reach a dynamic balance state, and collecting temperature signals of the temperature measuring resistor (8) when the condensation layer is in the dynamic balance state, namely dew point temperature.
2. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the humidifying pipeline (3) is made of nylon materials.
3. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the testing cavity (1) comprises a base (101) and a top cover (102) arranged on the base (101), wherein an air inlet (101a) and an air outlet (101b) are formed in two sides of the base (101), the bottom end of the top cover (102) is concave inwards to form a hollow cavity (103) with the base (101), the mirror surface (6) is positioned in the cavity (103), and the air inlet (101a) and the air outlet (101b) are communicated with the cavity (103) and positioned at two ends of the cavity (103); the transmitting light source (5) and the photosensitive receiver (7) are both positioned in the top cover (102), and a light path channel for light path transmission is arranged in the top cover (102); the base (101) and the top cover (102) are detachably and hermetically connected; the testing cavity (1) is formed by oxidizing and processing alloy materials, and the interior of the testing cavity (1) is blackened.
4. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the sampling pipeline (2) is a stainless steel pipeline with high-precision polishing inside.
5. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the mirror surface (6) is made of copper material, and the surface of the mirror surface is plated with rhodium or gold; a copper block is arranged between the lower part of the mirror surface (6) and the semiconductor refrigerator (9), and the temperature measuring resistor (8) is arranged in the copper block; the temperature measuring resistor (8) is a platinum thermal resistor.
6. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the gas circuit system also comprises a pressure sensor (11) and a flowmeter (12) which are arranged at the gas outlet (101b) of the test cavity.
7. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the semiconductor refrigerator (9) is formed by stacking four stages of semiconductor refrigeration sheets.
8. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the compressor chiller (10) includes a compressor, a condenser and an evaporator; the compressor sucks in low-pressure steam from the evaporator, the steam is compressed to increase the pressure of the steam and then sent to the condenser, the steam is condensed into high-pressure liquid in the condenser, the liquid is expanded to form low-pressure liquid and then sent to the evaporator, the low-pressure liquid is evaporated by absorbing heat in the evaporator to form low-pressure steam, and then the low-pressure steam is sent to the compressor to complete the refrigeration cycle.
9. The chilled mirror dew point hygrometer of claim 1, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the control system comprises a microprocessor, a mirror surface temperature measuring circuit, an A/D conversion circuit, a D/A conversion circuit, a power operational amplifier circuit and a power supply; the A/D conversion circuit and the D/A conversion circuit are electrically connected with the microprocessor, the mirror surface temperature measuring circuit is electrically connected with the A/D conversion circuit, and the power operational amplifier circuit is electrically connected with the D/A conversion circuit;
the mirror surface temperature measuring circuit is used for converting the resistance value of the temperature measuring resistor (8) into a corresponding voltage signal; the A/D conversion circuit is used for receiving a voltage signal of the temperature measuring resistor (8) and a photoelectric signal of the photosensitive receiver (7), converting the voltage signal and the photoelectric signal into digital signals and transmitting the digital signals to the microprocessor, processing the digital signals by the microprocessor and outputting refrigeration digital signals to the D/A conversion circuit, and feeding the refrigeration digital signals back to the refrigeration system through the power operational amplifier circuit to realize refrigeration and heating of the mirror surface (6); the microprocessor is also used for controlling the emission light source (5) to emit light and controlling the electromagnetic valve (4) to open and close; the power supply is used for supplying power to the emission light source (5).
10. The chilled mirror dew point hygrometer of claim 9, wherein the dew point hygrometer is capable of rapidly measuring an extremely low dew point: the mirror surface temperature measuring circuit is a four-wire temperature measuring circuit.
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| CN201911407807.6A CN111044567A (en) | 2019-12-31 | 2019-12-31 | Chilled-mirror dew point hygrometer capable of quickly measuring extremely low dew point |
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| CN112378956A (en) * | 2020-10-30 | 2021-02-19 | 上海交通大学 | Low-temperature gas humidity measuring system and method |
| CN112858387A (en) * | 2020-12-30 | 2021-05-28 | 广州奥松电子有限公司 | Dew point detection device capable of filtering gas |
| WO2022141175A1 (en) * | 2020-12-30 | 2022-07-07 | 广州奥松电子有限公司 | Chilled mirror dew point hygrometer probe |
| WO2022152035A1 (en) * | 2021-01-13 | 2022-07-21 | 约克（无锡）空调冷冻设备有限公司 | Measurement apparatus and refrigeration system comprising same |
| CN115326349A (en) * | 2022-10-17 | 2022-11-11 | 中国科学院合肥物质科学研究院 | Light path system for measuring and testing dew point of low-temperature wind tunnel test section |
| CN117491425A (en) * | 2024-01-03 | 2024-02-02 | 东方华瑞(成都)科技开发有限责任公司 | Detection device for flue gas acid dew point |
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