How to Control the Uniformity of Temperature and Humidity When the High and Low Temperature Test Chamber is Loaded?
High and low temperature test chamber "load" refers to the weight of our test product, or the product needs to be energized to test its heat is referred to the load. The "load" in the high and low temperature chamber is divided into non-heating load and heating load, and the test product that is not powered on or powered on is called non-heating load. This load has no effect on the temperature and humidity range of the constant temperature and humidity test chamber as a whole, but only affects the time of rising and cooling or rising and falling humidity. The test product that needs to be powered on and emits heat is a heating load, which has a relatively large impact on temperature and humidity, and the load that different temperature points or humidity points can withstand is not the same.
It is very important to select the appropriate test equipment when the product is undergoing temperature test.
1, The test range must be required to meet the product failure possibility test range, that is, whether it is a high temperature chamber or a low temperature chamber or a temperature and humidity test chamber or a thermal shock test chamber should be able to meet the extreme temperature conditions specified in the test requirements.
2, Ensure the volume of the test sample, it should not be greater than the working volume of the test equipment 1/5 of the principle standard to select the test equipment.
3, In order to ensure the uniformity of temperature in the test area, the convection mode of the test chamber is customized according to the heating power of the sample. The natural convection of hot air is used, which is especially suitable for drying powder, and most of the test equipment adopts the forced circulation of hot air. The difference in the temperature distribution of the equipment has a great impact on the test results. When a large sample is used, or the number of samples tested at the same time is large, the test results will vary greatly with the different locations, so the temperature uniformity of the equipment should be selected as best as possible. The uniformity performance of the high and low temperature alternating and humidity test chamber of the macro exhibition instrument can reach ≤0.5°C.
4, To prevent the sample heat absorption or heat release caused by heat radiation or heat load in the test area, the heating or refrigeration system device of the equipment has no effect on the temperature equalization and cooling rate of the sample during the test.
We can not be empty when using the high and low temperature test chamber, we will more or less place the test sample, and the user - generally after the test sample put into the heat is not too much concept, in order to avoid the temperature can not reach, can not fall down or rise and cool slowly this kind of situation, so we recommend that when purchasing equipment, to its heat requirements, or place the material, weight, size of the sample to tell the manufacturer, which will effectively help the test to make the test effect better.
Composition of Electrical Components of High and Low Temperature Test Chamber
The main parts of high and low temperature test chamber are refrigeration units, condensers, evaporators, and controllers. The main parts play a key role, so everyone pays special attention to its main parts raw materials. However, most of them ignore its auxiliary parts at this time, or feel that the role of auxiliary parts is not worth noting. Few people want to count the specific parts, so it is not clear what specific electronic components are fully used in the constant temperature and humidity test chamber.
1, Refrigeration unit:
Used to control the operation of refrigeration unit, to carry out refrigeration cycle, and there are single-phase and three-phase.
2, Fan motor:
Used to control the fan circulation steam body, heat exchanger heat conduction, and there are indoor and outdoor.
3, Electric heater equipment:
Used for heating indoor air quality quality, tubular, flocculent points.
4, Timer:
Used for automatic control system timing boot.
5, DC contactor:
Used for refrigeration unit motor breaking and connection.
6, Leakage protector power switch:
It can not only connect or disconnect the main circuit like other switches, with the effect of leakage current detection and discrimination, when the main control circuit caused by power outage or cable sheath damage, leakage protection switch power supply main switch can be connected or disconnected switch components according to the identification results. It can be combined with isolation switch and heat relay to form a full-function low-voltage switching electronic device.
7, Overtemperature protection equipment:
Its role can not be ignored, when the controller temperature is not sensitive, the implementation of the E double maintenance of the box overtemperature, when the alarm is caused, the maintenance standby, the alarm will be different with the test temperature, relative change, you can further have the role of overtemperature maintenance. The basic concept is that when the total current flow of the broken wire exceeds the limit value, the temperature of the broken wire rises and the broken wire is broken. When the heat value caused by the broken wire does not exceed its short circuit capacity, the balance between the heat value and the released heat value is guaranteed, the temperature of the broken wire cannot reach the melting temperature, it is not easy to break.
Like this kind of small electronic components, in the high and low temperature test chamber looks innocuous, but for the structure of a test chamber is also very useful, without these components, a test chamber is not used, in short, the details determine the success of failure, fine without size, in the grasp of the test chamber at the same time, more should be from its key links to grasp.
Operation Precautions of Constant Temperature and Humidity Test Chamber
1, In order to avoid machine failure in the constant temperature and humidity test chamber, please provide power supply within the rated voltage range.
2, In order to prevent electric shock or misoperation and failure, do not switch on the power supply before the installation and wiring is finished.
3, This product is a non-explosion-proof product, please do not use the constant temperature and humidity machine in the environment with flammable or explosive gas.
4, Please try not to open the test chamber door during the work of the instrument, open at high temperature may cause hot injury to the operator, open at low temperature may cause freezing injury to the staff, and may cause freezing of the evaporator, affecting the refrigeration effect. If you must open, please do some protective work,
5, It is prohibited to disassemble, process, transform or repair the constant temperature and humidity machine without permission, otherwise there will be abnormal action, electric shock or fire risk.
6, The chamber's ventilation holes should be kept unobstructed to avoid failure, abnormal operation, reduced life and fire.
7. If the machine is damaged or deformed when unpacking, please do not use it.
8, The machine installation and setting should be careful not to let dust, wire, iron filings or other things into, otherwise wrong action or failure will occur.
9, Wiring must be correct, must be grounded. Non-grounding may cause electric shock, misoperation accidents, abnormal display or large measurement errors.
10, Regularly check the terminal screws and fixed frame, please do not use in the case of loose.
11, During the operation of the instrument, the power input terminal cover must be installed on the terminal board to prevent electric shock.
12, The instrument in operation, modify the setting, signal output, start, stop and other operations, should be fully considered before the safety, wrong operation will cause damage to the working equipment or failure.
13, Please use a dry cloth to wipe the instrument, do not use alcohol, gasoline or other organic solvents, do not splash water on the instrument, if the instrument is immersed in water, please stop use immediately, otherwise there is the risk of leakage, electric shock or fire.
14, The internal parts of the instrument have a certain life period, in order to continue to use the instrument safely, please carry out regular maintenance and maintenance. When scrapping this product, please treat it as industrial waste.
15, Before starting to check whether the power supply is stable.
Use Principle of High and Low Temperature Test Chamber Low Temperature and Constant Temperature Tank
Because of its own circulation system, the uniformity of temperature field is very high, and more and more experiments are applied to the low temperature constant temperature tank. Mainly used in petroleum, chemical, electronic instrumentation, physics, chemistry, biological engineering, medicine and health, life science, light industrial food, physical property testing and chemical analysis and other research departments, colleges and universities, enterprise quality inspection and production departments, to provide users with a hot and cold controlled, uniform and constant temperature field source for test samples or products to perform constant temperature test or test. It can also be used as a heat source or cold source for direct heating or cooling and auxiliary heating or cooling.
What are the precautions for using a low temperature or constant temperature tank?
1, Before the use of low temperature constant temperature tank, the tank should be added to the liquid medium (pure water, alcohol, methyl silicone oil), the medium liquid level should be less than 20mm workbench, otherwise the power will damage the heater.
2, The selection of liquid medium in the low temperature constant temperature tank should comply with the following principles:
When the operating temperature is below 5 ° C, the liquid medium is generally alcohol;
When the operating temperature is 5 ~ 85℃, the liquid medium is generally water;
When the working temperature is 85 ~ 95℃, the liquid medium can choose 15% glycerol aqueous solution, which can reduce the evaporation of water;
When the operating temperature is higher than 95 ° C, oil is generally selected as the liquid medium, and the open cup flash point value of the selected oil should be higher than the operating temperature of 50 ° C or more; Generally, methyl silicone oil with low viscosity is used.
3, Power supply: 220V50Hz, the power supply should be greater than the total power of the instrument, the power supply must have a good "grounding" device.
4, The instrument should be placed in a dry and ventilated place, and there are no obstacles within 300mm around the instrument.
5, When the thermostat working temperature is high, should be careful not to open the cover, hands do not enter the groove, to prevent hot injury.
6, After using, all switches are placed in the off state, cut off the power.
7, Avoid acid and alkali substances into the tank corrosion coil and inner liner.
8, The instrument should do a good job of regular cleaning work, long-term use, empty the media in the tank, and wipe clean, keep the workbench and the operating panel clean.
9, Often pay attention to observe the liquid level in the tank, when the liquid level is too low, the liquid medium should be added in time.
10, Liquid external circulation, customers should pay special attention to the fastness of the connection of the leading pipe, strictly prevent falling off, so as to avoid liquid leakage.
Selection Method of Drying Oven Fan
Drying oven fan selection is a very technical work, and there are many specific selection methods, such as: according to the dimensionless characteristic curve selection, according to the logarithmic coordinate curve selection, according to the dimensional characteristic curve or performance table selection, variant selection, according to the pipe network resistance selection, etc. At present, there is also a Web selection system and the use of special selection software to select. Methods are numerous and complex, and some methods require certain professional knowledge to master.
When choosing a fan, first according to the two basic parameters of the air volume and total pressure of the fan, the model and number of the fan can be determined through the dimensional performance table of the fan (each fan product manual has relevant data), and more than one product may meet the requirements; At this time, combined with the use of the fan, process requirements, use occasions, etc., select the type, model and structural material of the fan to meet the required working conditions, and strive to make the rated flow rate and rated pressure of the fan as close as possible to the flow and pressure required by the process, so that the operating condition point of the fan is close to the efficient area of the fan characteristics.
The specific principles of the drying oven are as follows:
1, Before choosing the fan, we should understand the production and product quality of the domestic ventilation phase, such as the production of fan varieties, specifications and special uses of various products, the development and promotion of new products, etc., should also fully consider the requirements in order to choose the best fan.
2, According to the different physical and chemical properties of the gas transported by the fan, choose different uses of the fan. Explosion-proof ventilator should be selected if there are explosive and flammable gases; Dust or pulverized coal should be selected to exhaust dust or pulverized coal fan; Conveying corrosive gases should choose anti-corrosion fan; Working in high temperature occasions or conveying high temperature gas should choose high temperature fan.
3, When there are more than two kinds of fans to choose from on the fan selection performance chart, the higher efficiency and smaller machine number should be preferred; One with a larger range of adjustment, of course, should also be compared and decided by weighing the advantages and disadvantages.
4, If the selected fan impeller diameter is much larger than the original fan impeller diameter, in order to use the original motor shaft, bearing and support, it is necessary to calculate the motor starting time, the strength of the original fan components and the critical speed of the shaft.
5, Choose the centrifugal fan, when the motor power is less than or equal to 75KW, can not be installed only for the start of the valve. When high temperature flue gas or air is discharged and the centrifugal boiler induced draft fan is selected, a starting valve should be set up to prevent overload during cold operation.
6, For the ventilation system with noise reduction requirements, the ventilator with high efficiency and low impeller circular speed should be selected first, and the ventilator should work at the high efficiency point; According to the transmission mode of noise and vibration generated by the ventilation system, corresponding measures should be taken to reduce sound and vibration. Vibration reduction measures for fans and motors can generally use vibration reduction bases, such as spring shock absorbers or rubber shock absorbers.
7, In the selection of fans, should try to avoid the use of fans in parallel or series work. When unavoidable, the ventilator of the same model and performance should be selected for joint work. When the series is used, there should be a certain pipeline connection between the stage ventilator and the second stage ventilator.
8, The selected new fan should consider making full use of the original equipment, suitable for on-site production and installation and safe operation.
Lighting Installation Position of High and Low Temperature Test Chamber
According to the different needs of users, the installation position of the lamp in the high and low temperature laboratory is different. The constant temperature and humidity test chamber tests the heat resistance, cold resistance, dry resistance and moisture resistance of various materials. Suitable for electronic, electrical, food, vehicle, metal, chemical, building materials and other industries of quality control. This series of products is suitable for aerospace products, information electronic instruments, materials, electrical, electronic products, various electronic components in high and low temperature or temperature and humidity environment, to test its various performance indicators.
The most common temperature test equipment in environmental test equipment, and similar related products are high and low temperature alternating test chamber, constant temperature and humidity test chamber, high and low temperature and humidity alternating test chamber and so on. It is suitable for high temperature and low temperature reliability test of industrial products. Walk-in high and low temperature test chamber, walk-in high and low temperature test chamber is used for thermal test of national defense industry, aerospace industry, automatic components, automotive parts, electronic and electrical parts, plastics, chemical, pharmaceutical industry and related products. It provides large parts, semi-finished products, and large temperature and humidity test environment space for finished products. It is suitable for the test equipment with large quantity and volume.
Some are installed on the interal chamber or door, and some are not installed. Where is the best place to install light bulbs?
In fact, the high and low temperature test chamber lighting has advantages and disadvantages no matter where it is installed.
If the lighting is installed in the broadcast room, you can clearly see the condition of the entire broadcast room and observe the product at any time.
The lamp is installed on the door, and when the user conducts the double 85 test or the high temperature and high humidity test, the humidity is not easy to invade the lamp, and the lamp is not easy to damage, which can greatly reduce the after-sales service fee. However, its observation field is very small, can only observe the near attractions, customers observe the product is not very convenient.
If the lamp is installed on the right side of the internal chamber, it is recommended to be completely sealed to prevent moisture intrusion to ensure the long-term stable operation of the lamp. If it is installed on a door, it is recommended that the viewing window be trapezoid, so that you can have a wider field of view.
Of course, some corporate customers choose not to install lighting when purchasing high and low temperature test chambers to reduce production costs and later management costs. However, customers can not observe products at any time when doing tests, and they can not meet the needs of different customers who want to observe products.
Sealing Problems and Solutions of High and Low Temperature Test Chamber
High and low temperature test chamber is based on the natural environment such as high temperature, ultra-low temperature, high and low temperature and low temperature drying in the room during the construction of work, and then carries out high and low temperature test and temperature and humidity aging resistance experiment on the commodity, mainly used for industrial products, such as: electronic and electrical, instrumentation equipment, cars and motorcycles, universities and other manufacturing industries.
Because of high temperature testing, ultra-low temperature testing, high and low temperature test cycle system testing, high and low temperature test and other experimental standards, high and low temperature test chamber in the high temperature standards, such as doing 150 ° C extremity of high temperature and 98% of the ambient humidity conditions, and the pressure difference between inside and outside the laboratory to expand substantially, at this moment, the sealing effect of the test chamber really matters. If the airtightness is not very good, it will cause more serious vapor leakage, affecting the precision and accuracy of the temperature.
What are the factors that cause the sealing problem of the high and low temperature test chamber?
First, the constant temperature and humidity test chamber usually has cable holes and ventilation exhaust holes, and the design scheme is very strict.
If the design scheme and production are not scientific, the gap will be too large, and the sealing of the environmental test chamber will not be good. This punching studio should also remember to plug the suitable specifications of the bottle stopper, rubber stopper, etc., to ensure that the sealing of this punching place is intact.
Second, the problem of sealing rubber strips of high and low temperature test chamber. We usually ignore this problem, feel that the sealing strip is added to the door hinge, and should be very sealable under the inhibition of the door hinge, because the aging of the silicone seal, the selection of hard flexibility is unscientific, and the sealing strip is fixed and not the same, often causing steam leakage. It is also simple to handle, often test its tightness, and find that the embrittlement of the sealing strip must be replaced as soon as possible.
Third, because the general volume of the high and low temperature test chamber is relatively large, the tail door specifications are expanded, and the net weight is very large, and the vertical orientation of the door hinge is offset after the long-term load, and the tail door is shifted and closed. Such problems are usually dealt with according to the modified high-load door hinges and the total number of door hinges.
From the above analysis, it can be seen that the sealing problem of the high and low temperature test chamber has some design problems and some maintenance problems. Therefore, we should strictly follow the equipment maintenance manual for regular maintenance in the use of equipment to ensure the normal operation of equipment and no deviation of technical parameters.
Cooling Mode of Condenser in High and Low Temperature Test Chamber
High and low temperature test chamber is a common temperature test equipment in environmental test equipment, which is suitable for high temperature and low temperature reliability test of industrial products. The working principle of refrigeration in the high and low temperature test chamber is that the refrigerant flows out of the condenser under high pressure, passes through the throttling mechanism (capillary, thermal expansion valve, etc.), reduces its pressure, and then enters the evaporator. When the refrigeration medium enters the evaporator, it is a two-phase mixture (liquid and gas), which evaporates and absorbs heat under low temperature conditions in the evaporator. It then enters the condenser, where heat is released and condensed into a liquid. Xenon lamp aging test chamber uses xenon lamp with long arc as light source, which can provide corresponding environmental simulation and accelerated test for scientific research, product development and quality control. The vehicle environment simulation laboratory can simulate the test environment of engine cold start, vehicle high and low temperature, wind, frost, rain, snow, vehicle emission test, etc.
According to different refrigeration media, the cooling mode of the high and low temperature test chamber condenser can be divided into three types: air cooling, water cooling and liquid nitrogen refrigeration. Their medium is refrigerant, water and liquid nitrogen. Different media correspond to different evaporation temperatures, the same medium under different evaporation pressure, evaporation temperature is not the same.
The different cooling methods of the condenser in the high and low temperature test chamber make the components of the refrigeration different. The air cooling method consists of compressor, various refrigeration accessories, condenser, oil separator and so on. The water cooling method consists of: chiller, cooling tower, freezing pump and auxiliary equipment. Liquid nitrogen is composed of: liquid nitrogen tank, pressure transmitter, pressure gauge, flow meter, level meter, ultra-low temperature solenoid valve and so on.
No matter what kind of cooling method is used in the high and low temperature test chamber condenser, high reliability and safety are the most basic requirements. Instrument test equipment of Lab Companion can provide a variety of condenser cooling methods according to customer needs.
In addition to the high and low temperature test chamber, instrument of Lab Companion also produces all kinds of temperature and humidity test chamber, constant temperature and humidity test equipment, aging chamber (ultraviolet, xenon lamp, ozone aging chamber), thermal shock test chamber, high temperature aging machine and other equipment, all the equipment is produced according to national standards and industry specifications.
Efficacy of Electronic Expansion Valve in High and Low Temperature Test Chamber
The electronic expansion valve of the high and low temperature test chamber adjusts the water supply rate of the air conditioning evaporator according to the preset program flow, which is called the electronic expansion valve because it belongs to the electronic adjustment mode. It integrates the development trend of refrigeration mechatronics, with the unparalleled characteristics of the expansion valve, and presents the standard for the intelligent system operation of the refrigeration system of the quotation of the high and low temperature test chamber. It is a kind of automatic control environmental protection and energy-saving components with great development prospects, and is the orientation of the development trend of the quotation of the high and low temperature test chamber in the future.
The main purpose of the electronic expansion valve and the hot air conditioning expansion valve is basically the same, and the structure is various, but in the characteristics, the two have great differences. From the perspective of control and maintenance, the electronic expansion valve is composed of three parts: control board, electric actuator and controller. Generally speaking, most of the electronic expansion valve only refers to the electric actuator, that is, the controllable drive equipment and the oil circuit board. In fact, only this part is unable to operate.
The key hardware configuration of the electronic expansion valve control board is designed by single chip microcomputer, such as the control board also needs to operate the DC frequency conversion of the refrigeration compressor and the centrifugal fan, and the method of multi-machine cascade is generally selected. The controller of the electronic expansion valve generally uses thermal resistance or thermal resistance. As a new type of hydraulic control system, electronic expansion valve has been early to improve the definition of throttle organization, which is the key step of the intelligent system of refrigeration system, is the key way and ensure that the refrigeration system is upgraded enough to truly maintain, is a representative of the mechanical and electrical engineering of refrigeration system, has been used in more and more industries. Because of the selection of electronic expansion valves, the awareness of a certain type of system submission to expansion valves existing in the whole process of the refrigeration unit design scheme has been enhanced, and the new pattern of air conditioning expansion valves for system improvement services has played a key role in the development trend of the refrigeration manufacturing industry.
The high and low temperature test chamber can complete the test process according to the pre-set curve, and can accurately control the temperature rate within the range of the heating rate capacity, and can control the heating and cooling rate according to the slope of the set curve.
Temperature control is a heating process, high and low temperature test chamber heating using independent heating, far infrared nickel-chromium alloy high-speed heating wire, P.I.D+S.R system co-channel coordinated temperature control, through microcomputer calculation of output power, to obtain high-precision, high-efficiency electricity benefits. In order to achieve rapid heating and high temperature, the method of increasing the number of heating wires and improving the temperature control performance of software is generally adopted. By using international brand compressors and circulating fans, the chamber has uniform temperature distribution, high efficiency for environment-friendly refrigerant, low energy consumption and saved energy. The use of energy regulation technology in the design of refrigeration system can not only ensure the normal operation of the unit, but also effectively adjust the energy consumption and cooling capacity, so that the refrigeration system is in a good running state.
High and Low Temperature Test Chamber Requirements Specified in the Standard
The test chamber requirements formulated according to relevant standards should meet the following two points:
1. The temperature and humidity in the high and low temperature test chamber are monitored by the sensor installed in the working space. For the test of the heat dissipation test sample, the installation position of the sensor is formulated in the GB/T2421-1999 standard.
2, The temperature and relative humidity of the working space are required to be constant within the nominal value and its specified tolerance range, and the influence of the test sample should also be considered during the test.
Heat dissipation test sample test:
The volume of the high and low temperature test chamber should be at least 5 times the total volume of the test sample, the distance between the test sample and the internal wall of the test chamber should be selected according to the provisions of GB/T2423.2-2001 Appendix A (standard appendix), the wind speed in the chamber should not exceed 1M/S, and the structure of the mounting frame or support frame of the test chamber sample should simulate the real conditions in use as much as possible. Or otherwise, the effect of the sample mounting rack on the exchange of heat and moisture between the test sample and the surrounding space should be reduced to a minimum, and the relevant specifications may also specify dedicated mounting racks.
Test severity level:
The severity grade of the test chamber consists of the test temperature, relative humidity and test time, and is specified by the relevant specifications. The combination of temperature and relative humidity can be selected from the following values:
a, 30℃±2℃ 93%±3%
b, 30℃±2℃ 85%±3%
c, 40℃±2℃ 93%±3%
d, 40℃±2℃ 85%±3%
During the test, the test chamber shall be at the temperature and humidity of the laboratory, and the test sample at the ambient temperature of the laboratory shall be placed in the normal position or other specified position in the laboratory in an unpacked, unenergized, "ready for use" state, under certain circumstances (e.g. The relevant specifications may allow the test sample to be directly sent into the test chamber under the treated test conditions, but the test sample must be prevented from producing condensation, the temperature in the test chamber should be adjusted to a predetermined severity level, the time should ensure that the test sample reaches temperature stability, the test time should be calculated from the specified conditions, if the relevant specifications require, the test sample can be energized or worked in the conditional test phase, and the relevant specifications should specify the working conditions and working time or cycle of the test sample during the test. At the end of the conditional test, the test sample should still be left in the test chamber and the chamber should be adjusted to the standard atmospheric conditions of the test. The relative humidity should be reduced first, and the time should not exceed 2 hours. The temperature change rate in the test chamber should not exceed 1℃/min on average within 5min, and the relative humidity during temperature regulation should not exceed 75%. After the conditional test, the test sample should enter the recovery procedure.
Principles That Operating Constant Temperature and Humidity Test Chamber Should Follow
Constant temperature and humidity test chamber, also known as constant temperature and humidity test machine, programmable temperature and humidity alternating test chamber, thermostat or constant temperature and humidity chamber, can be used to test various environments and test equipment material performance, this material has heat resistance, cold resistance, dry resistance and humidity resistance. However, when using the constant temperature and humidity test chamber, the correct operation helps to obtain scientific data for the experimenter, so what principles should be followed in the operation of the constant temperature and humidity test chamber?
First, in the environmental test, the operator must be familiar with the required test sample performance, test conditions, test procedures and test technology, familiar with the technical performance of the test equipment used, and understand the structure of the equipment, especially familiar with the control operation and performance. At the same time, read the operation manual of the test equipment carefully to avoid abnormal operation of the test equipment due to operation errors, which may cause damage to the test sample and incorrect test data.
Second, in order to ensure the normal operation of the test, appropriate testing equipment should be selected according to the different conditions of the test sample, and a reasonable proportion between the temperature and humidity of the test sample and the effective volume of the laboratory should be maintained. For tests of heated test samples, the volume should not be greater than one-tenth of the effective volume of the test chamber. The volume of the unheated test sample should not exceed one-fifth of the effective volume of the test chamber.
Third, for environmental tests that need to add media to the test, it should be correctly added according to the test requirements. For example, there are certain requirements for water in temperature and humidity test chambers and the resistance should be reduced. There is a more economical and convenient form of pure water on the market. Its resistance is equivalent to distilled water.
Fourth, wet bulb gauze (wet bulb paper) has certain requirements for use in a temperature and humidity test chamber, and no gauze can be replaced, because the relative humidity reading is the difference between the root distance and temperature and humidity, and strictly speaking, it is also related to the local atmospheric pressure and wind speed at the time. The indicator value of wet-bulb temperature is related to the amount of water absorbed by the gauze and the amount of surface evaporation. These are directly related to the quality of the gauze, so the weather stipulates that the wet ball gauze must be a special "wet ball gauze" woven from linen. Otherwise, it is difficult to ensure the correctness of the wet bulb thermometer value, that is, the correctness of the humidity. In addition, the position of the wet gauze is also clearly specified. Gauze length: 100mm, tightly wrap the sensor probe, probe 25-30mm away from the humidity cup, gauze immersed in the cup to ensure the accuracy of equipment control and humidity.
Fifth, the location of the test sample should be more than 10 cm away from the wall of the chamber, and multiple samples should be placed on the same plane as far as possible. Samples should be placed without blocking air outlets and return vents, and temperature and humidity sensors should be kept at a distance. Make sure the test temperature is correct.
Operating the constant temperature and humidity test chamber in accordance with the above principles, the correct operation of the test process will greatly improve the level of test data. As long as the above principles are adhered to, it should be said that the temperature and humidity tests can be successfully performed.
Technical Means of Precise Temperature Control in High and Low Temperature Test Chamber
The high and low temperature test chamber is used to test the adaptability of materials or products in high and low temperature environments, and its accurate temperature control is achieved in the following ways:
1, Temperature control system
High and low temperature test chamber usually adopts temperature control system to achieve accurate temperature control. The system consists of temperature sensors, controllers and heaters. The temperature sensor is placed inside the test chamber to monitor the temperature change in real time, and the controller automatically controls the output power of the heater according to the signal of the sensor to achieve the purpose of accurate temperature control.
2, Temperature fluctuation control
Temperature fluctuation is an important index of accurate temperature control in high and low temperature test chamber. In order to ensure the stability of the temperature inside the test chamber, the controller will reduce the temperature fluctuation by adjusting the output power of the heater. Under normal circumstances, the accuracy of temperature fluctuations is required to be within 0.2°C.
3, Sealing control
The tightness of the high and low temperature test chamber is one of the important factors to ensure accurate temperature control. The tightness of the test chamber needs to be ensured by strict airtight testing to ensure that the heat inside the test chamber does not leak to the outside, or the heat from the outside does not enter the inside.
4, Time control
The time control of high and low temperature test chamber is also an important means to ensure accurate temperature control. The controller can set the test time according to the test needs, and automatically stop the test after the test time arrives to ensure the safety of the test sample.
In summary, the accurate temperature control of the high and low temperature test chamber is achieved through the joint action of many factors such as temperature control system, temperature fluctuation control, sealing control and time control.
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