Structural characteristics of temperature and humidity control test chamber
Suitable for various small electrical appliances, instruments, materials, and components for wet heat testing, it is also suitable for conducting aging tests. This test chamber adopts the most reasonable structure and stable and reliable control method currently available, making it aesthetically pleasing, easy to operate, safe, and with high precision in temperature and humidity control. It is an ideal equipment for conducting constant temperature and humidity tests.
(1) The test box body is in the form of an integral structure, with the refrigeration system located at the lower rear of the box and the control system located at the upper part of the test box.
(2) Inside the air duct interlayer at one end of the studio, there are devices such as heaters, refrigeration evaporators, and fan blades distributed; On the left side of the test box, there is a Ø 50 cable hole, and the test box is a single door (stainless steel embedded door handle)
(3) The double-layer high temperature and anti-aging silicone rubber seal can effectively ensure the temperature loss of the test chamber
(4) There are observation windows, frost prevention devices, and switchable lighting fixtures on the box door. The observation window adopts multi-layer hollow tempered glass, and the inner adhesive sheet conductive film is heated and defrosted. The lighting fixtures adopt imported brand Philips lamps, which can effectively observe the experimental changes in the studio from all angles.
The refrigeration cycle of the temperature and humidity control box adopts the reverse Carnot cycle, which consists of two isothermal processes and two adiabatic processes. The process is as follows: the refrigerant is adiabatically compressed to a higher pressure by the compressor, and the work consumed increases the exhaust temperature. Then, the refrigerant exchanges heat with the surrounding medium through the condenser and transfers heat to the surrounding medium. After the refrigerant undergoes adiabatic expansion through the shut-off valve, the temperature of the refrigerant decreases. Finally, the refrigerant absorbs heat from the object at a higher temperature through the evaporator, causing the temperature of the cooled object to decrease. This cycle repeats itself to achieve the goal of cooling down.
The refrigeration system design of this test chamber applies energy regulation technology, which can ensure the normal operation of the refrigeration unit and effectively adjust the energy consumption and refrigeration capacity of the refrigeration system, so as to maintain the refrigeration system in the optimal operating state. By using Balanced Temperature Control (BTC), the control system automatically calculates the output of the heater based on the set temperature point through PID calculation when the refrigeration system is working continuously, ultimately achieving a dynamic balance.
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Service conditions for high, low temperature, and low pressure test chambers
One of the usage conditions for high, low temperature, and low pressure test chambers: environmental conditions
a、 Temperature: 15 ℃~35 ℃;
b、 Relative humidity: not exceeding 85%;
c、 Atmospheric pressure: 80kPa~106kPa
d、 There is no strong vibration or corrosive gas in the surrounding area;
e、 No direct sunlight exposure or direct radiation from other cold or heat sources;
f、 There is no strong airflow around, and when the surrounding air needs to be forced to flow, the airflow should not be directly blown onto the box;
g、 The influence of magnetic field on the control circuit of the interference free test box in the surrounding area;
h、 There is no high concentration of dust or corrosive substances in the surrounding area.
Condition 2 for the use of high, low temperature, and low pressure test chambers: Power supply conditions
a、 AC voltage: 220V ± 22V or 380V ± 38V;
b、 Frequency: 50HZ ± 0.5HZ
Condition Three for the Use of High, Low Temperature, and Low Pressure Test Chambers: Water Supply Conditions
It is advisable to use tap water or circulating water that meets the following conditions:
a、 Water temperature: not higher than 30 ℃;
b、 Water pressure: 0.1MPa~0.3MPa;
c、 Water quality: meets industrial water standards.
Condition 4 for the use of high, low temperature, and low pressure test chambers: Test load conditions
The load of the test chamber should meet the following conditions every week:
a、 The total mass of the load shall not exceed 80KG per cubic meter within the working chamber volume
b、 The total volume of the load shall not exceed 5/1 of the working chamber volume
c、 On any cross-section perpendicular to the prevailing wind direction, the sum of the load areas should not exceed 3/1 of the cross-sectional area of the working chamber at that location, and the load should not obstruct the flow of airflow when placed.
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Our company has products such as rapid temperature change test chambers, UV accelerated weather resistance testing machines, and temperature and humidity control chambers. You can call our service hotline through our website to learn more about our products. Our pursuit is endless, and we welcome new and old customers to choose their favorite products with confidence. We will be dedicated to serving you!
User selection environment test box must read
1、 Equipment selection criteria
There is currently no exact number of natural environmental factors and induced environmental factors that exist on the surface of the Earth and in the atmosphere, among which there are no less than a dozen factors that have a significant impact on the use and lifespan of engineering products (equipment). Engineers engaged in the study of environmental conditions for engineering products have compiled and summarized the environmental conditions that exist in nature and are induced by human activities into a series of testing standards and specifications to guide the environmental and reliability testing of engineering products. For example, GJB150- the National Military Standard of the People's Republic of China for Environmental Testing of Military Equipment, and GB2423- the National Standard of the People's Republic of China for Environmental Testing of Electrical and Electronic Products, which guides environmental testing of electrical and electronic products. Therefore, the main basis for selecting environmental and reliability testing equipment is the testing specifications and standards of engineering products.
Secondly, in order to standardize the tolerance of environmental testing conditions in experimental equipment and ensure the control accuracy of environmental parameters, national technical supervision agencies and various industrial departments have also formulated a series of calibration regulations for environmental testing equipment and detection instruments. Such as the national standard GB5170 of the People's Republic of China "Basic Parameter Calibration Method for Environmental Testing Equipment of Electrical and Electronic Products", and JJG190-89 "Trial Calibration Regulations for Electric Vibration Test Stand System" issued and implemented by the State Administration of Technical Supervision. These verification regulations are also an important basis for selecting environmental and reliability testing equipment. Testing equipment that does not meet the requirements of these verification regulations is not allowed to be put into use.
2、 Basic principles for equipment selection
The selection of environmental and reliability testing equipment should follow the following five basic principles:
1. Reproducibility of environmental conditions
It is impossible to fully and accurately reproduce the environmental conditions that exist in nature in the laboratory. However, within a certain tolerance range, people can accurately and approximately simulate the external environmental conditions that engineering products undergo during use, storage, transportation, and other processes. This passage can be summarized in engineering language as follows: "The environmental conditions (including platform environment) created by the testing equipment around the tested product should meet the requirements of the environmental conditions and their tolerances specified in the product testing specifications. The temperature box used for military product testing should not only meet the requirements of the national military standards GJB150.3-86 and GJB150.4-86 for different uniformity and temperature control accuracy. Only in this way can the reproducibility of environmental conditions be ensured in environmental testing.
2. Repeatability of environmental conditions
An environmental testing equipment may be used for multiple tests of the same type of product, and a tested engineering product may also be tested in different environmental testing equipment. In order to ensure the comparability of test results obtained for the same product under the same environmental testing conditions specified in the testing specifications, it is necessary to require the environmental conditions provided by the environmental testing equipment to be reproducible. This means that the stress levels (such as thermal stress, vibration stress, electrical stress, etc.) applied by environmental testing equipment to the tested product are consistent with the requirements of the same testing specification.
The repeatability of environmental conditions provided by environmental testing equipment is guaranteed by the national metrological verification department after passing the verification according to the verification regulations formulated by the national technical supervision agency. Therefore, it is necessary to require environmental testing equipment to meet the requirements of various technical indicators and accuracy indicators in the calibration regulations, and to not exceed the time limit specified in the calibration cycle in terms of usage time. If a very common electric vibration table is used, in addition to meeting technical indicators such as excitation force, frequency range, and load capacity, it must also meet the requirements of precision indicators such as lateral vibration ratio, table acceleration uniformity, and harmonic distortion specified in the calibration regulations. Moreover, the service life after each calibration is two years, and after two years, it must be re calibrated and qualified before being put into use.
3. Measurability of environmental condition parameters
The environmental conditions provided by any environmental testing equipment must be observable and controllable. This is not only to limit the environmental parameters within a certain tolerance range and ensure the reproducibility and repeatability of the test conditions, but also necessary for the safety of product testing, in order to prevent damage to the tested product caused by uncontrolled environmental conditions and unnecessary losses. At present, various experimental standards generally require that the accuracy of parameter testing should not be less than one-third of the allowable error under experimental conditions.
4. Exclusion of environmental testing conditions
Every time an environmental or reliability test is conducted, there are strict regulations on the category, magnitude, and tolerance of environmental factors, and non test required environmental factors are excluded from penetrating into it, in order to provide a definite basis for judging and analyzing product failure and fault modes during or after the test. Therefore, it is required that environmental testing equipment not only provide the specified environmental conditions, but also not allow any other environmental stress interference to be added to the tested product. As defined in the verification regulations for electric vibration tables, the table leakage magnetic flux, acceleration signal-to-noise ratio, and total root mean square value ratio of in band and out of band acceleration. The accuracy indicators such as random signal verification and harmonic distortion are all established as verification items to ensure the uniqueness of environmental testing conditions.
5. Safety and reliability of experimental equipment
Environmental testing, especially reliability testing, has a long testing cycle and sometimes targets high-value military products. During the testing process, testing personnel often need to operate, inspect or test around the site. Therefore, it is required that environmental testing equipment must have the characteristics of safe operation, convenient operation, reliable use, and long working life to ensure the normal progress of the testing itself. The various protection, alarm measures, and safety interlock devices of the testing equipment should be complete and reliable to ensure the safety and reliability of the testing personnel, the tested products, and the testing equipment itself.
3、 Selection of Temperature and Humidity Chamber
1. Selection of Capacity
When placing the test product (components, assemblies, parts or whole machine) into a climate chamber for testing, in order to ensure that the atmosphere around the test product can meet the environmental testing conditions specified in the test specifications, the working dimensions of the climate chamber and the overall dimensions of the test product should follow the following regulations:
a) The volume of the tested product (W × D × H) shall not exceed (20-35)% of the effective working space of the test chamber (20% is recommended). For products that generate heat during testing, it is recommended to use no more than 10%.
b) The ratio of the windward cross-sectional area of the tested product to the total area of the test chamber on that section shall not exceed (35-50)% (35% is recommended).
c) The distance between the outer surface of the tested product and the wall of the test chamber should be kept at least 100-150mm (recommended 150mm).
The above three provisions are actually interdependent and unified. Taking a 1 cubic meter cube box as an example, an area ratio of 1: (0.35-0.5) is equivalent to a volume ratio of 1: (0.207-0.354). A distance of 100-150mm from the box wall is equivalent to a volume ratio of 1: (0.343-0.512).
In summary, the working chamber volume of the climate environment test chamber should be at least 3-5 times the external volume of the tested product. The reasons for making such regulations are as follows:
After the test piece is placed in the box, it occupies the smooth channel, and narrowing the channel will lead to an increase in airflow velocity. Accelerate the heat exchange between the airflow and the test piece. This is inconsistent with the reproduction of environmental conditions, as relevant standards stipulate that the air flow velocity around the test specimen in the test chamber should not exceed 1.7m/s for temperature environmental tests, in order to prevent the test specimen and the surrounding atmosphere from generating heat conduction that is not in line with reality. When unloaded, the average wind speed inside the test chamber is 0.6-0.8m/s, not exceeding 1m/s. When the space and area ratio specified in points a) and b) are met, the wind speed in the flow field may increase by (50-100)%, with an average maximum wind speed of (1-1.7) m/s. Meet the requirements specified in the standards. If the volume or windward cross-sectional area of the test piece is increased without restrictions during the experiment, the actual airflow speed during the test will exceed the maximum wind speed specified in the test standard, and the validity of the test results will be questioned.
The accuracy indicators of environmental parameters in the working chamber of the climate chamber, such as temperature, humidity, salt spray settling rate, etc., are all measured under no-load conditions. Once the test piece is placed, it will have an impact on the uniformity of the environmental parameters in the working chamber of the test chamber. The larger the space occupied by the test piece, the more severe this impact will be. Experimental data shows that the temperature difference between the windward and leeward sides in the flow field can reach 3-8 ℃, and in severe cases, it can be as high as 10 ℃ or more. Therefore, it is necessary to meet the requirements of a] and b] as much as possible to ensure the uniformity of environmental parameters around the tested product.
According to the principle of heat conduction, the temperature of the airflow near the box wall is usually 2-3 ℃ different from the temperature at the center of the flow field, and may even reach 5 ℃ at the upper and lower limits of high and low temperatures. The temperature of the box wall differs from the temperature of the flow field near the box wall by 2-3 ℃ (depending on the structure and material of the box wall). The greater the difference between the test temperature and the external atmospheric environment, the greater the temperature difference. Therefore, the space within a distance of 100-150mm from the box wall is unusable.
2. Selection of temperature range
At present, the range of temperature test chambers abroad is generally -73 to+177 ℃, or -70 to+180 ℃. Most domestic manufacturers generally operate at -80 to+130 ℃, -60 to+130 ℃, -40 to+130 ℃, and there are also high temperatures up to 150 ℃. These temperature ranges can usually meet the temperature testing needs of the vast majority of military and civilian products in China. Unless there are special requirements, such as products installed near heat sources such as engines, the upper temperature limit should not be blindly increased. Because the higher the upper limit temperature, the greater the temperature difference between the inside and outside of the box, and the poorer the uniformity of the flow field inside the box. The smaller the available studio size. On the other hand, the higher the upper limit temperature value, the higher the heat resistance requirements for insulation materials (such as glass wool) in the interlayer of the box wall. The higher the requirement for the sealing of the box, the higher the production cost of the box.
3. Selection of humidity range
The humidity indicators given by domestic and foreign environmental test chambers are mostly 20-98% RH or 30-98% RH. If the humid heat test chamber does not have a dehumidification system, the humidity range is 60-98%. This type of test chamber can only perform high humidity tests, but its price is much lower. It is worth noting that the corresponding temperature range or minimum dew point temperature should be indicated after the humidity index. Because relative humidity is directly related to temperature, for the same absolute humidity, the higher the temperature, the lower the relative humidity. For example, if the absolute humidity is 5g/Kg (referring to 5g of water vapor in 1kg of dry air), when the temperature is 29 ℃, the relative humidity is 20% RH, and when the temperature is 6 ℃, the relative humidity is 90% RH. When the temperature drops below 4 ℃ and the relative humidity exceeds 100%, condensation will occur inside the box.
To achieve high temperature and high humidity, simply spray steam or atomized water droplets into the air of the box for humidification. Low temperature and humidity are relatively difficult to control because the absolute humidity at this time is very low, sometimes much lower than the absolute humidity in the atmosphere. It is necessary to dehumidify the air flowing inside the box to make it dry. At present, the vast majority of temperature and humidity chambers both domestically and internationally adopt the principle of refrigeration and dehumidification, which involves adding a set of refrigeration light pipes to the air conditioning room of the chamber. When humid air passes through a cold pipe, its relative humidity will reach 100% RH, as the air saturates and condenses on the light pipe, making the air drier. This dehumidification method theoretically can reach dew point temperatures below zero degrees, but when the surface temperature of the cold spot reaches 0 ℃, the water droplets condensed on the surface of the light pipe will freeze, affecting the heat exchange on the surface of the light pipe and reducing the dehumidification capacity. Also, because the box cannot be completely sealed, humid air from the atmosphere will seep into the box, causing the dew point temperature to rise. On the other hand, the moist air flowing between the light tubes only reaches saturation at the moment of contact with the light tubes (cold spots) and releases water vapor, so this dehumidification method is difficult to keep the dew point temperature inside the box below 0 ℃. The actual minimum dew point temperature achieved is 5-7 ℃. A dew point temperature of 5 ℃ is equivalent to an absolute moisture content of 0.0055g/Kg, corresponding to a relative humidity of 20% RH at a temperature of 30 ℃. If a temperature of 20 ℃ and a relative humidity of 20% RH are required, with a dew point temperature of -3 ℃, it is difficult to use refrigeration for dehumidification, and an air drying system must be selected to achieve it.
4. Selection of control mode
There are two types of temperature and humidity test chambers: constant test chamber and alternating test chamber.
The ordinary high and low temperature test chamber generally refers to a constant high and low temperature test chamber, which is controlled by setting a target temperature and has the ability to automatically maintain a constant temperature to the target temperature point. The control method of the constant temperature and humidity test chamber is also similar, setting a target temperature and humidity point, and the test chamber has the ability to automatically maintain a constant temperature to the target temperature and humidity point. The high and low temperature alternating test chamber has one or more programs for setting high and low temperature changes and cycles. The test chamber has the ability to complete the test process according to the preset curve, and can accurately control the heating and cooling rates within the maximum heating and cooling rate capability range, that is, the heating and cooling rates can be controlled according to the slope of the set curve. Similarly, the high and low temperature alternating humidity test chamber also has preset temperature and humidity curves, and the ability to control them according to the preset. Of course, alternating test chambers have the function of constant test chambers, but the manufacturing cost of alternating test chambers is relatively high because they need to be equipped with curve automatic recording devices, program controllers, and solve problems such as turning on the refrigeration machine when the temperature in the working room is high. Therefore, the price of alternating test chambers is generally more than 20% higher than that of constant test chambers. Therefore, we should take the need for experimental methods as the starting point and choose a constant test chamber or an alternating test chamber.
5. Selection of variable temperature rate
Ordinary high and low temperature test chambers do not have a cooling rate indicator, and the time from the ambient temperature to the nominal lowest temperature is generally 90-120 minutes. The high and low temperature alternating test chamber, as well as the high and low temperature alternating wet heat test chamber, both have temperature change speed requirements. The temperature change speed is generally required to be 1 ℃/min, and the speed can be adjusted within this speed range. The rapid temperature change test chamber has a fast temperature change rate, with heating and cooling rates ranging from 3 ℃/min to 15 ℃/min. In certain temperature ranges, the heating and cooling rates can even reach over 30 ℃/min.
The temperature range of various specifications and speeds of rapid temperature change test chambers is generally the same, that is, -60 to+130 ℃. However, the temperature range for assessing the cooling rate is not the same. According to different test requirements, the temperature range of rapid temperature change test chambers is -55 to+80 ℃, while others are -40 to+80 ℃.
There are two methods for determining the temperature change rate of the rapid temperature change test chamber: one is the average temperature rise and fall rate throughout the entire process, and the other is the linear temperature rise and fall rate (actually the average speed every 5 minutes). The average speed throughout the entire process refers to the ratio of the difference between the highest and lowest temperatures within the temperature range of the test chamber to the time. At present, the technical parameters of temperature change rate provided by various environmental testing equipment manufacturers abroad refer to the average rate throughout the entire process. The linear temperature rise and fall rate refers to the guaranteed temperature change rate within any 5-minute time period. In fact, for the rapid temperature change test chamber, the most difficult and critical stage to ensure the linear temperature rise and fall speed is the cooling rate that the test chamber can achieve during the last 5 minutes of the cooling period. From a certain perspective, the linear heating and cooling speed (average speed every 5 minutes) is more scientific. Therefore, it is best for the experimental equipment to have two parameters: the average temperature rise and fall speed throughout the entire process and the linear temperature rise and fall speed (average speed every 5 minutes). Generally speaking, the linear heating and cooling speed (average speed every 5 minutes) is half of the average heating and cooling speed throughout the entire process.
6. Wind speed
According to relevant standards, the wind speed inside the temperature and humidity chamber during environmental testing should be less than 1.7m/s. For the test itself, the lower the wind speed, the better. If the wind speed is too high, it will accelerate the heat exchange between the surface of the test piece and the airflow inside the chamber, which is not conducive to the authenticity of the test. But in order to ensure uniformity within the testing chamber, it is necessary to have circulating air inside the testing chamber. However, for rapid temperature change test chambers and comprehensive environmental test chambers with multiple factors such as temperature, humidity, and vibration, in order to pursue the rate of temperature change, it is necessary to accelerate the flow velocity of the circulating airflow inside the chamber, usually at a speed of 2-3m/s. Therefore, the wind speed limit varies for different usage purposes.
7. Temperature fluctuation
Temperature fluctuation is a relatively easy parameter to implement, and most test chambers produced by environmental testing equipment manufacturers can actually control temperature fluctuations within a range of ± 0.3 ℃.
8. Uniformity of temperature field
In order to simulate the actual environmental conditions that products experience in nature more accurately, it is necessary to ensure that the surrounding area of the tested product is under the same temperature environment conditions during environmental testing. Therefore, it is necessary to limit the temperature gradient and temperature fluctuation inside the test chamber. In the General Principles of Environmental Test Methods for Military Equipment (GJB150.1-86) of the National Military Standard, it is clearly stipulated that "the temperature of the measurement system near the test sample should be within ± 2 ℃ of the test temperature, and its temperature should not exceed 1 ℃/m or the total maximum value should be 2.2 ℃ (when the test sample is not working).
9. Precision control of humidity
The humidity measurement in the environmental testing chamber mostly adopts the dry wet bulb method. The manufacturing standard GB10586 for environmental testing equipment requires that the relative humidity deviation should be within ± 23% RH. To meet the requirements of humidity control accuracy, the temperature control accuracy of the humidity test chamber is relatively high, and the temperature fluctuation is generally less than ± 0.2 ℃. Otherwise, it will be difficult to meet the requirements for humidity control accuracy.
10. Cooling method selection
If the test chamber is equipped with a refrigeration system, the refrigeration system needs to be cooled. There are two forms of test chambers: air-cooled and water-cooled.
Forced air cooling
Water-cooling
Working conditions
The equipment is easy to install, only need to power on.
The ambient temperature should be lower than 28℃. If the ambient temperature is higher than 28℃, it has a certain impact on the refrigeration effect (preferably with air conditioning), the circulating cooling water system should be configured.
Heat exchange effect
Poor (relative to the water-cooling mode)
Stable, good
Noise
Large (relative to the water-cooling mode)
Less
The walk-in high and low temperature (humid and hot) laboratory also needs maintenance
Reminder: Remember to maintain the walk-in high and low temperature (humid and hot) laboratory as well!
1. The temperature and humidity testing system of the walk-in high and low temperature (humid and hot) laboratory must be operated and maintained by a dedicated person. Strictly follow the operating procedures of the system and avoid others from operating the system illegally.
2. Long term shutdown of the walk-in high and low temperature (humid and hot) laboratory can affect the effective service life of the system. Therefore, the system should be turned on and operated at least once every 10 days; Do not repeatedly stop the system in a short period of time. The number of starts per hour should be less than 5 times, and the time interval between each start stop should not be less than 3 times; Do not open the door of the walk-in temperature and humidity testing system at low temperatures to prevent damage to the door sealing tape.
3. A system usage file should be established to facilitate system maintenance and repair. The use of archives should record the start and end time (date) of each system operation, the type of experiment, and the ambient temperature; When the system malfunctions, provide a detailed description of the fault phenomenon as much as possible; The maintenance and repair of the system should also be recorded in as much detail as possible.
4. Conduct a monthly main power switch (leakage circuit breaker) operation test to ensure that the switch is used as a leakage protector while meeting the load capacity. The specific steps are as follows: first, please confirm that the main power switch is turned to "ON", which means the system is powered on, and then press the test button. If the switch lever of the residual current circuit breaker falls down, this function is normal.
5. The main box of the walk-in temperature and humidity testing system should be protected during use and should not be subjected to strong impacts from sharp or blunt objects.
6. To ensure the normal and clean supply of cooling water, the cooling water filter of the refrigeration unit should be cleaned every 30 days. If the local air quality is poor and the dust content in the air is high, the cooling water tower reservoir should generally be cleaned every 7 days.
7. The leakage, overload, and short-circuit protection characteristics of the residual current switch are set by Lab Companion manufacturer and cannot be adjusted arbitrarily during use to avoid affecting performance; After the leakage switch is disconnected due to a short circuit, the contacts need to be checked. If the main contacts are severely burned or have pits, maintenance is required.
8. The test products placed in the walk-in temperature and humidity testing system should be kept at a certain distance from the suction and exhaust ports of the air conditioning channel to avoid obstructing air circulation.
9. Overtemperature protector action test. Set the temperature of the over temperature protector to be lower than the temperature of the box. If there is an E0.0 alarm and buzzing sound, it indicates that its function is normal. After completing the above experiment, the temperature protection setting should be reset appropriately, otherwise it may cause inappropriate termination.
10. Once a year, use a vacuum cleaner to clean and remove dust from the distribution room and water circuit room. Once a month, use a dry cloth to clean the accumulated water in the water tray of the refrigeration unit.
Maintenance of refrigeration compressor for constant temperature and humidity test chamber, cold and hot shock test chamber
Article summary: For environmental monitoring equipment, the only way to maintain long-term and stable use is to pay attention to maintenance in all aspects. Here, we will introduce the maintenance of the compressor, which is an important component of the constant temperature and humidity test chamber and the cold and hot shock test chamber
Detailed content:
Maintenance plan for refrigeration compressor:
As the core component of the refrigeration system in the constant temperature and humidity test chamber, the maintenance of the compressor is essential. Guangdong Hongzhan Technology Co., Ltd. introduces the daily maintenance steps and precautions for the compressor in the constant temperature and humidity test chamber and the cold and hot shock test chamber
1、 Carefully check the sound of the cylinders and moving parts at all levels to determine if their working condition is normal. If any abnormal sound is found, immediately stop the machine for inspection;
2、 Pay attention to whether the indicated values of pressure gauges at all levels, pressure gauges on gas storage tanks and coolers, and lubricating oil pressure gauges are within the specified range;
3、 Check if the temperature and flow rate of the cooling water are normal;
4、 Check the supply of lubricating oil and the lubrication system of the moving mechanism (some compressors are equipped with organic glass baffles on the side of the cross head guide rail of the machine body),
You can directly see the movement of the crosshead and the supply of lubricating oil; The cylinder and packing can be inspected for oil discharge using a one-way valve, which can check if the oil injector is inserted into the cylinder
Oil injection situation;
5、 Observe whether the oil level in the body oil tank and the lubricating oil in the oil injector are below the scale line. If they are low, they should be refilled in a timely manner (if using a dipstick, stop and check);
6、 Check the temperature of the intake and exhaust valve covers at the cross guide rail of the crankcase with your hand to see if it is normal;
7、 Pay attention to the temperature rise of the motor, bearing temperature, and whether the readings on the voltmeter and ammeter are normal. The current should not exceed the rated current of the motor. If it exceeds the rated current, the cause should be identified or the machine should be stopped for inspection;
8、 Regularly check whether there are any debris or conductive objects inside the motor, whether the coil is damaged, and whether there is friction between the stator and rotor, otherwise the motor will burn out after starting;
9、 If it is a water-cooled compressor and water cannot be immediately supplied after the water is cut off, it is necessary to avoid cylinder cracking due to uneven heating and cooling. After parking in winter, the cooling water should be drained to prevent freezing and cracking of the cylinder and other parts;
10、 Check whether the compressor vibrates and whether the foundation screws are loose or detached;
11、 Check whether the pressure regulator or load regulator, safety valve, etc. are sensitive;
12、 Pay attention to the hygiene of the compressor, its associated equipment, and the environment;
13、 Gas storage tanks, coolers, and oil-water separators should regularly release oil and water;
14、 The lubricating machine used should be filtered by sedimentation. Differentiate the use of compressor oil between winter and summer
Conduction Zone of Heat
Thermal conductivity
It is the thermal conductivity of a substance, passing from high temperature to low temperature within the same substance. Also known as: thermal conductivity, thermal conductivity, thermal conductivity, heat transfer coefficient, heat transfer, thermal conductivity, thermal conductivity, thermal conductivity, thermal conductivity.
Thermal conductivity formula
k = (Q/t) *L/(A*T) k: thermal conductivity, Q: heat, t: time, L: length, A: area, T: temperature difference in SI units, the unit of thermal conductivity is W/(m*K), in imperial units, is Btu · ft/(h · ft2 · °F)
Heat transfer coefficient
In thermodynamics, mechanical engineering and chemical engineering, the heat conductivity is used to calculate the heat conduction, mainly the heat conduction of convection or the phase transformation between fluid and solid, which is defined as the heat through the unit area per unit time under the unit temperature difference, called the heat conduction coefficient of the substance, if the thickness of the mass of L, the measurement value to be multiplied by L, The resulting value is the coefficient of thermal conductivity, usually denoted as k.
Unit conversion of heat conduction coefficient
1 (CAL) = 4.186 (j), 1 (CAL/s) = 4.186 (j/s) = 4.186 (W).
The impact of high temperature on electronic products:
The rise in temperature will cause the resistance value of the resistor to decrease, but also shorten the service life of the capacitor, in addition, the high temperature will cause the transformer, the performance of the related insulation materials to decrease, the temperature is too high will also cause the solder joint alloy structure on the PCB board to change: IMC thickens, solder joints become brittle, tin whisker increases, mechanical strength decreases, junction temperature increases, the current amplification ratio of transistor increases rapidly, resulting in collector current increases, junction temperature further increases, and finally component failure.
Explanation of proper terms:
Junction Temperature: The actual temperature of a semiconductor in an electronic device. In operation, it is usually higher than the Case Temperature of the package, and the temperature difference is equal to the heat flow multiplied by the thermal resistance. Free convection (natural convection) : Radiation (radiation) : Forced Air(gas cooling) : Forced Liquid (gas cooling) : Liquid Evaporation: Surface Surroundings Surroundings
Common simple considerations for thermal design:
1 Simple and reliable cooling methods such as heat conduction, natural convection and radiation should be used to reduce costs and failures.
2 Shorten the heat transfer path as much as possible, and increase the heat exchange area.
3 When installing components, the influence of radiation heat exchange of peripheral components should be fully considered, and the thermal sensitive devices should be kept away from the heat source or find a way to use the protective measures of the heat shield to isolate the components from the heat source.
4 There should be sufficient distance between the air inlet and the exhaust port to avoid hot air reflux.
5 The temperature difference between the incoming air and the outgoing air should be less than 14 ° C.
6 It should be noted that the direction of forced ventilation and natural ventilation should be consistent as far as possible.
7 Devices with large heat should be installed as close as possible to the surface that is easy to dissipate heat (such as the inner surface of the metal casing, metal base and metal bracket, etc.), and there is good contact heat conduction between the surface.
8 Power supply part of the high-power tube and rectifier bridge pile belong to the heating device, it is best to install directly on the housing to increase the heat dissipation area. In the layout of the printed board, more copper layers should be left on the board surface around the larger power transistor to improve the heat dissipation capacity of the bottom plate.
9 When using free convection, avoid using heat sinks that are too dense.
10 The thermal design should be considered to ensure that the current carrying capacity of the wire, the diameter of the selected wire must be suitable for the conduction of the current, without causing more than the allowable temperature rise and pressure drop.
11 If the heat distribution is uniform, the spacing of the components should be uniform to make the wind flow evenly through each heat source.
12 When using forced convection cooling (fans), place the temperature-sensitive components closest to the air intake.
13 The use of free convection cooling equipment to avoid arranging other parts above the high power consumption parts, the correct approach should be uneven horizontal arrangement.
14 If the heat distribution is not uniform, the components should be sparsely arranged in the area with large heat generation, and the component layout in the area with small heat generation should be slightly denser, or add a diversion bar, so that the wind energy can effectively flow to the key heating devices.
15 The structural design principle of the air inlet: on the one hand, try to minimize its resistance to the air flow, on the other hand, consider dust prevention, and comprehensively consider the impact of the two.
16 Power consumption components should be spaced as far apart as possible.
17 Avoid crowding temperature sensitive parts together or arranging them next to high power consuming parts or hot spots.
18 The use of free convection cooling equipment to avoid arranging other parts above the high power consumption parts, the correct practice should be uneven horizontal arrangement.
Temperature Cyclic Stress Screening (1)
Environmental Stress Screening (ESS)
Stress screening is the use of acceleration techniques and environmental stress under the design strength limit, such as: burn in, temperature cycling, random vibration, power cycle... By accelerating the stress, the potential defects in the product emerge [potential parts material defects, design defects, process defects, process defects], and eliminate electronic or mechanical residual stress, as well as eliminate stray capacitors between multi-layer circuit boards, the early death stage of the product in the bath curve is removed and repaired in advance, so that the product through moderate screening, Save the normal period and decline period of the bathtub curve to avoid the product in the process of use, the test of environmental stress sometimes lead to failure, resulting in unnecessary losses. Although the use of ESS stress screening will increase the cost and time, for improving the product delivery yield and reduce the number of repairs, there is a significant effect, but for the total cost will be reduced. In addition, customer trust will also be improved, generally for electronic parts of the stress screening methods are pre-burning, temperature cycle, high temperature, low temperature, PCB printed circuit board stress screening method is temperature cycle, for the electronic cost of the stress screening is: Power pre-burning, temperature cycling, random vibration, in addition to the stress screen itself is a process stage, rather than a test, screening is 100% of the product procedure.
Stress screening applicable product stage: R & D stage, mass production stage, before delivery (screening test can be carried out in components, devices, connectors and other products or the whole machine system, according to different requirements can have different screening stress)
Stress screening comparison:
a. Constant high temperature pre-burning (Burn in) stress screening, is the current electronic IT industry commonly used method to precipitate electronic components defects, but this method is not suitable for screening parts (PCB, IC, resistor, capacitor), According to statistics, the number of companies in the United States that use temperature cycling to screen parts is five times more than the number of companies that use constant high temperature prefiring to screen components.
B. GJB/DZ34 indicates the proportion of temperature cycle and random vibrating screen selection defects, temperature accounted for about 80%, vibration accounted for about 20% of the defects in various products.
c. The United States has conducted a survey of 42 enterprises, random vibration stress can screen out 15 to 25% of the defects, while the temperature cycle can screen out 75 to 85%, if the combination of the two can reach 90%.
d. The proportion of product defect types detected by temperature cycling: insufficient design margin: 5%, production and workmanship errors: 33%, defective parts: 62%
Description of fault induction of temperature cyclic stress screening:
The cause of product failure induced by temperature cycling is: when the temperature is cycled within the upper and lower extremal temperatures, the product produces alternating expansion and contraction, resulting in thermal stress and strain in the product. If there is a transient thermal ladder (temperature non-uniformity) within the product, or the thermal expansion coefficients of adjacent materials within the product do not match each other, these thermal stresses and strains will be more drastic. This stress and strain is greatest at the defect, and this cycle causes the defect to grow so large that it can eventually cause structural failure and generate electrical failure. For example, a cracked electroplated through-hole eventually cracks completely around it, causing an open circuit. Thermal cycling enables soldering and plating through holes on printed circuit boards... Temperature cyclic stress screening is especially suitable for electronic products with printed circuit board structure.
The fault mode triggered by the temperature cycle or the impact on the product is as follows:
a. The expansion of various microscopic cracks in the coating, material or wire
b. Loosen poorly bonded joints
c. Loosen improperly connected or riveted joints
d. Relax the pressed fittings with insufficient mechanical tension
e. Increase the contact resistance of poor quality solder joints or cause an open circuit
f. Particle, chemical pollution
g. Seal failure
h. Packaging issues, such as bonding of protective coatings
i. Short circuit or open circuit of the transformer and coil
j. The potentiometer is defective
k. Poor connection of welding and welding points
l. Cold welding contact
m. Multi-layer board due to improper handling of open circuit, short circuit
n. Short circuit of power transistor
o. Capacitor, transistor bad
p. Dual row integrated circuit failure
q. A box or cable that is nearly short-circuited due to damage or improper assembly
r. Breakage, breakage, scoring of material due to improper handling... Etc.
s. out-of-tolerance parts and materials
t. resistor ruptured due to lack of synthetic rubber buffer coating
u. The transistor hair is involved in the grounding of the metal strip
v. Mica insulation gasket rupture, resulting in short circuit transistor
w. Improper fixing of the metal plate of the regulating coil leads to irregular output
x. The bipolar vacuum tube is open internally at low temperature
y. Coil indirect short circuit
z. Ungrounded terminals
a1. Component parameter drift
a2. Components are improperly installed
a3. Misused components
a4. Seal failure
Introduction of stress parameters for temperature cyclic stress screening:
The stress parameters of temperature cyclic stress screening mainly include the following: high and low temperature extremum range, dwell time, temperature variability, cycle number
High and low temperature extremal range: the larger the range of high and low temperature extremal, the fewer cycles required, the lower the cost, but can not exceed the product can withstand the limit, do not cause new fault principle, the difference between the upper and lower limits of temperature change is not less than 88°C, the typical range of change is -54°C to 55°C.
Dwell time: In addition, the dwell time can not be too short, otherwise it is too late to make the product under test produce thermal expansion and contraction stress changes, as for the dwell time, the dwell time of different products is different, you can refer to the relevant specification requirements.
Number of cycles: As for the number of cycles of temperature cyclic stress screening, it is also determined by considering product characteristics, complexity, upper and lower limits of temperature and screening rate, and the screening number should not be exceeded, otherwise it will cause unnecessary harm to the product and cannot improve the screening rate. The number of temperature cycles ranges from 1 to 10 cycles [ordinary screening, primary screening] to 20 to 60 cycles [precision screening, secondary screening], for the removal of the most likely workmanship defects, about 6 to 10 cycles can be effectively removed, in addition to the effectiveness of the temperature cycle, Mainly depends on the temperature variation of the product surface, rather than the temperature variation inside the test box.
There are seven main influencing parameters of temperature cycle:
(1) Temperature Range
(2) Number of Cycles
(3) Temperature Rate of Chang
(4) Dwell Time
(5) Airflow Velocities
(6) Uniformity of Stress
(7) Function test or not (Product Operating Condition)
Temperature Cycling Test
Temperature Cycling, in order to simulate the temperature conditions encountered by different electronic components in the actual use environment, changing the ambient temperature difference range and rapid rise and fall temperature change can provide a more stringent test environment, but it must be noted that additional effects may be caused to material testing. For the relevant international standard test conditions of temperature cycle test, there are two ways to set the temperature change. Macroshow Technology provides an intuitive setting interface, which is convenient for users to set according to the specification. You can choose the total Ramp time or set the rise and cooling rate with the temperature change rate per minute.
List of international specifications for temperature cycling tests:
Total Ramp time (min) : JESD22-A104, MIL-STD-8831, CR200315
Temperature variation per minute (℃/min) : IEC 60749, IPC-9701, Bellcore-GR-468, MIL-2164
Example: Lead-free solder joint reliability test
Instructions: For the reliability test of lead-free solder joints, different test conditions will also be different in terms of the temperature change setting mode. For example, (JEDEC JESD22-A104) will specify the temperature change time with the total time [10min], while other conditions will specify the temperature change rate with [10℃/ min], such as from 100 ℃ to 0℃. With a temperature change of 10 degrees per minute, that is to say, the total temperature change time is 10 minutes.
100℃ [10min]←→0℃[10min], Ramp: 10℃/ min, 6500cycle
-40℃[5min]←→125℃ [5min], Ramp: 10min,
200cycle check once, 2000cycle tensile test [JEDEC JESD22-A104]
-40℃(15min)←→125℃(15min), Ramp: 15min, 2000cycle
Example: LED Automotive lighting (High Power LED)
The temperature cycle test condition of LED car lights is -40 ° C to 100 ° C for 30 minutes, the total temperature change time is 5 minutes, if converted into temperature change rate, it is 28 degrees per minute (28 ° C /min).
Test conditions: -40℃(30min)←→100℃(30min), Ramp: 5min
VMR- plate Temperature Cycle Transient Break Test
Temperature cycle test is one of the most commonly used methods for reliability and life test of lead-free welding materials and SMD parts. It evaluates the adhesive parts and solder joints on the surface of SMD, and causes plastic deformation and mechanical fatigue of solder joints materials under the fatigue effect of cold and hot temperature cycle with controlled temperature variability, so as to understand the potential hazards and failure factors of solder joints and SMD. The Daisy chain diagram is connected between the parts and the solder joints. The test process detects the on-off and on-off between the lines, parts and solder joints through the high-speed instantaneous break measuring system, which meets the demand for the reliability test of electrical connections to evaluate whether the solder joints, tin balls and parts fail. This test is not really simulated. Its purpose is to apply severe stress and accelerate the aging factor on the object to be tested to confirm whether the product is designed or manufactured correctly, and then evaluate the thermal fatigue life of the component solder joints. The reliability test of the electrical high-speed instantaneous break connection has become a key link to ensure the normal operation of the electronic system and avoid the failure of the electrical connection caused by the failure of the immature system. The resistance changes over a short period of time were observed under accelerated temperature changes and vibration tests.
Purpose:
1. Ensure that products designed, manufactured and assembled meet predetermined requirements
2. Relaxation of solder joint creep stress and SMD fracture failure caused by thermal expansion difference
3. The maximum test temperature of the temperature cycle should be 25℃ lower than the Tg temperature of the PCB material, so as to avoid more than one damage mechanism of the substitute test product
4. Temperature variability at 20℃/min is a temperature cycle, and temperature variability above 20℃/min is a temperature shock
5. The welding joint dynamic measurement interval does not exceed 1min
6. The high temperature and low temperature residence time for failure determination needs to be measured in 5 strokes
Requirements:
1. The total temperature time of the test product is within the range of the rated maximum temperature and the minimum temperature, and the length of the residence time is very important for the accelerated test, because the residence time is not enough during the accelerated test, which will make the creep process incomplete
2. The resident temperature must be higher than Tmax temperature and lower than Tmin temperature
Refer to the list of specifications:
IPC-9701, IPC650-2.6.26, IPC-SM-785, IPCD-279, J-STD-001, J-STD-002, J-STD-003, JESD22-A104, JESD22-B111, JESD22-B113, JESD22-B117 , SJR-01
EC-85MHPM-W, High load corresponding constant temperature and humidity tank (800L)
Project
Type
Series
ＭＨＰＭ－Ｗ
Function
Temperature and humidity mode
The way of wet ball
Temperature range
-40 ～ + 100 ℃
Humidity range
20 ～ 98%RH
（According to the anaphase 3 items）
Changes in temperature and humidity
± 0.3 ℃ ／ ±2.5%RH
Temperature and humidity distribution
± 0.5 ℃ ／ ±5.0%RH
The temperature drops the time
+20 ～ -40 ℃
Within 75 minutes
Temperature rise time
-40 ～ + 100 ℃
Within 50 minutes
The internal volume of the uterus was tested
800 Ｌ
Test room inch method (width, depth and height)
1000mm × 800mm × 1000mm
Product inch method (width, depth and height)
1400mm × 1190mm × 1795mm
Make the material
External outfit
Test room control panel
machine room
Cold steel plate, cold steel plate beige
(Color table 2.5Y8 / 2)
Inside
Stainless steel plate (SUS304,2B polished)
Broken heat material
Test room
Hard synthetic resin
―
Door
Hard synthetic resin foam cotton, glass cotton
Project
Type
Series
ＭＨＰＭ－Ｗ
Cooling removal, wet device
Cooling-down method
Mechanical section shrinkage mode
Cooling medium
Ｒ４０４Ａ
The oneself can shrink machine
Output (number of staff)
1.5kW （１）
Cooling and dehumidifier
Multi-channel mixed heat sink type
The condenser
Multi-channel mixed radiator sink (air cooling）
Calorifier
Form
Nickel-chromium heat-resistant alloy heater
Volume
3.5kW
Humidifier
Form
Steam generation
Volume
1.8Kw×2
Blower
Form
Multi-channel mixed radiator sink (air cooling）
Motor capacity
40W
Feed water unit
The water supply cylinder Water supply method
Water quality
Pure water ＊ Automatic water supply
（"Please refer to the automatic water supply."）
Volume
Gravity type
Moisturizing disk
Gravity type
Controller
Temperature setting range
-42.0 ～ + 102.0 ℃
Humidity setting range
0 ～ 98%RH （Dry Bulb Temperature 10 ～ 85 ℃ ）
Time set range
0 ～ 999Time of 59 min（Program setting type） 0 ～ 20000 Time of 59 min（The value type）
Set decomposition energy
Temperature 0.1℃, humidity 1% RH for 1 min
Indicate accuracy
Temperature ± 0.8℃ (tp.), humidity ± 1% RH (tp.), time ± 100 PPM
Vacation type
Value or program
Stage number
20-stage / 1 program
The number of procedures
The maximum number of incoming force (RAM) programs is 32 programs
The maximum number of internal ROM programs is 13 programs
Round-trip number
98 times maximum or unlimited
Number of round-trip repeats
Maximum 3 heavy
Displace the end
Pt 100Ω （ at 0 ℃ ）， grade Ｂ（ JIS C 1604-1997 ）
Control action
When splitting the PID action
Internal function
Early delivery function, standby function, setting value maintenance function, power outage protection function,
Power action selection function, maintenance function, transportation round-trip function,
Time delivery function, time signal output function, overrising and overcooling prevention function,
Abnormal representation function, external alarm output function, setting paradigm representation function,
Transport type selection function, the calculation time represents the function, the slot lamp lamp function
Project
Type
Series
ＭＨＰＭ－Ｗ
Control panel
Equipment machine
LCD operating panel (type contact panel),
Represents lamp (power, transport, abnormal), test power supply terminal, external alarm terminal,
Time signal output terminal, power cord connector
Protective device
Refrigerating cycle
Overload protection device, high blocking device
Calorifier
Temperature over-rise protection device, temperature fuse
Humidifier
Air burning prevention device, humidifying disc water level regulator
Blower
Overload protection device
Control panel
Leakage breaker for power supply, fuse (for heater, humidifier),
Fuse (for operating loop), temperature rise protection device (for testing),
Temperature rise overcooling prevention device (test material, in microcomputer)
Offproducts (sets)
House receiver (4), house board (2), wet ball wick (15), operation manual (1)
Equipment products
Adventitia
Hard borosilicate glass 800mm× 800mm
2
Cable hole
Bore size 50mm
１
The trough inside the lamp
AC100V 15W White hot ball
２
Wheel
４
Horizontal adjustment
４
Electrovirus characteristics
Source
AC three-phase 380V 50Hz
Maximum load current
25A
Capacity of the leakage breaker for the power supply
50A
Sensory current 30mA
Power distribution thickness
14mm2
Rubber insulation hose
Coarseness of grounding wire
5.5mm2
Tubing
Drain-pipe
PT1/2
Product quality
550kg
Comprehensive test box
Equipment features:
Can be connected to a vertical vibration table or to both vertical and horizontal vibration tables simultaneously;
You can choose functions such as device lifting and device translation;
High strength and high reliability structural design - ensuring the high reliability of the equipment;
The studio material is SUS304 stainless steel - with strong corrosion resistance, cold and hot fatigue function, and long service life;
High density polyurethane foam insulation material - ensuring minimal heat loss;
Surface spraying treatment - ensuring the long-lasting anti-corrosion function and appearance life of the equipment;
High strength heat-resistant silicone rubber sealing strip - ensures high sealing performance of equipment doors;
Multiple optional functions (such as test holes, recorders, water purification systems, etc.) ensure that users have multiple functions and testing needs;
Large area electric anti frost observation window and concealed lighting - can provide good observation effect;
Environmentally friendly refrigerants - ensure that equipment better meets your environmental protection requirements;
Customizable size/usage indicators/various optional functions according to user requirements
Temperature control
Can achieve temperature constant control and program control;
The full process data recorder (optional function) can achieve full process recording and traceability of the experimental process;
Each motor is equipped with overcurrent (overheating) protection/heater short-circuit protection to ensure high reliability of air flow and heating during equipment operation;
USB interface and Ethernet communication function enable the device's communication and software expansion functions to meet various customer needs;
Adopting the internationally popular cooling control mode, the compressor cooling power can be automatically adjusted from 0% to 100%, reducing energy consumption by 30% compared to the traditional heating balance temperature control mode;
The key components of refrigeration and electrical control are all made of internationally renowned brand products, which improves and ensures the overall quality of the equipment;
The equipment meets the following standards
GB/T 10592-2008 Technical Conditions for High and Low Temperature Test Chambers
GB/T 10586-2006 Technical Conditions for Damp Heat Test Chamber
GB/T 2423.1-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test A: Low Temperature
GB/T 2423.2-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test B: High Temperature
GB/T 2423.3-2006 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test Cab: Constant Damp Heat Test
GB/T 2423.4-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test Db: Alternating Damp Heat (12h+12h Cycle)
GB/T 2423.22-2008 Environmental testing for electrical and electronic products - Part 2: Test methods - Test N: Temperature changes
GB/T 5170.1-2008 General Principles for Inspection Methods of Environmental Testing Equipment for Electrical and Electronic Products
GJB 150.3A-2009 Military Equipment Laboratory Environmental Test Methods Part 3: High Temperature Test
GJB 150.4A-2009 Military Equipment Laboratory Environmental Test Methods Part 4: Low Temperature Test
GJB 150.9A-2009 Military Equipment Laboratory Environmental Test Methods Part 9: Damp Heat Test
Choosing different vibration table bodies can meet different vibration standard test methods
(e.g. GB/T 2423.35-2005, GB/T 2423.36-2005, etc.).
Three comprehensive test chambers; Temperature, humidity, and vibration three comprehensive test chamber; Technical specifications for temperature/humidity/vibration/three comprehensive testing equipment.
model
THV-500
THV-1000
THV-1500
inside dimension
D
700
900
1250
W
800
1150
1150
H
900
1100
1100
Size of connecting the vibration table（mm）
Horizontal stand ≤400*400 Vertical platform≤Φ400
Horizontal stand ≤600*600 Vertical platform≤Φ600 Single vertical platform≤Φ630mm
Horizontal stand ≤900*900 Vertical platform≤Φ900
Motor cover height（mm）
235
Source
AC380V.50HZ Three-phase four-wire system + grounding wire
Standard layout
One product manual, one test report, one quality certificate and quality guarantee, 2 panels, 2 strips, one blind board, one set of interface board, one set of silicone rubber soft plug
Structure
Hull
Surspray of cold rolled steel plate (ivory white)
Inner tank
Stainless steel sheet and plate
Heat insulating material
Polyurethane foaming
Refrigeration
Refrigeration method
Refrigeration mode of stacked compressor (water cooled)
Refrigerator
German valley wheel semi-closed compressor
Observation window （mm）
400*500
Instrument connection （mm）
One on the left and right sidesΦ100
Controller
Color LCD display touch screen
Recording device
Temperature and humidity recorder (optional)
Communication interface
The RS485 interface. The RS232 interface. Upper position computer operation software (optional)
Polarizer Test Conditions
Polarizer is one of the basic parts of the liquid crystal display, is a light plate that only allows a certain direction of light to pass through, in the process of making the liquid crystal plate, must be used above and below each piece, and into the staggered direction placed, mainly used for electric field and no electric field when the light source produces a phase difference and the state of light and dark, to display subtitles or patterns.
Relevant test conditions:
Because the molecular structure of iodine is easy to destroy under high temperature and humidity conditions, the durability of the polarizer produced by iodine dyeing technology is poor, and generally can only meet:
High temperature: 80℃×500HR
Hot and humid: working conditions below 60℃×90%RH×500HR
However, with the expansion of the use of LCD products, the wet and hot working conditions of polarizing products are becoming more and more demanding, and there has been a demand for polarizing plate products that work at 100 ° C and 90%RH conditions, and the highest conditions at present are:
High temperature: 105℃×500HR
Humidity and heat: test requirements below 90℃×95%RH×500HR
The durability test of polarizer includes four test methods: high temperature, wet heat, low temperature and cold and heat shock, of which the most important test is the wet and heat test. The high temperature test refers to the high temperature working conditions of the polarizer at a constant baking temperature. At present, according to the technical grade of the polarizer, it is divided into:
Universal type: working temperature is 70℃×500HR;
Medium durability type: the working temperature is 80℃×500HR;
High durability type: the operating temperature is 90℃×500H above these three grades.
Because the basic materials of the polarizing film PVA film and iodine and iodide are easily hydrolyzed materials, but also because the pressure sensitive adhesive used in the polarizing plate is also easy to deteriorate under high temperature and high humidity conditions, the most important things in the environmental test of the polarizing plate are high temperature and wet heat.
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