On the use and maintenance of environmental and re

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Talking about the use and maintenance of environmental and reliability test equipment

[Abstract]: This paper expounds the current situation of environmental test equipment rising with the price of raw materials such as steel and aluminum, the correct use of environmental test equipment and the general maintenance of environmental test equipment. The purpose is to help environmental testing personnel have a preliminary understanding of the correct use of environmental testing equipment

[key words]: use and maintenance of environmental test equipment

environmental test equipment is a combined test equipment that simulates one or more systems in the laboratory by manual methods, which will automatically record the new zero adjustment value, measure without grading, and do not adjust the zero harsh environment. It is an environmental test equipment for developing and developing new products and inspecting the quality and performance of products. It is our indispensable inspection and test equipment. Therefore, it is particularly important to use and maintain the environment and reliability test equipment correctly

according to the environmental factors simulated by the test equipment, the environmental test equipment can be roughly divided into: climatic environmental equipment (including biological environmental test equipment), mechanical environmental test equipment, climatic mechanical comprehensive environmental test equipment and other environmental test equipment. We have dozens of sets of environmental testing equipment. The environmental test equipment provides necessary information and data for the research and development of modern high-tech products and the regular inspection and acceptance test of products

I. current situation of environmental test equipment

at present, most domestic environmental test equipment are produced to meet the national standard GB2423 "Basic test procedures for electrical and electronic products", and these environmental test equipment now have corresponding product national standards, For example,

GB technical conditions of damp heat test chamber,

GB technical conditions of low temperature test chamber,

GB technical conditions of high/low temperature test chamber,

GB technical conditions of high/low temperature test chamber, etc

before the 1980s, most of the environmental testing equipment used in China was imported from western countries, and the price is relatively expensive. Now, with the development of electronic technology, especially the development of control technology, from analog control to digital control; The display mode is from pointer to number to current touch screen display; The control accuracy is improved from ± 1 ℃ to 0.1 ℃ or even within 0.01 ℃; The equipment volume ranges from a small box to a room (room) with a size of hundreds of cubic meters. China's environmental test equipment manufacturers have been able to produce equipment that meets the test requirements. The performance can be comparable with imported equipment, and the price is only about half of imported equipment. However, some special equipment, such as temperature impact equipment and equipment with rapid temperature change (15 ℃/min), cannot be localized or the production equipment cannot meet the requirements

II. The correct use of environmental testing equipment

needs the support and guarantee of the new material industry as much as possible, but environmental testing equipment is still a kind of precision and valuable equipment. The correct use and operation of environmental test equipment can not only provide accurate basis for inspectors, but also make the environmental test equipment operate normally for a long time and prolong the service life of the equipment

first, when doing environmental tests, you should be familiar with the sample performance, test conditions, test procedures and test technology of the required tests, the technical performance of the test equipment used, and the structure of the equipment, especially the operation and performance of the controller. Also read the operation manual of the test equipment carefully, so as to avoid the abnormal operation of the test equipment caused by operational errors, which will cause damage to the test samples and incorrect test data

secondly, choose the test equipment reasonably. In order to ensure the normal test, appropriate test equipment should be selected according to the different conditions of the test samples, and a reasonable proportion should be maintained between the effective volume of the test samples and the test chamber. For the test of heating test sample, its volume shall not be greater than one tenth of the effective volume of the test chamber. For the non heating test sample, its volume shall not be greater than one-fifth of the effective volume of the test chamber. For example, when a 21 'color TV is doing the temperature storage test, it can meet the requirements by selecting a test box with a cubic volume, but when it is powered on, it cannot meet the requirements. It should be replaced with a larger test box, because the characteristic of the pressure burst tester is that the TV needs to emit heat when it is working

third, place the test sample correctly. The test samples shall be placed more than 10cm away from the box wall, and multiple samples shall be placed on the same plane as far as possible. The sample shall be placed without blocking the air outlet and return outlet, and a certain distance shall be reserved for the temperature and humidity sensor. To ensure the correct test temperature

fourth, for the environmental test in which the medium needs to be added in the test, it should be added correctly according to the test requirements. If there are certain requirements for the water used in the damp heat test chamber, the water resistivity of the test chamber shall not be less than 500 Ω Meter, the resistivity of general tap water is 10-100 Ω Meter, distilled water resistivity 100-10000 Ω Meter, deionized water resistivity ohm Therefore, distilled water or deionized water should be used for damp heat test, and fresh water must be used, because water is easy to be polluted by carbon dioxide and dust after contacting with air, and water has the property of dissolving a variety of substances. After a long time, the resistivity will decrease. Now there is a kind of purified water on the market, which is economical and convenient. Its resistivity is equivalent to distilled water

fifth, the use of damp heat test chamber. There are certain requirements for wet ball gauze and wet ball paper used in damp heat test chamber, which can not be replaced by any gauze, because the reading of relative humidity is the root distance, the difference between temperature and humidity, and strictly speaking, it is also related to the local atmospheric pressure and wind speed at that time. The wet bulb temperature indication is related to the amount of water absorbed by the gauze and the surface evaporation. These are directly related to the quality of gauze, so the weather stipulates that wet ball gauze must be a special "wet ball gauze" woven from linen. Otherwise, it is difficult to ensure the correctness of the indicated value of the wet bulb thermometer, that is, the correctness of humidity. In addition, the placement of wet ball gauze is also clearly stipulated. The length of gauze is 100mm, which is tightly wrapped around the sensor probe. The probe is 25-30mm away from the humidity water cup, and the gauze is immersed in the water cup, so as to ensure the correctness of equipment control and humidity

III. maintenance of environmental test equipment

there are many kinds of environmental test equipment, but the most widely used environmental test equipment is the high-temperature, low-temperature, damp heat test box, which integrates high-temperature, low-temperature, damp heat test box. It is more difficult to repair than other environmental test equipment and is representative. Next, take the high and low temperature damp heat test chamber as an example to talk about the structure of the high and low temperature damp heat test chamber and some common faults and troubleshooting methods

(I) structure of common high and low temperature damp heat test chamber

in addition to correctly operating according to the operating procedures, the tester should also understand its structure. The high and low temperature damp heat test chamber is composed of a box, an air circulation system, a refrigeration system, a heating system and a humidity control system. The air circulation system generally adopts the structure with adjustable air supply direction; There are two kinds of humidification systems: Boiler humidification and surface evaporation; The cooling and dehumidification system adopts the refrigeration structure under air conditioning conditions; The heating system adopts two structures: Electric fin heating and electric furnace wire direct heating; The temperature and humidity test method adopts the dry and wet ball test method, and also uses the direct measurement method of humidity sensor; The control and display operation interface adopts the methods of independent temperature and humidity and combined temperature and humidity controller

(II) some common faults and troubleshooting methods of high and low temperature damp heat test chamber:

1 In the high temperature test, if the temperature change cannot reach the test temperature value, the electrical system can be checked and the faults can be eliminated one by one. If the temperature rises slowly, check the air circulation system to see whether the regulating baffle of the air circulation is opened normally. On the contrary, check whether the motor of the air circulation operates normally. If the temperature overshoot is severe, it is necessary to set the PID setting parameters. If the temperature rises directly and overtemperature is protected, then the controller fails and the control instrument must be replaced

2. If the low temperature cannot reach the test index, you need to observe the change of temperature. Whether the temperature drops very slowly or the temperature tends to rise after reaching a certain value, the former needs to check whether the studio is dried before the low temperature test, and then put the test samples into the studio for test after keeping the studio dry. Whether the test samples in the studio are placed too much, so that the air in the studio cannot be fully circulated, After eliminating the above reasons, it is necessary to consider whether it is a fault in the refrigeration system, so it is necessary to ask the professional personnel of the manufacturer for maintenance. The latter phenomenon is caused by the poor operating environment of the equipment. The ambient temperature and location of the equipment (the distance between the back of the box and the wall) should meet the requirements (specified in the equipment operation instructions)

3. In the damp heat test, the actual humidity will reach 100% or the actual humidity is very different from the target humidity, and the value is much lower. The former phenomenon: it may be caused by the drying of the gauze on the wet ball sensor, so it is necessary to check whether there is water shortage in the water tank of the wet ball sensor. The water level in the water tank is automatically controlled by a water level controller. Check whether the water supply system of the water level controller is normal and whether the water level controller works normally. Another possibility is that the wet ball gauze will harden due to long service time or the purity of water supply quality, so that the gauze cannot absorb water and dry. As long as the gauze is replaced or cleaned, the above phenomenon can be eliminated. The latter phenomenon is mainly that the humidification system does not work. Check the water supply system of the humidification system, whether there is a certain amount of water in the water supply system, whether the water level control that controls the water level of the humidification boiler is normal, and whether the water level in the humidification boiler is normal. If all the above are normal, check the electrical control system, which requires professional maintenance personnel

4. When the equipment suddenly breaks down during the test operation, the corresponding fault display prompt and audible alarm prompt appear on the control instrument. The operator can quickly check the type of fault according to the chapter "troubleshooting in the operation and use of the equipment", and then ask professional personnel to quickly eliminate the fault, so as to ensure the normal operation of the test. Label making

other environmental test equipment will have other phenomena in use, which requires specific phenomena, specific analysis and elimination. The environmental test equipment should also be maintained regularly, the condenser of the refrigeration system should be cleaned regularly, the moving parts should be lubricated according to the instructions, the electrical control system should be maintained and inspected regularly, etc. these works are essential

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