Usage and Maintenance Techniques for Environmental and Reliability Testing Equipment

Environmental testing equipment is a combination of testing equipment that simulates one or more harsh environments using manual methods in a laboratory. It is an environmental testing equipment used for the development and testing of new products and the quality and performance of products. It is an essential inspection and testing equipment for us. So it is particularly important to use and maintain environmental and reliability testing equipment correctly. According to the environmental factors simulated by the testing equipment, the environmental testing equipment can be roughly divided into: climatic environmental equipment (including biological environmental testing equipment), mechanical environmental testing equipment, climatic mechanical comprehensive environmental testing equipment, and other environmental testing equipment. Environmental testing equipment provides necessary information and data for the development and regular inspection and acceptance testing of modern high-tech products.

1、 Current status of environmental testing equipment

At present, most environmental testing equipment in China is produced to meet the national standard GB2423 "Basic Test Regulations for Electrical and Electronic Products". These environmental testing equipment now have corresponding product national standards, such as

GB10586-89 Technical Conditions for Damp Heat Test Chambers

GB10589-89 "Technical Conditions for Low Temperature Test Chambers"

GB10591-89 Technical Conditions for High/Low Temperature Test Chambers

GB10591-89 "Technical Conditions for High/Low Temperature Test Chambers", etc.

Before the 1980s, most of the environmental testing equipment used in China was imported from Western countries and was relatively expensive. However, with the development of electronic technology, especially control technology, analog control has now evolved into digital control; The display mode has changed from pointer to number to current touch screen display: the control accuracy has been improved from ± 1 ℃ to 0.1 ℃ or even within 0.01 ℃; The environmental testing equipment manufacturers of Beike Instruments have been able to produce equipment that meets the testing requirements, ranging from small box sizes to rooms (rooms) several hundred cubic meters in size. The performance of temperature shock equipment and rapid temperature changes (15 ℃/min) can be comparable to imported equipment, and the price is only about half of that of imported equipment.

2、 Correct use of environmental testing equipment

Despite this, environmental testing equipment is still a precise and valuable device. The correct use and operation of environmental testing equipment not only provides accurate basis for testing personnel, but also enables long-term normal operation of environmental testing equipment and prolongs its service life.

Firstly, when conducting environmental tests, it is important to be familiar with the sample performance, test conditions, test procedures, and test techniques required. It is important to be familiar with the technical performance of the test equipment used, understand the structure of the equipment, and especially be familiar with the operation and performance of the controller. It is also necessary to carefully read the operation manual of the test equipment, in order to avoid abnormal operation of the test equipment caused by operational errors, which can cause damage to the test sample and incorrect test data.

Secondly, choose the testing equipment reasonably. To ensure the normal operation of the test, appropriate testing equipment should be selected based on 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 samples, their volume should not exceed one tenth of the effective volume of the test chamber. For non heating test samples, their volume should not exceed one-fifth of the effective volume of the test chamber.

For example, when conducting temperature storage tests on a 21 ° C color TV, selecting a one cubic volume test box can meet the requirements, but when powered on, it cannot meet the requirements. It should be replaced with a larger test box because the TV needs to dissipate heat during operation.

Thirdly, place the test sample correctly. The placement position of the test samples should be at least 10cm away from the box wall, and multiple samples should be placed on the same plane as much as possible. The sample should be placed without blocking the air outlet and return air outlet, and a certain distance should also be left for the temperature and humidity sensors. To ensure the correct test temperature.

Fourthly, for environmental tests that require the addition of media, it should be added correctly according to the test requirements. There are certain requirements for using water in a damp heat test chamber, and the water and electricity resistance used in the test chamber should not be less than 500 ohms per meter. Generally, the water and electricity resistance of tap water should not be less than 10-100 ohms per meter, the distilled water and electricity resistance should be 100-10000 ohms per meter, and the deionized water and electricity resistance should be 10000-10000 ohms per meter. Therefore, distilled water or deionized water should be used for damp heat test, and fresh water must be used, as water in contact with air is prone to carbon dioxide and dust pollution, Water has the property of dissolving various substances, and over time, its resistivity will decrease. There is now a type of purified water on the market that is more economical and convenient, with a resistivity equivalent to distilled water.

Fifth, the use of a damp heat test chamber. There are certain requirements for using wet ball gauze and wet ball paper in the damp heat test chamber, and not any gauze can be used as a substitute because the reading of relative humidity is based on the root distance and the difference between temperature and humidity. 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 according to meteorological regulations, wet bulb gauze must be a specialized "wet bulb gauze" woven from linen. Otherwise, it is difficult to ensure the accuracy of the wet bulb thermometer readings, that is, the accuracy of humidity. In addition, there are clear regulations for the placement of wet ball gauze. The length of the gauze is 100mm, tightly wrapped around the sensor probe, and the probe is 25-30mm away from the humidity water cup. The gauze is immersed in the water cup to ensure the correctness of equipment control and humidity.

3、 Maintenance of environmental testing equipment

There are many kinds of environmental test equipment, but the most widely used environmental test equipment are high temperature, low temperature, damp heat test chamber, cold and hot shock chamber. Nowadays, it is more popular to use a test chamber that integrates high temperature, low temperature, damp heat test chamber, which is more difficult to repair than other environmental test equipment and is representative. Taking the high and low temperature humidity and heat test box as an example, let's talk about the structure of the high and low temperature humidity and heat test box, as well as some common faults and troubleshooting methods.

（1） Construction of Common High and Low Temperature Damp Heat Test Chambers

In addition to correctly following the operating procedures, testers should also have an understanding of their structure. The high and low temperature humidity and heat test chamber is composed of a box body, an air circulation system, a refrigeration system, a heating system, and a humidity control system. The air circulation system generally adopts a structure with adjustable air supply direction; There are two types of humidification systems: boiler humidification and surface evaporation; The cooling and dehumidification system adopts a refrigeration structure under air conditioning conditions; The heating system adopts two structures: electric fin heating and direct heating with electric furnace wire; The temperature and humidity testing method adopts the dry and wet bulb testing method, as well as the direct measurement method using humidity sensors; The control and display operation interface adopts methods such as temperature and humidity separation, independent control, and temperature and humidity combination controller.

（2） Some common faults and troubleshooting methods of high and low temperature humid heat test chambers:

1. In the high-temperature test, if the temperature change cannot reach the test temperature value, the electrical system can be checked and faults can be eliminated one by one. If the temperature rises slowly, check the air circulation system to see if the regulating baffle of the air circulation is open properly__________ Check whether the motor of the air circulation operates normally. If the temperature overshoot is severe, it is necessary to adjust the PID setting parameters. If the temperature rises directly and there is over temperature protection, then if the controller malfunctions, the control instrument must be replaced.

2. If the low temperature does not meet the test indicators, then you need to observe the temperature changes. Whether the temperature drops slowly or there is a trend of temperature recovery after reaching a certain value, the former needs to check whether the studio is dried before conducting the low temperature test. After keeping the studio dry, the test samples are placed in the studio before conducting the test. If there are too many test samples in the studio, the air in the studio cannot be fully circulated, After eliminating the above reasons, it is necessary to consider whether it is a malfunction in the refrigeration system, and then ask the manufacturer's professional personnel for maintenance. The latter phenomenon is caused by the poor operating environment of the equipment, and the environmental temperature and location of the equipment placement (distance from the back of the box to the wall) must meet the requirements (as specified in the equipment operation instructions).

3. In the damp heat test, if the actual humidity reaches 100% or the actual humidity differs significantly from the target humidity, the value is much lower. The former phenomenon may be caused by the drying of the gauze on the wet bulb sensor. Therefore, it is necessary to check whether there is a shortage of water in the water tank of the wet bulb 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 is working properly. Another possibility is that wet bulb gauze may become hard due to prolonged use or the purity of the water supply, making it unable to absorb moisture and dry. Simply replacing or cleaning the gauze can eliminate the above phenomenon. The latter phenomenon is mainly due to the humidification system not working. Check the water supply system of the humidification system to see if there is a certain amount of water in the water supply system, whether the water level control of the humidification boiler is normal, and whether the water level in the humidification boiler is normal. If everything above is normal, then it is necessary to check the electrical control system, which requires professional maintenance personnel for maintenance.

When the equipment suddenly malfunctions during the test operation, the corresponding fault display prompt and sound alarm prompt appear on the control instrument. Operators can quickly check which type of fault belongs to in the chapter on troubleshooting during equipment operation and use, and then ask professional personnel to quickly troubleshoot to ensure the normal operation of the test. There may be other phenomena in the use of other environmental testing equipment for label making, so it is necessary to analyze and eliminate the specific phenomena. Environmental testing equipment needs to be regularly maintained, the condenser of the refrigeration system needs to be cleaned regularly, moving parts should be lubricated according to the instructions, and the electrical control system needs to be regularly maintained and inspected. These tasks are essential.