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

This paper describes the current status of environmental testing equipment, the correct use of environmental testing equipment and the general maintenance of environmental testing equipment. The purpose is to help the majority of environmental testers have a preliminary understanding of the correct use of environmental test equipment.

The environmental test equipment is a combined test equipment that simulates one or more harsh environments by manual methods in the test room. It is an environmental test equipment for developing and developing new products and testing the quality and performance of the products. It is an indispensable test and test equipment. Therefore, the proper use and maintenance of environmental and reliability test equipment is especially important.

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

one. Status of environmental testing equipment
At present, most of the domestic environmental test equipment is produced to meet the national standard GB2423 "Basic Test Procedures for Electrical and Electronic Products". These environmental test equipments now have corresponding national standards, such as GB10586-89 "Technical Conditions for Damp Heat Test Chamber" 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 introduced from Western countries, and the price was relatively expensive. Nowadays, with the development of electronic technology, especially the development of control technology, from analog control to current digital control. Display mode from pointer to digital to current touch screen display; control accuracy increased from ±1 °C to 0.1 °C or even 0.01 °C; equipment volume from small box to hundreds of cubic meters of room (room) China's environmental test equipment manufacturers have been able to produce equipment that meets the test requirements. Performance can be comparable to imported equipment, and the price is only about half of imported equipment. However, some special equipment, such as temperature shock equipment, and rapid changes in temperature (15 ° C / min) can not be localized or produced equipment can not meet the requirements.

two. Correct use of environmental test equipment
Despite this, environmental testing equipment is still a sophisticated, valuable equipment. Proper use and operation of the environmental test equipment not only provides an accurate basis for the test personnel, but also enables the environmental test equipment to operate normally for a long time and extend the service life of the equipment.

First of all, when doing environmental tests, be familiar with the sample performance, test conditions, test procedures and test techniques of the required test, be familiar with the technical performance of the test equipment used, and have an understanding of the construction of the equipment, especially Be familiar with the operation and performance of the controller. Also carefully read the operating manual of the test equipment, in order to avoid the abnormal operation of the test equipment caused by the operation error, resulting in damage to the test sample, the test data is not correct.

Second, reasonable selection of test equipment. In order to ensure the normal operation of the test, appropriate test equipment should be selected according to the different conditions of the test sample, and a reasonable ratio should be maintained between the test sample and the effective volume of the test chamber. For the test of the heat test sample, the volume should be no more than one tenth of the effective volume of the test chamber. For non-fever test samples, the volume should be no more than one-fifth of the effective volume of the test chamber. For example, when a 21` color TV is used for temperature storage test, a one-cubic-volume test box can be used to meet the requirements. When it is energized, it can not meet the requirements. It should be replaced with a larger test chamber. Because the TV has to radiate heat while working.

Third, place the test sample correctly. The position of the test sample should be more than 10cm away from the wall of the box, 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 the return air outlet, and the temperature and humidity sensor should also be set a certain distance. To ensure the correct test temperature.

Fourth, the environmental test for the medium to be added in the test should be correctly added according to the test requirements. For example, the water consumption of the damp heat test chamber is required. The water resistivity of the test chamber shall not be less than 500 ohms. The general tap water resistivity is 10-100 ohms. The distilled water resistivity is 100-10000 ohms. Deionized water. The resistivity is 10,000-100,000 ohms. Therefore, the damp heat test water should be distilled or deionized water, and it must be fresh. Because the water is in contact with air, it is easily contaminated by carbon dioxide and dust. The water has a variety of substances. Nature, after a long time, the resistivity will decrease. There is now a pure water on the market that is economical and convenient, and its electrical resistivity is equivalent to distilled water.

fifth. Use of a damp heat test chamber. Wet ball gauze (wet ball paper) for wet heat test chambers has certain requirements, not any gauze can be substituted, because the relative humidity reading is the difference between the temperature and humidity, which is strictly related to the local atmospheric pressure and wind speed at that time. . The wet bulb temperature indication is related to the amount of water inhaled by the gauze and the surface evaporation. These are directly related to the quality of the gauze, so the meteorological regulations stipulate that the wet ball gauze must be a special "wet ball gauze" woven into linen. Otherwise it is difficult to ensure the correctness of the wet bulb thermometer, that is, the correct humidity. In addition, the placement of the wet ball gauze is also clearly defined. The length of the gauze is 100mm. The sensor probe is tightly wound. The probe is 25-30mm away from the humidity cup. The gauze is immersed in the water cup to ensure the correctness of the equipment control and the correctness of the humidity.

three. Maintenance of environmental test equipment
There are many kinds of environmental testing equipment, but the extensive environmental testing equipment used by Zui is a high temperature, low temperature and damp heat test box. Nowadays, it is popular as a test box that combines high temperature, low temperature and damp heat - high and low temperature damp heat test box, its repair The difficulty is larger and more representative than other environmental testing equipment. Let's take the high and low temperature damp heat test chamber as an example. Let's talk about the structure of the high and low temperature damp heat test chamber and some common faults and troubleshooting methods.

(1) The structural test personnel of the common high and low temperature damp heat test chambers should have some understanding of the structure in addition to the correct operation according to the operating procedures. The high and low temperature damp heat test chamber is composed of a box body, a wind circulation system, a refrigeration system, a heating system and a humidity control system. The air circulation system generally adopts a structure that can adjust the direction of air supply; the humidification system has two types of boiler humidification and surface evaporation; the cooling and dehumidification system adopts an air conditioning working condition refrigeration structure; the heating system adopts electric heating fin heating and electric furnace direct heating. Two kinds of structures; the temperature and humidity test method adopts the dry and wet ball test method, and also the direct measurement method of the humidity sensor; the control and display operation interface adopts the method of separate temperature and humidity separation and temperature and humidity combined controller.

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

1. In the high temperature test, if the temperature change does not reach the test temperature value, the electrical system can be inspected and the faults can be eliminated one by one. If the temperature rises very slowly, it is necessary to check the air circulation system to see if the regulating baffle of the wind cycle is normal. On the contrary, check whether the motor of the wind cycle is running normally. If the temperature is too high, you need to set the PID setting parameters. If the temperature rises directly and the temperature is over-protected, then the controller fails and the control instrument must be replaced.

2. If the low temperature does not reach the test index, then you should observe the change of temperature, whether the temperature drops very slowly, or the temperature rises after the temperature reaches a certain value. The former should check whether it will be before the low temperature test. Dry the studio, keep the studio dry, then put the test sample into the work room and then test it. If the test sample in the studio is too much, the wind in the workroom 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 of the manufacturer for maintenance. The latter phenomenon is caused by the poor use of the equipment. The ambient temperature at which the equipment is placed and the location where it is placed (the distance between the rear of the cabinet and the wall) must meet the requirements (as specified in the operating instructions for the equipment).

3. In the damp heat test, the actual humidity will reach 100% or the actual humidity will be very different from the target humidity. The value is much lower. The former phenomenon may be caused by the drying of the gauze on the wet ball sensor. Whether there is water shortage in the water tank of the 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 the water level controller works normally. It may be that the wet ball gauze is hardened due to the long use time or the purity of the water supply, so that the gauze becomes hard and the gauze cannot absorb moisture and is dry. The above phenomenon can be eliminated by replacing or cleaning the gauze. The latter phenomenon is mainly because 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 of the humidification boiler water level is normal, and whether the water level in the humidification boiler is normal. If everything above is normal, then check the electrical control system, which should be repaired by professional maintenance personnel.

4. When the equipment suddenly fails during the test operation, the corresponding fault display prompt appears on the control meter and there is an audible alarm prompt. The operator can quickly check which type of fault is involved in the troubleshooting chapter of the operation of the equipment, and then ask the professional to quickly eliminate the fault to ensure the normal operation of the test. Other environmental testing equipment will have other phenomena in use, and it will be specific phenomena, specific analysis and elimination.

The environmental test equipment should also be regularly maintained, 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 regularly maintained and checked, etc. These tasks are essential.

(Source: China Reliability Resource Network)