Use and maintenance of reliability test equipment

A brief discussion on the use and maintenance of environmental and reliability test equipment

[Abstract] : This paper describes the current status of environmental test equipment, the correct use of environmental test equipment and the general maintenance of environmental test equipment. The purpose is to help the majority of environmental test personnel to have a preliminary understanding of the correct use of environmental test equipment.

[Key words] : environmental test equipment use maintenance

Environmental test equipment is a combination of test equipment that simulates one or more harsh environments by artificial methods in the laboratory, and is an environmental test equipment for the development and development of new products and the inspection of product quality performance. It is our indispensable inspection and test equipment. Therefore, the correct use and maintenance of environmental and reliability test equipment is particularly important. According to the environmental factors simulated by the test equipment, the environmental test equipment can be roughly divided into: climate environmental equipment (including biological environmental test equipment), mechanical environmental test equipment, climate mechanical comprehensive environmental test equipment and other environmental test equipment. We have dozens of sets of various environmental test equipment. The environmental test equipment provides the necessary information and data for the development of modern high-tech products and the regular inspection and acceptance test of products.

one Current situation of environmental test equipment

At present, most of the domestic environmental test equipment is produced in order to meet the national standard GB2423 "Basic test Procedures for electrical and electronic products", these environmental test equipment now has the corresponding product national standard, Such as GB10586-89 "wet heat test box technical conditions" GB10589-89 "Low temperature test box technical conditions" GB10591-89 "high/low temperature test box technical conditions" GB10591-89 "high/low temperature test box technical conditions" and so on. Before the 1980s, most of the environmental test equipment used in China was introduced from Western countries, and the price is relatively expensive, and now, with the development of electronic technology, especially the development of control technology, from analog control to the current digital control; Display mode from pointer to digital and then to the present touch screen display; The control accuracy is improved from ±1℃ to 0.1℃ or even within 0.01℃. Equipment volume from very small box, to hundreds of cubic large room (room), China's environmental test equipment manufacturers have been able to produce equipment that meets the test requirements. The 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, rapid temperature change (15℃/min) can not be localized or produced equipment can not meet the requirements.

two The correct use of environmental test equipment In spite of this, environmental test 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 testing personnel, but also make the normal operation of environmental test equipment for a long time and extend the service life of the equipment. First of all, when doing environmental tests, it is necessary to be familiar with the sample performance, test conditions, test procedures and test technology required for the test, to be familiar with the technical performance of the test equipment used, to have an understanding of the structure of the equipment, especially the operation and performance of the controller. Also carefully read the operation manual of the test equipment, so as to avoid the abnormal operation of the test equipment caused by operational errors, resulting in damage to the test sample and incorrect test data. Secondly, reasonable selection of test equipment. In order to ensure the normal conduct of the test, the appropriate test equipment should be selected according to the different conditions of the test sample, and a reasonable proportion should be maintained between the effective volume of the test sample and the Test Chamber. For the test of the heating test sample, its volume should not be greater than one-tenth of the effective volume of the Test chamber. For non-heating test samples, the volume should not be greater than one-fifth of the effective volume of the test chamber. For example, a 21 'color TV in the temperature storage test, choose a cubic volume of the test box can meet the requirements, and in the power work, it can not meet the requirements, should be changed to a larger test box, because the TV at work to radiate heat.

Third, place the test sample correctly. The location of the test sample should be more than 10cm away from the box wall, and multiple samples should be placed on the same plane as far as possible.

Fourth, for the environmental test required to add media in the test, it should be correctly added according to the test requirements. If the water used in the damp heat test chamber is required, the resistivity of the water used in the test chamber shall not be less than 500 euros. Meters, general tap water resistivity of 10--100 euros. Meters, distilled water resistivity 100- 10000 euros. M, deionized water resistivity 10,000-100,000 ohms. Therefore, the wet heat test water to use distilled water or deionized water, and must use fresh, because water and air contact, vulnerable to carbon dioxide and dust pollution, water has the nature of soluble substances, after a long time, the resistivity to decline. Now there is a pure water on the market is more economical, and convenient, its resistivity is equivalent to distilled water.

Fifth. Use of damp heat test chambers. The wet bulb gauze (wet bulb paper) used in the wet heat test chamber has certain requirements, not any gauze can be used instead, because the relative humidity reading is the difference between the root distance and the temperature and humidity, strictly speaking, it is also related to the atmospheric pressure and wind speed of the local time. The value of wet-bulb temperature is related to the amount of water inhaled by the gauze and the situation of surface evaporation. These are directly related to the quality of gauze, so the weather stipulates that wet gauze must be a special "wet gauze" woven from linen. Otherwise, it is difficult to ensure the correctness of the value of the wet bulb thermometer, that is, the correct humidity. In addition, the placement of wet gauze is also clearly specified, the length of gauze is 100mm, the sensor probe is tightly wrapped, the probe is 25-30mm from the humidity cup, and the gauze is immersed in the water cup, so as to ensure the correctness of equipment control and humidity.

Three. Maintenance of environmental test equipment

There are many varieties of environmental test equipment, but the most widely used environmental test equipment is high temperature, low temperature, wet and heat test box, and today's more popular is a collection of high temperature, low temperature, wet and heat as one of the test box - high and low temperature wet and heat test box, which is more difficult to repair than other environmental test equipment, and representative. The following high and low temperature wet heat test chamber as an example, talk about the structure of high and low temperature wet heat test chamber and some common faults and troubleshooting methods.

(1) The structure of the common high and low temperature wet and heat test chamber

In addition to correct operation according to the operating procedures, the test personnel should also have an understanding of its structure. The high and low temperature wet heat test chamber is composed of box, air circulation system, refrigeration system, heating system and humidity control system. The air circulation system generally adopts the structure of adjustable air supply direction. There are two kinds of humidification system: boiler humidification and surface evaporation; The cooling and dehumidifying system adopts the refrigeration structure under the condition of air conditioning. The heating system adopts two structures: electric fin heating and electric furnace wire direct heating. Humidity and humidity test method adopts wet and dry bulb test method, and also uses humidity sensor direct measurement method; The control and display operation interface uses separate and independent temperature and humidity controllers or combined temperature and humidity controllers.

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

1. In the high temperature test, if the temperature change does not reach the test temperature value, you can check the electrical system and eliminate the fault one by one. If the temperature rises very slowly, it is necessary to check the wind circulation system to see whether the regulating baffle of the wind circulation is open normally, and on the contrary, check whether the motor of the wind circulation is running normally. If the temperature overshoot is severe then

You need to set the PID parameters. If the temperature rises directly and the temperature is too high, 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 temperature change, whether the temperature drops slowly or the temperature tends to rise after the temperature reaches a certain value. The former should check whether the studio is dried before the low temperature test, and the test samples are put into the studio after the studio is kept dry. So that the wind in the work room can not be fully circulated, after eliminating the above reasons, it is necessary to consider whether it is the fault in the refrigeration system, so it is necessary to ask the professional personnel of the manufacturer to carry out maintenance. The latter phenomenon is caused by the use of the equipment environment is not good, the ambient temperature of the equipment is placed, the position of the placement (the distance between the box and the wall) should meet the requirements (are specified in the instructions for the operation of the equipment).

3. In the wet 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 dry gauze on the wet bulb sensor, it is necessary to check whether the water is short of water in the sink of the wet bulb sensor, and the water level in the sink 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 gauze due to the long use time, or the purity of water supply quality, will make the gauze hardened, so that the gauze can not absorb water and dry, as long as the replacement or cleaning of the gauze can eliminate the above phenomenon. The latter phenomenon is mainly that the humidifier system does not work, check the water supply system of the humidifier system, whether there is a certain amount of water in the water supply system, whether the water level control of the humidifier boiler water level is normal, and whether the water level in the humidifier boiler is normal. If all the above is normal, it is necessary to 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 and sound alarm prompt will appear on the control instrument. The operator can quickly check which type of fault belongs to the troubleshooting chapter in the operation and use of the equipment, and then ask the professional to quickly troubleshoot the fault to ensure the normal conduct of the test. Other environmental test equipment in the use of other phenomena, it is necessary to specific phenomena, specific analysis and exclusion. The environmental test equipment should also be regularly maintained, the condenser of the refrigeration system is regularly cleaned, the moving parts should be lubricated according to the instructions, the electrical control system is regularly maintained and inspected, and so on.