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Basic understanding of thermal shock test chambers

Views: 233     Author: Wendy     Publish Time: 2023-08-10      Origin: Site

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Basic understanding of thermal shock test chambers

A thermal shock test chamber is a type of test device that quickly creates environments with extremely high and low temperatures for cold and hot shock environmental test equipment. primarily utilized in the fields of product safety and reliability testing and product screening in electronics, communications, materials, instruments, scientific research, and other fields. The appropriate environmental test equipment for technological development, production and quality control, as well as other scientific research and production, is used to test products that may experience structural and morphological changes as a result of temperature expansion and contraction and sustain physical damage.

Depending on the sample's condition at the time of the test. Thermal shock test chambers are divided into static thermal shock chambers (sample stationary) and dynamic thermal shock chambers (sample moves with the sample basket). According to the various ways of moving the sample basket, dynamic vertical lifting thermal shock chamber is primarily used for small load (such as IC module) test, while horizontal translation thermal shock chamber is used for testing larger loads.

1. Introduction to Equipment

The high temperature zone, low temperature zone, heating system, cascade refrigeration system, water circulation cooling system, sample basket transmission system, and control system make up the majority of the thermal shock test chamber. The sample basket is first placed in the high temperature zone in accordance with the set temperature for the high temperature test at this point, the low temperature zone is in a pre-cooling working state. The thermal shock chamber has two zones: a high temperature zone and a low temperature zone. The transmission mechanism will shift the sample basket from the high temperature zone to the low temperature zone when it reaches the predetermined thermal shock time. After being moved to the low temperature chamber, the sample is placed there and heated to the low temperature test temperature. The process from low temperature to high temperature shock test is the opposite of the aforementioned process at this moment; the high temperature zone is currently in the preheating operating stage.

This test chamber's primary control requirements are:

To meet the -75°C pre-cooling temperature and 5-min temperature recovery time requirements of the test chamber. The refrigeration system uses a binary cascading refrigeration cycle, which has specific requirements for the order in which the two compressors start up and the control of numerous refrigeration and bypass valves. In the case of temperature shock, in particular, regulation and control of the cooling amount have a direct impact on temperature control accuracy.

High-power heaters are installed in both the high and low temperature zones. During a temperature shock, it is necessary to resolve the conflict between rapid heating and precise temperature control, which raises the bar for heater control. In addition, the heater in the low temperature zone must also have a defrost function.

The sample basket transmission system uses a chain transmission mode that has a high transmission efficiency. When the temperature is affected, strict guidelines are put forth for the control of the transmission motor and the precise positioning of the sample basket movement. The accuracy of the sample basket positioning will directly affect the sealing of the low temperature chamber and the high temperature chamber, which will affect the temperature.

The control system configures a large number of alarm protection information, such as chamber door switch, water pressure alarm, overheating protection, compressor overload protection, etc., to ensure the operation safety of the thermal shock test chamber. This sets forth reliability requirements for the alarm signal processing of the control system.

2. Awareness of the effects of extreme temperature shock

As an illustration, the cyclic temperature shock with a high of 85 °C and a low of -55 °C is given. The thermostat's touch screen interface is used to initially set up the editing test procedure before it can begin. When operations begin, the sample basket will automatically choose the direction of movement based on the position. The sample basket will then be moved to the high temperature zone, where the heater will be turned on for an 85 ° C high temperature control test, and the refrigeration unit will be turned on for a -70 ° C pre-cooling temperature control test. The two side walls of the sample basket will then divide the thermal chamber's interior into two separate, closed spaces. The system will control the mobile motor to drive the sample basket from the high temperature zone to the low temperature zone to move quickly once the high temperature zone running time reaches the predetermined 60 minutes, which is when the PLC receives the end signal of the high temperature test issued by the thermostat. The high temperature zone and the low temperature zone will experience a brief period of cold and hot air convection as they move. The low temperature zone will see a quick rise in temperature while the sample load in the sample basket will also transfer heat from the high temperature zone to the low temperature zone. In addition, the sample basket will move into position during the 10 s temperature conversion period.

The system will regulate the sample basket to move quickly from the low temperature zone to the high temperature zone once the low temperature test has run for 45 minutes and the PLC has received the end signal.Similar to this, as a result of a significant amount of cold entering the air during the movement, the temperature in the high temperature zone will rise. The system will start the high temperature zone heater at full power to heat up quickly when the sample basket is quickly pushed to the place. Within five minutes, the temperature will rise to 85 °C, at which point the low temperature chamber will conduct a test on the temperature control at -70 °C. The entire temperature shock cycle experiment is over once the specified number of cycles has been completed.

There is also an automated defrosting feature in the low temperature zone. The defrosting temperature and runtime can be controlled using the touch screen when the thermal shock test is finished. In order to lessen the likelihood of frost in the low temperature zone, the low temperature zone is used for defrosting operations. It helps to safeguard the refrigeration system.

3. Finalization

The two-zone thermal shock test chamber control system satisfies the test chamber's requirements for high and low temperature shock, resolves the conflict between temperature control during temperature shock and rapid temperature rise and fall, and ensures the stability and dependability of the sample basket transmission. The user manufacturer's test chamber is now functioning well.

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