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Detailed understanding of high and low temperature humidity test chamber

Views: 234     Author: Wendy     Publish Time: 2023-08-10      Origin: Site

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Detailed understanding of high and low temperature humidity test chamber

1.Overview

The high and low temperature humidity test chamber is a type of apparatus that can be used to test the durability of lithium batteries, portable electronics, electronic materials, and other products, as well as for climate testing other products. High and low temperature damp heat laboratories typically have temperature adjustment ranges of +60 °C to -50 °C, and relative humidity adjustment ranges of +20 °C to +40 °C and +40 °C to +60 °C and 30% to 95% RH, respectively. The refrigeration system in the laboratory is relatively complex due to the wide temperature range and low negative temperature; as a result, utilizing the traditional relay control and manual operation techniques is not only difficult to operate but also inconvenient. The dry and wet bulb temperature control table and PLC were used to design the high and low temperature laboratory control system, which can be operated manually or automatically. In addition to having a straightforward circuit, it is also easy to use. Below is an introduction to this control system.

2. Chamber Organization and Functioning

The chamber body, heater, humidifier, refrigeration system, and air supply system make up the majority of the laboratory. The air dry and wet bulb temperatures, as well as the air distribution form of return air under the full orifice air supply, are adjusted and controlled using the method of balancing temperature and cooling capacity in order to achieve the air temperature and humidity required by the test and achieve the accuracy required by the test.

3. Control Strategy

For control, the heater in the lab is split into two groups. One group is the main heating, whose output power is automatically controlled and ranges from 0 to 100% (electric heating power) and is PID adjusted by the dry bulb temperature control device; The second category is auxiliary heating, which is initiated and terminated either manually or automatically by the computer. It is typically employed when the primary heating system's heat output is insufficient to meet test criteria. The humidifier is divided into two groups, same as the heater. One group consists of the main humidifier, whose output power is automatically controlled and ranges from 0 to 100% (electric humidification power) and is PID adjusted by the wet bulb temperature control device; The application can start and stop auxiliary humidification manually or automatically, which is the other group. It is typically employed when the main humidification system's humidity output is insufficient to meet test criteria. A cascade refrigeration system with two low-temperature compressors makes up the laboratory's cooling system. The system contains nine solenoid valves. Different solenoid valve and refrigerator configurations result in varying refrigerating capacities. The five stages of the refrigeration system can be classified based on the refrigerating capacity.

Automatic Control Techniques

The refrigeration system typically operates at a specific refrigeration level, and the relatively stable cooling capacity is input, in accordance with the laboratory's operating concept. The dry and wet bulb temperature control table automatically modifies the input for main heating and main humidification. Auxiliary heating or auxiliary humidification is started when the primary heating or humidification's power is insufficient. The system will immediately reach dynamic balance, and the temperature and humidity in the lab will swiftly stabilize. This happens when the cooling capacity is reasonably matched with the heating capacity and humidification capacity. Is the cooling capacity more or less invested in the refrigeration system By looking at the output variable from the temperature and humidity control table, indirect analysis can be performed. The temperature and humidity in the laboratory are still below the desired value even if the value of the output parameter out is very big (100%), indicating that the cooling input is excessive. When the out value is very low (0%), the lab's temperature and humidity are still over the desired level, which shows that the cooling input is insufficient. As can be seen, the refrigeration step can be automatically controlled using the output parameter from the temperature and humidity control table.

4. System Operation

Choose between manual and automatic switching options on the control panel. Each switch button on the panel can be used manually when manual operation is chosen. However, operating requires skilled workers because to the various input quantities of heating, humidification, and refrigeration under various working conditions. When automated is chosen, all equipment switches are turned on, and a software that is easy to use controls the actual input of heating, humidification, and refrigeration.

The switch on the panel can be used to interfere with automatic temperature and humidity management when it is in use if the stability time is too long.The refrigeration level, for instance, will decrease level by level while switching from low temperature to high temperature, necessitating a specific amount of delay time. You can now immediately turn off all refrigerators and preheat them. Restart the program-controlled refrigerator switch when the temperature is nearly at the desired level.

One can manually set the test time. After the test, sequentially switch off the device. The fan will run for an additional two minutes after the chiller, heater, and humidifier have shut off in order to exhaust the hot, humid gas from the air-conditioning cabinet and protect the metal parts from rusting.

Safety protection and alarm function

Conventional safety prevention features including overload, undervoltage, open circuit, and lack of power are present in the system control circuit. The cooling water pipeline has a water flow protector installed because the chiller is a chiller. The water flow protector activates and the chiller shuts off when the water flow falls below a certain threshold. The chiller also provides protection against temperature fluctuations, high and low pressures, and oil pressure. High temperature protection is a function of the laboratory. To avoid a fire, all equipment will be immediately turned off if the temperature rises above a particular point. The humidifier's purpose is to stop dry burning. The entire system has full protective features, including simultaneous sound and light prompts.

5.Summary

The equipment has been fitted with the aforementioned control system, and the automatic control performance is good. Although the stabilization time for temperature and humidity under automatic management is a little bit longer than under manual control, it still satisfies the contract's stabilization time requirements. The fluctuation range satisfies test criteria and achieves design accuracy following temperature and humidity stabilization. Because the operation is straightforward, it is more well-liked by operators, and automatic control is utilized at a pretty high rate.

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