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Technology of Temperature Test Chamber's Humidity and Temperature Control

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

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Technology of Temperature Test Chamber's Humidity and Temperature Control

Introduction

Many items in today's business must be processed in an atmosphere with a certain humidity and temperature range. Many goods' performance testing procedures, which include reliability, weather resistance, and service life tests, must be carried out in an environment with a particular temperature and humidity level. As an illustration, the benchmark testing of LED lamps includes tests for temperature and humidity such as the rapid temperature cycle test, the alternating damp heat test, the early reliability guarantee test, the limit stress sensitivity test, etc, where the environment must cycle between high temperature +85 °C and low temperature -40 °C at a pace of 10 °C/min for the quick temperature cycle test: The sample power supply is turned on and off during the high temperature and high humidity stage in each cycle of the alternating damp heat test, which calls for the product to be in proper working condition. The maximum temperature is 55 °C, the minimum temperature is -10 °C, and the power-off time is between 3 and 6 minutes;

In order to pass the early reliability guarantee test, the product must operate consistently under the rated electrical stress in a climate of 70 °C and 85% relative humidity while controlling the power status for 15 seconds; The ambient temperature must begin at 85 °C and be maintained for 1 hour in a 15 °C step for the limit stress sensitivity test.

Many manufacturers and scientific research organizations have investigated the product technology of high and low temperature test chambers, constant temperature and humidity test chambers, and so forth in order to establish a specific temperature and humidity environment. Although there are products with reasonably mature technology, such as high and low temperature test chambers, constant temperature and humidity test chambers, and others, on the market, their temperature and humidity precision has not yet produced satisfying results. In order to inform the product research and development of pertinent manufacturers and academic research institutions in connected disciplines, this study concentrates on the temperature and humidity regulation of high and low temperature test chambers and associated products.

Control engineering

The interaction of temperature and humidity

Temperature and humidity are not two separate control factors in a closed test room. They interact, affecting the coupling in control. Humidity fluctuations can be caused by changes in temperature. In general, raising the temperature causes some condensed steam to evaporate and raises the test chamber's humidity, while lowering the temperature causes some steam to condense into water droplets and lowers the humidity. The change in humidity will have a similar impact on temperature. The temperature of the test chamber will rise when the humidity is higher, fall when cold steam is injected, then rise again when water vapor condensation releases heat while lowering the humidity. Therefore, coupling must be taken into account during the control process, and decoupling must be realized during separate control.

Mode for controlling temperature and humidity

The anti integral saturation PID and bthc temperature and humidity regulation control mode is the control mode for the conventional temperature and humidity test chamber. The anti integral saturation PID control method primarily employs the integral separation method and PID separation method, which cancels the integral effect while tracking the controlled quantity and allows the proportional term to swiftly follow changes in deviation. The addition of the integral function occurs when the controlled quantity is close to the target value in order to reduce stability time, eliminate static error, and provide the integral correction effect. The dynamic properties of the system can be enhanced by this strategy, which fully utilizes each PID regulator component's regulating function. The coupling issue between temperature and humidity is not taken into account, as can be seen from its basic design, which makes switching the regulator more difficult to implement. Despite having a better control impact than a standard PID control, it is unable to match the demands of high performance.

Humidity and temperature technique using two closed loops for control

A traditional technique for DC speed regulation is the double closed-loop system. It benefits from a broad speed control range, good stability, high speed stability precision, quick reaction, and potent interference resistance. The main idea behind it is to incorporate a current loop into the speed loop in order to provide both current and speed negative feedback. Maximum current start is achieved using current negative feedback, which also increases response time and achieves steady-state error-free.

The control effect necessary for the temperature and humidity control of the test chamber is that the system must promptly and precisely attain the target value after the temperature and humidity have been set. In order to regulate the two control quantities of temperature and humidity, respectively, the double closed-loop system can be utilized. The researchers noted that for the aforementioned temperature and humidity coupling problem, the impact of humidity change on temperature is significantly less significant and can be disregarded than the impact of temperature change on humidity. That is, after the temperature reaches the desired level, the humidity is controlled to ensure that both variables are at the desired level. The goal of decoupling is achieved with this technique. Temperature and humidity can be controlled using a double closed-loop system with acceptable dynamic reaction time and steady-state precision. PI controllers with amplitude limits are used for both speed control and current control. According to the current requirements for heating and cooling after a certain temperature, the actuators are an electric heater made of alloy and a fully enclosed compressor.

Conclusion

In the world of testing and scientific research, high- and low-temperature test chamber is commonly employed. This paper suggests using the double closed-loop mode to control the temperature and humidity in order to achieve the quick and accurate control effect needed in the application. It also further analyzes its feasibility and superiority. This proposal is based on the rapidity and steady-state error of the control mode of the DC speed regulation system.

The theoretical and practical foundation of the double closed-loop DC speed regulation system is extremely developed, demonstrating the system's superiority, stability, and dependability. A novel notion that is anticipated to shed new light on the investigation of pertinent units is the use of the double closed-loop system to regulate the temperature and humidity of the test chamber. For a specific kind of test chamber, the parameter calculation and simulation experiment verification are not done in this paper but will be in the subsequent work.

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