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How to choose the temperature and humidity test chamber?

Views: 233     Author: Wendy     Publish Time: 2023-08-16      Origin: Site

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How to choose the temperature and humidity test chamber?

Control

Constant test chambers and alternating test chambers are two types of temperature and humidity test chambers.In general, the term "common high and low temperature test chamber" refers to the test chamber with a constant high and low temperature. Its mode of control is: Decide on a target temperature

The temperature in the inspection chamber can be set to automatically stabilize at the desired temperature. The constant temperature and humidity test chamber's control mode is similarly comparable. Decide on a target temperature and level of humidity. The test chamber has the capability of automatically adjusting the temperature and humidity to the desired levels. A program for setting one or more high and low temperature changes and cycles is available for the high and low temperature alternating test chamber.

The test chamber has the capacity to carry out the test procedure in accordance with the predetermined curve and can precisely control the temperature rise and drop rate within the bounds of the maximum temperature rise and drop rate, i.e., the temperature rise and drop rate can be controlled in accordance with the slope of the predetermined curve. The humidity and temperature curves can also be pre-set in the high and low temperature alternating damp heat test chamber, and those curves can then be controlled in accordance with the presets.

Although the alternating test chamber serves the same purpose as a constant test chamber, its manufacturing costs are quite high. In order to start the refrigerator when the chamber temperature is high, the alternating test chamber must be equipped with an automatic curve recording device and a program controller in the west. As a result, the alternating test chamber often costs more than 20% more than the continuous test chamber. As a result, we should be practical, start with the requirements of test techniques, and select either a constant test chamber or an alternating test chamber.

Temperature Variation Speed

The time from ambient temperature to the nominal lowest temperature is often measured using standard high and low temperature test chambers, which lack a cooling rate indicator.

90~120 min. The criteria for temperature change speed, which typically requires 1 °C/min, are included in both the high and low temperature alternating test chamber and the high and low temperature alternating moist heat test chamber, and the speed can be changed within this speed range. The quick temperature change test chamber has a rapid rate of temperature change. The pace of temperature change can vary from 3 to 15 degrees Celsius per minute, and in particular temperature areas, the rate of change can even exceed 30 degrees Celsius per minute.

The temperature range for determining cooling speed is vary, although it is typically the same for fast temperature change test chambers of various specifications and speeds, i.e., - 60 to +130 °C. Some of the temperature ranges of fast temperature change test chambers are -55 to +80 °C, while others are 40 to +80 °C, depending on the requirements of the test.

The average temperature rise and fall speed during the entire procedure and the linear temperature rise and fall speed (actually the average speed per 5 minutes) are two approaches to characterize the temperature change rate of the rapid temperature change test chamber. The difference between the highest temperature and the lowest temperature divided by the amount of time spent inside the test chamber's temperature range is known as the overall average speed.

Currently, international environmental test equipment manufacturers' technical descriptions of temperature change rates refer to the average speed of the entire procedure. The term "linear temperature rise and fall speed" refers to the specified rate of temperature change every five minutes. In reality, the rate of cooling that the test chamber can achieve in the final five minutes of the cooling phase is the most challenging and important component for ensuring the linear temperature rise and fall speed for the rapid temperature change test chamber.

The linear temperature increase and fall speed (average speed per 5 minutes) is considered to be more scientific from a certain angle. Therefore, it is preferable for the test apparatus to contain two parameters: the linear temperature increase and fall speed (average speed per 5 minutes) and the average speed of temperature rise and fall throughout the course of the entire process. In general, the average speed of the linear temperature rise and fall (every 5 minutes) is half of the average pace of the overall temperature rise and fall.

Wind velocity

In accordance with applicable requirements, the wind speed during the environmental test in the temperature and humidity chamber must be less than 1.7m/s. The wind speed should be as low as possible for the test itself. The test will not be accurate if the wind speed is too high since it will speed up the heat transfer between the test piece's surface and the flow inside the chamber. It is vital to have circulating air in the test chamber, nevertheless, to guarantee uniformity in the chamber. However, in order to pursue the temperature change rate, the flow rate of the circulating air in the chamber must be accelerated, and the wind speed is typically 2–3 m/s. This is especially true for the rapid temperature change test chamber and the temperature, humidity, vibration, and other multi factor comprehensive environmental test chamber. As a result, the wind speed limit varies depending on the intended use.

Temperature swings

A parameter that is reasonably simple to actualize is temperature variation. The majority of test chambers created by all environmental test equipment producers are actually temperature-controlled to within 0.3 °C.

Field uniformity of temperature

The surroundings must have the same temperature environment in order to more closely mimic the actual environmental conditions that items in nature experience.

Setting the test temperature gradient and temperature fluctuation to meet the requirement is therefore crucial.

Humidity regulation

The wet and dry bulb method is mostly used to assess humidity in the environmental test chamber. The humidity deviation must be less than 23% RH, according to the production requirement for environmental test equipment. The temperature control accuracy of the humidity test chamber is high and the temperature variation is typically less than 0.2 °C in order to meet the criteria of humidity control accuracy. Otherwise, it is challenging to adhere to the precision standards for humidity management.

Cooling

When a refrigeration system is used in a test room, the refrigeration system must be cooled. The test chamber features two different methods of water and air cooling.

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