6 Things to Consider Before Buying Humidity and Temperature Chamber

​Temperature and Humidity test chamber (which is also called environmental test chamber) is designed to evaluate the product’s quality and reliability against different environmental conditions, especially for temperature and humidity.

Temperature and Humidity Test Chamber is commonly used by researchers from different industries such as electronic, electrical, communication, automotive, medical, aerospace and so on. 

Let’s say, your company has a project to test a new product for various environmental conditions. You are given a task to source and identify a temperature and humidity test chamber that is able to perform the test.

How do you start? What criteria do you need to take note in the selection of a right chamber and supplier? Is price always your determining factor or quality of the product or after sales service is more important to you?

In order to make the best decision to purchasing a suitable temperature and humidity chamber, several factors need to be considered. This article is written with the purpose to help you make informed decisions. I am going to share 6 things you should consider prior to making a selection or choice.
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1. Temperature Range
2. Humidity Range
3. Temperature Change Rate
4. Internal Dimension
5. Product in Chamber
6. Cooling method 

Temperature Range

Firstly, the temperature range is a major parameter in selecting a chamber. Manufacturers have wide temperature range chamber with a different design in structure and insulation. In general, a standard temperature chamber can go as low as -70°C and as high as 150°C.

"Firstly, the temperature range is a major parameter in selecting a chamber"

If your test requires more than the standard temperature, it is possible to customize the chamber. Just make sure you give your chamber supplier the test details. The ultimate low temperature required for your testing determines the type of refrigeration system needed. 

Humidity Range

Relative humidity (RH) is dependent on water vapor pressure and temperature in the test chamber. At low temperature, the system may achieve high relative humidity with less water vapor. On the other hand, more water vapor is required at a higher temperature to attain high relative humidity.

The standard temperature-humidity range for most test chamber is 10°C to 85°C with 10% to 98% RH. There is a limit to the lowest temperature the chamber can go due to the possibility of dew or fog forming. The dew point of the test chamber is usually defined at 10°C. In the test chamber, the refrigerated coil is never set to 10°C or below freezing so that the frost will not form.

"The standard temperature-humidity range for most test chamber is 10°C to 85°C with 10% to 98% RH"
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Figure 1

​The RH range achievable by certain temperature is demonstrated in Figure 1. For instance, the lowest humidity level the chamber can go at 20°C is 40%RH. At a temperature of 60°C, the chamber can attain 20%RH. You must operate the test chamber within the range set by the manufacturer. Any attempt at setting outside the range may result in damage to the refrigeration system.
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Temperature Change Rate

There are different types of a profile in terms of temperature testing. Those testings can be classified into 3 groups as mentioned below:

1. Constant temperature or Temperature cycling test

​For constant temperature testing, it is set for a specific duration at a specified temperature. Whereas, for temperature cycling test, the temperature can be multiple temperatures at different duration.

Figure 2

Figure 2 illustrates a typical temperature cycling test profile. On top of this, the changing rate of temperature is usually not greater than 3 °C/min for heating and 1°C/min for cooling.   ​
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2. Rapid temperature change test

​Similar to temperature test cycling above, rapid temperature testing is conducted with temperature changing at a much higher rate, i.e. up to 20°C per minute. This test is also commonly known as ESS (environmental stress screening), HALT (Highly Accelerated Stress Test), or HASS (Highly Accelerated Stress Screening). The idea of this test is to allow you to evaluate the quality of product against rapid temperature changes.

Figure 3

​Figure 3 shows a rapid temperature change cycling test. It is important to note that the part (test specimen) temperature always fall behind the air temperature in the chamber.

​Chamber manufacturer will have to design the airflow inside the chamber so that that airflow has enough volume to move the part temperature at a closer rate to the air temperature.  
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3. Thermal shock

​In Thermal shock testing, products are brought to go through extreme low and high-temperature changes repeatedly at very fast transition pace. This test stimulates the accelerated stress to a product that is caused by the thermal shocks during normal use.

​The temperature change between cold and hot temperature occurs at very rapid pace, greater than 15°C per minute.

Figure 4

Thermal shock test chambers are typically classified into 3 zones or 2 zones chambers.

​For 3 zones thermal shock chamber, the chamber consists of hot temperature zone, cold temperature zone, and test zone. The product is placed in test zone and the hot and cold air is blown in from respective chamber alternatingly.

Some equipment uses 2 separate hot and cold compartments (2 zones) with an elevator mechanism that transits the products between these 2 compartments. 
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​​Internal Dimension

Chamber internal size is always neglected by buyers. Most people misunderstand that the chamber performance is not dependent on the space as long as the product can fit into the chamber, regardless of the size of the product. ​

It is important to know that the chamber must have sufficient airflow volume to ensure effective airflow.
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Thus, it is better to get a chamber that is slightly bigger than buying a chamber that is too small.

"It is important to know that the chamber must have sufficient airflow volume to ensure effective airflow"
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The size and dimension are wide in range and can be customized according to your requirement. The range of test chamber size can be a small benchtop chamber with a walk-in chamber.

Product in Chamber

An experienced manufacturer will always ask a question to a potential buyer: What is the test specimen/products and what is the quantity?
​The answer allows the manufacturer to offer the best chamber for your application.

"What is the test specimen/products and what is the quantity?"
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​There are many scenarios that the testing set up could be, chamber manufacturer will take into consideration the product characteristics and testing requirement when designing the construction of the chamber.

​The key is, ensure all the details of your tests to your chamber supplier.
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Cooling method

The air in the chamber is cooled with a refrigeration system. The heat extracted by the refrigeration system is dissipated through the condenser.

​There are mainly two types of condensers: air-cooled or water-cooled. Each one has its pros and cons.

Small chambers usually come with air-cooled as standard specification. This configuration is very convenient in terms of mobility and saving of space as the air-cooled condenser is built into the chamber.

However, on the other hand, the heat is dissipated into the room where the chamber is located. As such, air-conditioning in the room has to be able to handle the additional heat load generated by the chamber. 

​Secondly, dirt from the surrounding has to be minded. As the condenser is located near the floor, dirt can be picked up easily. Therefore, regular cleaning of the condenser is necessary. ​

Water-cooled could be a good solution if the chamber is positioned in a dirty environment. In a water-cooled system, the condenser is usually placed outdoors.

​Nevertheless, a water-cooled system is more complicated and expensive to install. Refrigeration piping,water tower mounting, electrical wiring and water supply works are required for this type of system. As you can see, installation can be messy and cost extra to you. 
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"Water-cooled could be a good solution if the chamber is positioned in a dirty environment​​"
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​Summary
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As a conclusion, there are many different types of test chambers available. To determine which type of chamber you need, you have to be clear about your application.

​It is essential that you communicate the test and product information to your supplier, as detailed as possible.

What is the chamber size needed? What is the test specimen? What temperature or humidity range is required? Is the chamber to be air-cooled or water-cooled?

​These are the fundamental questions that you must be clear before purchasing a temperature and humidity test chamber.
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Affordable Test Chambers with Excellent After Sales Support
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We offer a wide range of temperature chamber, humidity chamber, thermal shock chamber, walk-in chamber, other types of environmental chambers or even customized chamber to your special requirement. All our chambers are offered at an affordable price (we care your budget), come with product warranty and excellent after sales service which will surely satisfy your need.  Contact us to check it out.