Environmental chambers are useful tools in any facility seeking to learn how a product performs under realistic operating conditions. Since electronic products are not always used under ideal conditions, environmental chambers can duplicate such environmental effects as changes in temperature and changes in humidity. Environmental chambers can serve many applications, from design and development through the production line. Whether for adjusting the temperature surrounding a device under test (DUT) or controlling temperature and humidity, environmental chambers can reveal a great deal about an electronic product. Temperature and temperature/humidity chambers can be applied to various test applications, including QA/QC reliability testing, failure analysis (FA), accelerated life testing, and design verification and validation. The testing requirements for a DUT determine the best environmental chamber for that application and understanding the basic parameters of environmental chambers helps speed the process of selecting the best environmental chamber for a test application.
The simplest starting point in comparing environmental chambers is size: chambers range from portable benchtop units ideal for research and testing small production runs to room-sized units for treating large items and large volumes of smaller items. When determining the required size, the internal dimensions of an environmental chamber must exceed the dimensions of the largest electronic product to be treated by the chamber.
Temperature range is another essential requirement for an environmental chamber and specifying temperature is not simply establishing a range from the coldest to the hottest temperature but defining how fast and well an environmental chamber reaches those temperatures and with what degree of stability and accuracy. Electronic devices and components being evaluated in an environmental chamber are typically specified for an operating temperature range and a storage temperature range (temperatures it can survive without damage when not being used).
Temperature cycling is performed to determine an electronic device’s reliability and performance degradation with changes of temperature across a given temperature range. Whether according to military (MIL-STD) or international (such as IEC or JEDEC) standards for temperature cycling, an environmental chamber for temperature cycling must cover a required temperature range with rates of temperature change that make efficient enough use of power resources to make temperature cycling practical.
Temperature cycling takes time, so environmental chambers for temperature cycling can be compared by their temperature change rates, such as heat-up time and cool-down time. Fair comparisons of temperature change times and rates (which is the difference in temperature between the final temperature and starting temperature divided by the time required) require the same starting and ending temperatures. Environmental chambers can also be compared in terms of how accurately they can maintain temperature and/or humidity, typically as the amount of deviation from reported temperature and/or deviation in the amount of reported relative humidity (RH) according to a particular test standard.
For applications where space is at a premium, the Tenney Junior temperature test chamber is available in benchtop and floor-standing versions. Both provide temperature-controlled workspaces 16 × 11 × 11.75 in. (406 × 279 × 298 mm). The benchtop unit has exterior dimensions of 37 × 22 × 31.75 in. (940 × 559 × 806 mm), and the floor-standing model has exterior dimensions of 25.75 × 22 × 60 in. (655 × 559 × 1524 mm). These temperature chambers run on 120 V AC for simple powering arrangements. They control temperature from -68 to +180°C as a standard range and from -75 to +200°C as an optional range. After a changing temperature has stabilized, the temperature is controlled within a tolerance of ±1°C tolerance. They can change temperature from ambient (about +23°C) to +185°C in 50 minutes and from ambient to -65°C in 40 minutes.
Another compact benchtop temperature chamber, the model is the TestEquity 155, provides a more limited temperature control range, from -20 to +130°C, but the flexibility of running on either
115 or 230 V AC with high efficiency. The extremely accurate temperature chamber features typical temperature tolerance of ±0.05°C, for a workspace of 12 × 8 × 10 in. Its external dimensions are 16.38 × 21.88 × 22.72 in.
When a larger temperature-controlled volume is needed, the same TestEquity 1016C temperature chamber provides 16 cubic feet of temperature-controlled volume by measure of a 30 × 30 × 30 in. workspace. The temperature chamber features a lower-temperature limit of -73°C and upper-temperature limit of +175°C to cover military and industrial temperature test ranges. Built-in casters provide some mobility.
When space is tight but control of humidity along with temperature is part of any environmental testing, the Espec BTL-433 temperature and humidity chambers are compact benchtop units capable of controlling temperature from -20 to +180°C with fluctuation of ±0.5°C or less and humidity from 10 to 95% RH with humidity fluctuation of ±5%. Temperature rises at a heat-up rate of 1.5°C/minute and falls at a cool-down rate of 1.2°C/minute. The temperature and humidity are controlled within a workspace measuring 19.6 × 15.0 × 23.6 in. (500 × 380 × 600 mm) with exterior dimensions of 30.25 × 33.50 × 46 in. (770 × 850 × 1170 mm).
When simulating arctic conditions or outer-space environments, the TestEquity 1007H temperature/humidity chamber has a very wide temperature control range, -73 to +175°C, with typical temperature fluctuation of only ±0.2°C. In addition, it maintains ±2°C temperature uniformity throughout the temperature chamber. It has a humidity control range of 10% to 95% RH (with option for 5% to 95% RH), humidity deviation of ±3% RH, and RH display resolution of 0.1%. Its workspace measures 24 x 21 x 24 in. (609 x 533 x 609 mm) and the outside dimensions are 33 x 68 x 54 in. (838 x 1746 x 1372 mm). The chamber runs on 230 V AC, with a heat-up rate from ambient (+23°C) to +150°C in 20 minutes and a cool-down rate from ambient to -40°C in 18 minutes and from ambient to -65°C in 33 minutes.
Temperature cycling applications benefit from a temperature chamber with fast temperature change rates, such as the ESPEC BTZ-4200 temperature cycling chamber. It has a temperature control range of -70 to +180°C and 15°C/minute heat-up and cool-down rates. Temperature deviations are within ±0.5°C for a workspace of 19.6 x× 15.0 x× 23.6 in. (498 x 381 x 600 mm). The chamber’s exterior dimensions are 31.0 × 41.5 × 74.0 in. (788 × 1055 × 1880 mm).
These are a few examples of temperature and temperature/humidity chambers that can fit many testing situations. For more information on these and other environmental chambers, visit our Temperature and Humidity page or contact us by calling 760-806-6600 or emailing email@example.com.