Environmental Test Chambers
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Environmental test chambers

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Test Chamber FAQs

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What is an environmental test?
When performing an environmental test on a sample of equipment, it’s for simulating one or more environments that may be harmful to that equipment. Testing should be done during the development of a new product. This can increase the reliability and durability of that new product.
What's the difference between dynamic tests and climatic tests?
Dynamic tests simulate mechanical force inputs to a structure. That force could be induced by usage, such as inertial effects on aircraft electronics during flight. Or the force could be induced externally by accident, such as a piece of crated office equipment bumping during shipping. Examples of dynamic tests are vibration and shock testing. Climatic tests simulate inputs due to the natural environments, sometimes accompanied by motion. Examples include temperature, humidity and salt fog. In either dynamic or climatic testing, test inputs may closely match or simulate expected service environments, or they may exceed expected service environments to provide a factor of safety or they may be purposely exceeded in order to induce failures (if any) to occur quickly. The latter can be called stimulation. Although acceleration testing (as on a centrifuge) is often lumped with climatic testing for organizational purposes, it is actually a dynamic test.
What is a thermal or temperature test?
A test in which the air surrounding a test specimen is raised or lowered to pre-determined levels. The purpose is to observe the effect of the temperature extremes on the equipment, which may be operating or non-operating. Temperature extremes and rapid temperature transitions are also used to purposely induce failures to determine weak points or latent defects.
What is thermal vacuum testing?
Thermal vacuum or space simulation testing refers to the technique used for simulating or replicating the extreme temperature excursions and vacuum conditions of deep space. This is achieved using a pressure vessel outfitted with thermal shrouds and a vacuum system. The shroud is flooded with liquid nitrogen to achieve the cold side temperatures; alternately, spacecraft heating can be achieved using a series of infrared lamps. The air within the chamber is evacuated first using a conventional mechanical pumping system and then switching to a diffusion or cryogenic system to create the vacuum necessary for space simulation.

What is a humidity test?
A humidity test simulates the moisture-laden air found in tropical regions. There are typically two types of humidity tests, condensing and non-condensing. Condensing humidity tests consist of temperature cycling in high relative humidity air. The temperature cycling induces the moisture to condense on all surfaces of the test specimen. Additionally, the temperature cycling causes the test specimen to “breathe”, pulling moisture laden air inside; it then condenses to liquid form. This is an extremely severe test for electronics. Non-condensing humidity tests are run at a constant temperature, with a high relative humidity, typically greater then 95%. This test is not as severe as the condensing test because the moisture is not in liquid form. This test is much more difficult to perform because the temperature must be tightly controlled to prevent condensation at such a relative humidity.

What is a fungus test?
A fungus test determines if a material (or materials) will support the growth of specific fungi. The test is run under conditions that are extremely favorable to most fungi, warm and moist. It will only verify that the material(s) under test can be food for the fungi to which it is subjected. Test specimens must be carefully prepared, insuring that they are free of contamination that will support fungus growth, showing misleading results. Nutrient control strips must be in the chamber to verify that the test spores are viable.
What is environmental stress screening (ESS)?
Although ESS may use chambers and shakers resembling those used for an environmental test, the purpose is different. In ESS it stimulates just-produced or just-overhauled equipment (usually an electronic assembly or subassembly), usually using rapid thermal ramping and broad-spectrum random vibration.
It’s used to precipitate any latent or hidden defects so that the equipment malfunctions in ways we can observe. It best if malfunctions occur close to the production line rather than downstream at final assembly or (heaven forbid) when a customer is using the final product. Malfunctioning equipment goes to failure analysis, then to repair or to scrap.
ESS is not a test. Equipment does not ‘pass’ or ‘fail’. Most observers understand thermal ramping, typically over 100°C temperature range at 20°C to 50°C per minute. However, they have some difficulty understanding random vibration at, say 0.04g²/Hz spectral density.

What is a salt fog test?
A salt fog test subjects test specimens to an atomized fog of water having a high salt content (typically 5%). The purpose is to simulate a corrosive atmosphere. This test is not really useful other than comparing different materials or coatings. There is no way to correlate 24 or 48 hours of exposure with a 5% solution to a long period of exposure in an actual corrosive atmosphere.

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