- 2022-02-18 15:17:22
Preface: This article is the 3rd article belonging to an article series. You may find the introduction article from following link:https://pals.com.tr/blog/environmental-test-engineering-and-pals-service-article-series-1
We will proceed to elaborate the “Methods” and “Procedure”s of environmental standards of MIL-STD-810 in our article series. Instead of writing down the obvious information already given in the standard, we will be discussing more practical information on product design, features regarding “Equipment Under Test” (EUT), and conducting tests.
Test Method 502.5 - Low Temperature
This method uses low-temperature tests to obtain data to help evaluate the effects of low-temperature conditions on materiel safety, integrity, and performance during storage, operation, and manipulation.
Picture: PFA-370-MIL Outdoor Unit And De-ice Controller Inside Temperature Test Chamber For more info: https://pals.com.tr/product/pfa-370-mil
Procedures of this method are as follows:
Procedure I. Investigates to investigate how low temperatures during storage affect material safety during and after storage, and performance after storage.
Procedure II. Investigates how well the materiel operates in low-temperature environments.
Tips and Tricks;
- As a rule of thumb tailoring is essential. Meaning setting EUT test limits with the customers beforehand. Temperature limits are variable based upon the version of the standard.
- Discuss feedback and monitor (if needed) sensor placement with the end-user. Some operational uses require to be heat EUT until targeted temperature while in some scenarios heating ambient would be sufficient enough for conducting tests.
- Set pass/fail criteria clearly with the end-user; which operational features needed to be tested after storage or during tests. Prepare instructions for test laboratory experts step by step about how to test EUT.
- Decreasing temperature causes the shrinking of metal. This may have a negative effect when there are different kinds of metal compositions used in one EUT. Make sure there is enough gap between binding areas such as joints of enclosure surfaces to tolerate expansion.
- This test does not specify how to manipulate humidity. The application is generally managed under normal room humidity. Humidity may cause condensation on an object when the temperature decreases.
- Condensed humidity may cause stiffen or freezing on moving parts. Consider applying proper thermal insulating lubricant.
- Condensed humidity also may cause unwanted conductivity on parts. This may affect PCB parts. Consider applying thermal insulator paste.
- Lubricants tend to alter viscosity under heat. Checks MSDS paper of lubricant.
- Similarly to high temperature, Electronic components are known to be heavily affected by decreased temperature. This also causes thermal stress on them resulting in shortening of lifespan. Check MTTR value of components while choosing them as well as operational/storage temperature. How long components will operate under certain temperature conditions should be also taken into consideration.
- Some components might be heat operated, i.e. oscillators. Consider applying housing or encapsulated module solutions such as oven-controlled oscillators.
DID YOU KNOW?
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