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Latest News in Testing, Inspection and Certification

NTS News Center - Latest News in Testing, Inspection and Certification

Solar Radiation Testing in Accordance with Method 505 of MIL-STD-810

MIL-STD-810 Procedure 2 Solar TestingSolar radiation (sunshine) testing is one of the basic tests required for any military equipment planned to be deployed in the open and therefore subject to direct radiation from the solar source. The effects of this radiant energy can generally be divided into two groups or classes, heat effects and photochemical effects. Heat effects on exposed equipment can raise the internal temperatures of the equipment substantially above the ambient air temperature. Temperatures in excess of 160oF have been recorded in parked aircraft exposed to the sun while ambient air temperature was in the 90oF range. Photochemical effects of sunlight may hasten the fading of colors and lead to the deterioration of plastics, paints, rubber and fabrics. The combined effects may lead to the outgassing of plasticizers in some materials along with discoloration and a reduction in transparency.

MIL-STD-810, Method 505.5 outlines two procedures for performing the Solar Radiation test. Procedure I requires a cyclic exposure based on the diurnal cycle and is most useful for determining heating effects on exposed materiel as well as materiel enclosed within a container. Procedure II is a steady state (non-cyclic) exposure most useful for evaluating actinic (photochemical) effects of ultraviolet radiation on materiel since it represents an accelerated test with a factor of 2.5. Because Procedure I is more akin to a natural cycle and does not have the acceleration factor of Procedure II, it is not an efficient cycle with which to evaluate long term exposures. Therefore, when it is used mainly to evaluate the direct heating effect, Procedure I can be performed with source lamp arrays emitting less than the full solar spectrum. Procedure II however, demands full spectrum sources emitting light in the ultraviolet range if the total effects of long term exposure are to be properly evaluated.

The solar light spectrum has been accurately measured over the wavelength range of 280 – 3000 nm as well as the power distribution within this range, and it is this range that we would seek to reproduce in the Solar Radiation test.  Reproducing this entire range using lamp sources however can be quite challenging. Sources emitting ultraviolet wavelengths between 280 and 400 nm tend to be quite costly and their performance deteriorates quickly. Some of the MIL-STD recommended sources such as xenon arc and carbon arc fall into this category.  In fact, it was reported that the first commissioned sunshine test facility in 1945 fell short of the contract requirements due to several deficiencies, one of which was the amount of UV that could be produced at the test item. Cost and reliability issues are why many test labs have chosen to perform only Procedure I  with source lamps covering the visible and infrared spectrum range of 400 – 3000 nm (0.4 – 3.0 µm).

Reproduction of the required environment for the Solar Radiation test requires a chamber space in which the ambient air temperature and airflow over the test item can be controlled as well as a solar light source which may consist of a single source in the case of arc-type lamps or a multiple source array in the case of metal halide or incandescent type lamps. The distance of the light source from the test item may be varied to achieve the required irradiance. Airflow over the test item can significantly impact test results. When MIL-STD-810D introduced the “cycling for heat effects” (Procedure I) the guidance for airflow was to use airflow as low as possible consistent with achieving satisfactory control of the ambient air temperature at the test item or between 0.25 and 1.5 m/s (50 to 300 ft/min). The current guidance from MIL-STD-810G has changed for procedure I to 1.5 to 3.0 m/s (300 to 600 ft/min) in recognition of better field data. The requirement for peak radiation intensity at 1120 W/m2 has changed little over the history of the Solar Radiation test although there have been slight changes to the spectral energy distribution based on updated measurement techniques of the actual solar source.

When the primary concern is testing for heat effects, the question is often asked why an oven or chamber test for enclosed equipment could not be used in place of the Solar Radiation test.  The primary reason is that ovens and chambers transfer heat from a uniform ambient atmosphere surrounding the test item, whereas the solar test transfers heat through direct radiation. The directional effect of radiant heating produces temperature gradients through the test item that are not replicated in ovens or temperature chambers.

When a Solar Radiation test is required,

  • Perform the Solar Radiation test prior to the High Temperature test, as the product temperature measured in the solar chamber may need to be used as the ultimate high operating temperature for the product.
  • Consider the orientation of the test item within the solar chamber so as to replicate the in-use conditions with respect to both the direct radiant light energy and the airflow direction. This will affect both the temperature gradients and any cooling effects provided by the airflow.
  • When testing to Procedure I, remember that several consecutive cycles will likely be required for the product to achieve the ultimate high operating temperature for the most critical area of the test item to be within 2oC of the previous cycle. This usually means 3 to 7 cycles.
  • If operation of the test item is required, operational times will need to coincide with the peak response temperature of the test item in each cycle which will not coincide with the peak radiation intensity.

How can I relate the results of MIL-STD-810 salt fog testing to the life time of my product?

This is a very common question that we get asked quite often and unfortunately there is no correlation between what the product sees in the salt fog chamber to what it will experience out in the field. In order to understandSalt Fog Testing why, you must first understand the purpose of the test.

Originally stated by V.J. Junker in The Evolution of USAF Environmental Testing(1), the test is to determine the resistance of aerospace ground and aerospace equipment to the effects of a salt atmosphere.

According to Mil-STD-810G, the test is performed to determine the effectiveness of protective coatings and finishes on materials. The stated purpose of the test is to determine design flaws such as dissimilar metals, improper coatings, uncoated materials, electrolytic action, binding of parts, etc. Therefore, results can be related to the suitability or quality of parts or assemblies, but cannot be directly related to exposure time in the marine environment.

Salt Fog and Salt Spray testing are conducted at 14 NTS locations across the country. Visit our locations page to find the lab closest to you!

(1) Junkers, V.J. The Evolution of USAF Environmental Testing, Technical Report AFFDL-TR-65-197, October 1965.

Is there a preferred sequence for EMI, EMC Tests?

EMI Testing NTS BoxboroughOne of the questions we get asked often is about order of EMI/EMC testing.  Neither MIL-STD-461 nor RTCA/DO-160 specify the order of test performance.  Leaving aside the issue of Safety of Flight tests for aircraft (which typically must be performed prior to any other testing), there are a few different approaches to take in this regard.

The first approach is to perform an analysis of the equipment under test (EUT) before going to the lab to determine what tests are most likely to cause problems, and to start with them.

This approach works best if a customer does not have any idea how their product will stand up to the EMI/EMC compliance requirements. A design analysis tends to vet out significant concerns up front, potential design solutions can be discussed prior to qualification testing. At this point, the Subject Matter Expert (SME) should be able to prioritize the threats, and work with the customer to develop a suitable test order. This approach also provides an opportunity for pre-qualification evaluations to ensure the product will not have any issues during the qualification program.

The second approach is to begin with the most benign tests, usually the emissions.  These tests have virtually no chance of harming the EUT, but they sometimes prove to be the most problematic.  Emissions testing tends to reveal inerrant design flaws the most, and generally requires some level of redesign. Changes in design could necessitate repeating other tests if emissions is not completed first. However, there may be cases were a customer feels their product does not have any emissions concerns but is likely to be susceptible to a particular immunity test. They may choose to get the immunity evaluation out of the way first, and allow time for potential modifications prior to commencing with the remaining tests. This approach would also avoid costly retests or delays due to changes to the EUT.

The third approach is to begin with the most potentially damaging tests first. The philosophy here is that all is well and good if the EUT endures those tests with no issues.  However, if there are susceptibilities that require repair/redesign, those problems can be resolved before continuing with the other tests.

In summary, the EMC / EMI testing sequence used should be an iterative decision between the lab and the customer to determine which approach best suits the product and customer’s needs.

Meet Russ Presswood, Regional Sales Director for NTS Orlando

Russ-PresswoodWe are pleased to introduce Russ Presswood as the new Regional Sales Director for NTS Orlando. Formerly an NTS Account Manager based out of Detroit, he also served as Dynamics Manager for NTS Santa Clarita supervising engineering services, design and fabrication. During this time he worked on programs ranging from Space Shuttle components to the Mars Rover, though his personal favorite was a Ford F150 centrifuge test featured in Ford’s 2008 Super Bowl commercial.

Russ brings a wealth of environmental test experience and knowledge and is excited to help with your testing and product development projects. Please let him know how he can assist you with your specialized testing needs!

Russ can be reached at:

Office: 407-293-5844
Cell: 313-434-5319
Fax: 407-297-7376
Email: rpresswood@nts.com.

MIL-STD-461G Released

MIL-STD-461 Testing at NTS

The G revision of the MIL-STD-461 standard was released in December 2015 and is available here. NTS’s Jeffrey Viel’s wrote an article for InCompliance Magazine reviewing the proposed changes which was published back in August 2015. These changes have carried into the final released standard and are worth reviewing.

A few highlights of the MIL-STD-461G standard:

  • FFT receivers are now permitted for use
  • Interconnecting cable routing now specified for floor standing equipment
  • Test method CS106 has been removed
  • Test method CS114 system check updates
  • The addition of test method CS117, conducted susceptibility, lightning induced transients, cables and power leads
  • The addition of test method CS118, personnel borne electrostatic discharge
  • Test methods RE102 and RS103 technical updates

Contact NTS today to discuss your next MIL-STD-461 test program.

Q & A: What is the correct order for Sand, Dust, and Salt Fog in MIL-STD-810

Blowing Sand and Dust Test

Blowing Sand and Dust Chamber for MIL-STD-810, MIL-STD-202 and RTCA DO-160

Question: I have a military customer who requires Blowing Sand, Blowing Dust, and Salt Fog tests according to MIL-STD-810. However, my customer did not specify which test should be performed first. Is there a specific order in which these tests should be performed? Does it matter?

NTS Answer: Although not necessarily clear in previous revisions, guidance was added to Method 509 starting with the F revision of MIL-STD-810:

Although generally inappropriate, if sand and dust testing is required on the same test item, perform it following salt fog testing.

This is due to the fact that the sand and dust tests can produce severe abrasion of a test item. This is particularly true for the surface treatments often applied to the exterior surfaces of items in order to reduce or eliminate the possibility of corrosion. Paint, anodizing, iridite, and other surface preparations can all be adversely compromised by the sand and dust tests so that the test item could easily show corrosive effects if subsequently subjected to the salt fog test.
Additional guidance was also added to method 510 (Sand & Dust):

If both sand and dust procedures are to be applied to the same test item, it is generally more appropriate to conduct the less damaging first, i.e., blowing dust and then blowing sand.

Therefore, the most appropriate sequence for the three tests in question would be:
1. Salt Fog
2. Blowing Dust
3. Blowing Sand

NTS is now in Orlando, Florida!

We are pleased to announce that Qualtest of Orlando, Florida is now NTS Orlando!

Qualtest was established in 1986 and is an internationally accredited, full-service testing provider with two testing facilities in the greater-Orlando area. The environmental facility offers an expansive selection of tests including environmental, climatic, dynamic, hydraulic and pneumatic testing. The second facility specializes in EMI / EMC testing.

“The addition of Qualtest brings to NTS an excellent team of industry professionals with a solid reputation for their expertise and customer service,” noted William C. McGinnis, President and CEO of NTS.

Fritz Depenthal, President of Qualtest, Inc., said “Having known NTS over the years as industry leaders and friendly competitors, we couldn’t be more pleased to be joining the NTS family, and I look forward to playing our part in NTS’ future success.”

“NTS clients in Florida and the surrounding states will benefit from the convenience of NTS Orlando and the added capabilities we now bring to the region,” McGinnis said. “The addition of two facilities in central Florida further enhances our ability to be responsive to customer testing needs and increases the “one-stop shop” capability for which NTS has become known. This is an excellent acquisition and further establishes us as the largest and most comprehensive environmental simulation testing laboratory network in the U.S.”

Solar Testing Explained: MIL-STD-810 and Commercial

Solar 1

The first question a customer always asks is: “Why should I do solar testing and which test should I use?”

The answer to the first part is relatively simple. You should perform solar testing if your product will be exposed to sunlight. This could be in front of a window located indoors, beneath a transparent canopy, or permanently stationed outside. The second part of the question gets a bit more complicated. There are several different types of solar testing. It can incorporate halogen, full spectrum or UV only lamps and can include temperature, humidity and water spray.

First let’s focus on MIL-STD-810. It and other compliance standards require solar testing as part of product acceptance in which two different types of testing can be performed: Procedure 1 and Procedure 2.

Procedure 1 is primarily a heating effect test and is usually preformed with halogen lamps following a diurnal cycle profile. The purpose is to determine the highest maximum temperature the test unit will reach with repeated cycles in a controlled environment. The lamp intensity is varied from 0 W/m2 to 1120 W/m2 over a 24 hour cycle with the lamps and chamber temperature following a profile that simulates a natural day/night cycle.

Procedure 1 will reveal temperature related issues with the test unit and establishes the target test unit temperature for Procedure 2. This test can run 3 to 7 days in length with the equipment under test either powered on not. The airflow across the test articles is controlled to be the equivalent of a light breeze (300 to 600 feet per minute). MIL-STD-810 requires 3 days of stable and equal unit/chamber temperatures out of 7 days of testing. Full spectrum lamps can be used, but the difficulties controlling the intensity of full spectrum arc discharge lamps can sometimes be cost prohibitive.

Procedure 2 is a combination actinic and heating effects test using full spectrum lamps. The solar aging properties combined with heating effects can degrade items such as LCD or LED displays as well as coatings and seals causing deterioration, fading and discoloration. The lamp intensity is fixed at 1120 W/m2 by varying the distance of the test unit to lamps and the cycle normally runs in one of two variants. The first is 20 hours on and 4 off and the second is with the lamps continuously on. The purpose of the on and off lamp cycle is to expose issues related to rapid temperature changes caused by solar loading while continuous exposure will find the maximum actinic effects.

MIL-STD-810 calls for 20 hours on 4 hours off with exposure durations of 10 to 56 days or longer. Normally 10 days would be used for units that are primarily inside with some outdoor exposure while 56 day or longer would be for articles left outside such as transparent armor. With the 20 hour lights on cycle, solar aging is 2.5 times normal solar exposure. 10 days are the equivalent of 25 days outside in the sun and 56 days will be equivalent to 140.

It is important to note that Procedure 2 uses the maximum part temperature established in Procedure 1 as the target part temperature and the airflow across the test unit is controlled to maintain target temperature with the lights on. If Procedure 2 testing is to be performed, Procedure 1 should be run first to establish the maximum temperature.

Most commercial standards like ASTM or ANSI use similar lamp intensities and color spectrum as MIL-STD-810 (simulations with varying exposure times and environmental conditions), however some tests require a different type of simulator entirely.

One example would be fluorescent UVA or UVB lamps with a combination of temperature, humidity and water spray. This type of testing is usually performed on small samples and can run anywhere from 3 days to several hundred days. A specification such as this is written around a specific type of tester, one of which is a QUV environmental simulator. They do not incorporate significant heating effects and are mostly actinic UV and weathering tests.

Lastly, a common type of solar testing is performed on solar panels using lamps that provide high levels of UV and white light but little infrared and heating effects. This is typically done to establish power output and life cycle stability.

NTS Tempe performs fully accredited MIL-STD-810 Procedure 1 and Procedure 2 testing along with UV testing using a QUV environmental test unit. Our specialty is customizing solar testing to meet special customer requirements. For more information on how we can help qualify your products please call the lab directly at 480.966.5517 or email our technical specialist Harold.Sibert@nts.com

Why do I need EMC Compliance?

EMC TestingThere are a variety of reasons why your electrical/electronic products may be required to go through the Electromagnetic Compatibility (EMC) compliance process.

Regulatory Requirements

Most industrialized nations have established agencies or other regulatory bodies responsible for defining and enforcing EMC standards. If EMC regulations exist in a country, equipment manufacturers cannot legally ship their product into that country until compliance with those regulations is met. Professional compliance laboratories like NTS understand the global compliance process and possess the accreditations and capabilities needed to perform testing and certification to meet the relevant standards in all of your target markets.

Customer Requirements

There are many situations in which your customer may dictate EMC requirements. For example, if your customer is an RBOC (Regional Bell Operating Company), an extensive set of tests referred to collectively as Bellcore, are required before the RBOC will purchase your product. If your product or component will be included in a third-party product, your OEM customer will need proof that your product or component will meet appropriate regulatory standards. Your OEM customer will dictate the amount of testing and documentation they require. It is not unusual for an OEM customer to ask for compliance exceeding legal requirements.

Reliability/Performance

In some cases, you may want to self-impose reliability standards for your products; for example, if you only plan to ship your product in the United States, unlike in Europe, you are not required to pass immunity standards. However, you may want to establish your own immunity standards to ensure customer satisfaction by minimizing field failures.

How do I achieve EMC compliance?

Determining Relevant Standards

The first step in the compliance process is to determine the list of target markets where you plan to market and sell your products. Compliance regulations vary from country to country, so an investigation of current standards is required for each market where you intend to operate. Countries such as India have no formal Electromagnetic (EMC) requirements, whereas Taiwan has a very strict submission policy.

Self-Certification

Over the past several years, regulatory agencies around the world have been moving away from agency submittal applications because they are slow and inefficient. Most government agencies now allow for self-testing and self-certification. This means that you can simply affix a CE or FCC mark to your product and begin shipping without gaining government regulatory approval first.

However, self-testing and self-certification does not relieve your company from meeting the standards implied by the mark you place on your product. In fact, if you place a mark on your product when it doesn’t comply, it could result in serious consequences.

NTS has the formal accreditations to provide both the testing and the reports you need to meet a wide range of regulatory self-declaration requirements. We also create the reports that you must keep on file should an issue arise requiring proof of compliance.

Third party Verification

This is the process of having an independent party validate a product’s compliance. Third party verification adds significant credibility to a product’s test/compliance program, either for marketing or regulatory purposes.

Formal Certification

With certain types of products and in certain countries, a formal certification process may be required. For example, in Taiwan, a formal submission and approval is required, whereas the European Union might allow self-certification. In the USA a formal FCC submission, called a Certification, is required for any products designed to transmit radio signals. In addition to the testing costs to meet the relevant standards, you should also expect to pay agency submittal fees ranging from a few hundred to a few thousand dollars depending on the country and the type of product.