NTS News Center

Latest News in Testing, Inspection and Certification

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

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.

Q & A: Do I need a fixture for vibration testing?

Vibration Testing FixtureQuestion: One of the Qualification test requirements for my product includes vibration testing. Do I need to provide a test fixture in order to perform the vibration test?

Answer: The primary purpose of a vibration test fixture is to adapt the service mount of the unit under test (UUT) to the vibration test equipment (shaker, slip plate, etc) and to transmit the intended vibration to the UUT with as much fidelity as possible.

In order to accomplish these goals, a fixture should include good engineering design, specific materials and precision fabrication. Of course, all of these factors combine to make vibration fixturing both relatively expensive and time consuming to produce. This is undoubtedly why many companies seek to forego the design and build of dedicated fixturing and to seek other means of attaching their test items to the vibration equipment or simply leave it up to the test lab.

When no fixturing is provided, the test facility must find a way to attach the test item to the vibration equipment however they can. This usually means strapping or clamping the articles using eye bolts and nylon straps or threaded rod and clamp bars placed across the test item. As you can imagine, there are compromises inherent in this approach.

First, most test specifications are written with the assumption that the vibration will be input at the service mount of the test article. Strapping or clamping items to the vibration equipment rarely allows for this.

The second challenge is that there is a limit to the force that can be applied to an item by strapping or through clamp bars. Therefore, coupling between the test item and vibration system is usually compromised. This typically results in a frequency selective transmission of the vibration with some frequency bands being under the desired amplitude and other frequencies being over the intended amplitudes. The net result can be an under-test or over-test of the test article.

Finally, control of the input vibration levels can be compromised due to the ambiguity of sensor placement for control and monitor accelerometers. These locations are usually provided as an aspect of good fixture design.

So when vibration testing of your product is required, always weigh the time and expense of fixturing against all of the possible compromises inherent in the undefined approaches of clamping/strapping or “best way” mounting as decided by the test facility.

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.

Vibration Fixture Basics

VibrationBy Randall Cobb, P.E.  Inside Sales Manager, NTS Detroit.

Vibration testing is a necessary part of many programs, and there are a wide variety of vibration types, but the one thing every test has in common is that the energy must be transmitted into the test sample with some kind of fixturing. Fixturing can be as simple as mounting bolts into a flat plate, or it can be an elaborate weldment with responses tuned to match the final assembly. The best fixturing is rigid, lightweight, and simple. The following is a list of general guidelines to aid in choosing the best fixturing for your test sample.

Rigidity: A fixture should be very stiff in order to transmit the vibration without adding extra noise. A flexible fixture can resonate at test frequencies, affecting the amount of energy transmitted to the test sample, and thus test quality. A very flexible fixture may be difficult to control and will require a more powerful vibration system, affecting both quality and price. At 2000 Hz, a 1 g sinusoidal input only requires 0.000005” of shaker displacement. It doesn’t take much fixture bending to affect that!

Weight: A fixture with extra mass will require more force to vibrate at a given amplitude (g-level). Low mass fixtures will allow multiple samples to be tested simultaneously, improving costs per part and test throughput. Fixtures should be low profile and keep the sample as close to the system input as possible. Eliminate unnecessary features, but don’t skimp on material if it will affect stiffness.

Material Selection: Unfortunately, vibration fixtures are not always made of the most inexpensive materials available. Steel and Aluminum have roughly the same strength to weight properties, so it might make sense to pick steel as the less expensive option. However, aluminum has a density much lower than that of steel, and features can be made much larger and stiffer with no weight penalty. This makes it the superior material for high-frequency vibration. 1

For very high-performance fixtures, magnesium will sometimes be used as its performance is even better than aluminum. The tradeoff is difficulty in machining and much higher fixture costs.

Complexity: The best vibration fixtures are simple, with the minimum number of features. Vibration testing is not only stressful to the sample, but also to the fixturing. Extra features and thin sections can add more potential for unwanted resonances, and more components that can fatigue and break. Simple fixtures are usually less costly up front, and cost less over the long run.

It is advisable to use through-bolts for sample mounting instead of tapped holes whenever possible. Threads fatigue after heavy use and a nut and bolt can be cut away and replaced at the test site, but extracting a damaged threaded insert may require a trip to the machinist’s shop. If you must have a tapped hole, use a steel threaded insert (E-Z Lok or Keensert type), rather than a helical insert (Heli-Coil or STI type), and never thread a fastener directly into aluminum!

Other Considerations: Most vibration testing is performed in a single axis, and repeated in each orthogonal axis (X, Y, & Z). Vibration systems can either be vertical or horizontal, and fixtures are often rotated 90° to perform two of the three axes on a horizontal surface. If you only have one vibration system available, it may make sense to design a fixture with mounting holes on more than one surface so it can be rotated for each axis of testing.

Since few test parts are so simple they can mount directly to the shaker, most fixturing is a compromise of the qualities above. Samples may need to be mounted in a specific orientation, or have features that must be supported above the vibration table. Welded fixtures are often necessary since it is not always practical to carve a fixture out of a single block of aluminum. Be sure weld joints are continuous and smooth, with two or even three passes if possible.

Validating a Fixture: When a fixture is used for the first time, it is good practice to perform a resonance scan in order to check for any unwanted responses. This is done by instrumenting the fixture with multiple accelerometers, and sending a low-level random signal that covers the entire frequency range intended for the test. If you imagine a tuning fork that rings at a certain frequency (pitch), and that frequency was in the range of the test, then when the test hits that frequency the fixture will start ringing and add more energy into the sample than it should receive. A resonance scan will identify any problem frequencies, and can be performed with or without the test sample in order to observe any effects.

Repeatability/Liability/Fixture Ownership: The standard offering for many test labs is to build a custom fixture for your program, and they will then maintain responsibility for fixture responses. You are paying for the fixture design and build, as well as a guarantee from the test lab this fixture will perform reliably from one test to the next. The major caveat to this service is that the test lab retains ownership of the fixture, because they cannot be responsible for its use and measurements made at other facilities. If you choose to make your own fixture, be sure to review it with the lab during the design phase in order to confirm it will match the test system.

For more information about vibration testing, visit our webpage. You can also contact the author of this article at our Detroit location: 313.835.0044. For more details including specifications on NTS Detroit vibration testing, see our brochure.

Event Recap: Telecom Seminar, Best Design Practices and NEBS Workshop

On March 8, our Silicon Valley facility hosted its third annual Telecom Seminar: Best Design Practices and NEBS Workshop. The workshop focused on a variety of topics ranging from Environmental Reliability (GR-63 and GR-3108) and EMC (GR-1089), to Multimedia Standards (CISPR-32, KN 32, KN 35) and International Approvals.

Those that attended were able to take advantage of hearing directly from our guest presenter, Todd Talbot with Verizon. As Verizon’s ITL program manager and NEBS Compliance SME, Todd covered various aspects of the NEBS program including its role with compliance, clarifying misconceptions about the requirements, and finished up with highlighting a few hot topics.

In case you missed the event, we are making the presentations available for download!

Topic 1: Testing Pitfalls and Designs – GR-63, ETSI 019, GR-3108

Topic 2: GR-1089 Testing Pitfalls and Designs

Topic 3: Insights on International Approvals

Topic 4: Testing to New Standards – CISPR 32, EN 55032, KN 32, KN 35

Topic 5: Verizon NEBS Requirements

About
The goal of the Telecom Seminar and NEBS Workshop is to a) address real world design challenges, and b) provide solutions that will help customers streamline their test programs and overall deployment strategies.

The daylong event is broken up into specific topics and are facilitated by both industry and NTS subject matter experts. To learn more about the event, please contact Dean Eriksen at dean.ericksen@nts.com.

NTS Quick Guide to Reverberation Testing

Picture4

Inside the RF chamber

A reverberation chamber (mode tuned/mode stirred chamber) is a shielded enclosure or resonant cavity for RF testing which is statistically isotropic, random polarity, having RF uniformity within specified limits. Typically it has a paddle (or tuner) which stirs up the field, randomizing the boundary conditions. Mode tuned is where the paddle is stepped to a position and then RF is applied for a dwell time sufficient to exercise the equipment. Mode stirred is when the paddle is continually turned with RF energy applied for a full paddle revolution. Reverb chambers are useful for radiated susceptibility, radiated emissions (total radiated power), shielding effectiveness, and many other troubleshooting scenarios.

The benefits to reverberation testing are numerous. RF is applied to all exposed sides of the device under test (DUT) during a full 360° turn of the paddle, instead of a single side. For direct illumination testing, many standards require the all apertures of the DUT to be illuminated. On complex items this can be difficult – even impossible. Window effects testing, required when applying direct illumination, is not required during reverb testing because the field intensities are constantly changing. SAE ARP 5583 states that the reverb is the recommended and preferred method to show compliance for large and/or complex Level A (flight critical) systems. Test repeatability is much easier to obtain in a reverb chamber with proper processes, and running the test is much less complex than a single aspect angle test. Antenna distance, aim (focus), 3 dB beam width, location of the field probe, EUT layout, and location of the EUT in the working volume are all less of a factor in the repeatability of test.

Picture6

A view from outside

You should know if reverberation testing is right for your program. Reverb chambers are random in polarity which makes it challenging in determining directivity of RF energy. Testing multiple field levels on a system, such as outside the pressure vessel level and inside the pressure vessel level, can be difficult; all equipment in the chamber is exposed to the same field. There are limitations on pulse width due to a high Q (efficient) chamber having large amount of stored energy. If you have small, simple equipment, single aspect angle tests may be faster and sufficient for test coverage. There are ways to compensate for each, and an NTS engineer can help with suggestions or assist you with a test plan.

Both direct illumination and reverberation test methods are acceptable paths to certification. They both have benefits and drawbacks that champion each as a test method. Fortunately, NTS has the ability to test in both methods and the engineering expertise to support your path to certification.

For more detailed information about reverberation testing at NTS Rockford, Fullerton, Plano, Tempe, or Boxborough, call 800-270-2516 or email us at sales@nts.com. Request a quote today!

NTS Engineers Honored at IPC APEX Conference

IPC-APEX-2C_PosCongratulations to Renee Michalkiewicz, Russ Shepherd and Debora Obitz on their recognition at the IPC APEX conference held in Las Vegas, NV this week.

Renee Michalkiewicz, current chairman of the IPC TAEC committee, received an award for her leadership of the Technical Activities Executive Committee (TAEC), the top committee that makes IPC policy and procedure decisions. Additionally, Renee was recognized for her outstanding contribution to the D-33at Task Group in the development of IPC-6012D, Training and Certification Program.  NTS developed the latest IPC-6012 training program and will be soon working to update the IPC-A-600 training program.  These two documents drive Printed Circuit Board (PCB) production and conformance.

Russ Shepherd and Debora Obitz also received awards for their outstanding contributions to the 7-12 Microsection Subcommittee in the development of IPC-TM-650, Method 2.1.1F, Microsectioning, Manual and Semi or Automatic Method.  This method is at the core of the NTS materials laboratories capabilities.  Russ is the current chair of this committee and will be stepping into two additional positions, Chairman of the IPC D-15 Flex Test Methods Committee and Vice Chairman of the 7-10 Testing Committee. Deborah participated as an expert panelist on the APEX Buzz session on Conformal Coatings.

NTS Subject Matter Experts lend their expertise to the IPC through committee membership and participation in panels at the IPC APEX Conference.  Our SME’s will also be teaching a number of IPC courses at our Anaheim and Baltimore labs, click here to review the currently scheduled courses.

Renee Michalkiewicz, Vice President / MIT (IPC-A-600 / IPC-6012)

  • Expertise: Testing of PCB’s, Soldering Materials and Coatings, Assembly Process Qualification, SIR, ECM, CAF, Developer of Latest A-600 and 6012 Training Programs
  • Chair / Vice Chair: TAEC, 7-10 Testing Committee, 5-20 Assembly and Joining, 5-24 Assembly & Joining Materials

John Radman, Senior Applications Engineer

  • Expertise: Test Techniques, Failure & Contamination Analysis, Counterfeit Component Analysis
  • Chair / Vice Chair: 5-32a Ion Chromatography/Ionic Conductivity

Debora Obitz, Manager of IPC Training Programs / MIT (IPC-A-600 / IPC-6012)

  • Expertise: Conformal Coating, Failure Analysis, Microsectioning
  • Chair / Vice Chair: 5-30 Cleaning and Coating, 5-33b Solder Mask Performance, 5-33 Coatings, 5-33a Conformal Coating, D-30 Rigid Printed Board

Keith Sellers, Operations Manager – Baltimore

  • Expertise: Failure & Contamination Analysis, Ionic Cleanliness
  • Chair / Vice Chair: 5-32b SIR and Electrochemical Migration, 5-24a Flux

Russ Shepherd, Operations Manager / MIT (IPC-A-600 / IPC-A-610 / IPC-6012)

  • Expertise: Failure Analysis, Microsection, Environmental Testing, Training
  • Chair / Vice Chair: 7-12 Microsection, D-15 Flexible Circuits Test Methods, 7-10 Testing Committee, 5-32b SIR and Electrochemical Migration, 5-32e Conductive Anodic Filament (CAF)

Damon Rachell, Applications Engineer

  • Expertise: Failure Analysis of PCBs, PCBAs, and components/ICs; SEM/EDS, Plating systems, solderability, reliability testing, scanning acoustic microscopy, DPAs, and ESS

Emi Lee, UL Program Manager

  • Expertise: Material testing of polymers, solder resists and conformal coatings, films, laminates, and PCB for UL Recognition, Thermal aging of polymers per UL 746B for RTI
  • Member of: UL STP 94, 746A-F, 796, and 796F

 

International Approvals Update: Changes to Labeling and Logo Requirements

Changes to Labeling and Logo Requirements

Australia

RCM Replaces A-Tick and C-Tick (enforced March 2016)

Starting March 1, 2016, RCM replaced A-Tick and C-Tick. Products subject to mandatory approval will require to bear RCM logo to enter the Australia market. For formerly A-Tick or C-Tick approved products, the manufacturers may still use A-Tick or C-Tick logo as long as the manufacture date is before March 1, 2016.


Argentina

HSE Statement/Resolution 508 (enforced April 2016)

Starting on April 22, 2016, a HSE (High Specialized Equipment) statement must be on the equipment if the product is not safety certified in Argentina. Safety certification in Argentina has been voluntary for HSE, however, Resolution 508 was issued at the end of 2015 demanding that a HSE Statement (Spanish) be placed in a visible area on products shipped to Argentina.

Spanish Statement

“PRODUCTO NO CERTIFICADO EN SEGURIDAD ELÉCTRICA EN LA REPÚBLICA ARGENTINA. Apto para ser operado exclusivamente por personal con conocimientos en materia eléctrica. No instalar al alcance del público en general. No utilizar en procesos de enseñanza. No utilizar en comercios con atención al público”.


Brazil

Resolution 662 (enforced March 2016)

According to Resolution 662 that was issued and enforced on March 10, 2016:

  • EAN/GS1 number and barcode figure are NOT required anymore for ANATEL homologation projects
  • Local reps or license holders does not need to provide this information for new ANATEL homologations
  • Products to be certified and products already certified can use the label without EAN/GS1 number and barcode figure

ANATEL Homologation Number Format Change

The ANATEL homologation number now has two (2) more characters (numbers).
The new format is:

HHHHH-AA-FFFFF

(HHHHH = homologation code; AA = Year of the issuance; FFFFF = main product manufacturer)


India

DEITY/BIS Logo and Label Requirements (in-progress)

A new marking requirement was published by India DEITY/BIS on Feb 10, 2016. The requirement states: that beginning on June 30, 2016 the BIS logo will become mandatory for certified products.

  • The previous BIS compliance statement will no longer be acceptable after this date
  • Any products certified prior to this date will also be required to bear the new logo on the marking materials unless imported to India before June 30, 2016.

For reference, below is the BIS logo:

India BIS logo

(——– = Applicable Standard, XXXXXXXX= Approval/Registration number)

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.

FCC 5GHz UNII Rule Changes

Will the FCC Extend the June 2, 2016 Deadline?FCC Recognition

Our FCC certifications team has received many questions related to the FCC 5GHz rule changes implemented in FCC Report & Order 14-30, June 2014.

The FCC issued a Memorandum Opinion and Order (MO&O) – FCC 16-24 – on Wednesday March 2, 2016 that has added to the confusion.

The most often asked question: Is the FCC going to delay the June 2, 2016 deadline for all devices (new and older devices still being sold) to be approved using the new rules?

Answer:  No.  Come June 2, 2016 all 5GHz unlicensed devices still shipping must be approved using the FCC rules issued in June 2014.

The MO&O issue addressed spurious emissions limits for the 5725-5850MHz band.  This was a point of contention when the rules were updated to change the rule part under which devices using the this band were approved.  There has been an ongoing discussion between manufacturers and the FCC regarding this band.  Previously, most manufacturers approved their devices that operated in this band using the limits published in FCC §15.247.  The 5 GHz rule update made the limits more restrictive, specifically at the band-edges, and greatly impacted manufactures that used higher gain antennas intended for long distance links.

Manufactures that performed permissive changes to update to the new rules usually had to reduce power for channels at the edge of the band from their original approvals.

Under the MO&O, issued last week, the FCC is updating the rules to allow two different options for showing compliance with the spurious emission requirement for UNII devices operating in the 5725-5850MHz band (UNII-3 band).  One option is a mask that is less stringent than the current requirement.  This is the long term requirement.  The second option is a temporary option that allows manufactures to revert to the 15.247 limit in the rules prior to June 2014 for spurious emissions.  How temporary depends on the gain of the antennas used.  Devices with antennas >10dBi have until March 2, 2018 to update their approval to the mask.  If their antenna gain is <10dBi, they have until March 2, 2020 to update to the mask.

The MO&O can NOT be used for certification yet.  The updated rules need to be first published in the Federal Register and then there is a 30 day delay before TCBs can approve applications using either of the options.  When the MO&O will get published in the Federal Register is unknown.

Options for New Devices Seeking Authorization

For new devices seeking authorization, manufactures have a few choices at this time on how to test the UNII-3 band:

  1. Use the current (aka – new 5GHz rules, from 2014).
  2. Use the mask, and understand that certification will have to wait for the rules to go into effect.
  3. Use the 15.247(d) limits, knowing they will need to update their approval in the future (if still shipping), and understand that certification will have to wait for the rules to go into effect

Devices currently approved using the “old” rules, with the 5725-5850MHz band approved under the DTS/15.247 rules, still need to get updated to the new rules by June 2, 2016 or stop shipping.  The options are:

  1. Test the 5725-5850MHz band against the most stringent June 2014 UNII limit.  Reduce power, and file a Class II Permissive Change (C2PC)
  2. Test the band against the new mask.  File a C2PC once the rules go live
  3. Use the old 15.247 report (Note: we are still waiting confirmation from the FCC that this would be allowed), no testing, and file a C2PC once the rules go live.  This would give manufactures a couple of years to deal with the change.  It is likely that the FCC will require a new report with 15.407 references to be submitted.

An additional note, this does not address any of the other requirements that need to be met for the new rules (UNII-1, DFS, software security) that still need to be met by June 2, 2016. These must be included in new and C2PC filings.

For more information, please contact us at (800) 270-2516 or via email to sales@nts.com. If you would like to book your testing prior to the deadlines, please use our Request a Quote form for the quickest response.