NTS News Center

Latest News in Testing, Inspection and Certification

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

Holiday Bike Build in Silicon Valley

On Friday, November 17th our Silicon Valley location hosted over 30 people from both NTS and our customer Arista for a holiday bike build event. Four teams built three bicycles each for a total of 12 bikes donated to the local YMCA chapter.

The goal for each team was to work together to earn “build points” in order to collect parts to complete the bike build. Each team was given an iPad and had to solve riddles, take a picture or do a music video to collect the “build points.” Along with the 12 bikes each team created memories and putting smiles on the faces of children that wouldn’t have anything to play with this holiday season.. It was a great way to give back to our community and have fun at the same time.

Giving back to the community is a strong tradition between Arista and NTS. For the past 20 years events like this have been done in order to support and give back to the local community. With a focus on using local caterers and restaurants and local charities, both NTS and Arista find it very important to support the communities we work in.

If you would like to make a donation this holiday season click here.

Upcoming Changes for Wireless Equipment operating in 5 GHz Bands in the European Union EN 301 893

Manufacturers of wireless devices operating in the 5 GHz bands intended for sale in the European Union (EU) should take note of some important changes.

Manufacturers of these types of wireless equipment can still use the R&TTE Directive 1999/5/EC (Radio and Telecommunication Terminal Equipment  Directive) and it’s harmonized standard EN 301 893 V1.8.1 in their Declaration of Conformities (DoC) until June 12, 2017. After this date, manufacturers of any radio device that enters any country which requires CE marking have to use the RED (Radio Equipment Directive – 2014/53/EU) in their DoC. This is applicable for all new products as well as for products that are currently being sold and are intended to be placed on the market after this date. Products for which DoCs are not updated to the RED are not to be placed on the European Union market after June 12, 2017.

An issue with just declaring compliance with the RED as it is, that a RED harmonized version of EN 301 893 will not be listed in the Official Journal (OJ) of the EU by June 13, 2017. v2.1.0 of the standard is still in review and is scheduled to be published by ETSI on June 6, 2017 as v2.1.1. Harmonization is not expected (i.e. listed OJ) until September 19, 2017

Our recommendation to manufacturers is to schedule tests for the new requirements as soon as possible since test methods are significantly different.

Some of the changes are:

  1. Adaptivity has 3 different mandatory Interference signal types (AWGN, OFDM and LTE). Medium Access test methods have changed significantly. There are new procedures for Frame Based (other than 802.11) devices.
  2. The Receiver Blocking requirement is a new performance test applicable to all radio equipment.

With the absence of a harmonized version of this product standard, after June 12, 2017, any 5 GHz radio device must have a Notified Body Type Examination & Certificate in order to presume compliance with the Article 3.2 of the RED. Notified Bodies have to follow Article 3.2 of RED in their type examinations and will ask for evidence of presumption of conformity which must include a demonstration that the product meets Receiver Blocking requirements that are part of v2.1.0 of EN 301 893.

The new Adaptivity requirement as developed for the RED version of EN 301 893 is not aimed to address RED receiver requirements but future coexistence scenarios such as LTE-U which is not expected to be mass-marketed until 2018. Thus manufacturers can chose to submit the test cases to cover all the requirements of v1.8.1 version of the standard and receiver blocking testing of v2.1.0 for their Notified Body Type Examination applications until June 12, 2018.

When v2.1.1 is listed in the OJEU, the manufacturers will not have to have Notified Body Type Examination & Certificate if they follow this harmonized version of the standard but may still chose to use the Notified Body option to exclude new (enhanced) Adaptivity requirements until June 12, 2018.

Upcoming Changes for Wireless Equipment in the 5 GHz Band EN 301 893

By Deniz Demirci, Senior Wireless/EMC Engineer, NTS Silicon Valley 

Manufacturers of wireless devices operating in the 5 GHz bands intended sale in the EU should take note of some important changes.

Draft version of EN 301 893 V2.0.7 has been published in the ETSI web site in order to align with the Article 3.2 – Essential Requirements of Radio Equipment Directive 2014/53/EU.

Currently, manufacturers of these type of equipment can still use R&TTE Directive 1999/5/EC (Radio and Telecommunication Directive) and it’s harmonized standard EN 301 893 V1.8.1 in their Declaration of Conformities (DoC) until June 13, 2017.

After this date, manufacturers of any radio device who enters any country which requires CE marking, have to use RED (Radio Equipment Directive 2014/53/EU) in their DoC.

This is applicable for all new products as well as for products that are currently being marketed and intended to be sold after this date. Products which DoCs are not updated by this date, should not be sold in the European Union.

It is very likely that any RED version of EN 301 893 will not be ready and will not be listed in the OJ on June 13, 2017. The version V2.0.7 of the standard is still in review process and is scheduled to be published on July 8, 2017. The standard is expected to be listed on the Official Journal of the European Union on October 21, 2017.

With the absence of this product standard, there is a possibility that EN 301 893 V1.8.1 may be listed in the OJ with additional Adaptivity and Receiver Blocking requirements aligned with 301 893 V2.0.7 in order to presume compliance with RED until the new version of the standard is published.

Otherwise, after June 13, 2017, any 5 GHz radio device must have a Notified Body Opinion/Type Examination Certificate in order to presume compliance with the Article 3.2 – essential requirements of Directive 2014/53/EU – RED. Which means that, overwhelming number of products on the market will require Notified Body Opinion.

The Notified bodies also have to follow Article 3.2 of RED in their assessments and will ask for evidence of presumption of conformity which will include Adaptivity and Receiver Blocking tests.

Our recommendation to the manufacturers is to schedule the tests for the new requirements as soon as possible since the test methods are significantly different.

Some of the major changes are:

  1. Adaptivity has 3 different mandatory Interference signal type (AWGN, OFDM and LTE). Medium Access test methods have changed significantly. There are new procedures for Frame Based (other than 802.11) devices.
  2. The Receiver Blocking requirement is a new performance test and unconditionally applicable to all radio equipment.

Please contact us at sales@nts.com or call 800-270-2516 for additional details and how to test your product and update test reports for Radio Equipment Directive.

Changes for Medical Equipment IEC 60601-1

UL 60601-1 and CAN/CSA C22.2 No. 60601-1

With the publication of the fourth edition of IEC 60601-1-2 [1] and its European equivalent, EN 60601-1-2 [2] being listed in the Official Journal, the EMC requirements for medical electronic devices changed. Products that will remain in production after the mandatory effective date of December 31, 2018 may require redesign to comply with the requirements of the fourth edition. Changes in design will also affect the FDA approval. Even if no changes are required, testing will need to be performed to assess the product’s performance in light of the expanded scope of testing of this new edition for the EU. There is no grandfathering of equipment that was assessed using the third edition of the standard in the EU. A presumption of conformity with the essential requirements of the Medical Device Directive (MDD) may only be assumed if the new edition is employed after the transition date. For the sake of brevity, whenever I refer to the standard, I am talking about the fourth edition of IEC 60601-1-2 and EN 60601-1-2.

Test Requirements: Emissions

The emissions requirements are found in Table 2 of the standard and cover conducted and radiated emissions using the limits and methods of CISPR 11, harmonic distortion using IEC 61000-3-2 and voltage fluctuations and flicker using IEC 61000-3-3. The application of IEC 61000-3-2 and IEC 61000-3-3 depends on the use environment. Different requirements may be necessary based on other uses, such as in transportation.

Test Requirements: Immunity

Performance Requirements

As you read the standard, you eventually get to the section on immunity requirements for ME equipment and systems. The test levels to be used are described in the standard for two types of environments. Use of higher or lower values may be used depending on the outcome of the risk management process.

At first glance, you may decide that degradations of performance are not allowed during the tests and that your product will not be able to meet a performance criteria without a significant redesign. However, as stated, the intent of this section is to describe these degradations in light of the Essential Performance and Basic Safety of the product being tested. The product is allowed to exhibit degradations that do not affect Essential Performance and safety during the tests.

Basic Safety and Essential Performance

What are Basic Safety and Essential Performance? These are defined terms in the standard IEC 60601-1. Basic Safety is “freedom from unacceptable risk directly caused by physical hazards when ME equipment is used under normal condition and single fault condition.” Essential Performance is “performance necessary to achieve freedom from unacceptable risk.” According to the standard, a risk management process shall be used to identify risks from electromagnetic disturbances in addition to any other risks.” Annex F provides additional guidance for including the risks from electromagnetic disturbances in the risk management process described in ISO 14971. The risk management report produced by the process provides the description of pass fail criteria for each function of the product and how the basic safety and essential performance will be monitored during each immunity test. This information is incorporated in the EMC test plan. This test plan is required prior to starting any EMC testing. An example is provided in Annex G of the standard.

The implication here is that you should perform a risk analysis (see Annex F of the standard for more details) prior to establishing the compliance criteria to avoid the need to perform more tests against more stringent criteria. Depending on the class of device as determined from Annex I of the medical device directive, a notified body will likely need to be consulted in determining the performance criteria to apply based on the risk analysis. The establishing of the performance criteria is crucial to evaluating the observations made of product operation during immunity tests and in determining the methods used to monitor the product. The risk analysis must account for all manners of use of the product. After assessing all the risks and determining the residual risk level, you enumerate the compliance criteria. Examples of criteria can be found in Annex I of the standard.

Tests

Now that you have established the compliance criteria you will use during the immunity tests, you are ready to test. Not so fast. The standard requires a completed test plan be prepared prior to the start of formal testing. The recommended content of the test plan is given in Annex G of the standard. The standard includes the normal set of immunity tests that are to be applied and describes test levels for special environments in Annex E. The tests are the same tests that are applied for other products such as radio equipment, networking equipment and information technology equipment except that the standard incorporates some specific test application guidance notes that require special consideration. Tables 4 through 8 list the immunity tests applicable to medical devices and the basic levels for both professional healthcare facility and home healthcare environments.

The list may include additional tests and the test specification column may change based on the type of equipment to be evaluated and particular standard that would therefore apply. It is beyond the scope of this paper to present the appropriate specifications for all medical devices. However, some examples can serve to illustrate the point. EN 60601-2-24, particular to infusion pumps, modifies the test specifications: radiated immunity test level changes to 10 V/m even if the product is for professional healthcare environments; magnetic immunity test level increases to 400 A/m. EN 60601-2-10, particular to nerve stimulators, adds that patient leads are to be placed in saline solution during testing. EN 60601-2-2, particular to HF surgical equipment, modifies the compliance criteria and the emissions test configuration.

To evaluate the DFS functions of a system the regulatory standards describe waveforms to be used when evaluating DFS. These waveforms are defined in terms of the number of pulses, the pulse width and the pulse repetition frequency (or period) for the radar signal. The pulses may be modulated with an FM chirp, and may contain pulses of different widths and different periods.  Manufacturers should always bear in mind that their radar detection algorithms should be designed to detect all radar systems.

Table 1: Immunity Tests
Environmental Phenomena Test Specification Test Setup
Electrostatic Discharge ±8kV (Contact)

±2, 4, 8, 15kV (Air)

EN 61000-4-2
RF Fields 80 – 2700 MHz

3V/m (professional healthcare facilities) or 10V/m (home use)

80% AM, 1 kHz

EN 61000-4-3
RF Proximity fields Various frequencies up to 28 V/m EN 61000-4-3
Fast transients

Power

Signal

5/50ns, 100 kHz

±2.0 kV

±1.0 kV

EN 61000-4-4
Surges

Line to PE

Line to Line

Outdoor SIP/SOP

1.2/50μS

±0.5, 1.0 & 2.0kV

±0.5 & 1.0 kV

± 2 kV line to ground

EN 61000-4-5
RF Voltage (Conducted Immunity) 0.15 – 80 MHz

3V (6V in some frequency ranges)

80% AM, 1 kHz

EN 61000-4-6
Magnetic Fields* 50 Hz

30A/M

EN 61000-4-8
Voltage Dips 100%, 0.5 cycles at various phase angles

100%, 1 cycle

30%, 25/30 cycles

EN 61000-4-11
Voltage Interruption 100% for 250/300 cycles EN 61000-4-11
*Applies only if the product has magnetically sensitive components or circuity

 

The standard has higher test levels for ESD and magnetic field immunity, magnetic field immunity may not be needed, additional RF field immunity requirements with potentially higher levels and additional VDI requirements compared to the previous edition. It also makes clear the need for a test plan prior to testing. Depending on the product, the test plan may need to include other tests or test levels that will also need to be evaluated based on the intended use of the product.

Basic Immunity Test Modifiers

For some of the immunity tests, the standard specifies modifications to the methods of the basic standards listed in table 1 above.

For example:

The dwell time at each frequency step for conducted and radiated immunity must be set to allow the product to be fully evaluated at each step. Dwell times exceeding 15 seconds are not uncommon.

Electrical fast transient tests are not performed on patient cables.

During conducted emissions, electrical fast transient/burst and conducted immunity tests, patient coupled parts shall be terminated with artificial hands.

CDNs shall not be used for conducted immunity tests on patient leads.

Power input voltage and frequency are specified for each test in Table 1 of the standard. In most cases, the tests are performed at one voltage and one frequency from the ranges of voltage and frequency for which the product is rated. Voltage dips and short interruption tests shall be performed at the minimum and maximum rated voltages if the product has rated voltage range ≥ 25% of the minimum rated voltage.

Product Information

Assuming that you have performed all of the appropriate emissions and immunity tests using the compliance criteria specified in the test plan with acceptable results, the requirements of the standard are still not yet fulfilled. The standard requires information about EMC to be included in the instructions furnished to the user. These can be found in Clause 5. The tables of information there were part of the third edition of the standard are not included in the fourth edition.

The instructions shall also provide technical information such as compliance information for each test and test levels for immunity. The justification for using the levels other than described in the standard shall be provided in the instructions. Instructions necessary for maintaining BASIC SAFETY and ESSENTIAL PERFORMANCE with regard to electromagnetic disturbances shall also be provided.

Radio Functions in Medical Devices

If a radio is provided with the product either internally or as a separate unit, the radio part of the device or system may only need approval against the applicable radio standards. However, if the function of the radio affects the essential performance of the system, then the radio and medical device both must be evaluated for immunity using the medical equipment standard.

The emissions of the radio part must comply with the medical equipment standard except in the dedicated transmission band. This means that spurious emissions of the radio must meet the CISPR 11 limits, which in most cases are more restrictive than the spurious emissions limits for the radio device.

Summary

The new edition of EN 60601-1-2 presents many challenges to manufacturers. From the beginning of the design process, manufacturers are encouraged to seek assistance from test labs and certification agencies to understand the provisions of EN 60601-1-2 as they apply to their specific product.

References

[1] IEC 60601-1-2:2014, International Standard for Medical electric equipment – Part 1-2: General requirements for basic safety – Collateral standard: Electromagnetic compatibility – Requirements and tests.

[2] EN 60601-1-2:2015, European Standard for Medical electric equipment – Part 1-2: General requirements for basic safety – Collateral standard: Electromagnetic compatibility – Requirements and tests.

Upcoming Changes for Wireless Equipment in the 2.4 GHz Band EN 300 328

By Deniz Demirci, Senior Wireless/EMC Engineer at NTS Silicon Valley

EN 300 328 V2.1.1 was harmonized and listed in the Official Journal of the European Union under Directive 2014/53/EU for RED (Radio Equipment Directive) on January 13, 2017. This version of the standard covers the essential requirements of article 3.2 of RED for 2.4 GHz ISM band WiFi, Bluetooth and other Wideband transceivers.

Manufacturers of these type of equipment can still use R&TTE Directive 1999/5/EC (Radio and Telecommunication Directive) and it’s harmonized standard EN 300 238 V1.9.1 in their Declaration of Conformities (DoC) until June 13, 2017.

After this date, manufacturers of any radio device who enters any country which requires CE marking, have to use RED (Radio Equipment Directive 2014/53/EU) in their DoC.

This is applicable for all new products as well as for products that are currently being marketed and intended to be sold after this date. Products which DoCs are not updated by this date, should not be sold in the European Union.

Manufacturers should follow EN 300 328 V2.1.1 requirements and update their test reports for their current products as soon as possible since there is significant change in the essential requirements;

  • The Receiver Blocking Requirement is unconditionally applicable to all radio equipment regardless of receiver category or adaptivity capability. This is a major change from the previous version of the standard.

Since the Receiver Blocking was conditionally applicable to the adaptive equipment only and the test methods as well as the performance criteria were different, most products may have never been evaluated for this requirement before.

Note: After June 13, 2017, any radio device which the standards are not yet harmonized and listed in the Official Journal of the European Union, must have a Notified Body Opinion/Type Examination Certificate in order to presume compliance with the essential requirements in Article 3.2 of Directive 2014/53/EU – RED.

For more details and information on how to update test reports for the Radio Equipment Directive, other specification interoperability scenarios or test, design and engineering help is available by contacting NTS at 800-270-2516 or emailing sales@nts.com.

Radio Equipment Directive (RED) Transition Time Coming Soon

Is your organization ready for the transition to the Radio Equipment Directive (RED)? RED must be employed for all products included in its scope and not yet placed on the EU market after June 12, 2017. Even products that were already being sold as compliant with the R&TTE directive must comply with the RED to continue to be placed on the market after this date.

The EU Commission has continued to add standards to the harmonized standards list, visit the EU Commission website to review the latest updates, as of March 10, 2017.

To learn more, visit our RED page or contact us today!

EN 61326-1: EMC Emissions/Immunity Requirement Changes for Laboratory Equipment

By Conrad Chu, EMC Engineering Manager, NTS Silicon Valley

EN 61326-1 has been adopted and published in the EU’s Official Journal. As this standard is the applicable standard for Measurement, Control and Laboratory Equipment, it affects a large number of devices.

The EN 61326-1:2013 version of the standard superseded EN 61326-1:2006 and became mandatory on August 14, 2015. EN 61326-1:2013 is equivalent to international standard IEC 61326-1:2012.

Summary of Significant Changes

Emissions: The 2006 version references CISPR 11:2003, while the 2013 version references CISPR 11:2009 +A1:2010. The first amendment to CISPR 11:2009 has established alternative radiated emissions limits at 3 meters test distance for “small equipment”, where “small equipment” is defined as “equip­ment, either positioned on a table top or standing on the floor which, including its cables fits in a cylin­drical test volume of 1.2 m in diameter and 1.5 m above the ground plane”.

Basic Immunity Environment (Immunity)

The test levels for electrostatic discharge (ESD) have increased from ±4 kV contact discharge and ±4 kV air discharge in EN 61636-1:2006 to ±4 kV contact discharge and ±8 kV air discharge in EN 61326-1:2013.

For magnetically sensitive equipment, EN 61326-1:2013 adds a new requirement for power-frequency magnetic immunity (IEC 61000-4-8) at a test level of 3 A/m.

Controlled EM Environment (Immunity)

EN 61326:2006 has a port category called “Measurement I/O”, where the manufacturer is allowed to define the test level (i.e. no mandated test level) and state in the product documentation what level the EUT was tested to. In EN 61326:2013 this port category has been removed. Hence the ports that would previously fall under the “Measurement I/O” category would now fall under the remaining “I/O signal/control” category, where the required tests levels are defined by the standard and not left to the discretion of the manufacturer

Portable Environment (Immunity)

For magnetically-sensitive equipment, EN 61326-1:2013 adds a new requirement for power-frequen­cy magnetic immunity (IEC 61000-4-8) at a test level of 3 A/m.

How this Affects Existing and New Test Programs

NTS has been testing to this latest standard with all reports to be issued to the EN 61326-1:2013 version of the standard.

Customers who wish to update their product(s) to the 2013 version can do so based on applicable testing needed. Once the additional test requirements are fulfilled, the report (s) can be reissued to reflect the 2013 version.

Despite the addition of new magnetic immunity requirements in EN 61326-2:2013, in most cases magnetic immunity testing will still not be required as the testing is only required for devices that contain components inherently susceptible to magnetic fields.

Conclusion

Manufacturers should be testing to the EN 61326-1:2013 version of the standard.

For more information about how this change affects your products or for a price quote for services, please contact us at sales@nts.com or call 800-270-2516.

Declaration of Conformity Changes for Multimedia Equipment

By Deniz Demirci, Senior Wireless/EMC Engineer, NTS Silicon Valley

Manufacturers of Multimedia Equipment, including Information Technology Equipment (ITE), Audio, Video Equipment, Sound and Television Broadcast Receivers and Associated Equipment and Professional Use Audio, Video, Audio-Visual and Entertainment Lighting Control Apparatus or any combination of these equipment, intended for sale in the European Union (and other countries that base their EMC regulations on CE marking) should take note of the following changes that are slated to go into effect with regard to the Declarations of Conformity as per EMC Directive 2014/30/EU. All hardware products marketed in the European Union must comply with these newer editions of the standards and have updated Declarations of Conformity (DoC) by the dates listed below.

This is applicable for all new products as well as for products that are currently being marketed and intended to be sold after these dates. Products whose DoCs are not updated by the required date should not be sold in the European Union.

Multimedia Equipment Emission requirements:

  • After March 5, 2017 DoCs have to reference EN 55032:2012. EN 55032:2012 will replace EN 55013:2013+A1:2016, EN 55022:2010+AC:2011 and EN 55103-1:2009+A1:2012
  • If your Declaration of Conformity (DoC) references EN 55013 or EN 55020 or EN 55103-1, the DoC needs to be updated to EN 55032
  • DoCs have to reference EN 61000-3-3:2013. EN 61000-3-3:2013 has superseded the previous version (EN 61000-3-3:2008) on June 18, 2016. Any references to the EN 61000-3-3 standard in your Declarations of Conformity must be updated.
  • DoCs have to reference EN 61000-3-2:2014. EN 61000-3-2:2014 has superseded the previous version (EN 61000-3-2:2006 +A1:2009 +A2:2009) on June 30, 2016. Any references to the EN 61000-3-2 standard in your Declarations of Conformity must be updated.
  • Any future changes on these standards above will have 1 year transition period after they are harmonized and listed in the Official Journal of the European Union.

Multimedia Equipment Immunity requirements:

EN 55024:2010 is the current harmonized standard for EMC Directive 2014/30/EU for Information Technology Equipment.

EN 55020:2007+A12:2016 is not listed as an harmonized standard in EMC directive but it can be used as state-of-the-art standard for Sound and Television Broadcast Receivers and Associated Equipment until EN 55035 is published.

EN 55103-2:2009 is the current harmonized standard for EMC Directive 2014/30/EU for Audio, Video, Audio-Visual and Entertainment Lighting Control Apparatus for Professional Use.

CISPR 35:2016 (Electromagnetic compatibility of multimedia equipment – Immunity requirements) has been published and it is expected to be adapted by European Union. Although the exact dates are not known yet, when it is published and harmonized for EMC Directive, EN 55035 will cover Information Technology Equipment, Audio, Video Equipment Sound and Television broadcast receivers and associated Equipment and Professional Audio, Video and Entertainment Lightning control apparatus and any combination of this equipment.

When EN 55035 is harmonized and listed in the Official Journal of the European Union, there will be no transition period for Sound and Television Broadcast Receivers and Associated Equipment and EN 55035 will be immediately in use. Information Technology Equipment and Professional Audio, Video and Entertainment Lightning control apparatus will have 1 year transition period.

Korea has already adapted previous draft version of CISPR 35 as KN 35:2015 which supersedes KN 20 and KN 24.

For more information about how this change affects your products or for a price quote for services required to update your product, please contact us at sales@nts.com or call 800-270-2516.

Acoustic Noise Testing Explained

Fremont, CA 10 Mic Acoustic Set Up

NTS 10 Microphone Acoustic Set Up

Acoustic noise testing is the measurement of sound emissions radiating from the equipment under test. In other words, how loud is the equipment?

Why test for acoustic noise?

Many markets and industries require acoustic noise testing to protect the hearing of technicians and users of equipment.

  • Regulatory: OSHA and other international regulatory bodies require that acoustic noise emissions values of many different types of equipment be declared in order for the equipment to be legally sold.
  • Telecommunications: AT&T, Verizon and Telcordia require acoustic noise testing to be performed on products being deployed in central offices, data centers, customer premises and outside plant environments.
  • Medical: Life critical devices need to have a minimum loudness and frequency range for tones and alarms in order to be heard by doctors, nurses and medical technicians.
  • Business/ITE: Equipment that generates annoying or loud tones and buzzes can easily be heard throughout an office environment.
  • Military: Military and defense products are required to undergo acoustic noise testing to prevent hearing loss, permit acceptable speech communication and minimize aural detection by the enemy.

Industry standards which cover acoustic noise testing include: ISO 9296, ISO 7779, ISO 3744, GR-63-CORE, ETSI EN 300 753, IEC 60601, and MIL-STD-1474D (previously MIL-STD-740).

Sound Pressure vs. Sound Power

Sound pressure is the difference in pressure between the instantaneous pressure the audible wave generates and the static pressure of the background environment. This is what your ear actually perceives. The measurement is usually expressed in Pascals or Dynes per square centimeter.

Sound power is the sound pressure taken at multiple points through a surface in space (measurement surface). It is the product of the sound pressure and the particle velocity normal to the surface integrated over the surface. This is a measurement of sound energy over time radiating from a source. The measurement is usually expressed in Watts.

Some standards dictate measurements be expressed in raw sound pressure, and others in sound power. Sound pressure varies between environments based on background noise and reflections. Sound power is a calculation that tries to eliminate the variations that sound pressure is prone to. Using the measurement techniques of ISO 3744 and NTS’s semi-anechoic chambers, consistent reliable sound power values are achievable and can be easily used to compare different product configurations, cooling fan vendors and fan speeds.

A-Weighting & (1/3) Octave Bands

  • A-weighting is a weighting curve applied to sound pressure measurements that replicates the response of the human ear across the entire audible spectrum from 10 Hz to 20 kHz. Most standards require sound pressure measurements to be A-weighted.
  • Octave bands and 1/3 octave bands subdivide the spectrum into different bands to analyze which frequencies in the spectrum have the most sound pressure content. Some standards require specific octave and 1/3 octave bands (such as those closest to human speech) to have lower sound pressure content than others.

10 Microphone Array

NTS Silicon Valley recently upgraded our acoustic noise data acquisition system from a single microphone to a 10 microphone array. This new setup can capture multiple sound pressure measurements or an entire sound power field instantaneously. Our customers can now test many different product configurations in a single day long test session allowing faster troubleshooting and ultimately a quicker time to market.

NTS offers CAD/FEA Modeling for Direct and Indirect Effects Lightning, Reducing Test Costs and Time

The NTS Lightning Technologies laboratory in Pittsfield, MA is now offering finite element analysis, allowing the performance of complex simulations that accurately model the interaction of lightning with a variety of aircraft and avionics components for our customers. This service is available to all of the customers of the 10 NTS facilities across the US offering direct and indirect lightning testing.

Lightning Testing Figure 2

Figure 1 – Current Distribution and Magnetic Field in Two Current Carrying Copper Conductors

By decomposing complex CAD-generated objects into meshable geometrical shapes, these models are able to accurately portray the lightning environment (current distribution, electric and magnetic fields, pressure waves, temperature variations, induced transients) on high fidelity renditions of real objects. Once the geometry is built, highly customizable material parameters, boundary conditions, and applicable physics interfaces (Maxwell’s Equations) are applied that generate a system of equations that is solved in COMSOL. With accurate representation of test object geometries, the solutions of these models allow for conducted and induced transients to be determined at any point in the model.

Figure 2 - Magnetic Field Penetration through Apertures on a Fuselage

Figure 2 – Magnetic Field Penetration through Apertures on a Fuselage

Utilizing simulation and modeling along with laboratory testing provides customers with a new, cutting edge way to obtain valuable test data that can reduce testing costs substantially. Making use of these models allows for the easy acquisition of difficult or impossible to obtain lab measurements (equipment limitations) without having to perform the test on an actual object. Once a model has been developed, a similar test is performed on a real piece of equipment in order to validate the model. Once the model has been validated, lightning attachment locations, cable routing configurations, and material characteristics (to name a few) are all easily modifiable to allow for many permutations of the test environment to be modeled. The results of these models can provide valuable design constraints and necessary test levels for certification. Additionally, once validated, these models can serve as a firm basis for similarity analyses for future design changes, providing the potential for a cost and schedule reduction to future programs.

Figure 3 - Magnetically Induced Voltage on Conductor inside Fuselage

Figure 3 – Magnetically Induced Voltage on Conductor inside Fuselage

For questions about our new finite element modeling and how it can be applied to your testing program or for any other lightning test related inquiries please contact our General Manager Mike Dargi at 413.499.2135 or Mike.Dargi@nts.com

NTS has 10 facilities across the US capable of performing your complex direct effects and indirect effects lightning testing. We are able to meet the full scope of RTCA DO-160 testing, as well as numerous other specifications with lightning requirements including MIL-STD-461/462, SAE ARP 5416A, and IEC 61400-24 (wind turbines). Contact us today to discuss your next test program.