did you know

Did You Know

Compliance Topics:

Electrical Safety | EMI/EMC | Measurements | MIL-STD-461G | MIL-STD-810 | RED | Shielding | Wireless

Did You Know is an ongoing series featuring a variety of information about Compliance Concerns and Discussions, Product Approvals, Safety, Compliance Testing, Engineering, Design Topics and more.

Did You Know? EMI/EMC

Did you know that ESD neutralization should be used during test of ungrounded equipment?

IEC 61000-4-2 calls for neutralizing the test article for ungrounded equipment where a discharge event fails to occur.  This process is based on the premise that a residual charge is present when the next discharge trial is applied and the residual charge adds to the subsequent event voltage.  This could result in testing at an unknown value potentially higher that the specified voltage.  The residual charge will dissipate over time but it could take several seconds for complete neutralization especially if testing in a low humidity environment.

To meet the standard, testing should include a neutralization process to conform to the test standard.   This is accomplished by using a conductive cloth or brush through a resistive connection to the ESD simulator ground reference.

For more information contact us.

Article Reference ID: DYK00009

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Did You Know? MIL-STD-461G

Did you know that MIL-STD-461G (4.3.11) deleted the requirement for periodic calibration of passive antenna, current probe and LISN calibration unless repaired?

Concern: The premise for deletion of this calibration is that the system integrity check in the procedures would determine acceptability. However, the procedure integrity check removes the antenna so it is not checked with a known signal level. The procedure also calls for detection of a signal from a stub radiator without knowing the field strength of the signal. Antenna with a balun or connected elements that could be loose or corroded would go unchecked. If adopting the no calibration approach, you should generate a known signal level and fix radiator and receive antenna at a specific location to obtain a repeatable check and track the periodic integrity checks for trends to identify changes that could affect your measurements.

Article Reference ID: DYK00001

Did you know that MIL-STD-461G brought about the need for reducing facility power losses for the CS101 interfering signal?

Discussion: In MIL-STD-461G, A.5.7 if the specification limit cannot be developed and the pre-calibrated power limit is reached, it is “incumbent” that the tester check that the missing signal is not being dropped across the power source.  As shown in the sketch, a facility power filter often includes a series inductance that is not adequately bypassed by the bypass capacitor in the test circuit configuration at frequencies below 10 kHz.  Instructions indicate that the facility power filter may need to be removed to compensate and for DC power the bypass capacitor value increased to provide for the test voltage at the test article power input. Good idea – of course!

However the appendix (where this appears) is provided for guidance and is “not a mandatory” part of the standard.  If you would like more detail, don’t hesitate to contact us.

facility power filter

Article Reference ID: DYK00002

Did you know that MIL-STD-461G calls for verification of the EUT bonding prior to test before connecting cables (4.3.8.2)?

Discussion:  Over the years the test article configuration has been made to conform to the 2.5 milli-ohm standard for bonding the ground plane to the enclosure wall.  This basically violated the rule to configure as installed.  We have seen approval representatives go to extreme measures to attain a 2.5 milli-ohm impedance connection from an equipment connector to the ground plane with several bond connections in the measurement path.  If the equipment chassis to ground connection is provided by the protective ground connection only, then the measurement should be an open circuit until that cable is installed.  We should NOT allow the measurement to mis-lead us into making an artificial ground connection.  The goal is to make the intentional ground connection and measure without adding other parallel paths (cable shields, etc.).  If you record a measurement without the intended connection, then you may be encountering incidental connections that are not assured in the installation.  Remember that 2.5-milli-ohms is not an equipment grounding requirement unless the installation specifies.

Article Reference ID: DYK00003

 

Did you know that the new configurations using >28,000uF capacitors may need a pre-charge to prevent in-rush current from tripping the power source?

CS101 and CS117 configurations call for installation of a >28,000uF capacitor for DC powered devices.  At power on, the uncharged capacitor tends to act as a short circuit producing a significant in-rush current that may cause the power source to trip.  To help with this situation, a pre-charge circuit that controls the in-rush may be inserted to support charging the capacitor and then switching out when the charge is accumulated.  The drawing below shows a very basic pre-charge configuration – remember to use properly rated components if you decide to construct your own.

>28,000uF capacitors

For more information contact us.

Article Reference ID: DYK00011

Did you know that you can filter the power frequency to provide improved measurement resolution during CS101 testing?

The ability to measure the low level signals in the presence of the power frequency at high levels especially at the lower test frequencies is difficult.  The circuit below is a power filter that works with a 10X scope probe and 1MΩ oscilloscope input; it is designed to attenuate the power line frequency.  This circuit will need to be calibrated or characterized to determine the insertion loss across the frequency range of the test.  Note that using other than a 10X probe and 1MΩ input will yield different performance – calibrate your filter and observe component ratings – caution, high voltage circuit.

CS101 testing

For more information contact us.

Article Reference ID: DYK00012

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Did You Know? MIL-STD-810

Did you know that single axis vibration testing requires cross axis control?

Discussion:  MIL-STD-810 establishes a requirement to limit cross axis acceleration to 0.45 times the axis under test acceleration.  This calls for installing accelerometers in both axis orthogonal to the primary axis or using a multi-axis accelerometer.  If the cross axis vibration is greater than 3.5dB below the primary axis acceleration, then the cause needs to be determined.  If the cause is related to the vibration test fixture inducing the cross axis issue, then the fixture should be corrected to eliminate or move the resonant frequency outside the test range.  If the test article is the source, you may need to limit the drive spectrum or consider multi-axis testing.

Article Reference ID: DYK00006

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Did You Know? Electrical Safety

Did you know or I should say are you aware that product design features need to transfer to manufacturing properly?

Discussion:  Most product designers can relate to issues on obtaining a compliant design when it comes to electrical safety.  Standards and approving agencies require that selected tests be accomplished on 100% of units produced prior to shipment.  These aspects are considered so critical to operator safety that all are tested.  Insulation is a part of the critical tests evaluated by a dielectric strength test.  The idea is that if the insulation is compromised, it will be revealed in the test.  During the qualification testing rigorous tests are accomplished but the factory test allows a little relief (shorted duration, no conditioning, etc.).  In the example below a manufacturing flaw was noticed during a random sample inspection.  Note that the insulation is damaged because a cable tie was tightened to a corner reducing the insulation thickness.  Results provide for arcing to metal parts of the unit.  Would this be detected during factory testing – hopefully but atmospheric influences could allow a pass condition and shipping vibration makes this unsuitable for use.  Root cause – inadequate manufacturing instructions on placement or application of the tie.  The design must be supported by manufacturing.

Insulation Squeeze Play

click picture for detail

Article Reference ID: DYK00004

Did You Know that the Radio Equipment Directive (RED) requires Low Voltage Directive (LVD) compliance without regard to voltage?

Discussion:  RED 2014/53/EU paragraph 3 calls for LVD compliance and does NOT exempt equipment operating at less than the specified 50 or 75 V lower threshold.  Selecting an appropriate standard for the evaluation is not defined in the directive so a lot of questions regarding the evaluation standard are asked.  Many have arbitrarily chosen to use 60950-1 because the wireless feature places this into communications or the associated information technology category.  However, this may be a poor choice because we are not considering the primary function of the device.  If the primary function is used to determine the evaluation standard without regard to the radio feature, a more appropriate standard would be used.  For example, a medical device with a radio is still a medical device and 60601-1 (et al) would be appropriate – just don’t omit adding the radio back into the evaluation to assess RF exposure and other elements regarding RF safety.

 

Article Reference ID: DYK00005

Did you know that coin batteries can provide a Hot Pocket?

We are reminded every day during electrical safety evaluations that battery implementation requires paying attention to the details as our battery technology webinar series instructed.  But a little bit of info caught my attention during the webinars as a reminder about the coin batteries we encounter frequently.  We are so accustomed to these items that we forget about safety – danger associated with ingestion by small children and the ever familiar I’ll take it along so I can make sure I get the right replacement – taking along by tossing into a trouser pocket with loose change to have the change make a connection across the terminals resulting in a Hot Pocket  – just a reminder.

For more information contact us.

Article Reference ID: DYK00012

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Did You Know? Wireless

Did You Know that the Radio Equipment Directive (RED) requires Low Voltage Directive (LVD) compliance without regard to voltage?

Discussion:  RED 2014/53/EU paragraph 3 calls for LVD compliance and does NOT exempt equipment operating at less than the specified 50 or 75 V lower threshold.  Selecting an appropriate standard for the evaluation is not defined in the directive so a lot of questions regarding the evaluation standard are asked.  Many have arbitrarily chosen to use 60950-1 because the wireless feature places this into communications or the associated information technology category.  However, this may be a poor choice because we are not considering the primary function of the device.  If the primary function is used to determine the evaluation standard without regard to the radio feature, a more appropriate standard would be used.  For example, a medical device with a radio is still a medical device and 60601-1 (et al) would be appropriate – just don’t omit adding the radio back into the evaluation to assess RF exposure and other elements regarding RF safety.

 

Article Reference ID: DYK00005

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Did You Know? Shielding

Did You Know that the shielding effectiveness is determined by (effectiveness – leakage)?

Often a facility or enclosure specification calls out an overall shielding effectiveness stated in dB of attenuation and we are seeing where the requirements are based on a particular material’s spec sheet.  That seems like the two elements agree but the problem is that the leakage part of the equation is not considered.  Any gap or penetration in the shielding material can present a potential for leakage.  Doors are one of most difficult issues presenting a dis-continuity in the shield design – even shielded doors present gaps around the frame and hinges.  Wiring and plumbing items that penetrate the shield may present a means for signals to conduct through the shield presenting a leakage.  Details of shielding design have to consider the complexity or material and maintaining the integrity of the design – as well as the ability for integrating into the overall facility construction. – Questions or more information – contact us.

 

Article Reference ID: DYK00007

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Did You Know? Measurements

Did you know about voltage burden effects?

Review of the digital multimeter (Fluke 87) shows a discussion about making current measurements with the usual how to instructions. Near the end of that section, voltage burden is introduced. The “mA” range has about 1.8-ohms resistance, so as the current increases the voltage drop across the meter resistance starts to have an influence. If the source voltage is relatively low the voltage drop has a profound effect.

A short study using a 6Vdc source with various load resistance showed that the error at 400mA was greater than 10% and with burden compensation calculated the error was less than 1%.

Bottom line – you should become very aware of the voltage burden and compensation that may be required for any measurement. The “A” range has a voltage burden too because of 0.03-ohm resistance, so certain conditions could have an effect.

For more information about voltage burden effects – contact us.

Article Reference ID: DYK00008

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Did You Know? Radio Equipment Directive

Radio Equipment Directive FAQs

Radio Equipment Directive FAQs

Frequently Asked Questions
Radio Equipment Directive (RED)

1. Q. What is covered by the Radio Equipment Directive (RED)?

A. A radio transmitter, or receiver, or transceiver, which is used for radio communication or radio determination. It does not include transmitters used for other purposes, such as heating, cutting, treating materials, etc.

2. Q. What radio equipment is NOT covered by the RED?

A. Annex I of the RED covers equipment that is NOT covered by the RED. In general, equipment intended by radio amateurs is exempt. In addition, marine equipment and airborne equipment.

3. Q. When is the RED required?

A. After June 12,2017. Up until that time, both the R&TTED or RED can be used. From June 13,2017 and on, only the RED is allowed.

4. Q. What about products that use the RTTED?

A. From June 13, 2017, all products that are already physically in the market (in retail stores or in the supply chain that is not controlled by the manufacturer) can still be used or sold on to a final user. Any product that is placed on the market after June 13, 2017, must comply with the RED.

5. Q. Can I electronically label my device under RED?

A. No. This is not allowed for RED or any other Directive. The European Commission are looking at this option, which is allowed in several other markets, but not in the EU. Part of the concern is based around Market Surveillance and identifying a product without having to “turn it on.” There is also a concern that one cannot turn a product on until it is known to be CE-Marked. For example, in the EU, the CE Mark is not just about radio performance. It is safety too. Some argue that “maybe if we have it boot up in flight mode, so that it does not transmit until the CE Marking is displayed?” But CE Marking includes safety, one does not know that it is safe to plug it in or turn it on until the CE Marking is evident.

B. Finally, the EU commission say they have put a lot of effort into the CE Marking ‘brand’ and they don’t wish to dilute it now.

6. Q. Do I place an NB Number on my device if I use a Notified Body?

A. Under RED, this is only allowed for devices that are approved under Full Quality Assurance (Annex IV of the RED).

7. Q. What standards should I apply?

A. The recommended approach is to apply the harmonized standards (HS) that are listed in the Official Journal to self-declare to the RED. One difficulty lies in the fact that there is not a complete list of harmonized standards in the Official Journal.

8. Q. If HS are not accessible, how can I place a CE Mark on my product?

A. The RED allows for the use of a Notified Body (NB) to issue a EU-Type Examination Certificate (EU TEC). A manufacturer would submit an application for the EU TEC to a Notified Body who will evaluate the application for compliance with the RED. The NB would assess the Technical Documentation relating to the device and compare the test results or calculations to available standards (harmonized and non-harmonized) for compliance. A NB can accept testing to standards that are in various stages of development, including draft standards and committee working drafts, if available. There is some risk that draft standards are subject to change. A NB should give guidance on the potential risk for any of the approaches that may be used.

9. Q. Who can apply for an EU TEC?

A. The manufacturer or its authorized representative can apply for the EU TEC. Note that regardless of who submits the project to the Notified Body; the TEC would always be in the name of the manufacturer who places the product onto the market, with their brand name and company details on the product.

10. Q. What Documents are necessary for issuance of an EU-Type Examination Certificate?

A. The following information is required:

  • ACB Application Form: Review and Certificate – RED

  • External photos of the product

  • Internal photos of the product

  • User manual or instructions

  • Technical operation description

  • Block diagram

  • Parts list

  • Circuit schematic diagrams

  • Tune up tolerances

  • Product Safety test report

  • RF Exposure test report

  • EMC test report

  • Radio test report

  • Declaration of Conformity

  • Risk assessment by manufacturer

  • EFIS research evidence (for Class 2 devices)

  • Justification and explanation letters, in cases where full use of Harmonised Standards has not been used, or if any deviations or partial testing has been included.

  • Label

  • Packaging (optional)

NOTE: EU-Type Examination Certificates will feature an expiration date with the period of validity determined by the NB.

11. Q. What about scaled SAR?

A. “Scaled SAR” refers to the practice of adding transmitter tolerance to rated output power to determine SAR levels. This practice is referenced in Technical Guidance Note 20 (TGN20). This is guidance and it is not mandatory to comply with scaled SAR. However, there is a risk that market authorities may test devices at a higher-than-rated output power and so manufacturers are recommended to follow the guidance.

12. Q. What about Risk Assessment?

A. A manufacturer must prepare a Risk Assessment. Some of the ways to perform a Risk Assessment is to review the application and use of the device, such as its installation location, environmental conditions and end-use. If there is a good track record of performance with little risk, the risk assessment can be fairly straightforward. It is important for the manufacturer to check their products to the standards they have applied, to make sure there are no compliance risks to the Directive which were not covered by the standard.

B. It’s also important to remember that the standards will always lag behind technology. So, in cases where the device might do something (and therefore have a risk or mode) which is not covered by the standard (yet), they may need to do additional testing or research above and beyond the requirements of the standard. This is not certification to the standards; this is declaration to the Directive while using the standards as a ‘minimum starting point’ tool.

13. Q. Is an ISO 17025 accredited test report required?

A. No. The NB must be satisfied that the testing is being performed properly. Accreditation is not required for the testing lab.

14. Q. What additional tests are required under RED?

A. That depends. In many cases, you may have to perform some additional Receiver Tests if the new standard calls for the testing. There could also be additional spectrum sharing transmitter tests in some cases. Also note that the EMC immunity testing requirements have changed, to require more testing, notably for radio receivers.

15. Q. What about EMC and Safety? Are they still required?

A. Yes. The standards for EMC and Safety would be applied to satisfy EMC and Safety requirements for the Radio Device. It may be appropriate for the manufacturer to take standards from the EMCD and LVD to show compliance with the EMC and Safety requirements of the RED.

16. Q. What are the new reporting requirements for NBs?

A. NBs must file copies of the EU TEC with their designating authority. NBs must also update a central database with details of any EU TEC that was not issued, refused or recalled.

17. Q. Can you use HS that are harmonized under the EMC Directive for the RED?

A. Not directly. You can do it; but it will not offer immediate presumption of conformity with the RED. EMC standards may be harmonized under the EMC Directive, it does not extend to the RED. It is possible that some EMC and Safety standards may become listed in the RED OJ in the future.

Contact us for more information about RED

Did you know that RED compliance requires risk analysis?

Directive 2014/53/EU clause (40) cites decision 768/2008/EC to include conformity assessment procedures associated with the level of risk for meeting the essential requirements.  Module B clause 3. (c) calls for inclusion of risk analysis as part of the notified body (NB) application.  In cases where the use of harmonized standards support self-declaration, the file should contain the same risk analysis to confirm that risks have been identified and risk resolution is attained by application of the harmonized standard.  If a risk is identified that is not addressed by application of the harmonized standard, the risk resolution is documented as part of the file for NB approval.

For more information contact us.

Article Reference ID: DYK00010

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