EMC Sleuth: Mysterious Interference at the Doctor's Office

Ray Klouda, Elite President

Today's expert is Ray Klouda, Elite’s President and captain of this ship. Ray has 34 years of experience in the related fields of electromagnetic compatibility (EMC) and RF shielding design with a focus on military and commercial EMC specifications, quality systems, and TCB Certification.  As Membership Officer of the IEEE EMC Society’s Chicago Chapter and active member of the American Council of Independent Laboratories (ACIL) and various Smart Grid committees, he likes to stay involved in the industry and act as an “EMC Sleuth” if the occasion arises. Read below to see what he has for us today.

Sometimes, I have the fortunate opportunity to step outside of the EMC lab and investigate real-world EMI problems.  Several years ago, I received a call from a desperate general contractor who had an EMI situation in a new state of the art audio clinic.  The facilities included an MRI suite in the lower levels.  The doctors complained about issues of networking errors with their new computer system, electronic noise problems in their audio lab, and incorrect results from their blood analyzers.  They were threatening to withhold payments until the issues were resolved.  

The GC’s first thoughts were that the MRI equipment was the culprit.  He called us in the survey the site to determine if the MRI was indeed causing these interference problems.  We arrived at the site and set up a spectrum analyzer with various antennas and current probes in order to monitor the field intensity levels.  We started by taking measurements in the MRI suite and then moved on to the audio labs where the equipment problems had occurred.  

In a short time, we were able to diagnose the problem.  The interference was due to a broadband source.  We could see significant broadband switching noise throughout the high frequency (HF) spectrum.  These voltage spikes were both radiating from the power lines, as well as, conducting into the power lines.  We could not attribute any significant RF interference as generated by the MRI equipment.  We proceeded to walk into the waiting area of the office where the levels intensified.  This waiting room was state of the art and included high tech lighting that dimmed to create a soothing and relaxing atmosphere. 

Can you deduce what else the light system created?

At an opportune time, we turned off the lights in the waiting room.  We immediately noticed a significant drop in the HF noise level and the spikes all but disappeared.  The contractor was beside himself to think that such a low tech device as a dimmer switch could wreak such havoc upon the doctors’ offices.  We recommended that the dimmers be replaced with dimming technology that does not produce noise.  The problem was solved and everyone was happy.

Below are some questions for further thought and discussion on real-world interference applications:

What lighting technologies are significant sources of EMI?

What are some ways to reduce this interference?

Will interference problems increase as more high tech lighting is installed to reduce energy consumption?

What regulations are in place to control the level of interference from these sources?

Do you have answers to the above or any questions about Interference Issues, EMC Testing, or other related topics? Please share your comments or questions below and this week's expert, Ray Klouda, will get back to you as soon as possible. 

4 Things to Look For When Interpreting Standard Requirements

Craig Fanning, EMC Lab Manager

Today's Elite Expert is Craig Fanning, our EMC Lab Manager, US National Committee Technical Advisor for CISPR-D, and advisor on many other industry committees. Read below to see what he has for us this week. 

 

Being on several standards committees, I get a lot of questions about how to interpret the information provided in standards and specifications. Sometimes this is from a colleague who is thoroughly reviewing a specification in preparation for a quality audit. As a result of the thorough standard review and the possibility of being assessed a “deficiency” during the audit, they become overly concerned about all parts of the standard. Other times, the person has already been audited and overlooked a requirement. This resulted in a “deficiency” during the audit. The standards committees have content rules (what is and is not a requirement and how is that defined in the standard) that must be followed when a standard is being developed or revised. In addition, quality auditors are only supposed to audit against the requirements of a standard. Here is brief summary of what is a requirement within a standard…

1. Main Body of the Standard: In general, information provided in the main body of the standard and prefaced with the word “shall” is a requirement. Dimensions and values are also a requirement. If no tolerances are provided in the standard, then general tolerance rules apply (or the tolerances specified in the base standard of a series of standards would apply). Any information prefaced with a should, could, may, etc. (anything other than a shall) could be considered informational and not a requirement. 

2. Notes: Notes in a standard are for information purposes only. You will notice that notes within a standard do not contain the word “shall”. Do not confuse “Notes” with “Footnotes”. Notes will always be prefaced with the word “Note:” Footnotes are used many times in tables and can contain very important information. So pay close attention to footnotes (especially in tables).

3. Annex (Normative or Informative): At the beginning of each Annex (sometimes referred to as Appendix in some standards), the word “Normative” or “Informative” will appear. If the Annex is “Normative”, then the information in the annex is a requirement (again keeping in mind the preface word of “shall”). If the Annex is “Informative”, then the annex is for information purposes and is not a requirement.

4. Interpretations: Although the standards committees try to make the information provided within a standard as clear as possible, something always seems to get into the published standard which may need interpretation or clarification. In these instances, the reader will have to use good engineering judgment. When this happens, it is a good idea to ask others in the industry (especially persons on the standards committee responsible for the standard generation) how they interpret the information provided in the standard. They most likely have had the same question and have addressed the issue.

I realize that this is a “crash course” in standards interpretation, but it should provide someone with the basics for interpreting standards. Knowing the basics and what to look for in a standard (also what can and cannot be audited) can really be helpful during a quality audit.

Do you have any questions about EMC Standard Interpretation, EMC Testing, or other related topics? Please share your comments or questions below and this week's expert, Craig Fanning, will get back to you as soon as possible. 

How To Acquire Accurate & Efficient EMC Lab Equipment

Tom Klouda, Elite VP

Tom Klouda, local lightning expert and EMC equipment extraordinaire, tells us what it takes to obtain quality EMC laboratory test equipment that accurately and efficiently tests our customers' products.

Electromagnetic Compatibility (EMC) tests require the use of specialized and costly pieces of electronic equipment.  The electronic equipment must perform the measurements accurately and efficiently.  A process used to acquire equipment at Elite Electronic Engineering, Inc. that has been successful is a collaborative effort between Elite, our customers and the equipment manufacturers.

The process starts by identifying a need for the equipment.  The need can be identified from schedule bottle necks, missed opportunities, operation safety concerns or functionality.  Once the need is identified, various manufacturers of the test equipment are researched. In our research we consider the equipment’s features, cost, warranties and service.  Often, equipment on the market does not have the required features to meet our customer’s needs. This situation is where Elite’s personnel provide valuable insights.  Our customers and equipment manufacturers know everything about the design of their equipment. 

However, Elite is in the unique position of knowing how to test our customer’s equipment and how to use the manufacturer’s test equipment.  Knowing our customer’s need, Elite’s personnel work closely with the manufacturer to design equipment that accurately and efficiently performs the tests. This collaborative relationship has benefited everyone involved.  The EMC test industry also benefits because now the equipment Elite helped to design is available to everyone.      

Tom conducting an internal equipment training session in August.

Do you have any questions about choosing EMC Test Equipment, Lightning Testing, or other related topics? Please share your comments or questions below and this week's expert, Tom Klouda, will get back to you as soon as possible.