Interview with Bill Kimmel

Featured Engineer

Bill Kimmel

Bill Kimmel - Partner in the EMI Consulting Company, Kimmel Gerke Associates, Ltd.

How did you get into electronics/ engineering and when did you start?

I was fascinated by “Electronic Brains,” as computers were called around 1950. So I went to the University of Minnesota Institute of Technology right out of High School, got a degree in electrical engineering in the early 1960’s. Immediately went to work in the Microcircuits group at Univac, one of the leading computer companies at the time.

How did you get into EMI?

The Microcircuits group had just built the world’s first microelectronic computer, intended for guided missile applications. The key concern was gamma radiation and Electromagnetic Pulse (EMP) emanating from a nuclear burst, both of which can disrupt the operation of electronic equipment at distances far beyond the blast effects. This was my first introduction into EMI.

I moved to Control Data Corporation where I worked on magnetic core memories and high speed digital circuits – both of which are effectively EMI or Signal Integrity at the circuit board level.

I moved to Sperry Defense Systems, where I worked on EMI at the Systems level. In the early 1980’s, the FCC levied emission requirements on commercial equipment. My co-worker and present partner, Daryl Gerke (my co-worker at the time and present partner) and I, decided the commercial world would be fighting the same EMI problems that we had been fighting for 20 years, so we formed Kimmel Gerke Associates and started consulting on EMI problems on a part time basis. We took the business full time in 1987, and have been designing, troubleshooting and training EMI problems ever since.

What are your favorite hardware tools that you use?

My most commonly used tools are a spectrum analyzer and assorted antennas and probes, used for identifying emissions from equipment. I have an ESD gun that I use quite a bit, for forcing equipment failures..

What are your favorite software tools that you use?

I do fairly little EMI modeling. Most of my work is short term design and troubleshooting – I have to get the job done in a few days, so I don’t have the time for in-depth modeling. For basic modeling, I use MathCad or a spreadsheet. I do make heavy use of the Internet, searching vendor sites or other technical information.

What is the hardest/trickiest bug you have ever fixed?

I don’t typically have hard technical problems. I do maybe 25 consultations a year, and have been doing so for more than 20 years. After working 500 EMI problems, mostly I get variations of old problems, with the occasional wrinkle due to new technology.

What is the most interesting problem you have ever fixed?

My most interesting problems are usually the ones where the problem turns out to be something other than EMI. I had a case where something was causing sensor errors in a factory environment. The suspect was radar from a nearby Air National Guard station nearby. The problem occurred when the door facing the Guard station was open, but only in the summertime. The funny thing was, it took a minute or two after the door was open for the problem to occur, and the condition persisted for a couple of minutes after the door was closed. Ultimately, the problem was traced to condensation on the low level analog sensor lines – in the summer, the warm moist air flowed into the sensors, which were well cooled by the air conditioning.

What is on your bookshelf?

We have our own books, “EDN’s Designer’s Guide to EMC,” “EMI Suppression Handbook,” and “Electromagnetic Compatibility in Medical Equipment.” We like Henry Ott’s “Electromagnetic Compatibility Engineering,” Clayton Paul’s “Introduction to Electromagnetic Compatibility,” and Howard Johnson’s “High Speed Digital Design.”

Do you have any tricks up your sleeve? (special way to analyze circuits, special process you use to make something, etc.)

Avoid pigtail grounds and cable terminations like the plague. An amazing number of EMI problems can be avoided with this simple rule.

What has been your favorite project?

I don’t work on any one project long enough to establish a favorite. In general, I like the new wrinkles that arise with the advent of new technology. Years ago, the chip houses introduced the Voltage Supervisor, a chip that provided a clean power up reset, much superior to the old standby RC charging circuit. Unfortunately, the chips proved to be very sensitive to glitches and voltage variations that appeared on the voltage supply line, resulting in random unintentional resets. The first time I saw this, it took a couple of days to figure out what was happening. Then for the next six months, I had a steady stream of clients who encountered the same problem. Eventually, the chip houses worked out a solution, and the problems stopped.

Do you have any note-worthy engineering experiences? (blowing up things, getting shocked, etc.)

I have taken a few electrical shocks over the years, but the worst one was when I was working on an electric motor in a lab in college. I took a 220 VAC jolt across my body, from hand to hand – nasty shock. Of course, I didn’t dare tell the instructor, I would have been chewed out. I experienced mild shakes afterward, lasted about three days. Years later, I mentioned the incident to my doctor – he explained that shock causes nerve damage, and it takes a few days to heal. But I became a lot more cautious when dealing with electrical power.

What are you currently working on?

Our new project is to greatly expand our Web presence with a number of new activities. We are starting to offer focus EMI webinar sessions, augmenting our public EMI Design seminars which we have been co-hosting with Tektronix for nearly 20 years. We’ll take a specific topic and explore in greater depth than we can in our regular seminar program. We have started a Blog and are exploring other activities, as well. Link to our website.

What direction do you see your business heading in the next few years?

We expect to see EMI problems increase with the increasing density, increasing speeds and lower energy levels, and the proliferation of electronics.

What challenges do you foresee in our industry?

I think our biggest challenge in the US is staying technologically competitive with the rest of the world.

Visit William's EEWeb Profile

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