A how-to guide to piezoelectric accelerometers
Over the spring break I dropped by Meggitt Sensing Systems to ask Felix Levinzon to sign my copy of his new book, Piezoelectric Accelerometers with Integral Electronics, and I was able to spend some time with him discussing JFETs, MOSFETs, and Russian winters.
Tim McClune, president of Linear Integrated Systems.
Levinzon was a scientist working in the field of low-noise electronics in Russia before he came to the USA in 1993. He joined Endevco/Meggitt in 1996. "And I found this company’s product was very similar to what I did in Russia. This company manufactures sensors, which should be low noise and high temperature and small size, everything like this. So I specialized in these fields."
A native of Russia, Felix received his MS degree from the Radio Engineering University in Taganrog, Russia in 1961 and completed his PhD in Moscow in 1974. He specialized in low-noise electronics.
I made about 50 trips to Russia since 1998 to work with Russian scientists with a previous employer, and I talked with Felix about cold Russian winters and the year-round warmth of Southern California. But he said a difference – aside from snow and sub-zero temperatures, either C or F – between working for a U.S. high tech company and the scientific institute in Moscow was, "the biggest product [in Moscow] was to publish papers."
"When I came here, the company was not so interested in publishing, just designing sensors," Felix told me. "I like to design sensors, but I also like to publish my designs. Of course there were many restrictions to keep the secrets of the company, but I know how to do this and did this."
Next: three most-needed parameters
Levinzon said he’s always enjoyed publishing along with designing and producing new products. "So I’ve published already many papers, mostly in IEEE journals, and after this, maybe last year, I start to think it’s time to publish a book based on these papers," he said. "I found a publisher, and they agreed to publish the book. So I worked for about half of a year and finally they published it in August of last year."
When Levinzon was researching the literature about IEPE sensors, he found a lot of material had been published on the physics and theory of piezoelectric transducers, but no full-length work on the integrated electronics needed to make these devices useful in many applications.
Felix Levinzon, author of Piezoelectric Accelerometers with Integral Electronics.
The design of Integrated Electronics Piezoelectric (IEPE) accelerometers is driven by three basic design constraints, Levinzon said. The first his customers require is temperature range, from cryogenic to more than 200 ̊C. The second is low noise, "as low as possible." And the third parameter is size and weight, "as small as possible."
"These are the three parameters which are needed the most, and I specialize in all three," Levinzon said. "Other parameters are maybe not so critical, voltage supply, current supply," he said. "Sensitivity, of course it’s important. Range is also maybe not so important compared with the first three."
The book is an excellent compendium of practical design expertise necessary to develop IEPE devices, whether using an op amp or a low-noise discrete JFET or MOSFET. It’s richly detailed with curves, schematics, equations and test data in addition to descriptions and explanations.
Next: It’s actually a good book
"It’s actually a good book for designers, to know the designs of our sensors, piezoelectric with internal electronics," Levinzon said. "At the same time I included in the book some measurement results of MOSFETs and JFETs which are used in these sensors. Included also are two parts from [Linear Integrated Systems]. These JFETs have unique parameters, very nice parameters."
Levinzon often uses these small-signal, discrete semiconductors in die form to optimize his accelerometers for small size and performance in extreme temperatures. "JFETs and MOSFETs for analog applications with time have gotten better and better, in regard to noise and other parameters," he said. "But unfortunately there are just a few manufacturers of these devices."
Tim McCune is president of Linear Integrated Systems Inc. (Fremont, Calif.), a developer and manufacturer of small-signal, discrete semiconductors. McClune was a defense and wire service journalist in Washington during the 1980s and 1990s. He enjoys talking with analog enthusiasts, writing about the elegant world of non-digital electronics.
This article first appeared on EE Times’ Planet Analog website.
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