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Seven years have passed since the publication of the previous edition of this book.
During that time, sensor technologies have made a remarkable leap forward. The
sensitivity of the sensors became higher, the dimensions became smaller, the selectivity
became better, and the prices became lower. What have not changed are the
fundamental principles of the sensor design. They are still governed by the laws of
Nature. Arguably one of the greatest geniuses who ever lived, Leonardo Da Vinci,
had his own peculiar way of praying. He was saying, “Oh Lord, thanks for Thou do
not violate your own laws.” It is comforting indeed that the laws of Nature do not
change as time goes by; it is just our appreciation of them that is being refined. Thus,
this new edition examines the same good old laws of Nature that are employed in
the designs of various sensors. This has not changed much since the previous edition.
Yet, the sections that describe the practical designs are revised substantially. Recent
ideas and developments have been added, and less important and nonessential designs
were dropped. Probably the most dramatic recent progress in the sensor technologies
relates to wide use of MEMS and MEOMS (micro-electro-mechanical systems and
micro-electro-opto-mechanical systems). These are examined in this new edition with
greater detail.
This book is about devices commonly called sensors. The invention of a microprocessor
has brought highly sophisticated instruments into our everyday lives.
Numerous computerized appliances, of which microprocessors are integral parts,
wash clothes and prepare coffee, play music, guard homes, and control room temperature.
Microprocessors are digital devices that manipulate binary codes generally
represented by electric signals. Yet, we live in an analog world where these devices
function among objects that are mostly not digital. Moreover, this world is generally
not electrical (apart from the atomic level). Digital systems, however complex and
intelligent they might be, must receive information from the outside world. Sensors
are interface devices between various physical values and electronic circuits who
“understand” only a language of moving electrical charges. In other words, sensors
are the eyes, ears, and noses of silicon chips. Sensors have become part of everyone’s
life. In the United States alone, they comprise a $12 billion industry. |
