Fundamentals of Instrumentation and Measurement

Dominique Placko

• Publisher: Wiley-ISTE
• Year: 2013
• Print ISBN: 9781905209392
• eBook ISBN: 9781118613641
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria elettronica e telecomunicazioni

This title presents the general principles of instrumentation processes. It explains the theoretical analysis of physical phenomena used by standard sensors and transducers to transform a physical value into an electrical signal. The pre-processing of these signals through electronic circuits – amplification, signal filtering and analog-to-digital conversion – is then detailed, in order to provide useful basic information.

Attention is then given to general complex systems. Topics covered include instrumentation and measurement chains, sensor modeling, digital signal processing and diagnostic methods and the concept of smart sensors, as well as microsystem design and applications. Numerous industrial examples punctuate the discussion, setting the subjects covered in the book in their practical context.

Chapter 1¹

Measurement Instrumentation

The purpose of this chapter is to review the essential definitions and characteristics of measurement. We discuss measurement systems and the roles and classifications of instruments in a comprehensive and descriptive way, with more detailed discussions to follow later in the book. Throughout this book, we use the example of the car to illustrate the importance and relevance of instrumentation.

1.1. General introduction and definitions

Whether exploring Mars, measuring the brain’s electrical signals for diagnostic purposes or setting up robots on an assembly line, measurement is everywhere. In all human activities, the idea of measurement establishes a relationship between a natural or artificial phenomenon and a group of symbols, usually numbers, in order to create the most reliable representation possible. This representation is classified according to an “orderly” scale of values.

Measurement is the basis of scientific and industrial research. It allows us to understand the phenomena we observe in our environment by means of experimental deduction and verification [ROM 89]; [HEW 90]; [PRI 95] and helps us keep records of the results of these observations. Established models and scientific laws are available for all of us, doing away with the need to begin each experiment with the most basic observations. This is why perpetuating knowledge is so important in the long term.

In the short term, this perpetuation guarantees the quality of products and commercial trade by connecting them to legal standards. Achieved through instrumentation, measurement is thus the basis of progress in many forms of knowledge, as well as being essential to production and trade. In the world of science, it allows us to make discoveries and confirm them. In terms of technology, instrumentation helps us control, improve and develop production, and in the world of economics, it makes commercial exchange possible, helping us assign value to objects and transactions.

Measurement therefore brings together knowledge and technological progress. Universal and essential to many disciplines [PRI 95], it is, in fact, fundamental to most human activity. This universality explains the recent interest among some researchers in improving the forms of knowledge related to instrumentation [FIN 82].

1.2. The historical aspects of measurement

We can look at the evolution of measurement by focusing on invented instruments or by using the instruments themselves. In this section, we will list the steps of progress in measurement, which we define somewhat arbitrarily, according to human needs as these emerged throughout history:

- the need to master the environment (dimensional and geographical aspects);

- the need to master means of production (mechanical and thermal aspects);

- the need to create an economy (money and trade);

- the need to master and control energy (electrical, thermal, mechanical, and hydraulic aspects);

- the need to master information (electronic and optoelectronic aspects).

In addition to these is the mastery of knowledge which has existed throughout history and is intimately connected:

- measurement of time;

- measurement of physical phenomena;

- measurement of chemical and biological phenomena.

Let us look at several examples from history regarding the measurement of time. The priest-astronomers of ancient Egypt were close observers of natural phenomena, especially the sky. Simply by observing the natural effects of solstices (including the floodings and harvests around the Nile coinciding with the rising of the star Sirius) they were able to invent a 365-day calendar. Their observations also enabled them to develop a system of measurement based on a daily recording, made between summer solstices, of the shadows cast by a stick placed vertically in the ground. By about the year 2,500 BC, Egypt had three calendars: a civil calendar of 365 days, an equivalent lunar calendar, as well as one based on the earlier lunar year based on the heliacal rising of Sirius. Such progress was made by the Egyptian priest-astronomers that around the year 1,450 BC, during the reign of Thutmose III, they were able to measure days and hours, again only through observation. As can be seen on wall paintings of star clocks in tombs of that era, ancient Egyptians knew that the day consisted of 12 hours, compensating for the 12 dark hours of night. Their sundials - or, more accurately, “shadow clocks” - were very simple ancestors of the gnomons later used by the Greeks. These consisted of a rectilinear piece of wood in five sections, with a horizontal piece at one end. Through careful observations and corrections, the Egyptians of that era came very close to achieving our present level of knowledge of the duration and number of days in a year.

Throughout history, these kinds of advances in measurement have come about for specific motives. Economic motives drove the development of cartography and the growth of trade; militaristic motives spurred the creation of new armaments, with everything from cannon powder to the radiation levels emitted by nuclear weapons needing to be measured; strategic and expansionist motives prompted the need to control maritime routes and colonial territories; religious motives created a need to restrain and monopolize certain kinds of knowledge. Nowadays, these motives have developed with the disappearance of certain needs being replaced by new ones. An instance of this is how the need for sophisticated, three-dimensional maps of Earth that have become possible through the technology used by American space shuttles, has supplanted older colonial expansionist motives that gave birth to scientific bodies such as the Bureau des longitudes in France.

History is full of examples of the development of measurement to such an extent that no progress can be described or reported without a measurement being a result of completed experiences for the validation of theories [RON 82] [JAC 90], whether these are scientific, economic, technical, expansionist or even religious. Usually, the instrument used for such validation already exists but is used in a somewhat different way or is adapted for the new use. Instruments developed for a specific measurement are more rare. Religious motives have often brought about new ways and tools of measurement, especially in antiquity. As discussed above, ancient Egyptians used the sky to develop their calendar of 365 days and to measure days and hours. In our own time, some physicists confronting the mystery of particles and the Big Bang theory have turned to a spiritual explanation of these phenomena [HAW 89].

1.3. Terminology: measurement, instrumentation and metrology

The expression of measurement needs or tests are an everyday occurrence in science and industry [MAS 90]; [COM 92]. All existing tools that help us carry out measurement are part of instrumentation. Rules for using and guaranteeing measurement created metrology. It is important to point out that definitions¹ of these related terms are sometimes confused, as with “measure” and “metrology”.

The word measurement has many meanings. The International Vocabulary of Basic and General Terms in Metrology (VIM), using International Organization for...

Table of contents

• Cover
• Title Page
• Copyright
• Introduction
• Chapter 1: Measurement Instrumentation
• Chapter 2: General Principles of Sensors
• Chapter 3: Physical Principles of Optical, Thermal and Mechanical Sensors
• Chapter 4: Analog Processing Associated with Sensorssss
• Chapter 5: Analog Filters
• Chapter 6: Real-time Data Acquisition and Processing Systems
• Chapter 7: The Contribution of Microtechnologies
• Chapter 8: Instruments and Measurement Chains
• Chapter 9: Elaboration of Models for the Interaction Between the Sensor and its Environment
• Chapter 10: Representation and Analysis of Signals
• Chapter 11: Multi-sensor Systems: Diagnostics and Fusion
• Chapter 12: Intelligent Sensors
• List of Authors
• Index