chapter  1
38 Pages

Measurement Systems

In this introductory chapter we will examine the architecture of typical measurement systems and discuss how noise, calibration errors, sensor dynamic response and nonlinearity can affect the accuracy, precision and resolution of measurements. We will also discuss the modern, physical and electrical standards used by the U.S. NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards) and discuss how these standards are used to create secondary standards used for practical calibration of measurement systems. Measurement systems are traditionally used to measure physical and electrical quan-

tities, such as mass, temperature, pressure, capacitance and voltage. However, they can also be designed to locate things or events, such as the epicenter of an earthquake, employees in a building, partial discharges in a high voltage power cable, or a land mine. Often, a measurement system is called upon to discriminate and count objects, such as red blood cells, or fish of a certain size swimming past a checkpoint. A measurement system is often made a part of the control system. The old saying ‘if you can’t measure it, you can’t control it’ is certainly a valid axiom for both the control engineer as well as the instrumentation engineer. The reader should realize that the fields of instrumentation and measurements are

rapidly changing and new standards, sensors and measurement systems are continually being devised and described in journal literature. The IEEE Transactions on Instrumentation and Measurement, the Review of Scientific Instruments, the IEEE Transactions on Biomedical Engineering and the Journal of Scientific Instruments are four of the important periodicals dealing with the design of new measurement systems, instruments and standards.