Abstract

In this lecture instrumentation will be interpreted as the ways and means to transport and modify signals SO as to make them suitable for the input channels of human beings and automatic controllers. A difference may be made between measuring and control systems; the first present the value of the measured quantity in an appropriate way, the second also formulate and execute command signals. Modern control theory and techniqucs have an increasing influence on the arts of instrumentation. An important part of all instrumentation systems is the transducers, which convert the value of the signal to be measured to another physical dimension, more suited for transport or evaluation. Typical are the conver-sions to electric voltages, pneumatic or hydraulic pressures. The main requirements for the design of a transducer are a low energy consumption from the measuring source, fast response and low susceptibility to disturbing signals and noise. At the input there exist besides the value of the signal to be measured xm an associate signal ym, such that xmym has the dimension of energy W (watt). The generalized impedance Z is defined as Z = xm/ym, so that W = xm2/Z. In general W should be small, requiring Z being large, sometimes approaching infinity. On the other hand, examples will be given wherezmust have a certain specified value. A low value of W can be obtained either by using a very sensitive primary sensor and applying sufficient signal amplification afterwards or by using