Introduction

Medical instrumentation uses transducers, signal conditioners, and displays to convert real-time information about living systems to a form that people can interpret. Medical instrumentation is used for research, monitoring, and diagnosis purposes. Ideally, the instrumentation will not alter the quantities being measured. Medical instrumentation should also be designed to assure the safety of the subject and investigator.

Systems

The physical quantity that is measured is called the measurand. Most measurands fall into the following categories: biopotentials, pressures, movements, impedances, temperatures, and concentrations.

Some measurands change so slowly that they require only occasional sampling. Some rapidly changing measurands require continuous monitoring. The frequency content of the measurand, the objective of the measurement, the condition of the subject, and the liability of the investigator all influence data acquisition.

A transducer is a device that converts one form of energy to another. Ideally, a transducer will respond to only one form of energy, and to the exclusion of all other forms of energy.

Often times, measurands can be coupled directly to a transducer because the measurand is directly available. When the measurand is not directly available, another measurand that bears a known relationship to the desired measurand is utilized, or a transducer that interacts with the desired measurand to create an indirect measurand is utilized.

Usually transducer outputs cannot be directly fed to display devices. Signal conditioners often only amplify and filter transducer outputs, but often also compensate for adverse transducer characteristics, or average out noise.

The ideal form...