This chapter outlines the key tasks associated with setting up and using a data acquisition system. It is essentially a checklist with pointers to the sections of the book that cover the topics in more detail.

DEFINE THE VARIABLES TO BE MEASURED

The first task is to decide what specific physiological effects are to be recorded. For example, suppose the effects of a drug on cardiovascular function are being investigated. There is quite a range of variables that can be used as indicators of cardiovascular function: heart rate, blood pressure, cardiac output, systemic vascular resistance, rate of change of pressure (dp/dt), end diastolic volume, ejection fraction, myocardial fibre shortening, etc. Some of these are relatively easy to measure and some are quite involved. Often the starting point is to replicate a published method and this considerably shortens the development process.

CONVERT THE PHYSIOLOGICAL EFFECT TO A VOLTAGE

All data acquisition systems fundamentally only measure one thing: voltage. A transducer is needed (Chapter 4) to convert the variable(s) of interest (e.g. vascular pressure) into a representative voltage. Each transducer will also need an amplifier, and this is usually specific for the particular type of transducer. Even if biopotentials (which are already voltages) are being measured, one cannot just hook up an electrode to the input of a data acquisition system – it is very unlikely to work well. An amplifier specific for the type of biopotential (intracellular potential, ECG, EEG, EMG, etc.) is needed in order to obtain usable results. In addition, if recordings are being made from human subjects, an isolation amplifier is essential for safety.