Computerized Data Acquisition and Analysis for the Life Sciences

PREFACE

There has been a small revolution in data acquisition systems for scientific use in recent years. It was not so long ago that hardware and processing power were expensive. and software nonexistent. Every program had to be written from scratch in a low-level language and, if you did not want your program to.take all night to run, it usually included large chunks of assembler code as well. Nowadays there are many data acquisition systems to choose from, with good hardware and vastly improved software running on fast personal computers. Many such systems are purchased with the aim of using them as the primary method ofrecording experimental data in the laboratory. Unfortunately, it is not always as easy to set up the system as the manufacturers would have us believe and getting the machine to do what you want it to do with your apparatus can be a daunting and frustrating task. This book was written to help people collect and analyse experimental data using digital data acquisition systems and is particularly for those whose field of expertise is not engineering or computing. The book explains how data acquisition systems work, how to set them up to obtain the best performance and how to process the data. Terms which may be unfamiliar are explained so that manufacturer's specifications and literature become clearer and the differences between systems can be appreciated. The topics covered in the book are general but the examples are slanted towards the life sciences because this is often the discipline in which people have the greatest trouble setting up data acquisition systems. For people with an engineering background some of the material will be familiar but there are still useful tips and short cuts.

Program listings are not included in the book. There are some practical problems associated with publishing programs: they have to be cross-platform and written in several languages if they are to be useful to everyone. But the main reason is that I would strongly urge you to forget about low-level coding altogether. Buy a high-level language designed for signal processing (LabView, IDL,Matlab, etc.) and spend your programming time assembling algorithms from the building blocks that these programs provide, not reinventing the wheel. Ifyou absolutely have to write code, use a library of prewritten functions (such as those sold by National Instruments) that have been tested and debugged for you.

This book would not have been possible without the help and encouragement of many people. The original idea arose out of the author's work with graduate students at the Universities of Cambridge, Guelph and Waterloo when it became clear that there was a need for a book on data acquisition and analysis written for non-engineers. Dr. Robin Gleed provided the initial encouragement that launched the project. Data for some ofthe examples used in Chapter 6 were provided by Dr. Jeff Thomason, Dr. Janet Douglas, and Dr. Zoe Dong. Dr. Richard Hughson ran the research project that led to the development of TSAS. Dr. Craig Johnson reviewed early versions of the manuscript and provided data for some of the examples. Dr. Robin Smith and Dr. Michael Penn ofCambridge University Press were invaluable at all stages of writing and editing the book. And most of all, I am indebted to my wife, Janet Douglas, for endless patience, encouragement, and manuscript reviews'.

CONTENTS

1.      The Bare Essentials

2.      How a Data Acquisition System Works

3.      Important Concepts

4.      Connecting to the Real World with Transducers

5.      Data Manipulation

6.      Examples

Appendix: Suppliers of Data Acquisition/Analysis Hardware and Software and Electronic Components