Springer Advanced Texts in Life Sciences David E. Reichle, Editor J. Leo Fritschen LloydW. Gay Environmental Instrumentation With 66 Figures Springer-Verlag New York Heidelberg Berlin Leo J. Fritschen Lloyd W.Gay College of Forest Resources School of Renewable Natural Resources University of Washington University of Arizona Seattle, Washington 98195 Tucson, Arizona 85721 USA USA Series Editor: David E. Reichle Environmental Sciences Division Oak Ridge National Laboratory Oak Ridge, Tennessee 37830 USA Library of Congress Cataloging in Publication Data Fritschen, Leo. Environmental instrumentation. (Springer advanced texts in life sciences) Bibliography: p. Includes index. I. Environmental monitoring-Instruments. 2. Physi cal instruments. I. Gay, Lloyd Wesley, 1933- II. Title. TDl70.2.F73 550' .28 79-10437 The use of general descriptive names, trade names, trade marks, etc. in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. All rights reserved. No part of this book may be translated or reproduced in any form without written permission from Springer-Verlag. © 1979 Springer-Verlag New York Inc. Softcover reprint of the hardcover lst edition 1979 9 8 7 6 5 432 1 ISBN-13:978-1-4612-6207-7 e-ISBN-13:978-1-4612-6205-3 DOl: 10.1007/978-1-4612-6205-3 Preface The rapid increase in environmental measurements during the past few decades is associated with (1) increasing awareness of the complex relations linking biological responses to atmospheric variables, (2) development of improved data acquisition and handling equipment, (3) the application of modeling to environmental problems, and (4) the implementation of large, cooperative studies of international scope. The consequences of man's possible alteration of the environment have increased our interest in the complex nature of biological responses to meteorological variables. This has generated activity in both measurements and in the application of modeling techniques. The virtual explosion of modeling activity is also associated with the development oflarge computers. The testing of these models has demonstrated the need for more, different, and better environmental data. In addition, technological developments, such as integrated circuits, have reduced the cost, power consumption, and complexity of data acquisition systems, thus promoting more environmental measurements. The emergence of scientific cooperation on a global scale has increased measurement activities markedly. The International Geophysical Year (1958) has been followed by the International Hydrologic Decade, the Inter national Biological Program, the Global Atmospheric Research Program, and a host of environmental studies of a regional nature that have all emphasized field data collection. With few exceptions, space-age technology has led to improved methods for data recording and handling, rather than changes in instruments used to sense the environment. Thus, while recording methods have progressed from mechanically driven pens to data systems coupled with on-line com puters, the same basic sensors have remained in use. vi Preface These developments have made it easier to collect large quantities of data, but all too frequently sensors are not properly exposed, electrically isolated, or even compatible with the recording instruments. Vast quantities ofrecorded data have often turned out to be invalid. Courses on environmental instrumentation are not common on uni versity campuses, despite the need for training on this topic. Earlier books on the subject, such as Meteorological Instruments by Middleton and Spil haus, are out of date and out of print. This book is designed to be used as a text for advanced students and a guide or manual for researchers in the field. Our purpose is to present the basic theory of environmental variables and transducers, report our experiences on methodology and use, and provide certain essential tables. The user is expected to have a basic physics and mathematics background and to be knowledgeable in the area of his speciality. We will concentrate on the principles that govern the use of sensors and the operation of recorder systems as these are less rapidly affected by technological process. The applications will use currently available equip ment. September, 1979 Leo J. Fritschen Lloyd W. Gay Contents Chapter 1 Measurement Fundamentals 1.1 Introduction and Scope 1 1.2 Measurement Errors 2 1.3 Estimating Error 3 1.4 Measurement Systems 12 1.5 Significant Digits 12 Bibliography 15 Literature Cited 15 Chapter 2 Review of Physical Fundamentals 16 2.1 Thermal and Latent Energy 17 2.2 Basic dc Circuits 25 2.3 Basic Measuring Instruments 29 Bibliography 35 Chapter 3 Temperature 36 3.1 Temperature Scales 36 3.2 Time Constant 38 3.3 Measuring Devices 42 3.4 Air Temperature 73 3.5 Soil Temperature Measurements 82 Bibliography 84 Literature Cited 84 viii Contents Chapter 4 Soil Heat Flux 86 4.1 Soil Heat Flux Transducer 86 4.2 Soil Heat Flux Measurements 88 4.3 Sampling Requirements 88 4.4 Calibration of Heat Flux Transducers 89 Bibliography 91 Literature Cited 91 Chapter 5 Radiation 93 5.1 Radiation in Various Wave Bands 93 5.2 Methods of Radiation Measurement 96 5.3 Radiation Instruments 98 5.4 Site Requirements III 5.5 Calibration 112 5.6 Photometry 114 Bibliography 117 Literature Cited 117 Chapter 6 Humidity and Moisture 119 6.1 Fundamental Concepts and Definitions 119 6.2 Methods of Measurement 130 6.3 Calibration of Humidity Sensors 160 Literature Cited 162 Chapter 7 Wind Speed and Direction 164 7.1 Wind Speed 164 7.2 Wind Direction 178 Literature Cited 184 Chapter 8 Pressure 186 8.1 Introduction 186 8.2 Mercury Barometer 190 8.3 Aneroid Barometer 192 Literature Cited 194 Contents ix Chapter 9 Data Acqu isition Concepts 195 9.1 Signal Characteristics 196 9.2 Digital Data Acquisition Systems 199 9.3 Some Sampling Considerations 201 9.4 Signals and Noise 203 Bibliography 209 Subject Index 211 List of Symbols Symbol Unit Definition a constant, low temperature, absorption coefficient, ratio A constant, aspect ratio, intercept, variable metal, analog domain A °C-1 thermodynamic psychrometric constant A m2 area Ac m2 convective area Ar m2 radiational area Ao Ferrel psychrometric constant b constant, midrange temperature B amplitude, constant, slope, variable, metal B W(m2 sr)-I steradiancy C J(kg K)-I specific heat C speed of light, constant C m S-I speed of sound in still air C high temperature c J(kg K)-I specific heat at constant pressure p C constant, slope, variable, metal, correction factor C J(m3 K)-1 heat capacity d m diameter, delay distance D Wm-2 diffuse radiation flux density xii List of Symbols D V thermoelectric potential D m distance constant D variable, digital domain e natural logarithm e Pa vapor pressure E V applied voltage, thermal emf E edge correction, combined value, error E Wm-2 irradiance E Einstein (mole of photons) j E Imm-2 illumance j velocity error E" f Hz sound wave frequency F kg(ms2)-1 force F variable F 1m luminous flux F OF Fahrenheit degree g m S-2 acceleration due to gravity g Vm2 W-1 calibration coefficient Gr Grashof number G Wm-2 heat flow through a medium G variable h m height h W(m2 K)-l convective heat transfer coefficient h Plank's constant h damping ratio H Wm-2 sensible heat flux density H constant i A current, electrical I kg2 m-1 moment of inertia I W sr-1 radiant intensity I Wm-2 direct-beam solar radiation perpendicular to sun's rays ~ 1m sr-1 luminous intensity J mechanical equivalent of thermal energy J constant k Boltzmann's constant, coefficient k wavelength dependent coefficient k m2 S-1 thermal difTusivity