THE SMOOTH SOUNDING GRAPH. A Manual for Field Work ... - BGR

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29 The process will be repeated: Enlarging L/2 and keeping a/2=5m fixed we get a smooth change from ρa (W) into ρa (S) . Assuming we are <strong>for</strong>ced to shift the potential electrodes again at L/2=60m the ρa (W) -value "jumps" again but now upward into the dotted Wenner-curve <strong>for</strong>ming the starting point of branch (3). At L/2=120m we just pass the curve minimum. Due to the instrument another shifting of the potential electrodes is necessary. In this position we will record crossing branches (3) and (4).The field opera- tor should not be irritated. His record is correct because it is a conse- quence from theory. As this chapter is only dealing with basic laws, prac- tical advices concerning the shifting of potential electrodes will be given later on in chapter 2 but making use of the theoretical knowledge just de- scribed. As there will be no description of instruments in this manual only one re- mark should be made concerning unpolarisable potential electrodes. The main principle is a copperstick put into a solution of copper sulphate con- tacting the earth via porous porcelain. The type used in our institute is shown in Fig.23. There are other types, f.i. having a larger bottom or be- ing porous only in the deeper part. The principle is the same and we must take care that no crust on the porcelain will interrupt the contact to the surrounding earth.
30 Fig.21 Fig.22 Fig23
Page 1 and 2: THE SMOOTH SOUNDING GRAPH A Manual
Page 3 and 4: Preface 2 This manual shall be a pr
Page 5 and 6: 1. Basic rules 4 The first chapter
Page 7 and 8: This current density is marked as j
Page 9 and 10: 8 Fig.2 Fig.3 Fig.4 Fig.5
Page 11 and 12: 10 1.3. The four-electrode arrangem
Page 13 and 14: 12 Fig.6 Fig.7 Fig.8
Page 15 and 16: 14 If we compare equations (10) and
Page 17 and 18: Case 2 (Fig. 10) 16 Now we observe
Page 19 and 20: 1.5. The fundamental principle for
Page 21 and 22: Case 3 (Fig.14) 20 The electrode di
Page 23 and 24: with just the same factor K. 22 Aft
Page 25 and 26: 24 Fig17 layers with different resi
Page 27 and 28: 26 Simulating this zooming by enlar
Page 29: 28 1.6. Shifting of potential elect
Page 33 and 34: 32 2.1. How to carry out a field me
Page 35 and 36: L/2 a/2 1,5 6,28 2 11,8 2,5 18,9 34
Page 37 and 38: 36 Fig.27 Fig.28 Before we start th
Page 39 and 40: 38 fence, ditch) especially, if the
Page 41 and 42: 40 by experience. The measurement i
Page 43 and 44: 42 2.2. Possible errors influencing
Page 45 and 46: 2.2.4. Crossing a ditch (Fig.26/29)
Page 47 and 48: 46 accuracy is not so important the
Page 49 and 50: 2.2.8. Insulation and leakage curre
Page 51 and 52: 50 Fig.31. They are ascending with
Page 53 and 54: 52 If j' is negative, i.e. the dist

THE SMOOTH SOUNDING GRAPH. A Manual for Field Work ... - BGR

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