Resistance Measurement: Finding a Ditch w/ 4 Electrodes

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Discussion Overview

The discussion revolves around the measurement of resistance using a four-electrode method to detect the presence of a ditch, particularly in the context of archaeological research. Participants explore the theoretical and practical aspects of this measurement technique, including the application of Ohm's law and the significance of various parameters involved in the calculations.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant describes the formula for apparent resistivity ρz = k * AU / I and notes that the depth of measurement is approximately 1/3 of the distance between electrodes A and B.
  • Another participant questions the clarity of the problem statement and requests additional context, such as a diagram and the type of source material (geology, physics, or archaeology) from which the problem originates.
  • Details about the ditch are provided, including its estimated depth of around 6 meters and width of 6-8 meters, with assumptions about the material filling the trench.
  • Some participants suggest that the problem may require different approaches depending on whether it is viewed from an elementary algebra or engineering perspective.
  • There are requests for clarification on known values and additional formulas that may be relevant to the calculations.
  • One participant expresses frustration and seeks direct assistance with the homework problem.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and clarity regarding the problem, with some seeking more information while others provide context. There is no consensus on how to approach the problem or what specific values should be used in calculations.

Contextual Notes

Participants note the need for additional information, such as the voltage of the battery and the specific arrangement constant k as a function of the distance between electrodes, which remains unresolved.

nicco35
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Hello,
Could you help me with the homework, please...For the conventional resistance measurement used four electrodes: two current (A, B) into the country "deserts" and the current I between two measuring (M, N) is then measured voltage AU, resistivity, which is the goal of our measurement is determined according to Ohm's law; in its formula is needed to add a so-called. arrangements constant k, which depends on the distance of the individual electrodes. The calculated value is then referred to as "apparent resistivity" ρz, because it describes the whole "block" hemisphere, where penetrated current:

ρz = k * AU / I

Depth of this measurement is approximately 1/3 of the distance between the electrodes A and B. How far AB hypothetically you chose if you think that the resistance measurements would allow to determine the presence of a ditch.
 
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The general subject of this post is "electrical ground probing" ( Described in http://www.reeve.com/Documents/Ground%20Testing%20R1-1.pdf)
However, the statement of the problem is unclear
Can you show a diagram?
What type of book poses this problem? - a geology book? a general physics book? an archaeology book?
 
The depth of the ditch given? Is the width of the ditch given?
 
He's going to archaeological research the castle, which
will be preceded by geophysical measurements. The challenge is also localization
said ditch. According to available information,
it is almost certain that trench was carved into the rock, its depth could be around 6 meters and width of 6-8 meters. We can assume that filling the trench extinct forms loamy - stony material with a share flushes cultural layers.
 
Last edited:
If this is elementary algebra you would say 2 = (1/3) X and solve for X.

If this is an engineering course, you might have to use more equations.
 
Please, help me..
 
No, that is homework from high school
 
Please, its depth is 6 meters and width 6-8 meters. How far AB hypothetically you chose if you think that the resistance measurements would allow to determine the presence of a ditch. Formula is ρz = k * AU / I. What am I substitute. Please, help me...
 
  • #10
You must reveal all the known information and perhaps other formulas.
Which values are known?
Is the voltage of the battery known? AU = voltage? = ?
Do you know a formula that tells the value of k as a function of the distance between the electrodes? k = (constant)(distance between electrodes) ?
 
  • #11
Where in the sketch is the ditch?
 
  • #12
He's going to archaeological research the castle, which
will be preceded by geophysical measurements. The challenge is also localization
said ditch. According to available information,
it is almost certain that trench was carved into the rock, its depth could be around 6 meters and width of 6-8 meters. We can assume that filling the trench extinct forms loamy - stony material with a share flushes cultural layers.For the conventional resistance measurement used four electrodes: two current (A, B) into the country "deserts" and the current I between two measuring (M, N) is then measured voltage AU, resistivity, which is the goal of our measurement is determined according to Ohm's law; in its formula is needed to add a so-called. arrangements constant k, which depends on the distance of the individual electrodes. The calculated value is then referred to as "apparent resistivity" ρz, because it describes the whole "block" hemisphere, where penetrated current:

ρz = k * AU / I

Depth of this measurement is approximately 1/3 of the distance between the electrodes A and B. How far AB hypothetically you chose if you think that the resistance measurements would allow to determine the presence of a ditch.

On the picture http://nicco35.rajce.idnes.cz/nastenka/#9.jpg I find the distance between points A and B. Please, help me
 

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