What is the measured value used to calculate resistivity using the Wenner 4-pin method?

The measured value used to calculate resistivity using the Wenner 4-pin method is resistance. This method involves placing four equally spaced pins into the ground to measure the electrical resistivity of a material.

In this setup, a known current is passed through the outer two pins, and the voltage drop across the inner two pins is measured. The resistance is then calculated using Ohm's Law, which relates the voltage (V) and the current (I) through the relation R = V/I. Once the resistance is determined, it can be used in the formula for resistivity, taking into account the geometry of the electrode arrangement.

The reliance on accurately measuring the resistance is crucial to ensure that the derived resistivity value reflects the true characteristics of the subsurface materials being investigated. The correct application of the Wenner method allows for an effective assessment of material properties, making resistance the key measurement in this context.