The spacing of the four electrodes is up to you 

 Measuring parameters: SP, NR, LR and IP
 Measuring range: 0 to 10KΩm
 Measurement sensitivity: 0.04Ωm
 Scale accuracy error: <5%
 Pressurization: less than 15Mpa

IP: its specifications are up to a ground meter.

Applications: thickness of rock, water resistivity, clay content, permeability, resistivity of erosion belt, lithology and oil stratum thickness.