Caliper Logging The caliper probe, a simple mechanical device, whose main functionality is to measure the internal diameter of a borehole or casing string within a borehole. Another purpose of a caliper arm is to push a section of a probe against the side of the borehole (for example density logging), known as sidewalling. Additional data measured from a caliper log includes: 🔹The roughness or rugosity of the borehole wall. Soft rocks can be washed away significantly by the drilling process giv