The QL40CAL sub records a single continuous borehole diameter log by means of three mechanically coupled arms in contact with the borehole wall. The 3 arm caliper measurement is a useful first log to determine the borehole condition before running other more costly probes or those containing radioactive sources.
Opening and closing of the caliper arms is surface controlled from the MATRIX LoggerSuite application, allowing the probe to be run into the borehole with the arms closed. Once positioned at the bottom of the borehole, the caliper arms are opened, and the spring-loaded arms respond to borehole diameter variations as the probe is moved up the borehole.
Other QL probes commonly stacked with the QL40CAL include the QL40GR (Natural Gamma), QL40RES (Multi-point Resistivity), QL40IP (Induced Polarisation), and the QL40FTC (Temperature & Fluid Resistivity)