Laboratory tests of a motorized snow surface hardness gage

A motor-driven, spherical probe controlled by a handheld calculator and a microprocessor developed to measure the force and probe travel distance needed to break individual snow surface elements was tested for consistency and reliability. Consistency tests were run on automatic pencil leads; reliability tests on ice rods. Both proved satisfactory. Tests on two man-made snow surfaces showed the probe capable of measuring the strength of individual snow surface elements. Brittle failure occurred in such elements at loads varying from 0.200 to 174.631 grams (median 11.560 grams) for 118 samples. Probe travel distance varied from 0.003 to 0.099 mm (median 0.017 mm). The load needed to cause the first break was less than 1 gram for 21 (18%) of the samples.