The penetrometer is dropped on the test subject or pressed against it and the depth of the resulting hole is measured.
[citation needed] Penetrometers are furthermore used in glaciology to measure the strength and nature of materials underlying a glacier at its bed.
Penetrometers are also used to measure the firmness of apples and other hard fruit.
[2] Penetrometers equipped with a known needle and mass are used to determine the hardness of bitumen and thus its efficacy and material properties when applied to roads as asphalt concrete.
Penetrometers, equipped with a plunger and a needle or cone, penetrate food samples through gravitational force for a selected period of time.