Determining magnitude of compressive loading

An apparatus for determining a magnitude of a compressive load, the apparatus comprising:

• a cap affixed to and movable with an upper portion of a piston in a movement direction along which the magnitude of the compressive load is to be determined;
• a spring disposed in contact with the cap;
• a pin disposed to extend through the upper portion of the piston and urged by the spring toward a lower portion of the piston, the pin being thereby movable with the lower portion of the piston in the movement direction;
• and
• a sensor to measure a distance between the cap and the pin in the movement direction, the measured distance being related to a deformation of a compliant film disposed between the upper and lower portions as the compressive load is applied.