A PIEZOCERAMIC BENDER AS A FORCE TRANSDUCER FOR SURFACE-TENSION MEASUREMENTS

When connected to the appropriate electronic circuit, an inexpensive ($10) piezoelectric ceramic bender is a sensitive force transducer for accurate surface tension measurements. Although these devices are not suitable as steady-state transducers, they do function as sensitive transducers when used in the detachment made of the Wilhelmy method. Under such conditions, the voltage output of the transducer is linearly related to the applied force with an output of millivolts or more per dyne. Tension measurements with a Wilhelmy plate of a centimeter or less perimeter have a precision of 0.5 dyn/cm over the observed range of surface tension from 23 to 72 dyn/cm. Because of the low cost, dozens of measurements can be done simultaneously using common computer multiplexing interface boards.