78 INSTRUMENTATION IN SCIENTIFIC RESEARCH [Chap. 1 



electric signals, the piezoelectric systems illustrated in Figs. (1-2)61 

 and (1-2)62 are more suitable. 



bimorphs, benders. The elements shown in Fig. (1-2)61 (Bi- 

 morphs, trade name of the Brush Electronics Company) consist of 

 two transverse expanding plates cemented together in such a manner 

 that one plate contracts and the other expands. If a voltage is 

 applied to such an element and if the element is permitted to move 



(c) 



Fig. (1-2)62. Piezoelectric crystals combined to form "bimorph 

 twisters." 



freely, it will bend as shown (greatly exaggerated) in part a if it is 

 made from a crystal, or in the form of part b if made from a piezo- 

 electric ceramic (bimorph bender). 



The bimorph bender can be used for input transducers; a bending 

 of the element causes the development of a potential between the 

 electrodes. Examples of such systems are shown in part c (end- 

 supported, center-driven mounting) and part d (cantilever mount- 

 ing) . Systems of this type are frequently used in phonograph pickup 

 cartridges. 



twisters. In Fig. (l-2)62a two face-shear plates are cemented 

 together so that their expanding diagonals are perpendicular. If a 

 voltage is applied to both plates and the system is permitted to move 

 freely, it will assume a shape as shown, greatly exaggerated, in the 

 figure (bimorph twister). This motion comes about because the 

 diagonal AC contracts while the diagonal A'C expands; similarly 

 BD expands and B' D' contracts. 



Mechanical twisting of these elements will cause a voltage between 

 the electrode terminals. An application for input transducers is 

 shown in Fig. (1-2)626. The twister is held fixed at the three corners 



