1210 THK BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



10 per cent of maximum in the direction perpendicular to the sensitive 

 axis. Some improvements in directivity were obtained by utilizing the 

 elements in shear. Fig. 4(b) illustrates a tandem shear type acceler- 

 ometer. The construction of this unit is somewhat more complicated. The 

 elements first have to be poled in the proper direction. The conducting 

 layers used for poling in this direction then have to be removed and new 

 conductive coatings have to be applied on the areas facing the base and 

 mass M. The unit shown is sensitive to accelerations in the radial direction. 

 The improved directivity of the shear elements over compression ele- 

 ments is shown in Fig. 5. Although shear elements are superior for de- 

 tecting acceleration components along desired directions, it is difficult 

 to make their internal capacity sufficiently high without increasing the 

 over-all weight of the accelerometer for a given sensitivity. The use of 

 cantilevers for these applications also suggested itself, for relatively high 

 tensile and compressive stresses can be produced in such structures. 

 Cantilever type elements have been constructed as shown schematically 

 in Fig. 6(a). Here thin laminations of active material are cemented on op- 

 posite sides of a small metal cantilever. Under the action of external 

 forces bending of the inner member subjects the outer laminations to 



MINIATURE 

 TUBE-TYPE 

 METAL BULB 



MINIATURE 



TUBE -TYPE 



BASE 



MINIATURE 

 TUBE-TYPE 

 METAL BULB 



>MASS 



(a) 



(b) 



Fig. 4 — (a) Radial miniature tube compression type accelerometer and (b) 

 radial miniature tube shear type accelerometer. 



