MANUFACTURE OF QUARTZ CRYSTAL FILTERS 



521 



Preliminary tuning is accomplished with a fixture, simulating the 

 final holder, which grips the plate at the center by four contact points, 

 one on either side of the division in the plating of each face. These 



ELECTRICAL 



AXIS 



X 



MECHANICAL 



AXIS 



Y 



Fig. 4 — Orientation of a typical quartz plate with respect to its electrical, 

 mechanical and optical axes. 



contacts introduce very little damping, since the mode of vibration 

 normally employed is longitudinal, with maximum amplitude at the 

 ends of the plate and a node at the center. The test set-up normally 

 used consists of two oscillators with a meter arranged to read the 



