ACCELERATION EFFECTS ON ELECTRON TUBES 



1219 



20 



5 8 



t 



VIBRATION FREQUENCY IN CYCLES PER SECOND 



Fig. 9 — Frequency response of a tube that exhibited microphonism in equip- 

 ment. The direction of vibration is perpendicular to the major diameter of grids 

 and tube axis. 



SHOCK AND VIBRATION REQUIREMENTS AND TEST EQUIPMENT 



General requirements 



Certain tests have been written into the MIL-E-IB^ and other speci- 

 fications to control the shock and vibration characteristics of tubes, and 

 to check on their behaviour under given mechanical excitation. Long 

 usage has given these specifications some validity in that they control 

 the quality of the product even though actual field conditions may not 

 necessarily be simulated in the tests. 



At present, one or more of the following three types of tests are called 

 for on tube specifications: 



(a) Shock tests. These are high acceleration tests to insure that tube 

 structures will withstand occasional shocks of given maximum magni- 

 tudes. Since, in general, tubes are not required to function during high 

 peak shocks, no operating voltages are applied to the tubes for this test. 

 The post shock requirements are that the tube characteristics must not 

 have drifted out of their limits. In many cases, the type of shock tester 

 to be used is specified, because it is difficult to define the shock output of 



