TIMERS, COUNTERS AND RATE MEASUREMENT 



+300V 



•+A75V 



130k>a001aF 



GCIOB 



From outpufL- . . 

 cathode of n^ 



previous 

 GCIOB or of 

 GC10D 



-100V 

 Figure 41.16 



Figure 41.17. Glow transfer is achieved in the GC 10 D by applying a 

 single pulse only. This is done by making use of both the leading and 

 trailing edges of the transfer pulse, and by the phenomenon called 'auto 

 transfer', which may be explained as follows: 



In Figure 41.18 we have the anode and two electrodes A and B, which 

 may be cathodes or guides. If the glow can by some means be caused to 

 alight on electrode A, the glow current will charge C to a definite potential 

 difference determined by R. If by this process A becomes sufl5ciently 

 positive the glow 'auto-transfers' to the more negative electrode B. C then 

 discharges again through R, but the glow will remain at B. 



HT* 



Anode 



First guides 

 Second guides 

 Third guides 



Output 

 third guide 



Cathode Output 

 cathode 



Figure 41.17 



Direction of 



glow 

 prog ress ion 



C±SR 



Figure 41.18 



Thus a typical GC 10 D drive circuit is shown in Figure 41.19. Let the 

 glow be on the nih. cathode. On the arrival of the leading edge of the 

 transfer pulse the first and second guides are driven sufficiently negative 

 to draw the glow on to the first guide, whereupon it auto-transfers to the 

 second. The back edge of the transfer pulse then comes along, driving 

 the first and second guides positive again. The third guides are now relatively 



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