plots interval velocities and integrated travel times versus depth. At the top 

 right is the auxiliary panel containing the depth counter and the intercommuni- 

 cation system with the cable truck. In the middle right is the CVL measuring 

 panel with the precision electronic measuring equipment which includes a 

 monitor oscilliscope. The meter on the left indicates interval times in micro- 

 seconds. At the bottom right is the power supply panel. Power is furnished 

 by a 1.5-kilowatt gasoline-driven generator. On the left, at the rear of the truck, 

 is the 12-trace seismic equipment which is used to record well geophone travel 

 times whenever calibration of the integrated travel-time curve is required. 



CV 



Figure 21-3. CVL truck — interior view. 



THEORY A pictorial diagram of the continuous velocity 



logger is shown in Figure 21-4. The basic 

 principle of the system is that during recording a voltage is produced which 

 is proportional to the time elapsed between transmitting and receiving the 

 signal. This voltage is impressed on a galvanometer GAL-1 whose pointer traces 



411 



