the value of the interval time U directly on the log at the indicated depth. The 

 over-all travel time T for the interval logged is traced simultaneously on the log 

 by the pointer of galvanometer GAL-2, which is activated by a ball and disc type 

 integrator. This device continuously integrates the interval time ti with respect 

 to the distance Z travelled by the logger. The instrumentation is described in de- 

 tail by Summers and Broding (1952). 



Basically, a log of the formations penetrated is developed by obtaining veloci- 

 ties over short intervals. This is accomplished by the measurement of the travel 

 time (ti) of the sound wave through the formation sidewalls over the distance 

 separating the transmitter and receiver. 



!Eta 



PoUntiomeUr 



Integrator 



Oscillc«op« 

 Display 



100 Volt* per 

 Millisecond 



Figure 21-4. Pictorial diagram of continuous velocity logger. 



412 



