e. Switch "Function Selector" of HP 523 counter to "Time Interval ." 



f . Switch "Time Unit" switch to external . This will convert readings 

 from time to distance. Check to see that the external oscillator (Krohn-Hite Model 

 420-A) is set to 2.5 kc, and its output is connected to the counter through "std freq 

 ctd" input in front or back. If there is a time base toggle switch in the back of this 

 counter it must be set to "EXT." 



g. Switch EDO from "Standby" to "Fathoms." Adjust EDO gain and 

 "Start" and "Stop" trigger levels of counter for reliable triggering. 



h. The rep-rate of the EDO on the fathom scale is equivalent to 

 about 523.2 meters. This number will indicate that the "Start Circuit" is adjusted 

 properly. Adjust "Stop" trigger level until the counter reads approximately the same 

 as the depth counter, when the latter is reset manually. 



IV. CALIBRATION AND CHECKOUT PROCEDURES 



A . Temperature 



Temperature probe calibrations are accomplished by use of a decade box, 

 the resistances varying with the individual probes. The following are the tempera- 

 ture calibration procedures: 



1. Energize equipment . 



2. Connect decade resistance to "Cal" jacks. 



3. Connect Dymec Voltage to Frequency converter to output jacks. 



4. Connect temperature probe to input jacks. 



5. On to 10 volt range, check B+ on counter, (should be 5,5 to 6.0 

 volts) switch on B+ position. 



6. Switch to "Cal" position and set decade for 0°C setting. With zero 

 control on bridge, set for 0000 on counter, converter on 0-to 1-volt range. 



7. Set decade for 30°C setting with sensitivity control on bridge, set 

 counter for 3000. 



8. Set decade for 15°C setting, and check for 1500 on counter. 



9. Switch to temperature position on bridge, and read temperature on 

 counter . 



15 



