II. GEOPHYSICAL DATA COLLECTION SYSTEM 

 Gilbert Jaffe 



A. INTRODUCTION 



The requirement for a unified system for collecting geophysical data 

 at sea is such that the resultant instrumentation must be capable of 

 producing a nearly continuous analog record of each variable measured. 

 The system must provide a relatively easy method of annotating the data 

 collected and must lend itself either directly or indirectly to automatic 

 data processing methods. In addition, in order to be of maximum benefit 

 to other interested activities the system must provide an output from 

 which data can be extracted in a form suitable for analysis by relatively 

 simple means. 



B. THE SYSTEM 



1. Collection and Recording 



Since the advantages of audio frequency modulation have been dis- 

 cussed in a previous committee report (Appendix A), they will not be 

 covered further in this report other than to confirm the versatility and 

 desirability of employing audio frequency as the telemetered signal. The 

 basic block diagram for a prototype system for shipboard geophys- 

 ical data collection is contained in Figure II- 1. It is assumed that most 

 transducers will lend themselves to audio frequency conversion. The 

 transducers then would be the plug-in type and selected for a particular 

 measurement. The connector would be a type which is completely 

 waterproof and yet allows quick disconnection. The signal would be 

 transmitted along an electrical cable to either a slip-ring or stationary 

 drum-type winch. From the winch, the signal would be recorded on 

 magnetic tape and simultaneously, but sequentially, annotated. An 

 electronic counter would provide for monitoring the record, and the 

 printer would make a permanent record of the monitored signal. 

 Auxilliary monitoring equipment could be provided as required. 



2. Auxilliary Data Annotation 



In order to provide a relatively easy means of annotating the data 

 collected, an electronic gate would be used to impress on the magnetic 

 tape a fixed number of cycles, from a crystal oscillator, which would 

 be proportional to digits through 9. In this way unlimited auxilliary 

 information such as cruise number, position, time, etc. could be 

 annotated in a fashion which is compatible with the basic system. 



II- 1 



