calibrate trace exceeds ±.1°C from 16.7°C. In addition, a once 

 per day check using an A4 XBT test box provides a quick 

 indication of incipient launcher leakage before it becomes 

 severe enough to affect system accuracy." 



The preceding should be standard operating procedure for all users of Sippican's XBT 

 systems. If this is not possible, independent surface measurements should be made 

 simultaneously with each XBT profile. These measurements may be used to check whether 

 or not an XBT system is properly functioning. 



• When a system malfunction is recognized while making measurements keep 

 intact the configuration of the system. Contact Sippican Corporation upon return to port 

 to investigate the cause of the system malfunction. 



• Enter the identification number of the XBT probe carton on the XBT log. 



• When it is recognized that a system has malfunctioned while making measure- 

 ments, the configuration of that system should be kept intact. The Sippican Corp should 

 be contacted promptly after the vessel returns to port, so that the cause of the system 

 malfunction can be investigated. 



• Modify the XBT system to include a depth sensor that would measure a single 

 depth independent of the drop time and provide an indication of this depth on the analog 

 record. This measurement could be used to correct for depth bias. 



• Develop a method or technique for identifying visually acceptable but gradient- 

 biasing XBT profiles before they are used in any application and before they are archived. 



• Implement a precision digitizer and/or a more accurate analog display in the 

 recording system of the XBT system. The accuracy of a good profile (ie, one free from 

 problems) warrants the use of an improved recorder. 



• Investigate possible causes of XBT system malfunctions. Once the cause, or 

 causes, are identified, modify the XBT system to eliminate the causes. 



• Conduct similar studies based on measurements made by means of several XBT 

 systems and following the Sippican operating procedure. These new data sets may be used 

 to determine whether the new procedure corrects the anomalies revealed in the present 

 studies. 



SIPPICAN RESPONSE TO THE 

 ANDERSON REPORT 



In response to the report, EXPENDABLE BATHYTHERMOGRAPH (XBT) 

 ACCURACY STUDIES, by E. R. Anderson, outlining various temperature-depth inaccu- 

 racies found with Sippican's XBT system, a brief summary of the major XBT system error 

 sources is outlined below. 



( 1 ) Recorder 



Zero (Adjustment) 

 Full Scale (Adjustment) 

 Response Time 

 Chart Paper 



134 



