10.5. Further Studies of the Errors of the Bathythermograph 



10.5.1. Bathythermograph Sets 



19. At present, average depth correction factors are used for an entire series of 

 Bathythermograms. It is felt that a study of anchor stations representing a 

 cross-sectional range from accurate data to poor data should be made in order 

 to compare the advantages of applying depth correction factors to each card in- 

 dividually versus the present practice of applying an overall average correction. 

 It is hoped that a formula can be evolved which will show when each practice 

 would be most advantageous. 



20. The bucket temperatures used to correct Bathythermograms are often subject 

 to greater error than the Bathythermograms themselves. It is desired to study 

 these variations between bucket and surface values of Bathythermograms 

 through statistical analyses. It is hoped in this manner that factors can be 

 found which will indicate whether to use correction factors or not. Other 

 methods of investigating temperature correction factors would be curve fitting 

 through superimposition and least square fit. 



10.5.2. Variation in Bathythermograph Sets 



21. A study of change or variation in set with each lowering should be further in- 

 vestigated, being easily accomplished through analysis of data from the anchor 

 stations employed to accomplish Recommendations 19 and 20. An evaluation of 

 the extent and amount of this variation should be forthcoming from such in- 

 vestigations. 



22. Variation from fatigue and extended use of the Bathythermograph is best 

 evaluated by the direct measure of the change which occurs in its calibration. 

 This can be accomplished in the calibration procedures by measuring the cali- 

 bration before the Bathythermograph is repaired. This can be compared to the 

 last calibration. 



23. Abnormal handling is indicated by a quite sudden change in the set. Sudden 

 changes in set affect the averaging techniques employed in set corrections and 

 should be studies with respect to their lack of recognition in computing average 

 corrections. This should be studied in the anchor stations employed for Recom- 

 mendations 19, 20, 21 and 22. 



24. There are studies which show the depth set varies with depth. Further inves- 

 tigation is in order to determine the change as a function of depth. This is best 

 accomplished by further experimental procedures involving comparisons to 

 independent measuring instruments. Comparison of calibration slides periodi- 

 cally can also show the presence of a depth error. 



25. Since pressure effects the bourdon tube, there may be a variation in the tem- 

 perature set which is a function of depth. The study is best accomplished as 

 outlined in Recommendation 24. 



10.5.3. Calibration Errors 



26. Calibration sets can occur unless duplicate tests are run, especially when new 

 bellows are installed. Calibration sets are best evaluated experimentally 

 through the calibration procedure. 



27. A study is in order to determine the extent of variation present due to the as- 

 sumption of linearity over the temperature scale and depth scale. At present, 



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