time, while the other side was ossumed to remain at atmospheric 

 pressure. The calibration technique, then, was not able to simulate 

 differential pressure loading while both sides were subjected to a 

 pressure head as would be felt on the seafloor. (Both chambers 

 leaked somewhat, so that it was not feasible to pressure each side to 

 a particular head and then begin the differential loading.) 



The calibration technique described herein entailed static 

 loading whereas the operating instrument would be subjected to 

 dynamic loading. This was not of great concern, however, since the 

 in- situ loading is of relatively low frequency. The calibration 

 technique could be improved by using an oscillating pump to pressure 

 the chambers sinusoidally over time. 



2. Testing for Air Bubbles 



Theoretically the calibration system can be used to check for 

 the presence of air bubbles in the transducer sensor lines. Firstly, 

 air in a line will compress under a load and bias the pressure value 

 that the transducer will report. Secondly, it is hypothesized that 

 the loading and unloading of the air bubble will delay the response 

 time of the system. If this is true, then it may be possible to 

 detect an air bubble by loading each side of a differential 

 transducer equally, then unloading them simultaneously. The side 

 with the greater air volume will lag in response. (It is assumed 

 that the inherent lag in arm-side response due to the longer arm 



