- 55 - 



If it is decided that the instrument is stable over time, 

 (i.e., there is no further settlement), then changes in the mean of 

 the differential gauge signals could be used to calculate the 

 ambient seawater temperature. This estimate could then be used to 

 develop the temperature-corrected specific gravity of the seawater 

 and back-fill fluid. (This calculation is not included in the 

 present software package.) Temperature estimates could not be made 

 if the back-fill fluid volumes on both sides of the differential 

 pressure transducers were equal. (See Section V.C.6.) 



5. Tide Calculation 



The mean voltage of the absolute transducer record is 

 converted to pressure and is used to calculate the tide level. The 

 total average water column above the sensor, Zs , can be found from 



^s ~ r^^mean ^atm " ^bf^bf " ^bf^ (A. 35) 



where Pmean = mean absolute pressure 



Patm ^ atmospheric pressure 



y = specific weight of seawater 



T^f - specific weight of back-filling fluid 



i (jj = height of sensor above the transducer 



Pbf = back-fill pressure. ^ 



Both the specific fluid weights should be temperature corrected. The 



