                CTD SENSOR CALIBRATION: CRUISE CHALLENGER 6/84             
                                                                           
Date:   August - September 1984                                            
Area:   Porcupine Bank, North East Atlantic Ocean                          
                                                                           
                                                                           
Neil Brown CTD, recording and analysis                                     
Recording and analysis was by digi-data logger and BBC micro,  with  screen
plots  and  hard  copy  printer   of  temperature  and  salinity  profiles.
Preliminary comparison with rosette sampler temperature and salinity values
suggested that the CTD maintained calibration well during the cruise.      
                                                                           
                                                                           
Calibration values                                                         
(a) Pressure:                                                              
P(true) = 0.1003*P(raw) - 11.0                                             
                                                                           
(b) Temperature:                                                           
T(true) = 0.49928 E-3*T(raw) + 3.04 E-2                                    
                                                                           
(c) Conductivity:                                                          
C(true) = 0.001*C(raw)                                                     
                                                                           
(d) Salinity:                                                              
In the first instance                                                      
S(true) = S(raw) + 0.034                                                   
                                                                           
Then  salinities were made to fit the relationship between S and  theta  as
found from the plot of theta vs. S using CTD log and                       
Rosette samples:                                                           
S = 34.697 + 0.098*theta (for 2.1 < theta < 2.4 deg C)                     
                                                                           
For  theta < 2.4 deg C the ratio R can be found for a number of samples  at
theta,                                                                     
                                                                           
where R = S(measured at theta) / (34.697 + 0.098*theta)                    
                                                                           
An  average  value  for  the  ratio was found  for  each  station  and  the
salinities for that station were multiplied by that ratio.                 
