Dynamic Response Calibration of the Nell Brown Conductivity Cell

CTD Aliasing Investigation

“…The independent work of Gregg et al, 13 described in Section 4.0, has provided a means of assessing the validity of the results of this study, at m least insofar as the conductivity sensor power transfer function estimate is concerned. As indicated previously, the results of Gregg fell outside the upper and lower bounds obtained in this investigation for some frequencies.…”

“…In addition, Gregg et al 13 have pointed out that the relative phase of temperature and conductivity must also be known in order to produce a correct salinity.…”

“…it is not possible to infer results from one drop rate to another. However, Gregg, et al, 13 report results for several drop rates near 1.0 m/sec, showing that the power transfer function plotted in k' space does not change dramatically with drop rate. We may conclude that the value of the transfer function will be somewhat changed under operational conditions, but will still allow a good signal-to-noise ratio for the sensed signal.…”

“…13 From the point of view of potential aliasing, the more rapid response is of greater concern, since rapid response in the time domain suggests greater response to high frequency inputs and therefore greater susceptibility to aliasing. Furthermore, any subset will be valid if the process causing the jitter is truly stationary.…”

“…A third problem which Gregg et al 13 have also identified is that of data correction due to variation in the sensor drop rate. The variation in drop rate is primarily due to ship motion, particularly heave and roll.…”