Argo - negative drifting pressure sensor behaviour


Contents: 1. Can -ve SP become +ve? , 2. Onset time of microleaks

This analysis was updated on 02-Nov-2010, using GDAC state as at 30-Oct-2010


Can the Surface Pressure series be significantly negative but later be positive?

In order to learn what behaviours may exist in surface pressure (SP) in Apex floats which truncate negative SP, we examine floats which do not truncate surface pressure and observe the probability of signficant negative SP prior to consistent positive SP later in float lifetime. Although ourr main concern is with Druck sensors which may experience "microleak" fault, we separately examine each pressure sensor type. Only floats with appropriate Surface Pressure Offset parameter names are used:

    pres_surfaceoffsetnottruncated_dbar
    pres_surfaceoffsetnottrancated_dbar
    pres_surfaceoffsetnottruncatedplus5dbar_dbar

We find that cases of significant negative SP drift followed by recovery to reasonable positive values are extremely rare or never actually occur.


How late in the life of a float can Druck "microleak" problem develop?

Look for point of onset of "microleak" negative pressure drift in the lifetime of an Argo float. Examine only floats where "Druck" is explicity identified in the SENSOR_MAKER or SENSOR_MODEL fields, only non-SOLO floats, and only where one of these three Surface Pressure Offset parameter names is used:

    pres_surfaceoffsetnottruncated_dbar
    pres_surfaceoffsetnottrancated_dbar
    pres_surfaceoffsetnottruncatedplus5dbar_dbar

The Surface Pressure (SP) values are read from tech files and despiked. We examine all float series where the SP goes below -5 dbar.

Of 2309 floats with the right parameter names, 1501 are also identified as Druck, but 630 of these are excluded as SOLO.


 

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