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:
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:
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.