Float technology progress - Riser - Argo

Recent Technical Developments with Argo Floats
Stephen Riser
University of Washington
riser@ocean.washington.edu
• Apex air pump solenoid problems
• First tests of ARGOS-3
• Pressure sensor updates
• SBE conductivity drift

Air pump (back)
Air pump (front)
The Apex air pump is used to
inflate the air bladder at low
pressures (< 100 dbar) so that the
float rides on the sea surface with
the antenna well out of the water.

UW- added PCB
solenoid
The air pump is controlled by a solenoid (switch), shown above. For
reasons unknown, a number of these solenoids (cost: < $100) have failed
in laboratory tests at UW in recent months. A failure in the field would
mean the air bladder would not inflate, resulting in possible loss of the
ability to communicate with a satellite. This is especially problematic for
Iridium floats.

ACTIONS
(1) The cause was found (by D. Swift) to be an inability of the solenoid to latch
closed over the duration of an applied transient current. If the duration of the
transient current was increased, the solenoid would always latch properly. There
are no known changes in the controller electronics or the solenoid itself that
would lead to this problem.
(2) The problem can be corrected by adding a small, inexpensive (< $50) printed
circuit board near the solenoid that regulates the current to the solenoid and
insures that it always opens and closes on command. The board was designed
by D. Swift, and 100 units were built commercially in Seattle. This fix has been
added to all UW and PMEL floats since February 2011.
(3) Individual floats can be tested for this problem by connecting a laptop prior
to deployment and inflating the bladder.
(4) Teledyne/Webb has been notified of this problem and the suggested remedy.
As of March 1 2011 they have NOT instituted this remedy, and they continue to
build and ship floats with this potential problem. It is not clear whether or not
they intend to add the auxiliary PCB in their production process.

FIRST TESTS OF ARGOS-3 PMT:
• UW has developed a prototype float that uses a Kenwood PMT to
communicate with ARGOS-3 satellites. Reasons to do this: (1) ARGOS-3 will
someday provide bidirectional communications, a possible alternative to
Iridium; (2) the Seimac PTT used in Apex floats is no longer being
manufactured, so alternative communication methods for Apex ARGOS floats
need to be explored.
• First tests of the Kenwood PMT have shown that energy use is larger than
with present ARGOS-2 PTTs. The PMT float has been running on a simulator
at UW for several months. The PMT consumes more than twice the energy per
transmission of the present ARGOS-2 Seimac PTT or Telonics PTT units.

SeaBird CTD ISSUES:
• SBE claims the microleak problem is now understood and fixed at the
Druck factory. The glass/metal seals that caused the problem have been reengineered.
These new sensors will be installed in SBE float CTDs
beginning in July 2011. Until then, SBE is screening all Druck pressure
sensors that are installed in float CTD units (possibly resulting in continued
reduced production of CTD units).
• SBE continues its warranty return program for CTDs with documented
microleak or snowflake problems. A number of Argo groups have already
received compensation. See the SBE website for details.
• Kistler pressure sensors: some groups have tried these in tests (SIO, UW,
PMEL, ??) with good results so far in a limited number of floats for a limited
time. SBE claims laboratory tests show the Kistler sensor to be as good as
or better than the new Druck sensors.
• Conductivity drift: both Jamstec and PMEL have noted floats with
unacceptable conductivity drift after deployment (>0.01 PSU equivalent).
This problem was traced to erosion of the platinum in the CTD electrodes.
The cause of the problem has been found and new QC procedures have
been installed at SBE. It is believed that this problem occurred in an
isolated group of floats (CTDs built late in 2010) but all groups should
check for this.