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APPLICATION NOTE NO. 2D Revised September 2008
Instructions for Care and Cleaning of Conductivity Cells
This application note presents new recommendations (as of October 2006), based on our recent research, for cleaning
and storing conductivity sensors. In the past, Sea-Bird had recommended cleaning and storing conductivity sensors
with a Triton X-100 solution, and cleaning conductivity sensors with an acid solution. Our latest research leads us to
recommend adding the use of a dilute bleach solution to eliminate growth of bio-organisms, and eliminating the
use of acid in most cases.
The application note is divided into three sections:
• General discussion
• Rinsing, cleaning, and storage procedures
• Cleaning materials
General Discussion
Since any conductivity sensor’s output reading is proportional to its cell dimensions, it is important to keep the cell
clean of internal coatings. Also, cell electrodes contaminated with oil, biological growths, or other foreign material will
cause low conductivity readings. A desire to provide better control of growth of bio-organisms in the conductivity cell
led us to develop revised rinsing and cleaning recommendations.
• A dilute bleach solution is extremely effective in controlling the growth of bio-organisms in the conductivity cell.
Lab testing at Sea-Bird indicates no damaging effect from use of a dilute bleach solution in cleaning the
conductivity cell. Sea-Bird now recommends cleaning the conductivity sensor in a bleach solution.
• Triton X-100 is a mild, non-ionic surfactant (detergent), valuable for removal of surface and airborne oil ingested
into the CTD plumbing as the CTD is removed from the water and brought on deck. Sea-Bird had previously
recommended, and continues to recommend, rinsing and cleaning the conductivity sensor in a Triton solution.
• Sea-Bird had previously recommended acid cleaning for eliminating bio-organisms or mineral deposits on the
inside of the cell. However, bleach cleaning has proven to be effective in eliminating growth of bio-organisms;
bleach is much easier to use and to dispose of than acid. Furthermore, data from many years of use shows that
mineral deposits are an unusual occurrence. Therefore, Sea-Bird now recommends that, in most cases, acid
should not be used to clean the conductivity sensor. In rare instances, acid cleaning may still be required for
mineral contamination of the conductivity cell. Sea-Bird recommends that you return the equipment to the
factory for this cleaning if it is necessary.
Sea-Bird had previously recommended storing the conductivity cell filled with water to keep the cell wetted, unless the
cell was in an environment where freezing is a possibility (the cell could break if the water freezes). However, no
adverse affects have been observed as a result of dry storage, if the cell is rinsed with fresh, clean water before storage
to remove any salt crystals. This leads to the following revised conductivity cell storage recommendations:
• Short term storage (less than 1 day, typically between casts): If there is no danger of freezing, store the
conductivity cell with a dilute bleach solution in Tygon tubing looped around the cell. If there is danger of
freezing, store the conductivity cell dry, with Tygon tubing looped around the cell.
• Long term storage (longer than 1 day): Since conditions of transport and long term storage are not always under
the control of the user, we now recommend storing the conductivity cell dry, with Tygon tubing looped around the
cell ends. Dry storage eliminates the possibility of damage due to unforeseen freezing, as well as the possibility of
bio-organism growth inside the cell. Filling the cell with a Triton X-100 solution for 1 hour before deployment will
rewet the cell adequately.
Note that the Tygon tubing looped around the ends of the conductivity cell, whether dry or filled with a bleach or Triton
solution, has the added benefit of keeping air-borne contaminants (abundant on most ships) from entering the cell.
Sea-Bird Electronics, Inc.
1808 136th Place NE
Bellevue, WA 98005
US
Phone: (425) 643-9866
Fax: (425) 643-9954
E-mail: seabird@seabird.com
Web: www.seabird.com
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