Laboratory calibrations of the CTD pressure and temperature sensors were used to generate tables of corrections applied by the CTD data acquisition and processing software at sea.
Pressure calibrations were last performed on CTD #1 (S/N 50619) at the Paroscientific, Inc Calibration Facility in Redmond, WA and Sea-Bird Electronics, Inc. at Bellevue WA, immediately prior to WIMP14. This pressure sensor is rated to drift less than 200 ppm or less per year (2.0 dbar for the 10,000 dbar sensor).
Temperature calibrations were last performed on both the primary Temperature sensor (SBE 3-02/F S/N 1609) and the secondary sensor (SBE 3-02/F S/N 1701) on April 15, 1997 at Sea-Bird Electronics, Inc. Accuracy of these calibrations is 1 mK, while the precision can be greater than 0.235 mK. Both sensors showed a similar small drift over the year proceeding this cruise (about 0.0005 C/yr). The primary sensor shows a possible slight secondary temperature response with largest residuals found near 15C.
Conductivity sensors (model SBE 4-02/O) were calibrated on April 15, 1997 at Sea-Bird Electronics, Bellvue WA. The primary conductivity sensor (S/N 1347) showed slightly larger drift than the secondary conductivity sensor (S/N 1346) over the one year period prior to this cruise (0.0009 vs 0.0002 psu/month).
Oxygen sensors were calibrated April 12, 1997 at SBE. For WIMP14 only the primary sensor (S/N 130353) was used. During ACCE2, a secondary oxygen sensor was added after station 68. During ACCE3, the secondary oxygen sensor experienced larger drift relative to the bottle samples than the primary sensor.
These calibration procedures will be repeated when the instrument is returned to AOML. At first inspection based on pre-cruise calibrations and sensor history, except for oxygen, the secondary sensor pairs will most likely prove the most stable.