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WET Labs

I want to change the pressure sensor on my CTD, swapping it as needed to get the best data for a given deployment depth. Can I do this myself, or do I need to send the instrument to Sea-Bird?

On most of our instruments, replacement of the pressure sensor should be performed at Sea-Bird. We cannot extend warranty coverage if you replace the pressure sensor yourself.

However, we recognize that you might decide to go ahead and do it yourself because of scheduling/cost issues. Some guidelines follow:

  1. Perform the swap and carefully store the loose sensor on shore in a laboratory or electronics shop environment, not on a ship. The pressure sensor is fairly sensitive to shock, and a loose sensor needs to be stored carefully. Dropping the sensor will break it.
  2. Some soldering and unsoldering is required. Verify that the pressure sensor is mounted properly in your instrument. Properly re-grease and install the o-rings, or the instrument will flood.
  3. Once the sensor is installed, back-fill it with oil. Sea-Bird uses a vacuum-back filling apparatus that makes this job fairly easy. We can provide a drawing showing the general design of the apparatus, which can be modified and constructed by your engineers.
  4. For the most demanding work, calibrate the sensor on a deadweight tester to ensure proper operation and calibration.
  5. Enter the calibration coefficients for the new sensor in:
  • the CTD configuration (.con or .xmlcon) file, using Seasave V7 or SBE Data Processing, and
  • (for an instrument with internally stored calibration coefficients) the CTD EEPROM, using the appropriate terminal program and the appropriate calibration coefficient commands

Note: This discussion does not apply to the SBE 25 (not 25plus), which uses a modular pressure sensor (SBE 29) mounted externally on the CTD. Swap the SBE 29 as desired, use the CC command in Seaterm or SeatermAF to enter the new pressure range and pressure temperature compensation value, and type the calibration coefficients for the new sensor into the CTD configuration (.con or .xmlcon) file in Seasave V7 or SBE Data Processing.