Sensor Care

Video: Membrane Replacement for ULTRA series DO Sensors

Not sure how to replace the membrane on your Turtle Tough ULTRA Series Dissolved Oxygen (TT-ULTRA-DSS-DO-GAL-SUB) sensor? Learn how easy it is, with our step by step video. 



  1. Use the tool provided to unscrew the ring.
  2. Remove the used membrane and O-ring.
  3. Rinse the cap and ring. Dry both parts thoroughly.
  4. Put a new O-ring in the bottom of the cap.
  5. Put a membrane on top of the O-ring.
  6. Replace ring & tighten it firmly with the supplied tool.


Precautions and Caveats

  • It is very important that all parts must be clean & dry before performing this procedure.
  • The membrane must not be wrinkled before or after it is installed. If the membrane is wrinkled at any point in time it must be replaced with a new membrane immediately.
  • Fill the cap to the brim with electrolyte. Hold probe upright & slowly screw on cap until it is completely flush. Some electrolyte solution may leak out during this step.
  • Wait one hour before performing a calibration after changing the membrane. For best results calibrate once again approximately 24 hours after membrane is changed as the galvanic DO cell will have reached full equilibrium by this point in time.



The probe's membrane must be kept free from deposits. A film composed mostly of bacteria will cover ALL surfaces in a biologically active system. This bacteria film acts as a diffusion barrier for the oxygen that must diffuse through the membrane. For industrial type process solution the most likely form of contamination and build-up will be particulates and solids from the solution if the media has high turbidity or viscosity, or is an abrasive slurry in nature. The membrane must, therefore, be cleaned at regular intervals, the frequency depending on the actual conditions.

Cleaning can be performed with a cloth or soft paper. The membrane is strong and not easily damaged, but do not try to scratch it clean with a fingernail! There is no need to exchange the electrolyte regularly, and there is no sensor element that will need replacing!

The probe should not be taken apart for membrane replacement and rebuilding of the DO cell unless the membrane is damaged or you cannot calibrate to the correct value after long use.