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Dissolved Oxygen (DO) Sensor Maintenance Guide HORIBA U-50 Series

HORIBA U-50 Series Dissolved Oxygen (DO) Sensor Maintenance Guide (Every 3-6 Months)

DO Membrane and Filling Solution Replacement:

Remove Sensor: Detach the DO sensor from the probe assembly using the DO spanner.
Unscrew Membrane Cap: Remove the old DO membrane cap.
Clean Electrodes: Wash the gold tip (cathode) and silver electrode (anode) with water. Refer to the cleaning section for further cleaning if needed.

Replace Silicone Gasket: Remove the old gasket and replace it with a new one (provided with each membrane cap).

Add Filling Solution: Using a dropper, fill the new membrane cap with DO filling solution #306.

Remove Air Bubbles: Drop the membrane cap on a bench to eliminate air bubbles.

Reassemble Sensor: Reattach the sensor to the probe assembly, tightening gently with the DO spanner.

Check for any air bubbles in the membrane cap. Make sure there are no wrinkles in the membrane.

Membrane Cap Attachment and Sensor Reassembly

Check for Proper Fit: Ensure the membrane cap is securely attached to avoid loss of sensitivity or slower response times.
Reattach Sensor Cartridge: Fit the DO sensor cartridge back into the main probe assembly using the provided DO spanner, but avoid overtightening.
Grease O-Rings: Apply silicone grease to the O-rings on the DO sensor cartridge (provided with the U-50) to facilitate easier fitting and ensure a snug seal.
Secure Sensor into Socket: Press the DO sensor firmly into the socket on the main probe assembly using the flat side of the mounting ring. Apply downward pressure while tightening with the spanner.

This process helps maintain proper attachment and prevents leaks, ensuring optimal sensor performance.

Cleaning DO Electrodes:

Silver Electrode (Anode): Lightly polish with #600 or finer sandpaper and rinse with water. Avoid excessive polishing to protect the silver plating.

Before cleaning:

After cleaning:

Gold Electrode (Cathode): If not visibly dirty, wipe the tip with a tissue. If cleaning is necessary, use the green polishing sheet (grade 8000) provided. Wash with water afterward. DO NOT use coarse sandpaper on the gold tip as it will remove the gold plating.