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4.1.5
pH Sensor Maintenance
In order to maintain accurate measurement values, the sensor will need occasional maintenance. The harsher the process, the more
maintenance the sensor will require. Proper and regular maintenance will yield a longer sensor life.
The recommended pH sensor cleaning procedure is as follows:
1.
Remove sensor from service and rinse or spray it with warm water to remove heavy deposits.
2.
Soak the sensor in a container of hot detergent water for 30 minutes. Do not use detergents that contain oily skin softeners
like aloe or lanolin that can coat the glass electrode. Powdered Alconox™ and Dawn™ dishwashing liquid work well.
3.
Use a soft-bristled brush, such as a soft toothbrush, and hot detergent water to scrub the entire electrode end of the sensor,
being careful not to scratch or break the glass electrode.
4.
Rinse the electrode end with clean warm water.
5.
If deposits are still present on glass electrode repeat steps 2 and 3. In the case of lime or other mineral deposits a weak
solution (about 0.1 M) of hydrochloric acid may be used. In some cases, a dilute solution (about 10:1) of water and chlorine
bleach or a solution of water and EDTA may also work. Stubborn oil or grease deposits may require cleaning with a solvent
such as acetone or alcohol. Assure that the sensor body in compatible with the solvent. Protein deposits may be cleaned with
a pepsin-based cleaning solution. Bacterial or mold growths may be removed with dilute chlorine bleach.
Note: Cleaning can be process-specific. Some users will have to develop a procedure that works
best for them.
Caution: Ensure that a dangerous chemical reaction will not occur between process deposits and
the cleaning solution, such as compounds of cyanide, and the hydrochloric acid. Cyanide is often
used in electroplating and in gold refining. If in doubt check with a chemist.
Caution: When using dangerous chemicals such as hydrochloric acid or chlorine bleach, use all
appropriate safety precautions, especially eye protection.
Before returning the sensor to service, allow it to soak in water or buffer at ambient temperature for about an hour to stabilize.
After cleaning the sensor, always calibrate the sensor head before installing in the process.
Thermo Scientific AquaSensors™ DataStick™ Measurement System User Guide
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Troubleshooting
