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Maintenance
6.2 Cleaning the Sensor
CAUTION
Before cleaning with acid, determine if the chemical reaction between the acid and
the sample will create a hazardous chemical reaction. (For example, do not put a
sensor that is used in a cyanide bath directly into a strong acid for cleaning
because this chemical combination may produce poisonous cyanide gas.)
1. Clean the exterior of the sensor with a stream of water. If debris remains remove loose
contaminate buildup by carefully wiping the entire measuring end of the sensor
(process electrode, concentric metal ground electrode, and salt bridge) with a soft
clean cloth. Rinse the sensor with clean, warm water.
2. Prepare a mild soap solution of warm water and dish detergent or other non-abrasive
soap that does not contain lanolin such as laboratory glass cleaner.
Note: Lanolin will coat the glass process electrode and can adversely affect sensor performance.
3. Soak the sensor for 2 to 3 minutes in the soap solution.
4. Use a small soft bristle brush (such as a toothbrush) and scrub the entire measuring
end of the sensor, thoroughly cleaning the electrode and salt bridge surfaces. If
surface deposits cannot be removed by detergent solution cleaning, use muriatic acid
(or other dilute acid) to dissolve them. The acid should be as dilute as possible.
Experience will determine which acid to use and the appropriate dilution ratio. Some
stubborn coatings may require a different cleaning agent. For assistance, contact
Technical and Customer Service (U.S.A. only) on page 43.
DANGER
Acids are hazardous. Always wear appropriate eye protection and clothing in
accordance with material safety data sheet recommendations.
5. Soak the entire measuring end of the sensor in dilute acid for no more than 5 minutes.
Rinse the sensor with clean, warm water then place the sensor back into the mild
soap solution for 2 to 3 minutes to neutralize any remaining acid.
6. Remove the sensor from the soap solution, and rinse the sensor again in clean, warm
water.
7. After cleaning, always calibrate the measurement system.
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