Xylem EXO Series User Manual page 101

pH and pH/ORP Sensors
6.13
Maintenance
pH and pH/ORP sensors will require occasional maintenance to clear contamination from the sensing elements.
These contaminants can slow the sensor's response time. Clean the sensors whenever deposits, biofouling, or
other contamination appear on the glass, or when the sensor's response time slows perceptibly. Remove the
sensor from the sonde before performing the following cleaning steps. Do not attempt to physically scrub or
swab the glass bulbs. The bulbs are very fragile and will break if pressed with sufficient force. Maintain connectors
as instructed in the "Connectors" section.
1 M H
Cl
Chlorine
Bleach
1 Soak in dishwashing liquid solution.
Soak the sensor for 10-15 minutes in a solution of clean
water and a few drops of dishwashing liquid. Following
the soak, rinse the sensor with clean water and inspect. If
contaminants remain or response time does not improve,
continue to the HCl soak.
2 Soak in HCl solution.
Soak the sensor for 30-60 minutes in one molar (1 M)
hydrochloric acid (HCl). This reagent can be purchased
from most distributors. Following the HCl soak, rinse the
sensor in clean tap water and allow it to soak for an hour
in clean water. Stir the water occasionally. Then, rinse
the sensor again in tape water and test response time. If
response time does not improve or you suspect biological
contamination of the reference junction, continue to the next
soak. If HCl is not available, soak in white vinegar.
A
Follow the HCl manufacturer's instructions carefully to
avoid personal harm.
3 Soak in chlorine bleach solution.
Soak the sensor for approximately one hour in a 1:1
dilution of chlorine bleach and tap water. Following the
soak, rinse the sensor in clean tap water and allow it to
soak for at least one hour in clean water (longer if possible).
Then, rinse the sensor again in tap water and test response
time.
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