YSI ProDSS - Manual (Page 63)

61
Maintenance and storage
pH - pH/ORP sensors
NOTE: pH and pH/ORP sensors require periodic maintenance to clear contamination from the sensing elements.
These contaminants can slow sensor response time. Clean the sensors when deposits, bio-fouling or
other contamination appears on the glass or when the sensor response time is noticeably slow.
NOTICE: Do not physically scrub or swab the glass bulb. The bulbs are fragile and will break if pressed with
sufficient force.
1 M HCl
Chlorine
bleach
Figure 70 pH and pH/ORP sensor
maintenance
pH - pH/ORP sensor maintenance
1. Remove the sensor from the bulkhead and soak for 10 to 15 min-
utes in a mild solution of clean water and dish soap
(
Figure 70 ).
2. Rinse the sensor with clean tap water and inspect.
3. If contaminants are removed, attach the sensor to the bulkhead
and test the response time ( ProDSS sensor installation/removal on
page 9 ).
OR
If contaminants remain or response time does not improve,
continue to the hydrochloric acid (HCl) soak in step 4.
4. Soak the sensor for 30 to 60 minutes in one molar (1 M) HCl.
NOTE: HCl reagent can be purchased from most chemical or
laboratory distributors. If HCl is not available, soak in white
vinegar.
CAUTION: To prevent injury, carefully follow the HCl
manufacturer’s instructions.
5. Rinse the sensor in clean tap water.
6. Soak the sensor in clean tap water for 60 minutes, stirring
occasionally. Repeat the clean tap water rinse.
7. Attach the sensor to the bulkhead and test the response time.
If response time does not improve or biological contamination
of the reference junction is suspected, continue to the chlorine
bleach soak in step 8.
8. Soak the sensor for approximately one hour in a 1:1 dilution of
chlorine bleach and tap water.
9. Rinse the sensor with clean tap water.
10. Soak the sensor in clean tap water for one hour or longer. Repeat
the clean tap water rinse.
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