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5.0 MAINTENANCE
5.1 M
S
AINTENANCE
CHEDULE
The HYDRA-DS sensor requires little maintenance since most of the required cleaning is accomplished by the Air Blast
Spray Cleaner. Determining the proper cleaning cycle and duration for the application will keep the front end of the
sensor clean for extended periods, but weekly inspection of the sensing end is recommended.
Weekly calibration checks versus a grab sample are recommended to minimize any drift in the sensor. Once the stability
of the sensor has been established in the process, the time between calibration checks can be adjusted. A calibration
check must occur at least one per month.
The HYDRA-DS should be checked monthly in calibration solutions for proper span of both the ammonium and
potassium electrodes. The electrodes start life with a span in the 55 mV/decade range and drop off into the 40
mV/decade range as they age. Readings below 40 mV/decade indicate the electrode should be replaced. Depending on
the characteristics of the water being measured the Ion Selective electrodes should last 3-6 months.
5.2 C
S
LEANING THE
ENSOR
The HYDRA-DS sensor can be rinsed with water and wiped with a soft brush or cloth to remove most coatings. DO NO
clean the potassium or ammonium ion electrodes with a stiff brush or vigorous wiping as the sensing membrane is
easily torn. DO NOT use strong detergent solutions or Spray Class cleaners to clean the sensor, the potassium and
ammonium electrodes will be irreparably harmed. The sensor can be soaked in dilute HCI, 2-3%, for 15 minutes to help
remove stubborn coatings. Use a weak detergent solution, a couple of drops detergent per liter of water, to remove
any oily coatings. The pH electrode and HYDRA-DS housing can be cleaned in a more rigorous manner since the plastic
body and glass membrane are more durable than the Ion Selective Electrodes.
5.3 R
E
EPLACING THE
LECTRODES
The three electrodes—Nitrate, Chloride, and pH—are easily replaceable by simply removing the electrode guard,
screwing out the old sensor and screwing in the new one using the supplied installation tool. Make sure no water gets
inside the sensor when removing the electrodes. Water will cause the internal electronics to fail. If the electronics are
compromised the HYDRA-DS sensor must be replaced.
The nitrate electrode, the chloride, and pH electrodes are combination electrodes. The reference electrodes are
combines to a single signal which is for all the measurements.
Apply a thin film of o-ring lubricant to the o-rings on the electrode before installing it into the sensor housing. Use the
supplied electrode installation tool to remove or install electrodes into the sensor. The use of pliers or other tools is not
recommended as they may crack the electrode housing.
HYDRA-DS NO
-N
3
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